th second in a series of guidebooks written for elementary school … · 2013-10-24 · The book emphasizes processes of. science and creativity as well as science content. ... reviewer

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ED 021 745 SE 004 823By- Hubbell, LawrenceINVESTIGATING SCIENCE WITH CHILDREN VOLUME 2, THE EARTH.Natio-nal Aeronautics and Space Administration Washington D.C.; National Science Teachers Assnciation

Washington, D.C.Pub Date 64Note- 96pAvailable from- Teachers Publishing Corporation 23 Leroy Avenue, Darien Connecticut 06820.EDRS Price MF-S0.50 HC Not Available from ORSDescriptors-*EARTH SCIENCE *ELEMENTARY SCHOOL SCIENCE GEOLOGY, *INSTRUCTIONAL MATERIALS,LABORATORY EXPERIMENTS *SCIENCE ACTIVITIES *TEACHING GUIDES

Identifiers- Investigating Science With Children National Aeronautics and Space Admir.istration NationalEducation Association National Science Teachers Association

This is th second in a series of guidebooks written for elementary schoolteachers to help improve their science teaching. The book emphasizes processes ofscience and creativity as well as science content. The book is divided into threesectionsthe atmosphere, the lithosphere, and the hydrosphere. Each chapter beginswith simple concepts, and leads to more complex concepts. (BC)

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INVESTIGATING SCIENCE WITH CHILDREN

VOLUME 2

T"E E RTH

LAWRENCE HUBBELL, Science SupervisorOak Park Public Schools, Oak Park, Illinois

Produced as a Joint Project ofNational Science Teachers Association and

National Aeronautics and Space Administration

Published byTEACHERS PUBLISHING CORPORATION

Darien, Connecticut

i

INVESTIGATING SCIENCE WITH CHILDREN SERIES

Volume 1 LIVING THINGS

Volume 2 THE EARTH

Volume 3 ATOMS AND MOLECULES

Volume 4 MOTION

Volume 5 ENERGY IN WAVES

Volume 6 SPACE

"PERMISSION TO REPRODUCE THIS COPYR IGHTEDMATERIAL BY MICROFICHE ONLY HAS BEEN GRANTEDBY firsroqTO ERIC AND ORGANIZATIONS OPERATING UNDER

AGREEMENTS WITH THE U. S. OFFICE OF EDUCATION.

FURTHER REPRODUCTION OUTSIDE THE ER IC SYSTEM

REQUIRES PERMISSION OF THE COPYRIGHT OWNER."

©National Science Teachers Association 1964

All rights reservedno part of this book may be reproduced in anyform without permission in writing from the publisher, except by areviewer who wishes to quote brief passages in connection with a

review written for inclusion in magazine or newspaper.

The National Science Teachers Association is a department of theNational Education Association (NEA) and an affiliate of theAmerican Association for the Advancement of Science (AAAS) .

About the coven The solid portion of the Earth, called the lithosphere, isdivided into three concentric spheres. From the surface of the Earth to its

center, the spheres are called the crust, the mantle, and the core.

Printed in the United States of AmericaLibrary of Congress Catalog Card No. 64-22842

,

1 INTRODUCTION

What Is the Earth Made of?

Summary and Looking Ahead

CONTENTS

PAGE

5

2 INVESTIGATING THE LITHOSPHERE10

How Can Minerals Be Identified?

How Are Crystals Formed?

What Are Rocks?

How Are Soils Made?

3 INVESTIGATING THE HYDROSPHERE38

Where Is Water Found?

What Are Some of the Characteristics of Water?

How Does the Water Cycle Take Place?

How Is Water Used?

4 INVESTIGATING THE ATMOSPHERE62

What Are the Characteristics of Air?

What Are the Characteristics of Air Masses?

How Does Moisture Get Into the Atmosphere?

What Are the Characteristics of Different Forms of Precipitation?

*5 INVESTIGATING THE WAYS THE EARTH CHANGES 83

What Is Erosion?

How Do Chemical Changes Affect the Earth?

1.7.ow Do Earthquakes Change the Earth?

What Can Fossils Tell Us About the Earth and Change?

About theINVESTIGATING SCIENCEWITH CHILDRENSeries

These six handbooks for the teaching of science in theelementary school have the distinguished sponsorship of two

leading groups concerned with the improvement of science

teaching: NSTA (The National Scielce Teachers Associa-tion) and NASA (The National Aeronautics and SpaceAdministration). Initiated by NSTA, the series receivedtechnical and financial assistance from NASA. The sixauthors were carefully chosen by NSTA and NASA fromamong leading science educators in the United States and

Canada. The series has been carefully planned, developed,and edited over a period of two years. It updates and re-places the widely successful SCIENCE TEACHING TO-DAY series by Dr. Guy Bnice, published by NSTA in 1950.

General approach and philosophy. As they planned thisseries of books, members of the writing team were con-cerned with the following questions: What are some thingswe can or should do to help teachers as they investigate the

world of science with children? In what direction shouldwe move? How can we incorporate into our writings theprocesses and content of science, the fostering of creativityin children, provisions for children's varying abilities?

The age and culture in which we live demand that chil-dren in the elementary schools have a variety of real scienceexperiences that lead them to an understanding of the world

about then-1. Through a variety of science experiences, eachindividual will come to understand and to use scientificprocesses and skills, as well as to acquire the specific sciencelearnings that will help him live intelligently.

Since each book in the series is concerned with one areaof science and moves from simple concepts to more com-plex ones within each chapter, each teacher, at any gradelevel, will find that all the books have materials that shecan use in her teaching.

Questiondiscovery approach used. Throughout each book,questions are used in several different ways. At the beginningof each chapter is a list of questions that children of dif-ferent ages might ask. Answers to these questions and others

are found when the children become involved in doing the

Activities of the specific chapter. Other questions, withanswers containing the science information given in paren-theses for the teacher, are included within each Activity tohelp teachers as they guide the children's learning. Morequestions are listed later, as open-end Activities to be used

with those children who may wish to make furtherinvestigations.

Organization keyed to varying abilities. To provide forvarying abilities of the children in a group and at dif-ferent grade levels, as well as to make possible a develop-mental approach to concept formation, the Activities andlearnings are purposely not "graded," but are designatedby the following symbols: x for those Activities involvingbeginning !earnings; y for those Activities requiring moreskill and involving several learnings; and z for those Activi-ties of considerable difficulty and involving more complexthought patterns. An introduction is included with each

Activity, which is merely suggestive and which may givethe teacher ideas helpful in challenging children's thinking.

Illustrations and format. All six of the volumes are filledwith helpful illustrations that will help the teacher as shedirects the children's participation in the Activities. A two-column format allows for easy reading and clear organiza-tion, for in-class presentation.

Summaries and references. Each chapter concludes with asummary of the main ideas developed by the author.

Throughout each book, cross references are made toActivities and science content found in the other books ofthe series. At the end of each book there is a list ofbAiographical references that contain additional science

information.

Scientific accuracy assured. One of the concerns of thewriting team was the scientific accuracy of the informationappearing in each book. To insure such accuracy, leadingscientists who are specialists in their respective fields were

asked to read and review the content during the preparationof the manuscripts. Their names appear at the end of thissection.

It is hoped that this series of books, INVESTIGATINGSCIENCE WITH CHILDREN, will be helpful in providingopportunities for children to use many processes of inquiryinvestigating, observing, problem-solving, hypothesizing,

experimenting, thinking, checking, analyzingas they tryto find the what, how, and why of the world around them.There are no final answers in these books. Let the series bethought of as a challenge to teachers to further learning.

Acknowledgments. Many people have made this series

possible. The authors and series editor wish to express theirappreciation to Robert Carleton, Executive Secretary ofthe National Science Teachers Association, for his confidencein the project and for his many words of encouragement; toFrank Salamon, Specialist in Elementary Science, National

Science Teachers Association, for his guidance throughvarious stages of the project; to Everett Collin, MattisonL. Story, and George Gardner, Specialists, National Aero-nautics and Space Administration Education Program, fortheir interest in the project and for their reading of themanuscripts; and to Lila J. Phillips, Editor for this series,Teachers Publishing Corporation, for her suggestions andaid in the preparation of the final manuscripts for publication.

To the following scientists, who read the manuscriptsin their preliminary form for scientific accuracy, theauthors and series editor are deeply indebted for theirmany helpful comments and reactions: Dr. M. G. Seeley,University of Arizona, Tucson, Arizona; Dr. Alexander

Calandra, Washington University, St. Louis, Missouri;

Dr. Albert R. Hibbs, Jet Propulsion Laboratory, CaliforniaInstitute of Technology, Pasadena, California; Dr. WilliamMathews III, Lamar State College of Technology, Lamar,Texas; and Dr. Barbara Collins, Geologist, Northridge,

California.

RUTH L. ROCHE, Series EditorARTHUR COSTALOUIS T. COX, JR.LOIS E. DUNNLAWRENCE HUBBELL

SEYMOUR TRIEGERJAMES R. WAILES

1

INTRODUCTION

"What do you mean when you talk about science?

What is science?" Mrs. Arnold asked her fourth

grade class these questions one day before start-

ing a new science unit."Isn't science knowing about interesting things

like bees and ants?" Janie volunteered."That could be part of it," answered Mrs.

Arnold. "Are there any other ideas?""I think science is discovering things. You

know, like cutting up animals to see what's in-

side them," said Jack."Discovery is certainly an important part of

science," said Mrs. Arnold, "but it's a particular

kind of discovery. Let me ask you another

question. Would you call the early explorers

who discovered the Americas scientists?"The children responded by saying, "No, I

don't think you'd call them scientists." "I guess

discovering isn't exactly what science is." "Maybe

you have to discover certain kinds of things."

"Now you're getting closer to the real answer,"

said Mrs. Arnold. "What kind of things do

scientists discover or find out?"

"One thing scientists do is discover cures for

diseases.""Yes, that's right. Any other ideas?""My uncle's a scientist and he is trying to find

out about outer space," Mary ventured."Scientists also work with chemicals and dis-

cover new things," said Bill.This discussion might occur in any classroom.

Mrs. Arnold was introducing the concept of

science and scientific thinking to her class. She

correctly realized that science is more thanlearning a collection of facts taken out of a book.

It is a way of thinking, a way of discovering the

answers to problems. It also includes the develop-

ment of concepts and ideas."We've already said that science is trying to find

answers to problems," continued Mrs. Arnold.

"How do you suppose a scientist finds a prob-

lem?""That shouldn't be very hard," spoke up

Richard. "You could just ask 'why' about any-

thing around you'Why is the sky blue?' or 'Why

does it snow in the winter?' ""Yes, to find a problem all you have to do is

look around you and then be curious. But now

that you have a problem," said Mrs. Arnold,

"how would you go about finding the answer?

You look as though you might have an idea,

Jane.""I've always heard that scientists make ex-

periments. Maybe these come in here somehow."

"Yes, Jane, you're right. Scientists perform

experiments to answer their problems. Suppose

you want to know what the shape of theEarth is. First you must make a guess and then

test it with an experiment. What kind of a guess

could you make?""Well, you could guess that it was flat like a

table," Sally said."But that's crazy," spoke up Bill, "our geog-

raphy book says it's round."5

"Yes," said Mrs. Arnold, "but we didn't al-ways know it was round. Suppose you lived inthe time of Columbus and didn't know the shapeof the Earth. How would you find out what itwas? You must first make a guess and test it.Your guess might be right and it might be wrong.But this is the only way of finding the rightanswer.

"Suppose you did guess that the Earth wasflat, like a table. What kind of experimentwould you make to test your guess?"

"I know what you could do," spoke up John."If it was like a table, you would be able to travelto the edge and look over it."

"Yes, you should be able to. What exactlywould you do to test your guess?"

"I guess I'd take a boat or a train and keepgoing in a straight line until I reached the edge."

"And, if you never reached the edge, thenwhat?" asked Mrs. Arnold.

"Then I guess I'd decide the Earth wasn't flat.""Exactly," said Mrs. Arnold. "But now there's

one more thing to the scientific method that wehaven't mentioned as yet. What happens whenyou have finished your experiment and find thatyour guess was correct?"

"Well, you know the answer to what you askedin the first place."

"And now what do the scientists do?" askedMrs. Arnold..

"Maybe 'ley make laws or something aboutwhat they found out."

Mrs. Arnold was pleased with the responsesof her class in their discussion of scientificmethods. She wanted to help her children developthose skills and abilities necessary to approachproblems scientifically. With a series of plannedActivities, she hoped to stimulate their interestand ability to question, to make intelligentguesses, and then to test them. By using such amethod she could introduce important scientific

concepts.The Activities in this book are designed to

present children with useful experiences in earthscience. These Activities will introduce importantconcepts about the nature of the Earth and theprocesses that are continually shaping and chang-ing it.

WHAT IS THE EARTH MADE OF?

Children usually think of the Earth as just the

solid rock and soil they stand on, but the Earthis made of much more. The rock layer that ex-tends through the Earth makes up a huge ball orsphere called the lithosphere. The Earth also hasa water layer which covers parts of the rocklayer and is known as the hydrosphere. An airlayer, which surrounds the Earth, is also shapedlike a sphere and is called the atmosphere. Thesethree spheres, the lithosphere, the hydrosphere,and the atmosphere, make up the Earth.

To demonstrate that the Earth is made up ofthese three spheres and to discover the nature ofeach sphere, you may want your children tocarry on some or all of the following preliminaryActivities. The first of these Activities will developthe concept of density as an aid to an under-standing of the three spheres. Density is a relation-ship between weight and volume. If two objectshave the same volume, the object that is heavierhas a greater density. For example, a cubic foot ofwater weighs 62.5 pounds; a cubic foot of ironweighs 490 pounds. Iron, then, would have amuch greater density than water. Density isusually expressed in weight per unit volume,such as pounds per cubic foot.

ACTIVITY 1 (x,y,z)

DISCOVERING THE MEANING OF DENSITY

Purpose: To introduce the meaning of density

Concept to be developed: The density of an object isexpressed as its weight per unit volume.

Materials needed:Small wad of cottonCork stopperWood blockSmall piece of ironPiece of glassSmall stonePiece of plasticPiece of aluminum

INTRODUCTION: Place several different kinds ofobjects on the table and have the children decidewhich one takes up the greatest amount of space(which has the greatest volume), which has the leastvolume, and whether any are almost equal in volume.

When the children understand what volume is,

have them compare two objects of similar volumebut obviously different weights. Why is oneheavier than the other? (Because it is made of adenser material.) * Density is a measure of weight

* For a further discussion of weight, see Motion, by LoisDunn (Investigating Science with Children Series; Darien,Conn., Teachers Publishing Corporation, 1964).

per unit volume. When two objects have the

same volume, the heavier object has the greaterdensity.

Let the class test all the various objects fordensity by weighing and measuring them. Havethe class determine which are the most dense andwhich are the least dense.

Learnings: (x) The volume of an object is theamount of space that it occupies. (y,z) Densityis the weight per unit volume. If two objects havethe same volume, the heavier object is the moredense.

ACTIVITY 2 (x,y,z)

MIXING SUBSTANCES OF DIFFERENT DENSITIES

Purpose: To show why the atmosphere, the hydro-sphere, and the lithosphere assumed their respectivepositions

Concept to be developed: The relative densities offreely moving objects determine their relative positions.

Materials needed:

Olive jar with a capWaterPebbles

INTRODUCTION: Discuss with the children themeaning of the words solid, liquid, and gas. Makea list on the chalkboard of all the things they knowthat are solid, liquid, and gas. Ask the class, "Whatparts of the Earth are solid? What parts liquid? Whatparts gas?" (Relate your children's answers to thethree spheres of the Earththe ..olid lithosphere,the liquid hydrosphere, and the gaseous atmosphere.)

Now ask your children if liquids and gases havedensities. (Yes.) Why? (Because they take up spaceand ha:ve weight.)

Have the children think of ways to tell whether aliquid or a gas has the greater density. (Liquids aremore dense than gases.) How will two substances thathave different densities and are free to move behavewhen mixed together? Suggest that the children per-form the following Activity to discover the answer.

Have a child fill the olive jar half full of waterand screw on the top. Shake the bottle and ob-serve what happens. What happened to the water?

(Bubbles of air were in the water and theycuald be seen rising to the surface.) What isabove the water? (Air.) Why did the bubblesgo up? (They floated up because they werelighter, or less dense, than the water.)

Next add a few pebbles to the jar. Cover andshake again. What did the children observe thistime? (The bubbles went up to the top and the

INTRODUCTION

1---- Jar top

Olive jar

Air

Water

Pebbles

pebbles sank down to the bottom of the jar.)Why did the pebbles sink to the bottom? (Theywere heavier, or mare dense, than the water.)

Lead the children to apply what they observedin this jar to the Earth and its three layers orspheres. Which sphere do the pebbles represent?(The rock layer, or lithosphere.) Which spheredoes the water represent? (The water layer; orhydrosphere.) Which sphere does the air repre-sent? (The air layer, oratmosphere.)

Learnings: (x) Gases, liquids, and solids all have

densities. (x) Heavier objects, or objects ofgreater density, sink beneath lighter objects, orobjects of lesser density. (x,y) It is the relativedensity of freely moving objects that determinestheir relative positions. (x,y) The Earth's rocklayer, or lithosphere, has the greatest density and

is below the hydrosphere, or water layer, and theatmosphere, or gas layer. Gases rise to the top,as they are the least dense.

ACTIVITY 3 (x,y,z)

COMPARING TWO SOLIDS OF DIFFERENT DENSITY

Purpose: To show why the Earth's core, mantle, andcrust assumed their respective positions

Concept to be developed: When certain solids are freeto move,- the more dense solid will settle below theless dense solid.

Materials needed:Olive jar (big enough to hold more than two cups

of liquid)1 cup sand1 cup sawdustSpring scale

INTRODUCTION: Show' the children the cup ofsand and the cup of sawdust and have them notethat the two have the same volume (since they

7

EARTH

occupy identical amounts of space). Ask the chil-dren which they think will have the greater densityand why. Have them test their ideas.

Have several children weigh the cup of sandand the cup of sawdust and record the weights.Which is heavier? (The sand.) Put both the sandand the sawdust into the olive jar, screw on the

cap, and shake the jar vigorously up and down.Have the children observe which material settles

to the bottom in larger amounts. (Tim safid.)Why does the sand settle to the bottom and thesawdust come to the top? ( The sand weighs more

per unit volume; the sand is denser and is pulleddown with a greater gravitational force.)

Jar cap

Olive jar

, Pure sawdust

Mixture ofsand andsawdust

.Pure sand

Relate their observations to the solid part ofthe Earth. The solid part of the Earth, the litho-

sphere, is also divided into spheres of differ-ing densities. The central core consists of verydense material. Surrounding this is a less densemantle; on the outer surface is the crust, the leastdense. With which layers of the lithosphere, orsolid Earth, do the sand and sawdust compare?(The sand might be compared with the densermantle or central core, and the sawdust mightbe compared with the less dense crust.)

Learnings: (x) When certain solids are free tomove, the denser solid settles below the lessdense solid. (x,y) The Earth's rock layer, orlithosphere, also consists of layers with the leastdense layer on the surface and the most denselayer in the center, or core.

8

ACTIVITY 4 (x,y,z)MAKING A CLAY MODEL OF THE EARTH

Purpose: To illustrate the structure of the lithosphere

Concept to be developed: The lithosphere consists ofthree layers: the core, the mantle, and the crust.

Materials needed:Modeling clay or wallpaper cleanerTempera paints

To illustrate the zones of the solid earth, thechildren may want to make a clay model. Havethem roll some modeling clay or wallpapercleaner into a .sphere, cut out sections as illus-trated, and paint the various layers with temperapaint.

CRUST

10-30miles

The thin outer layer represents the solid crust,thought to be about 10 to 30 miles thick. Thecentral section represents the inner core of theEarth. The.area in between represents the mantle.The mantle is about 1,800 miles thick; the coreis about 2,200 miles thick. These zones mightbe labeled with stickers on toothpicks stuck intothe clay.

The clay model of the Earth can be furtherelaborated by painting the hydrosphere (on theportion of the model that has not been cut away)blue. The children might also wish to show theatmosphere on the model by supporting a sheetof cellophane or transparent plastic above thecrust with toothpicks. If they do this, they canmake the atmosphere appear more realistic bysimulating clouds with puffs of absorbent cotton.

Some of the children may have heard of theMoho, the division between the outer crust andthe mantle. Scientists are planning to drill downto the Moho to see what kind of rock composesthe mantle, and some of the ,..hildren may wantto find information about the Moho le project.

Learnings: (x) The solid Earl consists of threelayers: the crust, the mantle, and the centra' mre.The outer crust is very thin when compared withthe other rock layers of the Earth. (x,y) TheMoho le project is the attempt to drill through theEarth's crust to reach the mantle. Scientists wouldlike to know more about the nature of the rockin the mantle.

SUMMARY AND LOOKING AHEAD

We have seen that science Is a method of think-ing. It involves, first of all, curiosity and obs va-tion. A scientist observes the world about himand asks, Why? He next formulates possibleanswers to his problems, and these are knownas hypotheses. A scientist must next perform ex-periments to test his hypothesis. When he ac-

INTRODUCTION

cumulates enough facts to prove his hypothesiscorrect, he formulates a theory and finally, afterenough evidence has been gathered, a law.

This book is designed to develop scientificthinking in children. Activities are designed todevelop important concept§ and give meaningfulexperiences to the children.

The main topic of the book is the Earth. Onechapter will cover each of the three spheres ofthe Earth: the solid lithosphere; the water, orhydrosphere; and the gaseous atmosphere. Thenext three chapters show how .these three spheresare continually interacting and how they helpto shape the surface of the land. The last chapterwill illustrate some of the processes and forcesat work in changing and shaping the Earth'ssurface. Children will find the answers to suchquestions as "Why do we have hills and valleys?""What made the mountains?" "Where did thesand come froth on the beach?" "What is aglacier?" "What do fossils tell us?" and "Whydoes the desert look so different from otherareas?"

9

2

INVESTIGATING THE LITHOSPHERE

What kind of rock is this?Why are some rocks smooth and others rough?What is the difference between a rock and a

mineral?How can I grow my own crystals?Where do soils come from?Why are some soils black and others red?What is the white stuff that farmers put on soil?These are some of the questions your children

may have asked about rocks, minerals, and soil.The Activities in this chapter will deal with theseand many other questions your children may haveasked. The topics will be concerned with thelithosphere, the rock phase of 'the Earth. TheEarth's crust is the upper layer of the lithosphere.Since the crust is the only part of the lithospherethat we can see, it is this part that will be studied.For these investigations, much of the laboratoryand materials will be furnished by the out-of-doors. Discovering the nature of the Earth's crustcan be a fascinating study in science and shouldprovide many activities of interest for yourchildren.

HOW CAN MINERALS BE IDENTIFIED?

The solid crust of the Earth is made up of manydifferent kinds of rocks, which, in turn, arecomposed of minerals. Rocks may contain oneor more minerals. Since the number and kindsof minerals differ in each type of rock, no twotypes are identical.

Minerals, on the other hand, are relativelyconstant in composition. They are naturally oc-curring elements or inorganic cOmpounds. Anelement is a substance that cannot be brokendown into simpler substances by ordinary chem-ical means. A compound consists of two or moreelements chemically combined. An inorganiccompound is a compound formed from a non-living source.*

* For a further discussion of elements and compounds, seeAtoms and Molecules, by Seymour Trieger (InvestigatingScience with Chi'dren Series; Darien, Conn., TeachersPublishing Corporation, 1964).

10

To clarify further the difference betweenminerals and rocks, think of a pudding or fruit-cake made with a variety of fruits and nuts. Thepudding or cake represents the rock, while theraisins, currants, and figs represent the variousminerals that compose the rocks.

Minerals can be identified by their physicaland chemical characteristics. The more commoncharacteristics include streak, luster, color, cleav-age, fracture, hardness, specific gravity, reactionto acids, and crystalline formation. Other proper-ties that can be tested include magnetic proper-ties, taste, melting point, and heat conductivity.

The following Activities indicate how yourchildren may use some of these properties toidentify minerals. Before they begin the Activitieson minerals, it is suggested that a series of min-erals be purchased from "rock-hounds" or col-lections sold in stores. Some of the more impor-tant minerals to obtain include the following:

apatitequartz (pink, white)feldspar (pink, white)calcite (blue, white)mica (black, white)graphitegalenapyritesulfurjasperchalcopyrite

hematitemagnetitelhnonitetalcasbestoshalite (rock salt)icaolinitefluorite (green, purple,

white)gypsummalachite

azurite

ACTIVITY 5 (x,y)

IDENTIFYING MINERALS BY STREAK

Purpose: To show that many minerals leave charac-teristic colored streaks when rubbed across a whitesurface

Concept to be developed: The streak test is one of thetests used in identifying minerals.

Materials needed:

Unglazed porcelain tile (1 piece for every 3 childrenif possible)

Fi lesSamples of different minerals

INTRODUCTION: Have a display of different min-

eral specimens on a table in front of the children.

As you hold each specimen up, let the children tell

what they can observe about it just from looking

at it. Point out that this is one of the ways scientists

use to identify minerals. Then tell them that they will

discover another way in the following Activity.

Have one child rub a sample of pyrite orzlIalcopyrite across the unglazed porcelain tile.

What do the children see on the tile? (A greenish-

black mark that has been made by the mineral.)

Point out that this method of testing is called a

streak test and is one way of identifying certain

minerals. (Streak refers to the powder a mineral

leaves when rubbed on a rough surface. The color

of the powder is often different from the color of

the mineral itself. This difference in color is one

means of identifying minerals.)

You may want the children to make their

own discoveries of streak by rubbing the other

minerals you have obtained on the unglazed

pieces of porcelain tile. Have the children work

ih mall groups. What do they discover? (Some

minerals leave no apparent streak; others leave

streaks of a particular color.) The streak or color

of the powder may also be obtained by powdering

the mineral with a file. Some children might want

to use this way of discovering the streak left by

their mineral samples. In some cases, minerals

will appear to leave no streak and will scratch

the tile instead. These minerals are harder than

the tile and will not be powdered in this manner.

Have the children make their own list of the

minerals, to include the minerals' external color

and streak. Have them note which minerals have

a distinctive enough difference between external

color and streak to help in identification. The

following table illustrates what your children can

discover:


Minerals

apatitecalcitechalcopyritefluorite

galenahematite

limonitetalcmagnetitemalachitepyrite

External Color

blue-greenblue or whitebrass yellowgreen, purple,

whitelead graysteel gray, red-

brownbrowngray or greenblackbright greenpale brass yellow

Streak

whitewhitegreenish blackwhite

lead graybrownish red

ocher yellowwhiteblackpale greengreenish black

From their findings, the children should beable to answer such questions as "What is themost common color of the streak?" (White.)"Would a white streak be a conclusive test for

;identification?" (No, too many minerals have

a white streak.) "Do you note any streaks that

seem to be a distinctive color and are different

from the external color of the mineral?" (Yes,the streak of hematite and limonite particularly.)"Can these streaks be used for identification?"(Yes, this is one of the chief tests for hematiteand limonite. )

Learnings: (x) The color of the powder or streak

of a mineral is not always the same.as the externalcolor of the mineral. (x,y) A streak test is onemeans of identifying minerals. In most cases itmust be used with other tests, since many min-

erals leave the same color streak. A few minerals,

however, leave a very distinctive and character-

istic streak, which identifies them.

ACTIVITY 6 (x,y)

IDENTIFYING MINERALS BY LUSTER

Purpose: To show that luster is a characteristic thataids in the identification of minerals

Concept to be developed: The luster of a mineral is ameasure of the way it reflects light.

Materials needed:Samples of different minerals

INTRODUCTION: This Activity will help children

to discover another way to test mineral samples.This way to identify minerals is by means of their

luster. Explain that luster refers to the way mineralsreflect light. Ask the children to name some minerals

that have a very shiny, metallic look. These minerals

are said to have a metallic luster. (Such minerals are

EARTH

usually compounds of a metal and sulfur, calledsulfides, or a metal and oxygen, called oxides.) Min-erals with g metallic luster are said to be opaquesince they do not let any light pass through them.Write the terms metallic and opaque on the chalk-board. Brass, bronze, aluminum, and silver have thismetallic luster. Pyrite and galena are good examplesof minerals with a metallic luster. Other kinds oflusters include adamantine (brilliant or flashing),vitreous (glassy), resinous or waxy, pearly, satiny,silky, and dull.

Have the children make a luster guide byfirst using common materials. Hold up samplesof common materials and let the children de-scribe the way each one reflects light. Developthe meaning of the word luster. For example, adime would have a metallic luster. Ice would bedescribed as glassy. Soil or clay would be calleddull.

Next, let the children work with their mineralsand demmine the type of luster for each one.They may wish to add this list to the previousone on streak so that they now have two charac-teristics for each mineral.

The partial table of lusters below may be aguide for luster determinations.

Luster Mineral

metallicadamantinevitreousresinouspearlysatinydull

galena, pyrite, chalcopyrite, some hematitediamond, corundum, gems (ruby, emerald)transparent quartz, calcitesulfurtalcasbestoskaolinite

In obcerving the luster of the minerals, thechildren may have noted that some of the min-erals transmit light or let it pass through. Ex-plain to them that such minerals are calledtransparent, in contrast to those which do notallow any light to pass through them and arethus called opaque. Write the twO terms on thechalkboard for review.

Learnings: (x,y) Minerals reflect light in dif-ferent ways. This results in the property calledluster, which may be used to identify minerals.Frequently minerals are classified as having ametallic or a nonmetallic luster. (x) If a mineraltransmits light, it is called transparent; mineralsthat let no light pass through are called opaque.

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ACTIVITY 7 (x,y)

IDENTIFYING MINERALS BY COLOR

Purpose: To show that the external color of a mineralis sometimes a means of identification

Concept to be developed: The color of a mineral is aresult of the light that is reflected from the surface;this color, however, may be affected by impurities inthe mineral.

Materials needed:

Samples of different minerals

INTRODUCTION: Children are only generallyaware that minerals have different colors. This Ac-tivity will help them to discover that color is anothermeans of identifying minerals.

Remind the children that minerals often havecharacteristic colors. Explain briefly why: the colorof the mineral is determined by the light that isreflected, or bounced back, from the mineral to theeye. (This color may be different from the color ofthe transmitted light, the light that passes throughthe mineral.) But point out that the color of amineral is not always constant and may be causedby certain impurities within the mineral. For ex-ample, copper impurities often produce a green orblue color. Iron impurities often produce a yellow,red, or brown color.

Ilave the children observe and record the colorsof the various minerals you have obtained. For thoseminerals that have more than one color, such asquartz, it will be helpful to have samples of at leasttwo different colors.

The children may want to list separately thosemin' erals that have a variety of colors. Can thecolor test be used to identify these minerals?(No.) Do any minerals have characteristic colorsthat might be used for identification? (Yes. Sul-fur, azurite, malachite, jasper, pyrite, and galenaare examples of these.)

The following list will suggest how your classmight record the different colors.

Minerals with a Constant Color

sulfurmalachiteazuritejaspergraphitegalenapyritechalcopyritekaolin

yellowgreenblueredlead graylead graybrass yellowbrass yellowwhite

Minerals with More Than One Color

fluoritequartzmicacalcite

green, purple, blue, whitepink, white, graycolorless, pink, blackblue, white

Learnings: (y) The color of a mineral is a resultof the light that is reflected from the surface. Thiscolor may be affected by impurifies in the min-eral. (x) The color of a mineral may be useful inidentification. It cannot be used alone, however,since many minerals have more than one color.

ACTIVITY 8 (y,z)IDENTIFYING MINERALS BY CLEAVAGE

Purpose: To show how cleavage may aid in theidentification of some minerals

Concept to be developed: Cleavage is the tendency ofsome minerals to break along smooth, parallel planes.

Materials needed:

Magnifying glassHammerKnifeSamples of different minerals

INTRODUCTION: Explain to the children that oneof the most important properties for identificationof a mineral is cleavage. Write this term on thechalkboard. Tell them the definition: cleavage refersto the tendency of some minerals to break alongcertain parallel planes. Minerals having cleavagewill show one or more directions of cleavage whenfractured. Because the cleavage planes are smooth,they are usually quite easy to observe since theywill reflect light like a smooth piece of glass ormirror. A test for cleavage is to turn the mineral inthe light to see if there are any shiny surfaces.

Suggest that the children discover cleavage forthemselves by prying into a piece of mica witha knife. (Caution them on the proper method ofusing the knife.) Split the mica into thin sheets.These thin sheets can be split into thinner sheets.In what way have the sheets separated? (Alongparallel planes.) Have the children feel thesmoothness of each sheet. How many differentexamples of parallel planes can be seen? (Onlyone.) What is the nature of the cleavage surface?( lt is very shiny and smooth.)

Have other children strike a sample of galenawith a hammer. (Caution them about the useof the hammer. Put the galena in a paper bagor wrap it in cloth before breaking it. ) What is thecleavage of galena? (The cleavage faces makelittle cubes.) How many directions of cleavageare there now? (Th/eethe three dimensions ofthe solid cube.) Next have the children strike asample of calcite with a hammer. What is thecleavage here? (The cleavage results in rhomb-shaped fragments, the sides of which are paral-


lelograms.) How many directions of cleavage arethere in this case? (Again there are three, onefor each of the different sides.)

Have the children observe the other mineralsto see if they can detect any cleavage by lookingfor shiny surfaces. Remind them that cleavageis an inherent property of the mineral and theword refers to the way the mineral will break.The children may be able to discover cleavagein gypsum, feldspar, and fluorite.

Learnings: (x) Cleavage is the tendency of someminerals to break in smooth parallel planes. Itis present in certain minerals and can aid inidentification. (y) Cleavage varies in its com-pleteness and perfection. Some minerals, such asmica, have a very discernible cleavage, alsocalled perfect cleavage. Other minerals have acleavage that is difficult to observe. (y) Cleavagemay be in one, two,' or three directions, depend-ing upon the mineral. If the cleavage is in onedirection only, parallel sheets will be observed.If the cleavage is in three directions, solid geomet-ric figures, such as tubes or rhombi, will beobserved.

ACTIVITY 9 (y,z)IDENTIFYING MINERALS BY FRACTURE

Purpose: 'To show that fracture may aid the process ofmineral identification

Concept to be developed: Fracture is a description ofthe broken surface of a mineral that does not showcleavage.

Materials needed:

HammerChipped glassIndian arrowheadObsidianSamples of different minerals

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INTRODUCTION: Tell the children that althoughthey learned about cleavage in the last Activity, theyshould realize that many minerals have no cleavage.The term used to describe how these minerals breakis fracture. Explain that the term fracture describesthe surface of the mineral. For example, the surfacemay appear fibrous, earthy, even, or uneven. Themost distinctive type of fracture is known as con-choidal fracture, which is shell-like in appearance.Mention the conch shell, from which this term isderived, and show the children a picture of one ifit is available. Tell the children that fracture is an-other characteristic by which some minerals can beidentified.

Show the children a piece of obsidian. (Ob-sidian is not a mineral. It is a rock that hascooled very rapidly and thus has a glassy textureor appearance.) Let them handle different pieces.To be sure they understand the meaning of theterm fracture, have one of them strike the pieceof obsidian with a hammer. (Wrap the obsidianin cloth first.) What does the broken surfaceresemble? (Concentric arcs or shells.) (If youcannot obtain obsidian, try ordinary glass, whichalso has a conchoidal fracture. Be sure to wrapthe glass in cloth before striking it with a ham-mer.) To further demonstrate fracture, note thefracture on an Indian arrowhead. (It is alsoconchoidal.)

Now have your children'observe what happensto the various minerals upon breaking to deter-mine which ones have distinctive fractures. Whatmineral has a fibrous fracture? (Asbestos.)What kind of fracture does clay have? (Earthy.)Quartz has a very characteristic fracture whichis one of the main ways of distinguishing it fromother similar-looking minerals. What is thc frac-ture of quartz? (Conchoidal.) The Indian arrow-head has a conchoidal fracture because it ismade of chert, or flint, a nontransparent quartz.

Learning: (y,z) Fracture is a description of thebroken surface of a mineral that has no cleavageConchoidal fracture is one of the most distinctivetypes and in some cases may be an importantclue to the identification of a mineral.

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ACTIVITY 10 (X,y)

IDENTIFYING MINERALS BY HARDNESS

Purpose: To show that hardness may aid the process ofmineral identification

Concept to be developed: The hardness of minerals isalways constant for the same mineral and thus maybe considered a characteristic property of minerals.

Materials needed:

Knife bladePennySteel fileWindow glassSamples of different minerals

INTRODUCTION: Have children recall the dif-ferent ways they have discovered of helping toidentify a mineral. Now they will see another meansof identificationhardness.

Tell the children that hardness is dnother veryimportant characteristic used in the study and deter-mination of minerals. The hardness of a mineralis its resistance to scratching. The hardness is usuallydetermined by seeing what substance will scratchthe mineral. For example, if quartz can scratchcalcite, we would say that quartz is harder thancalcite; if quartz cannot scratch calcite, we wouldsay that calcite is harder than quartz.

Have a group of children experiment to deter-mine the relative hardness of a fingernail, a steel file,a penny, and a knife blade. How are they listed inorder of increasing hardness? (Fingernail is the soft-est, penny is next, then the knife blade, and thesteel file is last.)

Have the children experiment with the hard-ness of minerals, determining what minerals thethumbnail will scratch, what minerals the pennywill scratch, those that the knife will scratch,and those that the file will scratch. (After a min-eral has once been scratched, there is no needto attempt to scratch it with the harder instru-ment, since it will obviously be scratched.) Thechildren could make a chart of their findings

something like the following:

Mineralsscratched bythe fingernail

Mineralsscratched bythe penny

Mineralsscratched by

the knife

gypsumtalc

calcitehalite

fluoritelimonite

The relative hardness of the mineral is usuallyindicated by a number from 1 to 10. A hardnessscale known as Mohs' scale, which lists commonminerals in order of increasing hardness, is the

one most frequently used. This scale lists thehardness of minerals as follows:

1. talc 6. feldspar2. gypsum 7. .quartz3. calcite 8. topaz4. fluorite 9. corundum5. apatite 10. diamond

No. 10 (diamond) is the hardest mineralknown, and it cannot be scratched by any othermineral. No. 1 (talc) is the softest and can bescratched by the fingernail.

Using the minerals of Mohs' scale as a refer-ence, how can the children determine the hard-ness of their fingernails? (The fingernail willscratch tak and gypsum but not calcite. There-fore, the fingernail is harder than 2 and softerthan 3. lt is considered to have a hardness of 2.5.)

In the same way have the children determinethe hardness of the penny, the knife blade, andthe steel file. The results will be penny, 3; knifeblade, 5.5; steel file, 6.5.

Using the fingernail, penny, knife, and fileas guides, how can the children determine thehardness of the minerals in the collection or inunknown minerals they find? (If they can scratchthe mineral with a fingernail, they know itshardness must be less than 2.5; if they canscratch it with a knife but not a penny, its hard-

ness must be between 3 and 5.5; if they cannotscratch it with the file, then it must be harderthan 6.5.)

The following list will be a helpful guide tothe hardness of the most common minerals.

calcite 3 kaolinite 2.5

chalcopyrite 4 limonite 4-5.5feldspar 6.5 magnetite 6

fluorite 4 malachite 4galena 2.5 mica 2-2.5graphite 1.5 pyrite 6.5

halite 2.5 quartz 7hematite 5-6 sulfur 2hornblende 5-6 zircon 7.5

Learnings: (x) The hardness ofminerals is always

constant for the same mineral, and thus it is avery good means of identifying minerals. (y)Hardness is usually indicated by a number from1 to 10, with No. 1 representing the softest and

No. 10 the hardest. Minerals that have the higher

numbers will scratch those lower on the scale;for example, a mineral of hardness 8 will scratch


a mineral of hardness 7. (x) By using commonobjects of known hardness, such as a knife, apenny, the fingernail, and a steel file, it is possible

to estimate the hardness of unknown minerals.

ACTIVITY 11 (y,z)

IDENTIFYING MINERALS BY SPECIFIC GRAVITY

Purpose: To show that specific gravity is another char-acteristic that may aid in mineral identification

Concept to be developed: Specific gravity is a ratio ofthe weight of an object to the weight of an equalvolume of water.

Materials needed:

Spring balanceGlass of waterSmall piece of aluminumSamples of different minerals

INTRODUCTION: Tell the children that you havea puzzle for them. How can a piece of aluminumweigh different amounts at different times if it is notchanged in any way? Elicit their theories about thisproblem. Then have the children weigh a piece ofaluminum on a spring balance and record the weight.Then have them immerse the aluminum (still sus-pended from the spring balance) in a beaker ofwater and record its weight again. Does the alumi-

num weigh more or less when it is immersed? (Itweighs less.) Why? (The aluminum is buoyed up by

a force equal to the water it displaced.) Explain tothe children that this loss of weight is the basis ofanother way to identify mineralsby their specificgravity. Specific gravity is the ratio of the weightof a substance to the weight of an equal volume ofwater. How is specific gravity determined? The

specific gravity of a mineral equals the weight of themineral in air divided by the loss of weight when itis weighed in water. (This loss of weight in water is

equal to the weight of an equal volume of water

Springbalance

Aluminumweignt

Aluminumweight

Water

15

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the weight of the water the object displaces. Thisis known as Archimedes' Principle.) Review theweights of the aluminum in and out of water. Thenask the children to subtract the weight of the alumi-num in water from the weight of the aluminum inair. This will give the loss of weight in water. Thenask them to divide the weight in air by the loss ofweight in water. This ratio is the specific gravityof aluminum. The following is an example of themethod used.

Weight of aluminum in air = 50.0 gramsWeight of aluminum in water = 31 .5 gramsWeight loss in water = 18.5 grams

Weilht of aluminum in airSpecific gravity =

Weight loss in water50.0 grams18.5 grams

= 2.7Note that specific gravity is a pure number, sinceit is a ratio and is not measured in grams, pounds,etc.

After the children understand how to find thespecific gravity of aluminum, they might wantto determine the specific gravity Of other familiarobjects. The following is a list of some familiarobjects and their specific gravity:

cast iron 7.0-7.7copper 8.9glass 2.4-3.5lead 11.3zinc 7.1water 1.0

Now have the children investigate the specificgravity of some of the minerals. They can suspendthe minerals from the spring balance by a piece ofthread and determine the specific gravity as theydid for aluminum.

The following is a list' of the specific gravitiesof some common minerals:

borax 1.7 fluorite 3.2sulfur 2.0 topaz 3.5halite 2.1 corundum 4.0graphite 2.2 chalcopyrite 4.3gypsum 2.3 zircon 4.7feldspar 2.5 pyrite 4.9quartz 2.7 magnetite 5.2calcite 2.7 hematite 5.3talc 2.8 galena 7.6hornblende 3.1 gold 19.3

The specific gravities as listed are in some casesonly an average. Certain minerals vary in

16

specific gravity depending on the presence ofcertain impurities.

After the children have determined and re-corded the specific gravity of a number of min-erals, let them lift various minerals of knownspecific gravity (and similar volume) to com-pare the weights of the minerals. For example,let them see how galena feels when compared withquartz. (It is much heavier than quartz.) Whichminerals are the heaviest? (Metallic ones.) Canthe app-mimate specific gravity be estimated bykiting r mineral? (Yes, if its volume is known.)

Learnings: (x) The specific gravity of a mineralis a relatively constal t characteristic and can beused as one means of identifying the mineral.(y,z) Specific gravity is equal to the weight ofthe substance divided by the loss of weight inwater. (x) Specific gravity can be roughly esti-mated by lifting the minerals. Those of highspecific gravity will be quite heavy.

ACTIVITY 12 (x)IDENTIFYING MINERALS BY USING AN ACID

Purpose: To show that certain minerals react whentreated with an acid and that this reaction can beconsidered a characteristic for the purposes of min-eral identification

Concept to be developed: If a mineral effervesces whentreated with hydrochloric acid, the mineral must be aca rbonate.

Materials needed:

Weak solution of hydrochloric acidMedicine dropperSamples of different minerals

INTRODUCTION: Tell the children that some min-erals react with acid, and this can be a useful aid inidentification. Show the children a sample of themineral calcite, and tell them that it is composed ofcalcium carbonate. Explain that acid reacts withcalcium carbonate in a special way; the reactionresults in the bubbling off of carbon dioxide, a gas.

Drop a small amount of dilute hydrochloric acidon a piece of calcite and have the children notewhat happens. (A bubbly effervescence occurs.)(Caution: The acid will not bum the skin at thisdilution, but wash it off immediately if anytouches the skin. Make certain it does not spillon clothesit can burn holes in certain fabrics.)

What causes the bubbles? (A chemical re-action occurs, resulting in the evolution of carbondioxide.)

,..... -.................

You may want to use the chemical equationfor this reaction:CaCO3 + 2HC1(calcite) (hydrochloric

acid)CaC12 + CO, + H20

(calcium (carbon (water)chloride) dioxide)

This equation shows why the carbon dioxide isformed when calcite is treated with hydrochloric

acid. The calcite is composed of calcium (Ca)and carbonate (CO3), while the hydrochloricacid is composed of hydrogen (H) and chloride(CI). When the calcite reacts with the acid,the calcium combines with the chloride to formcalcium chloride (CaC12), and the hydrogencombines with the carbonate to form hydrogencarbonate (H2CO3), also called carbonic acid.

The hydrogen carbonate, however, is unstable,

and it immediately decomposes into water (H20)and carbon dioxide (CO2).*

Put a -small drop of dilute hydrochloric acid

on some of the other minerals in the collections.

What happens? (lf the mineral is a carbonate,it effervesces.) What can be concluded about the

use of dilute hydrochloric acid as a test in min-

'eral identification? (The test is .helpful in deter-mining whether a mineral is a carbonate com-pound, since minerals that do not containcarbonate will not effervesce.)

It should be pointed out to the children thatthis test does not specifically identify calcite.Other minerals that are also carbonate com-pounds, such as magnesite (magnesium car-

bonate), dolomite (calcium magnesium car-

* For a further discussion of chemical reactions, see Atoms

and Molecules, by Seymour Trieger (Investigating Sciencewith Children Series; Darien, Conn., Teachers Publishing

Corporation, 1964).


.

bonate), siderite (ferric carbonate), and

strontianite (strontium carbonate), will alsoevolve carbon dioxide gas when treated withdilute hydrochloric acid. If one or more of theseother minerals are available, the children shouldbe allowed to test them.

Learnings: (y)- When dilute hydrochloric acidreacts with a mineral that contains carbonate,the evolution of carbon dioxide gas results. -(x)Calcite is composed of calcium carbonate and-will effervesce when treated with dilute hydro-chloric acid. However, since other mineral car-bonates will also effervesce when treated thisway, the test is not specific for calcite.

Extending Ideas: The children have now seenvarious techniques for identifying minerals. Have

them make a chart with the characteristics of

each mineral on it. This chart can be used as areference key in determining the name of anunknown mineral. The children may wish toexperiment with several types of charts to seewhich might be the most useful to them inidentifying minerals. One such chart might' bearranged in the order of hardness as shown in

the accompanying illustration. *How is such acompleted chart used to determine minerals?(First the children determine the hardness of

the mineral. After. this, they look at all theminerals that have this hardness to see which one

fits the characteristics of the unknown mineral.)

In the more advanced grades, to help the chil-

dren learn how to do research, you might assign

individual children or committees the job ofmaking reports on various minerals, the topics

for the reports might be the uses of the minerals

or the geographic locations of their deposits.Other students may wish to make their own

mineral collections. They might keep the min-

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erals in a shoe box or a cigar box. Duplicatespecimens can be traded.

The children will have fun trying to identify"mystery" minerals you might exhibit every otherday. The properties of the mineral could belisted as "clues" to its identity. The child whoidentifies it could be given the specimen for hiscollection.

Summing Up Ideas: In this section the childrenhave learned the characteristics of mineralsand how these characteristics can be used in theprocess of identification. They have seen that thecolor of the streak left by a mineral is not neces-sarily the same as the mineral's external color.They have seen that a mineral may have eitherfracture or cleavage, which may be distinctiveor characteristic. They have learned about thecharacteristic hardness of minerals and howMohs' scale is used in mineral identification.The children have also seen that a mineral maybe either transparent or opaque and that it mayhave a characteristic luster. They have learnedthat specific gravity is the ratio of the weightof an object to the weight of an equal volume ofwater and how to measure and calculate a body'sspecific gravity. In addition, they have seen thatonly certain minerals react with dilute hydro-chloric acid to produce carbon dioxide gasand that this test can be used to identify thoseminerals that are carbonates.

HOW ARE CRYSTALS FORMED?

Crystals are solids with a natural geometricform. They may be cubes, rectangles, or complexgeometric figures. A crystal reflects the internalstructure of the mineral or substance, since thecrystal form is the structural form of moleculesthat make up the mineral. Crystal shape can bean important means of identifying minerals.

Certain factors regulate the growth of crystals:the temperature of the liquid that contains thedissolved material; the rate of evaporation of thesolution; the presence of foreign particles inthe solution; the degree of solubility of thedissolved substance; the degree of supersatura-tion (an excess over what is normally dissolved)of the solution; and the tendency of the particularsubstance to crystallize or form crystals.

The study of crystals is a fascinating one andcritical in mineral identification. The six basic

18

<=,

CUBIC CRYSTALShave three equal axesat right angles toone another.

TETRAGONAL CRYSTALShave two equal horizontalaxes and one longeror shorter vertical axis,all at right angles toone another.

HEXAGONAL CRYSTALShave three equal horizontalaxes, intersecting at anglesof 600, and a longeror shorter vertical axisat right anglesto the first three.

ORTHORHOMBIC CRYSTALShave three unequal axesat right anglesto one another.

MONOCLINIC CRYSTALShave three unequal axes,two at right angles toeach other and the third atright angles to onlyone of these.

TRICLINIC CRYSTALShave three unequal axesintersecting at threedifferent angles.

systems of crystals (and minerals showing eachtype) are cubic (galena and garnet), tetragonal(zircon), hexagonal (quartz and calcite), or-thorhombic (sulfur), monoclinic (gypsum),triclinic (rhodonite).

As an introduction to the following Activities,the children can observe crystals of mineralswith a magnifying glass. Calcite, quartz, andpyrite crystals are easily obtained. The childrencan also observe crystals of salt and sugar.

In the following Activities, the children willbecome more familiar with crystals as naturalgeometric formations in the crust of the Earth.

ACTIVITY 13 (x,y)

PRODUCING CRYSTALS THROUGH THE EVAPORA-TION OF A LIQUID

Purpose: To establish the basic ideas of crystals andcrystal formation

Concept to be developed: As a salt solution evaporates,the particles of that salt form crystals of characteristicgeometric shape.

Materials needed:

Table salt (sodium chloride)Microscope or magnifying glassesMicroscope slideShallow dishTest tubes or small jarsMedicine dropper

INTRODUCTION: One way to introduce a studyof crystals is to point out to the children that eachparticle of the table salt they use daily has anotherspecial characteristic besides its taste. Let themspeculate about what it might be. Give each childsome salt crystals on a square of paper. Ask thechildren to look at them, feel them, and then de-scribe their findings. Are the grains separate or allclumped together? (Some might be clumped together,but they can be separated into individual particles.)What do they feel like? Can the children tell theirshape? Explain to the children that they can learnmore about the shape of the grains ,by looking at someparticles under a microscope or magnifying glass.Have them put some of the salt on a glass slide andobserve the crystals under a magnifying glass or amicroscope. What is the shape of a salt grain?(It looks like a perfect cube.) Do all the cubes lookalike? (Almost all of them have the cube shape.)

Have the children place some grains of saltin a test tube half full of water. What happensto the grains? (They sink to the bottom, getsmaller, and then disappear.) What happened tothem? (They dissolved in the water.) Can thechildren see them when they are dissolved?


(No.) Can the children tell that salt is in thewater just by looking at the water? (No.) Howcan they tell that salt is in the water? ( The waterwill taste salty if it contains enough salt.) Dis-solve more salt in the water: What happens tothe height of the liquid in the test tube? (Theliquid rises.) Why did the liquid rise? (The salttook up room.) Add more salt until no more willdissolve, that is, until the water is saturated withsalt. Why will no more salt dissolve in the water?(The water can hold only a particular amountof salt. )

Pour a little of the saturated salt solution on amicroscope slide and project the image of theslide, using a film strip projector. Children cannotice the formation and growth of the crystals

as the image is projected on a screen. Wheredoes the growth first appear? (At the edge ofthe drop of water.) Why does the growth first

appear along the edge? (This is the shallowestpart and evaporates first.) Why does the waterevaporate so raiiidly? (The heat generated bythe projector speeds up the evaporation of thewater.) What is formed on the slide? (Crystalsof salt.) What shape do they have? (The sameas beforea cube shape.) How do they differfrom the salt crystals first obscr,ed? (These aremuch smaller, and there are more of them.) Whathappened to the water? (It evaporated.)

A few members of the class may want to dis-

solve two crystals of salt in a 'drop of water,evaporate the water, and count the number ofcrystals produced. Children might be encouragedto find out if the speed of evaporation determinesthe size of the salt crystals formed. (It does. Thefaster the evaporation, the smaller the crystals.)How might they do this? (They, should considerthe amount of heat needed to achieve various

rates of evaporation.)Other children may want to try other crystals,

such as those of Epsom salts, to see their shapeand the patterns formed in crystallization.

Some children may want to tell of their ex-periences in visiting caves and seeing crystalformations formed from the evaporation of aliquid. Beautiful formations of stalactites, stalag-mites, and columns can be observed in caveslike the Mammoth Cave in Kentucky, the LurayCaverns in Virginia, and Carlsbad Caverns in

New Mexico.19

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Have any of the children ever seen or foundgeodes? These are rocks with a central cavitythat is lined with crystals, usually quartz orcalcite. The crystals formed from the evapora-tion of a liquid that was once enclosed in therock.

Learnings: (x,y) As salt solutions evaporate,the particles of that salt form crystals withcharacteristic geonietric shapes. (x,y) The rateof evaporation affects the size of the crystals. Aslow rate of evaporation will result in largercrystals. (x,y) Crystals form in nature by slowevaporation of a liquid that contains dissolvedsalts. (x) A saturated solution is one that con-tains all the dissolved substance that it can hold.

ACTIVITY 14 (x,y)

.PRODUCING CRYSTALS FROM A SUPERSATURATED

SOLUTION

Purpose: To show that large crystals can be grownin supersaturated solutions

Concept to be developed: Large crystals can be grownby depositing particles of a salt upon crystals of thatsalt.

Materials needed:Alum (available at drugstores)Glass beakerWaterHot plateStringPencilCupStirring spoon

INTRODUCTION: Point out to the children thatthere is another way of producing crystals. Havethem dissolve about one-quarter cup of alum inone cup of Water. What happens to the alum? (Itall dissolves.) Can any more dissolve in the liquid?(Yes.) Have the children add more alum until nomore can dissolve, even if the solution is stirredvigorously. Point out that the children have madea solution that is saturated. Ask them how they mightdetermine this and test their ideas. .

Now have a child pour half of this saturatedsolution into a beaker, place the beaker on a hotplate and heat it. When the solution is boiling,

a 2ew more crystals of should be added.What happens to the crystals? (They dissolve.)Why do they dissolve now, although they did notbefore? (The water is hot and can hold moreaim" in solution.) Have another child stir thesolution and dissolve more crystals until no more

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linhlol I

Stringor thread

Beaker

Alum solution

can dissolve. Children will discover that theyhave made a solution that holds more alum thanit normally would at room temperature. This iscalled a supersaturated solution.

Next, remove the beaker from the hot plate.Suspend a cotton thread from the center of apencil and place the pencil over the beaker asshown in the illustration. Have the children ob-serve the thread after several hours and then afterseveral days. What is observed? (Crystals formand grow on the string.) What is the purpose ofthe string? (It acts as a point for crystals tostart forming.)

Other children could try sugar instead ofalum and make "rock candy" by crystallization.(Caution the children against eating any materialmade, however, because of contamination.)

Learnings: (x) Crystals can be grown from asupersaturated solution. (y) A supersaturatedsolution is one that holds more salt than thenormal amount at room temperature. A super-saturated solution can be produced by heatingthe solution and then dissolving more salt.

ACTIVITY 15 (x)PRODUCING CRYSTALS BY COOLING A LIQUID

12;,:rpose: To show that crystals can be formed by thecooling of certain liquids

Concept to be developtd: Molten sulfur forms char-acteristic crystals when It is cooled slowly.

Materials needed:Propane torch, Bunsen burner, or hot plateSulfurTest tubeFilter paperFunnelBeaker

INTRODUCTION: Show the children a sample ofsulfur and ask them where it comes from. Somechildren may know that it is mined. Explain that insome operations the sulfur is heated underground,forced up a tube, and cooled in large containers onthe surface. It is then crushed and powdered.

Remind the children that they have learned thatsome crystals are formed by heating and evapora-ting. Now they will discover another way in whichsome crystals are formed.

Have the children examine some powderedsulfur. Who' . .r is it? (Yellow.) Ask them todescribe ht,,. ieels. (It feels like dry talcumpowder.) Have them examine some sulfur powderwith a magnifying glass. ..',, re there any crystalshapes present? (No.)

Have the children fill a test tube half full ofsulfur and heat it over a propane torch, Bunsenburner, or hot plate. (Be sure to open the win-dows because irritating fumes will be given off.)As the sulfur heats, have the children notice thevarious changes. What happens to the sulfur?(It melts.) Does the color change? (Yes, itbecomes dark yellow and then red.) Next havethe children pour the molten sulfur into thefilter paper (as shown in the illustration) andallow it to cool slowly. What happens? (Crystalsform as the liquid cools.)

To show what happens if the molten sulfur iscooled rapidly, have the children pour some intoa glass of cold water. What happens? (It rapidlysolidifies.) Are there any crystals? ( No.) Whynot? (Rapidly cooled liquids solidify into amor-phous, or noncrystalline, glasslike solids.)

Molten_.------' sulfur

Filter paperin funnel


Test tube

Purple iodine vapor

Iodine crystals

Hot plate

Learnings: (x) Sulfur can be melted by heatingand will form its characteristic crystals if themolten sulfur is cooled slowly. (x,y) Rapidcooling results in an amorphous, or noncrystal-line, solid.

ACTIVITY 16 (x,y)

PRODUCING CRYSTALS BY COOLING A VAPOR

Purpose: To show that crystals can also form by thecooling of a vapor

Concept to be developed: The vapors of certain sub-stances produce crystals when they are cooled.

Materials needed:

Iodine crystalsTest tubeHot plateGlass plateMagnifying glass

INTRODUCTION: Have the children recall theirprevious experiences with producing crystals. Youmay want to summarize their learnings in this way:They produced crystals by heating and evaporating(alum, salt, and sugar) and by cooling a liquid(sulfur). N ext they will discover another way crystalsare formed. They will be working with iodinecrystals. Most children know about iodine and itsuse as an antiseptic, tincture of iodine. Mention thatiodine is also found in sea water, in the salt waterof gas wells, and in compounds of Chile saltpeter.

Have the children place a few iodine crystals ina test tube and heat it over a hot plate. Whathappens to the crystals? (They turn into a gas.)What is th2 color of the gas? (Purple.) Placethe test tube on its side and continue to heat it.

21

EARTH

Pour some of the purple vapor onto a cold glass

plate. What happens to the vapor? (Some of itis cooled and forms crystals of iodine on theplate.) Examine the crystals. What can be seen?(Blue-gray crystals of iodine.) How do theydiffer from the original crystals? (They are moreregular in shape and smaller in size.) After allthe iodine in the test tube has been. vaporized,allow the vapor inside to cool slowly to roomtemperature. How do the crystals look? (Verysimilar to the original crystals. )

Learning: (x) A vapor of an element or com-pound can change directly into crystals of thatelement or compound.

Extending Ideas: Some particularly interestedstudents may want to investigate crystals a littlefurther. You might suggest that they make crys-tal models using such materials as sponge, wood,

or Styrofoam.Some children might enjoy growing crystals

of minerals other than the ones used in thepreceding Activities. The children might try togrow crystals of each of the six types and dis-

play them when the crystals have grown.

Summing Up Ideas: In this section the childrenlearned how the crystals of the various mineralsare formed. They learned the six basic types ofcrystalscubic, tetragonal, hexagonal, ortho-rhombic, monoclinic, and triclinic. They saw howcrystals can be produced by the evaporation ofa liquid, by growth from a supersaturated solu-

tion, by cooling a liquid, and by cooling a vapor.

WHAT ARE ROCKS?

A rock is any natural material that makes up partof the Earth's crust. Most rocks are made ofmany minerals, but some, such as pure marble,contain only one. Some rocks, such as coal, aremade of materials that are not mineral.

Rocks have been named for localities (syeniteafter Syene, Egypt), for people (charnockiteafter Job Charnock, the founder of Calcutta),for their mineral composition (quartzite forquartz), for their grain size (sandstone for itssand-size particles), and for various physicalfeatures (soapstone for its smoothness).

The geologist studies the mineral compositionof a rock as well as the texture and structure of

22

its component parts. Rocks are classified on the

basis of the way they were formed. Through ob-servation and experimentation the geologist candetermine if the rock was formed by the coolingand hardening of molten material to formigneous rock, by the deposition of material toform sedimentary rock, or by the alteration ofpreviously formed rocks by heal, pressure, move-ment of the crust, and chemical action of liquidsand gases to form metamorphic rock. These threerock types are the main divisions in the rockclassification and will be treated separately in the

following Activities.Igneous Rock: Igneous rock originates as a

hot molten liquid, or magma. Two importantfactors that affect the type of rock are thecomposition of the magma and the rate of cool-ing. These factors are the basis for the system ofclassification used. Grain size, structure, andmineral content are the main features of impor-

tance to be observed. The grain size, or texture,is associated with the rate of coolinga coarsetexture resulting from slow cooling and a fine

texture from rapid cooling. The children willremember hcw sulfur behaved when cooledslowly and when cooled rapidly (see Activity 15).

The mineral composition depends upon thechemical composition of the material from which

the igneous rocks were formed. Although tworocks may have the same mineral composition,coming from the same "mother material," ormagma, they may appear very different because

of the texture.Geologists no longer believe that the Earth

is composed of molten materials beneath the thinsurface layers. In addition, they no longer believethat there is a complete zone of molten rockanywhere. They believe that the interior rock isprevented from melting because of the greatamount of pressure put upon it by the weight ofthe rock above it, and thus it is kept in a semi-

plastic condition.When pressure is reduced, as by cracks in the

solid rock above, the hot semiplastic materialbecomes molten. If the molten material hardens

before it reaches the surface, rocks that have acoarse texture, such as granite, are formed. These

are called intrusive igneous rocks. If the moltenmaterial reaches the surface and then hardms,such very fine-grained rocks as obsidian, basalt,

and pumice are formed. These rocks are calledextrusive igneous rocks.

Sedimentary Rock: Sedimentary rock is classed

as a secondary rock, since it is formed from

already existing rock particles or sedimentspressed together and cemented by materials de-

posited from solution. Sedimentary rocks canalso be formed by precipitation, that is, by the

accumulation of material being carried as dis-solved matter in water. Individual grains of sand,

for example, may accumulate and be pressed

together to form sandstone; finer particles ofclay and mud may accumulate to form shale.

Metamorphic Rock: Metamorphic rock is also

a secondary rock. Igneous and sedimentary rocks

may alter their structure and conformation when

subjected to drastic changes of heat and pressure.

The product is a metamorphic rock.

ACTIVITY 17 (x,y)

CLASSIFYING IGNEOUS ROCKS

Purpose: To show on what basis igneous rocks areclassified

Concept to be developed: Igneous rocks are formedby the cooling of molten material.

Materials needed:Igneous rozks: basalt, obsidian, pumice, granite,

and gabbro (Rocks can be purchased fromscientific supply companies and from museumshops.)

Magnifying glasses

INTRODUCTION: Show the children specimens of

the different igneous rocksbasalt, pumice, obsid-ian, granite, and gabbro. Emphasize that these areall igneous rocks and develop the meaning of thatterm, to be added to the children's vocabulary. Use

as much information as you think appropriate fromthe introduction to this section.

The children should work in small groups toexamine the rocks closely. Have them see whatthey can discover about each rock. You maywant to have each rock labeled and have eachgroup make a list of their findings for the various

rock specimens. A magnifying glass for eachgroup will be useful for examining the rocks.After the groups have completed their work, use

such questions as the following to assist children

in summarizing their findings: Which rocks have

minerals large enough to be seen with theunaided eye? (Granite and gabbro.) Which ones

have minerals so small that they cannot be


seen even with a magnifying glass? (Basalt,

pumice, and obsidian.) What do the childrenobserve that is unusual about pumice? (lt is fullof holes and is very light in weight.) Remind the

children of their experience with the cooling ofsulfur to form large crystals and small grains.Then ask whether pumice cooled slowly orrapidly? ( Rapidly, since it is very fine-grained.)

What is the reason for all the holes? (A com-parison could be made between pumice andordinary bread. Both are full of holes. The holes

in the bread were caused by a leavening agent,which produced carbon dioxide gas. The holesin the pumice were also caused by gases, which

were within the liquid magma as it solidified.)

Which of the rocks are dark in color? (Obsidian,basalt, and gabbro. ) Which are light in color?(Pumice and granite.)

With this information, the children can make

a key, such as the following, to identify the five

igneous rocks.A. Those that have visible minerals

1. Dark in colorgabbro2. Light in colorgranite

B. Those that have novisible minerals1. Full of holes and very lightpumice2. Not full of holes

a. Glassy in appearanceobsidianb. Not glassy in appearancebasalt

Another key the children could devise for thesame five rocks- is the following:

A. Light in color1. Visible mineralsgranite2. Minerals notvisiblepumice

B. Dark in color1. Visible mineralsgabbro2. Minerals not visible

a. Glassyobsidianb. Not glassybasalt

There are other keys the children could devise.

For example, they might have keyed the rocks

by hardness or by density, but this would be

much more difficult.

Learnings: (y) Rocks can be grouped into a key,

which can later be used to identify these rocks.

(x) Very-tine-grained rocks cooled rapidly;

coarse-grained rocks cooled slowly. (x) Pumice,

an extremely light rock, cooled very rapidly.

Gases contained within the molten rock as it

hardened produced the holes.23

r-

ACTIVITY 18 (y)

CLASSIFYING DEPOSITED SEDIMENTARY ROCKS

Purpose: To show how sedimentary rocks are formed

Concept to be developed: Some sedimentary rocks areformed of deposited grains or pellicles that are laterpressed close together by overlying layers, ceinentingthe particles together.

Materials needed:

ClaySandFine gravelSandstoneConglomerateShaleWater1-quart jar

INTRODUCTION: Tell the children that this Ac-tivity will help them classify another kind of rock,sedimentary rock. Develop the meaning of the termas you consider appropriate, using material fromthe introduction to this section. For this Activity,the .children can work in small groups. Give eachgroup a sample of sandstone, conglomerate, andshale. Let the children look at the samples, feelthem, and give their ideas about how they mighthave been formed. They may recognize the sand-stone just by the small grains of sand they can feel.Tell them the names of the other rocks. Then havethem make some artificial rocks to compare withthe natural ones they have examined.

Let the children mix together one-half cup eachof clay, sand, and fme gravel. Put the mixturein the quart jar and add two cups of water.Shake the contents and then allow the mixtureto settle.

Have the children examine the mixture throughthe glass and compare this mass with the rocks(shale, sandstone, and conglomerate).

In which are the grains more compacted? (Therocks.) Why? (There was more pressure uponthem when they were formed.)

How would the three rocks be classified accord-ing to size of grain particles? (Shale has the finestparticles, and conglomerate has the largest. Con-glomerate is often called "puddingstone" becauseof the larger stones found within the rock.)

Learnings: (x,y,z) Some sedimentary rocks areformed of deposited grains pressed close togetherby subsequent layers and then cemented together.(x,y,z) Shale resulted from very fine particlesbeing pressed together; sandstone is the resultof cemented sand grains; and conglomerate isformed from various sized particles, some of

which may be quite large, that are cementedtogether.

ACTIVITY 19 (y)

CLASSIFYING PRECIPITATED SEDIMENTARY ROCKS

Purpose: To show another way sedimentary rocks areformed

Concept to be developed: Sedimentary rocks can beformed by the precipitation of rock particles fromsolulions.

Materials needed:

Pint jarWaterSaltLimestone, chert, or gypsum

INTRODUCTION: Show the limestone, chert, orgypsum to the children and explain that these wereformed in a different manner from sandstone. Ex-plain that rocks like limestone, chert, and gypsumwere particles once dissolved in water. The mineralsprecipitated, or came out of solution, and weredeposited to form rocks.

To show how this might happen, have a groupof children make a saturated solution of salt bydissolving as much salt as possible in one-half cupof water. Allow the solution to evaporate forseveral days.

Examine the resulting salt formations. Whereis the salt found? (At the water's edge.) Whatcolor is the salt? (White.) Why were the crystalsnot visible in the saturated solution? (Becausethe salt was dissolved in the water.) Precipitatedsedimentary rocks are formed in much the sameway.

Compare the salt with precipitated rocks likelimestone, chert, and gypsum. Which is theharder, the salt or the precipitated rock? (Therock.) Why is it harder? (There was More pres-sure placed above it.)

Learnings: (y,z) Particles in precipitated sedi-mentary rocks were once dissolved in water andlater precipitated out of solution.

ACTIVITY 20 (x,y)

COMPARING DIFFERENT KINDS OF SEDIMENTARYROCKS

Purpose: To show the differences between differentkinds of sedimentary rocks

Concept to be developed: Many types of sedimentaryrocks are easily distinguished from one another.

1

Materials needed:

ShaleSandstoneConglomerateLimestoneFossiliferous limestoneBituminous coalChalkCoquina

INTRODUCTION: Have the children make col-lections of sedimentary rocks and use them in makinga key. You may have to supplement their collections.Help them plan the key.

Grain differences can be compared as onemeans of separation. The children can also trythe acid test (dilute hydrochloric acid) on allthe rocks. Which ones show a reaction? (Thoserocks containing carbonate will effervesce. Theseinclude limestone, chalk, and coquina. Sandstonesometimes effervesces if the cementing substancearound the sand grains is calcite.) This reactionof the rocks to acid can be included in the key.

What differences do the children observe be-tween chalk and coquina? ( Coquina is composedof visible animal shells cemented together. Chalkis very fine grained in comparison.) If you havea microscope, you night want to have the chil-dren observe the chalk grains under magnifica-tion. The children nay be able to observe thatchalk also is composed of shellsvery minuteones of tiny microscopic animals.

Point out how coal is different from the otherrocks (besides being black and smudgy). Coalis formed by the compacting of plant remainsunder great pressure. Peat and lignite are earlierstages in the formation of coal. They are lesscompacted and more plantlike. The harder thecoal, the more it has been compacted by heatand pressure. Hard-coal burns with a hot, cleanflame; peat and lignite are poor fuels that burnwith a very smoky flame. The class can comparethe various stages of coal if peat and lignite are

obtainable.Have the children observe the animal fossils

in the limestone. How did the impressions getthere? ( Animals were among the material de-posited. ) What do fossils indicate about therocks? ( They indicate the conditions that ex-isted when the rocks were formed and whatanimals were present.) No fossils are observed in


igneous rocks because the rocks were formedunder conditions too hot for any plant or animalremains to have been preserved.

Next have the children observe the sandstone,conglomerate, and shale. In what ways do theydiffer? (Mainly in grain size. ) Which has thelargest grains? ( Conglomerate.) Ask the chil-dren to think of ways conglomerate could haveformed. (This rock results from the cementing-together of pebbles and rock fragments.) Whatdoes it remind them of? (Some conglomerateresembles ordinary cement. )

What can the children discover about thesandstone? What happens when it is rubbed?(Sand . particles fall off.) What mineral is thesand? (Quartz, usually.) Will the sandstonenormally react to acid? (No.)

Ask the children where sandstone might beformed. Where is sand particularly abundant?(Sand is found on beaches near, and on thebottoms of, large bodies of water, such as lakes or

oceans. Sand deposits in deserts indicate that alone time there was a lake that has since dried up.)How is the sandstone formed? ( Sand grains be-come compacted together and cemented withsome mineralsubstance.)

How does shale differ from the other tworocks? (It is very fine-grained.) Of what is shaleOrobably composed? (The children may suggestsuch things as mud, clay, or fine dirt. Shale isgenerally considered a rock composed of clayparticles cemented together.)

Learnings: (y) Dilute hydrochloric acid may beused as a test to classify sedimentary rocks ascarbonates or noncarbonates. Any rock withcalcite or animal shell will effervesce. (x) Coalresults from plant remains that have been com-pressed by overlying beds. (x) Chalk and co-quina are composed of animal shells that havebeen cemented together. The shells in chalk aremicroscopic. (x) Fossils can be found only insedimentary rocks. They indicate the conditionsand the life present when the rock was formed.(x) Some of the rocks may be separated on thebasis of grain size. Conglomerate is composed ofpebble-size grains; sandstone is composed ofsmaller "sand" grains; while shale is very finegrained and probably a result of cemented clay.

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ACTIVITY 21 (x,y)

COMPARING SEDIMENTARY ROCK WITHMETAMORPHIC ROCK

Purpose: To illustrate the differences between sedi-mentary and metamorphic rock

Concept to be developed: Metamorphic rocks areharder than the sedimentary rocks from which theywere derived.

Materials needed:

Shale and slateLimestone and marbleSandstone and quartziteWaterMedicine dropperMagnifying glassDilute hydrochloric acid

INTRODUCTION: Display the rocks and a magni-fying glass on a table. Over a period of several dayslet the children go to the table to examine the rocks.Suggest that they use a hardness test on each rock.Have them list their findings. After all the childrenhave had this opportunity, let them share what theyhave discovered about each rock.. You might askthem to list the characteristics of each.

Now discuss the shale and slate. Explain thatblackboards are often made of slate. Have themexamine some pieces of blackboard (obtainedfrom the custodian). What characteristics makeslate a good blackboard material? (It is hard,fine grained, can be smoothed to a fiat surface,does not have a high glare, and takes chalk well.)Compare slate with shale. Why would shale bean ineffective blackboard material? (It is toosoft.)

Have the children examine a piece of limestoneand a piece of marble. Have them guess whichis harder. How could they find out? (By tryingto scratch one with the other; the harder rockwill scratch the softer rock.) Let the childrenexamine both with a magnifying glass. Which onehas particles closer together? (Marble.) Place adrop of dilute hydrochloric acid on each rock,using a medicine dropper. What is the result?(Bubbles of a gas evolve from both.) What doesthis indicate? (They are both composed of car-bonates; actually, both are made of calciumcarbonate.)

Next have the children compare the sandstoneand the quartzite. Remind them that sandstoneis a sedimentary rock composed of sand-sizegrains of quartz cemented together. Do they ob-serve any differences? What happens when sand-

26

stone is rubbed? (The grains separate and fallaway.) What happens when quartzite is rubbed?( Nothing; the grains cannot be separated. ) Whichrock is harder? (Quartzite; the sandstone can beeasily scratched.) What is the difference betweenthe two rocks? (Quartzite is much harder thanthe sandstone. During the process of metamor-phism, great heat and pressure caused the sandgrains to melt and become welded together.)

After examining the rocks, the children mightmake a chart similar to the one shown.

Rock

sandstonequartziteshaleslatemarblelimestone

Soft Hard Sedimentary Metamorphic

x xx

x xx

xx

Learnings: (y,z) Metamorphism is a process bywhich rocks become changed by heat and pres-sure. This change alters their appearance andmakes them harder and more compact. (x)Metamorphic rocks are harder than the sedimen-tary rocks from which they came.

Summing Up Ideas: The preceding group of Ac-tivities has given the children a chance to examinevarious kinds of rocks found in the Earth's crust.They have compared several different kinds andhave seen how some have been formed. They havelearned that igneous rocks are formed by solidi-fication of molten rock; that sedimentary rocksare formed by precipitation from solutions;and that metamorphic rocks are formed by theaction of increased heat and pressure on igneousand sedimentary rocks. They have been en-couraged to make their own collections and to tryto identify them by the use of keys.

HOW ARE SOILS MADE?

Soil is the loose surface material of the Earth'scrust in which plants take root and grow. It is animportant product of weathered rock. Weatheringinvolves the breaking up of rocks into smallpieces. Weathering is brought about throughphysical, chemical, and biological processes, someof which will be discussed in this section. Theseprocesses depend upon the moisture and tem-perature present in tho geographic location.

Physical processes involve .the fragmenting ofthe rock. The fragmentation is often due to iceforming in small rock fractures or cracks. Otherfragmentation may be caused by sudden changesin temperature.

Chemical processes involve changes in thecomposition of the rock. These changes can bedue to reactions with oxygen, water, or carbondioxide.

Biological processes involve the splitting ofrocks by plants and animals. This splitting canbe caused by the pushing of plant roots or bythe burrowing of animals.

Through these physical, chemical, and biologi-cal processes soil is made.

The following Activities illustrate how physicaland chemical processes can be important factorsin the weathering, or breaking up, of rocks toeventually form soil. -

ACTIVITY 22 (x)OBSERVING AN EFFECT OF FREEZING WATER

Purpose: To demonstrate that the formation of ice isone of the physical processes that weather rock

Concept to be developed: When water, freezes, the iceoccupies a greater volume than did the water.

Materials needed: -

Flat-sided glass bottle (syrup often comes in thistype of bottle)

Cloth wrappingWaterRefrigerator

INTRODUCTION: Ask the children if they haveseen large cracks in rocks or in pavement and if theyknow what might have caused them. One child willprobably mention the force exerted by freezing water.This Activity will demonstrate to your children theforce water can exert when it freezes.

Have a child fill the bottle with water and putthe top on securely. Wrap the bottle in a cloth(to prevent the shattered glass from droppinginto the refrigerator). Put the bottle in the freez-ing compartment of a refrigerator. After 24 hoursremove the bottle and examine it. What can beobserved? (The bottle will probably be cracked.)Why is the bottle cracked? (Pressure was exertedupon it.) .What caused the pressure? (The forceexerted by the ice as it expanded.) Why did theice exert a force? (As water freezes, it expandsand takes up more space.)


Cutaway View of Bottle

Water

Cloth

Guide the children's thinking as they applytheir findings to what might happen out-of-doors.As water in a crack of a rock freetes, the rock issplit farther apart because the ice takes upmore space than the liquid did.

Learnings: (x) Water expands with freezing andmay enlarge the cracks in rocks, eventuallybreaking the rocks into smaller pieces. (x,y) Theexpansion of water as it becomes ice is strictly aphysical process, since no chemical change takesplace.

ACTIVITY 23 (x)OBSERVING AN EFFECT OF CHANGES OF TEMPERA-TURE

Purpose: To demonstrate that variation in temperatureis another of the physical processes that weather rock -

Concept to be developed: Sudden changes of tempera-ture may cause rocks to split into smaller pieces,forming soils.

Materials needed:

Frying panClear glass marblesCold waterHot plate

INTRODUCTION: Reminti the children that theyhave seen how freezing water can break rocks. Askthem if they can think of other ways that rocks canbreak. One of the children may mention temperaturechanges. Some of the children may have gone oncamping trips and used rocks to form a ring tocontain their campfire. Ask them whether they haveever poured water on the fire and observed what

27

EARTH

happened to some of the hot rocks. This Activitywill help them to discover how changes in tempera-ture can affect rocks.

Ask some children to donate several clearglass marbles for this Activity. (Six marblesshould be enough.) Have the children examinethe marbles and observe how easily they can seethrough them. Have the children make certainthere are no cracks in the marbles.

Have the children place five of the six matigets

in a frying pan and heat the marbles over thehot plate for about five minutes. Allow themarbles to roll into a glass of cold water while

they are still hot. After they have cooled, removethem and have the children examine them oncemore. How are they different? (They now con-tain many cracks.) Compare them with the un-heated marble. (The unheated marble is stillclear.) Why did the heated marbles crack? (Thesudden cooling cracked the marbles because ofthe sudden contraction of the glass. As glass getshotter, it expands; as it cools, it contracts.)

Heated marbles

Cold water

Marbles

Frying pan

Hot plate

Relate this experiment to rocks that expandwhen heated by the sun and contract when thetemperature drops at night. Describe how thesudden temperature change, especially noted indeserts, produces a cracking of the rocks. Thisis called weathering.

Learnings: (x) Marbles become cracked withsudden changes of temperature. (x,y) Rocks alsobecome broken and fractured when exposed tosudden and extreme temperature changes. Thistype of physical weathering process occurs mainlyin desert areas, which are known to have widetemperature variations.

ACTIVITY 24 (y)

MEASURING THE WATER CONTENT OF LOAMY SOIL

Purpose: To demonstrate one of the characteristics ofloamy soils

Concept to be developed: Loamy soils may contain largeamounts of water.

Materials needed:

Spring balanceTin canSeveral 1 quart pans with coversOven or hot plateSamples of different gardensoils

INTRODUCTION: Discuss the kinds of soil chil-dren have observed in different placescolor, sizeof particles, and other characteristics. Have severalchildren bring to class a samPle of black garden soil,about one cup of each sample. Have the class num-ber the samples and examine each sample carefully.You may want to write the following questions onthe blackboard to direct the children's examinations.Do the samples show differences in color? (One maybe darker than the others.) Do they feel the same?(Onó may be heavier than the others.) How ekedo the samples differ? (They may vary in loosenessof particles or in moisture content.)

After the children hre, made their observa-tions, have them weigh at'1:1 :ecord the weights ofeach sample. They can punch two holes in a tincan and use the cat-t as a soil holder. ,The canshould be suspended from a spring balance by awire bale. The children must be cautioned to beaccurate in their weighing measurements. Toobtain the weight of the soil, the weight of theempty container must be subtracted from theweight of the soil and container. After eachsample has been weighed, have the children placeeach soil sample in a pan and keep it in an oven

9


at 350°F. for an hour. If no oven is available,they can improvise by placing a large looselifcovered ceramic bowl on a hot plate. Pike thesoil sample in a pan. Cover the pan and put itin the bowl, cover the bowl, and allow the soilto heat for several hours.

How do you know that water escapes from the

Spring balan.cesoil during this heating? (The soil looks andfeels dry after heating. Since water boils at212°F. and the oven wac set at 350°F., the waterin the soil must have boiled away.)

Have the children remoye the dried soilsample, weigh the sample as before, and recordthe weight. Was, there a loss in the amount ofmoisture in the sample? (Yes.) How much of aloss? (It will vary for each sample.) Perhapsyour children might record their findings bymaking a graph, such as the one shown in theillustration, showing the percentage of moisture,

can in the various samples. The percentap of mois-ture is equal to., the weight loss divided by* theweight before drying. What might make the dif-

soil sample ferences in the water content in the variousSamples? (Soil found near a surface or under-ground supply of water, soil that has been re-cently irrigated, and soil taken from a protected,shaded area that allows minimum evaporationwill all have large water contents.)

Wire support

Cover

-

BowlA more accurate measurement will be observed

if the class has access to a balance scale. Youprobably can borrow one from the high school.

The children may want to heat the soil for asoil sample longer period to see if there is still further water

fHot plate loss.

Percentage of waitr conterri-

I -,,,,,,,-- ,me

.

4, ,...,....:_,-.,..

MIT, ,,.-*:-,-

..,,..,..,,..--,,,y,. ...,, .,

. 4

3

Learning: (x) Loamy garden soil can hold con-siderable water.

ACTIVITY 25 (y)

MEASURING THE. HUMUS CONTENT OF LOAMY SOIL

Purpose: To show that loamy soil contains a detectableamount of humus

Concept to be developed: Humus is composed of de-cayed organic matter that burns when strongly heated.

Materials needed:Bunsen burner or propane burnerPorcelain container or crucibleGarden soilSpring balance or tray balance scale

INTRODUCTION: In the previous Activity, thechildren observed and measured the amount of

29

EARTH

moisture in loamy soils. This Activity will give theman opportunity to observe and measure the amountof humus in loamy soils. It may be interesting forthe children to collect samples of black garden soilfrom around the schoOl. Number and dry the sam-ples, as in Activity 24, or use the same dry samplesthat were prepared in Activity 24. Quartir-cupsamples should be adequate.

Have the children weigh the empty crucible

or porcelain container. the children can weighthe crucible on a. tray balance or a spring balance.Then have them place a dry sample in the con-.tainer. These containers will not crack whenplaced over direct flame. Weigh the dry soil inthe container on a tray or a spring balance. Sub-tract the weight of the empty container from theweight of the container and the soil. This givesthe weight of the dry soil alone. It is importantto get accurate readings and keep accurate rec-ords in all Activities involving measurements.

Crucible

Stand

Ring

Burner

Apply heat to the samples, using a Bunsenburner or propane burner. (Most hardware storessell propane burners.) The container may be-

come red-hot as the organic material is tiurnedup. Caution the children to be careful of theflame and the hot container.

Apply heat to the samples for at least fifteenminutes. Is there any change in the soil? ( Some

particles may flame, some may smolder and giveoff smoke, and there may be a change to a graycoloration.) Allow the container to cool. Havethe children weigh and record the weight of eachsoil sample. Was there a loss of weight for eachsoil sample? (Yes.) How much? (It varied foreach sample.) Why was there a weight loss?(Humus is made up of decomposed organicmatter. Organic matter contains carbon, whichwill burn if strongly heated and give off a gas asan end product. As the humus burned, theweight of the soil decreased.) Why are there dif-ferences in the humus content in the various

30

samples? (Humus content varies, depending oncloseness to trees, shrubs, and other plants, onthe application of fertilizers, and on the amountof animal life near the location.)

The children might like to make a graph,similar to the one made in the last Activity forpercentage of water content, to show the per-centage of humus in each soil sample.

Learnings: (x) Loamy garden soil contains ameasurable amount of hamus. (x,y,z) Humus iscomposed of decayed organic matter from livingthings. (x,y) Organic matter burns when strongly

heated.

ACTIVITY 26 (y)

OBSERVING THE SAND IN LOAMY SOIL

Purpose: To show that loamy soil contains particles ofsand

Concept to be developed: The sand particles in loamysoil may exhibit various physical properties.

Materials needed:Heated soil from Activity 25SandSandpaperMagnifying glassMicroscopeSamples of loamy soilWire screen

INTRODUCTION: The children have already dis-covered the presence of moisture and humus inloamy soil. What else is to be found in it? Thechildren may have observed that some of theirsamples of garden soil contained sand.

Have the children examine samples of sand.(Some of the best sand for this Activity is washedaquarium sand. It is made of larger particlesand is easily procured in pet shops.) Point outthat sand is made of small rock particles varyingin size from 1/12 inch to 1/400 inch and thatsand may be made of different minerals. (Remindthe children that a mineral is a natural earthsubstance with a definite chemical composition.)Mention that the most common mineral making

up sand is quartz. The children will rememberobserving quartz and noting some of its charac-teristics. Quartz is a compound of the elementssilica and oxygen. Questions such as the follow-ing may be helpful to childr-Ai as they examinetheir samples: Are sand grains the same shape?(No, they have many shapes.) Are the grainsthe same size? (No, they vary in size.) Have the

children sift the sand grains through a fine wirescreen. What does this tell about the size of thegrains? (Those that pass through are smallerthan the size of the openings.) What colors areobserved among the sand grains? (White, black,and red, among others.) Why are there sandgrains of different colors? (Because of the dif-ferent minerais)'ound in sand.)

Have a child pour about one tablespoonful ofsand into a glass of water. What happens tothe grains? (They sink to the bottom.) Is sandmore dense or less dense than water? (Moredense.)

Next tell the children that sand may have someproperties related to the way light passes throughit. These are called optical properties. Matteris said to be transparent, translucent, or opaque.These are terms the children should note andremember when making exact observations inthis and other Activities. Point out that a trans-parent object is one through which light passeseasily and which one can see through. (Windowglass is an example) A translucent object isone through which light passes, but Which onecannot see through. (Frosted glass is an exam-ple.) An opaque object is one through which lightdoes not pass and which one cannot see through.(Iron is an example.) Have a child place somesand grains on a printed page and examine thegrains with a magnifying glass. What opticalproperties do they show? (Many are translucent,most are opaque, some may be transparent.)


Introduce the idea that some minen Is havemagnetic properties, or characteristics. For in-stance, some iron ores are attracted to a magnet,just as an iron nail is attracted. Have the childrenplace a strong magnet on some sand particlesand detennine the number of particles out of agiven sample of particles that are magnetic.

Some children may want to examine with amagnifying glass some of the particles found onsandpaper. How do these grains differ from thegrains of sand from another source)? (The grainson sandpaper are probably much MOre uniformin size and color.) How is this explained? (Sand-paper is prepaeed by gluing only a certain sizeand kind of sand particles to a paper backing.)

Have the children collect samples of loamysoil and some samples of heateid soil from Ac-tivity 25 (in which they measured the humuscontent of loamy soil). They should examinethese samples with a magnifying glass or micro-scope. What size, shape, and color do they have?Do they have any magnetic properties? Ask thechildren what they think made the differences insand particles. How might they verify their as-sumptions orrideas?

Learning: (x,y,z) Loamy garden soil has sandparticles in it that may exhibit various physicalproperties, such as optical and mapetic proper-ties.

tCTIVITY 27 (x,y)

MEASURING THE DEPTH OF LOAMY SOIL

Purpose: To show that the depth of loamy soil variesfrom area to area

Concept to be developed: The amount of organic ma-terial (material that can decay into humus) suppliedto an area will determine the depth .of the loamy soil.

Materials needed:

YardstickShovel or post-hole digger

INTRODUCTION: Take the children to an areanear the school where they can examine the soil.Carefully dig up some of the soil. Lay it on asheet of newspaper spread on the ground. Youmay want the children to work in small groups,each group examining a shovelful of soil. Ask thechildren what they think contributes to the humusof the soil in the location. Is there any evidence tosupport their hypothesis? (They should look forevidence of leaves, roots from grass plants, or per-haps insect bodies.)

31

EARTH

Let the children find the depth of the surfacesoil by digging to the point where the darkhumus soil ends and anotht-r soil type begins.The underlying soil. type can be identified bycolor and texture (size, compactness, and com-position of particles) .

Why would the soil have a greater depth ofloam in a forest than in the region of a sanddune? (The forest area accumulates the leavesand other organic matter at a faster rate than thearea near a sand dune. )*

Perhaps the class has other areas available forexamination. If possible have them examine thesoil in a prairie area. What does the prairiecontribute to the richness of the soil? ( Decayedgrass and roots.) How deep is the prairie soil?Perhaps they might also examine the soil, of amarshland. The class may want to prepare achart showing the various depths of loamy csoil

found in various areas, such as garden soil,prairie soil, forest soil, and marshland.

Learnings: (x) Loamy soil varies in depth indifferent areas. (x,y) The amount of organicmaterial supplied to the area will influence thedepth of loath.

ACTIVITY 28 (y,z)

MAKING A SOIL PROFILE

Purpose: To introduce the idea of soil horizons

Concept to be developed: Soil horizons are layers ofsoil, each layer having a distinctly different compositon.

Materials needed:

Tall cylindrical jarShovel

INTRODUCTION: ln measuring the depth of aloamy soil, the children have observed that a dif-ferent type of soil was beneath the loamy soil.Point out that all soils are composed of differentiayers. The children can visit another area to seethese layers of soil.

Have them dig a hole into some garden soil.As they dig downward, do they notice a changein the soil? (They should.) In what ways doesthe soil change? (There is less humus. There isalso more clay in most cases.)

Introduce the idea that mature or well-de-veloped soils have typical "profiles" or sequencesof layers. Children may know that all soils havethe same type of layering, but there is consider-

32

able variation within the layers. Explain that eachlayer, or "hOrizon" as it is called, is designatedby a letterA, B, or C. The A horizon is thetopsoil and is usually rich in humus and organicmaterial. The B horizon, or subsoil, is beneaththe A horizon and frequently contains clay andiron minerals. It is less rich in organic materialand humus. The bottom part of the B horizonmay be quite hard and compact because of anaccumulation of clay. The C horizon lies justabove the hard rock and just below the 13 horizon.It consists of weathered rock particles. Have oneof the children write these definitions on thechalkboard for the *class to remember.

Plants

Humus

Less humus

Clay andiron Minerals

Compactclay

Loose rockpitiifes

If there are any suitable road cuts or streamsnear your school, the children can observe anentire soil profile. Have some of the membersof the class take samples from each portion ofthe profile that has a different type of soil. Placethe samples in small labeled containers thatindicate the location of the specimen, that is,

which was the topmost specimen, which was thenext beneath it, etc. To get a better understandingof the soil profile, the children can determinewhich is the A horizon, which is the B horizon,and which is the C horizon. Have them measurethe depth of the horizons. Which is the largest?(Usually the B horizon.)

With the samples that the children have col-lected, they can make their own miniature soilprofile. Have them place the different soils intothe tall cylindrical jar with the C horizon on thebottom and ending with the upper part of the Ahorizon on the top. Adhesive tape or smallgu.nmed labels can be used to identify the hori-zons in the jar.

Have the children observe the profile for anydifferences in the soil. Are there any colorchanges? Does texture change?

To illustrate that soils differ in different locali-ties, have the children observe soil profiles indifferent areas. Have them compare colors. (Somesoils may be quite red and others black or gray.)Is the depth of each horizon the same? (No, somesoils may have almost no A horizon and a verylong B horizon. Others may have a greater Ahorizon.)

Learnings: (y,z) Soils are described as havingprofiles, or typical layers designated as A, B,and C horizons. The A horizon is the topsoil,the B horizon the subsoil, and the C horizonthe weathered rock material. (y,z) The horizonsdiffer in size, color, and texture. (y,z) Soils indifferent localities have different profiles. Thosein forests have a larger A horizon with morehumus. The size and appearance of B horizonsvary considerably. Some may be very red, othersgray or ashy or blackish. The amount of clay inthe B horizon is also variable. Some profilesmay have a very compact layer of clay at thebottom of the B horizon.

,:,-", Screen

Chimney

Sand

Water collector


ACTIVITY 29 (y,z)

COMPARING THE RATE OF PERMEABILITY OF SAND,LOAM, AND CLAY

Purpose: To compare the rates of permeability of sandy,loamy, and clay soils

Concept to be developed: The rate of permeability ofa soil is the rate at which a liquid will pass through it.

Materials needed:Samples of sandy, loamy, and clay soils3 glass chimneysFine mesh wireMeasuring cupStringWater

INTRODUCTION: The children have observedsome of the characteristics of loamy soils, that is,soils containing considerable quantities of humus.Next they should discover that not all soils containa large amount of humus. Some soils are largelysand, while others are largely clay. Pose the ques-tion: Will these soils behave differently and appeardifferent? The following Activity will introduce thechildren to some of the characteristics of sandy andclay soils.

Tell the class that soils differ in the degree towhich they will allow water to move throughthem. Mention that this characteristic of allow-ing water to pass through is called permeability.Have the children check the meaning of the verbpermeate in the dictionary before they proceed.Then make the point that in this case permea-bility refers to the rate at which a liquid will passthrough a substance. Have the children set upthe Activity as follows: Attach a fme wire-meshscreen to the bottom of each glass chimney.

33

EARTH

A string can be used to attach the bent screen tothe chimney. Fill one chimney half full withsand, another half full with loam, and the thirdhalf full with clay. Pour one-half cup of waterinto each. Have the children observe what hap-pens, using a stopwatch to determine the time ittakes for the water to permeate the samples. Theyshould keep a record for each sample. Whichsample did the water pass through first? (Prob-ably the sand, then the loam, and last, the clay.)Why did the sand have the greatest permeability?(The grains did not hold back or absorb thewater particles.)

Which type of soil will have the least "holdingeffect" on rain watersandy, loamy, or clay soil?( Sandy soil, for water permeates the sand fasterthan the loam or clay.) Why is forest soil gen-erally moist? (It has a greater amount of humus,which tends to hold the moisture.)

Learning: (y,z) In comparing rates of permea-bility, sand is first in permeability, followed byloam, and then by clay.

ACTIVITY 30 (x,y,z)

COMPARING THE SIZE AND SHAPE OF CLAY PAR-TICLES AND SAND PARTICLES

Purpose: To show that clay particles are much smallerthan sand particles

Concept to be developed: The primary difference be-tween sandy and clay soils is the size of the soilparticles.

Materials needed:

Microscope or magnifying glassFine wire-mesh strainer or hobby-shop ceramic

strainerClay samplesSand grains

INTRODUCTION: Give each child some sand anda sample of dry clay. (You can use dry clay powder,dry water-base clay, or clay from a road cutting.)Have each child rub some particles from the dryclay and compare the size of clay particles with thesize of sand particles. Which are smaller? (Clayparticles are much smaller.) Have the children com-pare the ease with which clay particles and sandparticles pass through a fine wire-mesh strainer.

Have children examine the particles of clayand sand under a microscope of magnifying glassto compare their relative size and shape. Do theclay particles vary? (Yes, both vary in shape andsize.)

34

Now have some members of the class slowlyadd water to the clay sample and observe theresults. (The clay takes up the water and be-comes very gummy and compact.) What hap-pens when the children add water to a sampleof sand? Is there a difference in behavior be-tween the two samples? (Yes, the water passesright through the sand, and the grains still remainseparated.) WWch would be better for growingplants, sand or clay? ( Sand, because clay wouldform a hard compact mass through which theroots could not penetrate.)Learnings: (x) Clay particles are much smallerthan sand particles. (x,y,z) Clay particles adsorbwater and become compacted together. Someclays can be molded and are said to be plastic.(x,y) Sand would be better than clay for growingplants, since water passes through sand moreeasily, and the texture is loose enough to allowroot growth.

ACTIVITY 31 (x)

TESTING SOILS FOR pH

Purpose: To show that soils vary in their degree ofacidity or alkalinity

Concept to be developed: The pH of a soil indicates itsdegree of acidity or alkalinity: the lower the pH, thegreater the acidity; the higher the pH, the greater thealkalinity.

Materials needed:

Red and blue litmus paper or hydrion paperWater6 different soil samples7 test tubesMedicine dropperFilter paperFunnel

INTRODUCTION: Review with the children whatthey have learned: that besides differing in the sizesof their particles, soils differ in many other respects,including color, composition, and texture. An ad-ditional way in which soils differ is called pH, a termindicating the amount of acidity or alkalinity of aliquid. Acid substances, such as vinegar and lemonjuice, have a low pH. Alkaline, or basic, substances,such as ammonia or baking soda, have a high pH.Explain to the children that pH can be determinedby using an indicator such as litmus paper. Bluelitmus paper, for example, turns red in the presenceof an acid; red litmus paper turns blue in the pres-ence of a base. Another pH indicator is hydrionpaper, which has an indicating range of I to I I. ApH value of 7 indicates that the sample is neutral,that is, neither acidic nor alkaline. A value lowerthan 7 indicates an acid condition. A value higher

than 7 indicates an alkaline or basic condition. Acolor chart accompanying the paper indicates thepH through color comparisons. Hydrion paper isreadily available through most chemical supplycompanies.

Have the children select soil samples fromvarious locations and place the samples in labeledtest tubesone level teaspoonful of soil in eachtest tube. Then have them add three medicinedroppers of water to each test tube. Shake andallow each mixture to settle. (You may wantthe class to filter the mixture instead of allowingit to settle. If a filter paper is used, the test is

made on the liquid that filters through the paperand not on the material remaining on the filterpaper.)

Now have the children test the clear waterwith blue and red litmus paper or hydrion paper.Several children may want to prepare a chart toshow the condition of the soil samples as acid,

basic, or neutral. Some children may ask whysome soils differ in the characteristic of acidity.( Underlying rocks may make a difference. Fertil-

izers and decompositions of organic matter mayalso alter the pH condition.)

Learnings: (x) The acidity or alkalinity of thesoil can be determined by the use of certainindicators. (x) Soils will differ in acidity in dif-ferent localities.

Soil andwater mixture

Filter paper

I

i-)7N3

TO FOLD FILTER PAPER

Filtered water

Fold up Fold again

'EtoN

)Final

appearance

INVESTMATING THE LITHOSPHERE

ACTIVITY 32 (xly)

CHANGING THE pH OF A SOIL

Purpose: To show that the acidity of a soil can beartificially controlled

Concept to be developed: Acidic soils can be madealkaline by adding crushed limestone.

Materials needed:

Acid soil sampleTest tubesWaterPowdered limestoneLitmus or hydrion paper

INTRODUCTION: Discuss with the children theimportance of changing the acidity of some soils.Some plants will grow better in a more basic soil.For this reason it may be desirable to change thepH of the soil. Suggest that it is possible to bringabout such a change.

Have each of several groups of children selecta sample of an acid soil. (One teaspoonful ofsoil is sufficient.) Have them place this samplein a test tube, add several medicine droppers ofwater, and shake. (Water must be added, forindicators do not react in a dry state.) Allow thesoil to settle Or filter the mixture through a filterpaper. Then test the liquid with blue litmus orhydrion paper.

If blue litmus paper turns red, the soil is anacid soil. If the color of hydrion paper is of therange lower than pH 7, the soil is an acid soil.

Have the children secure some powdered lime-stone or crush some limestone rock with a ham-mer, being careful of flying chips. Have themplace one teaspoonful of powdered limestone ina test tube, add two medicine droppers of water,and shake. Let the mixture settle and test theliquid with red litmus or hydrion paper. Whatdoes the test indicate? (A basic, or alkaline, con-dition.) Have the children collect about one tea-spoonful of water from the acid soil mixture. Addto it some limestone water, one drop at a thne,testing the solution with blue litmus or hydrionpaper after each drop is added, until the acidcondition changes. Record the number of dropsit takes to produce a change for each of the soilsamples. Why does it take more drops to producea change in certain soil samples? (The soil ismore acid.) How do you know when 'the acidcondition changes? (The color of the indicatorthe litmus or hydrion paper changes.) Whydo farmers add powdered limestone to their

35

EARTH

Acid soilmixture

Limewater

Litmus turns blue

soils? (To change the soils from an acid to abasic condition. ) Why do they want the soils tochange from an acid condition? ( Certain plantsgrow better in a nonacid soil. Clover may doubleits yield if it is grown in a soil that has beentreated with limestone.)

Learnings: (x) Acid soil can be made basic byadding crushed limestone. (x,y) Farmers fre-quently add lime to soil, since many plants growbetter in a basic soil.

ACTIVITY 33 (y,z)

EXAMINING ANIMAL LIFE IN SOIL

Purpose: To show that many kinds of animal life existin the soil

Concept to be developed: The activities of animals inthe soil change the texture and the composition of thesoil.

Materials needed:

Soil sampleMagnifying glassAlcohol or Forinalin solutionPreserving bottles

INTRODUCTION: Tell the cliildren that besidesbeing acidic or alkaline, the soil may have animallife of Various kinds in it. Explain that the kind andainount of plant and animal life in soils varies indiffereu soils. The important thing is that this lifeis often a factor that can change the makeup ofthe ,soil. In the following Activity the class willexamine the kinds of life found in samples 'of soil.

Have the class examine the surface of a squareyard of soil. Note any earthworm ir -mnds, ant-hills, or other signs of animal activities. Care-

36

fully remove the surface plant life and examinethe soil for further signs of animal life. You maywant to preserve in an alcohol solution the formsof animal life found at different depths (on andbeneath the surface). Snails, slugs, and earth-worms can be preserved in a 6%-8% Formalinsolution (obtainable from the high school orfrom a chemical supply house) . Insects, spiders,and other jointed-leg animals can be preservedin an 85% alcohol solution (obtainable from adrugstore).

Present these questions to the children: Howdo earthworms enable more air to enter the soil?How do they turn over the soil? Does their eatingsoil particles change the composition of the soil?Do their droppings and dead bodies change thecomposition of the soil?

To get an idea of the great amount of soilearthworms bring up to the surface, the classcan weigh the amount of soil found in an earth-worm mound or the mound of a raised anthill.They should count the number of such mounds ina square yard and then try to estimate the wightof soil turned over in an acre.

Learning: (x) Many kinds of animals live in thesoil. Their activities change the texture and com-position of the soil. Earthworms, for example,are important in keeping the soil texture looseand in adding a certain amount of organicmaterial to the soil.

ACTIVITY 34 (X)

EXAMINING PLANT LIFE IN SOILS

Purpose: To demonstrate that soils contain largeamounts of dormant plant life

Concept to be developed: The dormant plant life insoils can be activated under the proper conditions.

Materials needed:

TopsoilBean seedsWaterWater glass

INTRODUCTION: Tell the children that animallife is not the only type of life that can be foundin soils. Suggest that they investigate the soil forthe presence of any 'plant life. Have members ofthe class take samples of topsoil during the dormantwinter period. They should provide the sampleswith moisture, warmth (room temperature), andsunlight and observe the kind and amount of plantgrowth that appears.

Light andmoisture

Soil

Have a group of children collect soil samplesfrom dry areas in vacant lots or along roadsides.Give these samples warmth, moisture, and lightand note any germination. Why did this growthnot take place before? (Favorable conditions forgrowth were not present.) Which factors wereprobably the most important? (Moisture andtemperature.)

Have the children soak bean seeds in waterfor 24 hours and then place the bean seeds in aglass filled with soil, so that the seeds are visible.What is the growth that often forms around theseeds? (It is a fungus, which is a mold.) What


is the source of the fungus? (Spores dormant inthe soil.)

Learning.- (x,y) Soils contain much plant lifethat does not appear until the conditions arefavorable for its growth.

Summing Up Ideas: The Activities in this sectionwere designed to extend the children's experienceswith soils. The children should have learnedthat there are three types of soils: loamy soils,sandy soils, and clay soils. Loamy soils have ahigh' humus content and retain a great deal ofmoisture. The primary difference between sandysoils and clay soils is the size of their particles;the particles that make up sandy soils are muchlarger than those that make up clay soils. Thechildren should also have learned that the acid-ity and alkalinity of soils may vary, and that pHis a measure of the acidity and alkalinity. Inaddition, the children should have become awareof the large amount of animal and plant lifepresent in soils.

IMPORTANT IDEAS IN THIS CHAPTER

For the kindergarten, primary, and inter-mediate grade children, the ideas with themost meaning and application are these:

Minerals can be identified by certaincharacteristic's.

The external color and the color of thestreak left by a mineral may not be the same.

The luster of a mineral is the way itreflects light.

Cleavage is the tendency for some min-erals to break in smooth, parallel planes.

Minerals that do not exhibit cleavage ex-hibit fracture.

The hardness of a mineral is always con-stant for the same mineral and thus is a goodmeans of identification.

The specific gravity of a mineral is a rela-tively constant characteristic.

Minerals that contain carbonates will ef-fervesce when treated with dilute hydro-chloric acid.

Crystals form in nature by the slow evap-oration of liquids that contain dissolved salts.

A rock is any natural material that makesup part of the Earth's crust.

Very-fined-grained rocks cool rapidly;coarse-grained rocks cool slowly.

Soils are produced by the weathering ofrocks.

Loamy garden soil is a soil type that canhold a large amount of water.

Loamy garden soil contains a measurableamount of huMus.

Sandy soils are better for root growth thanare clay soils.

The acidity or alkalinity of the soil can bedetermined by certain indicators.

In addition to these ideas, in the inter-mediate and upper grades the children shouldbe led to develop concepts that are morecomplex and more quantitative:

Cleavage can be in one, two, or threedirections, depending on the mineral.

Fracture is the description of the brokensurface of a mineral that has no cleavage.

The hardness of minerals is usually in-dicated by a number from 1 to 10, with No. 1the softest and No. 10 the hardest.

Specific gravity is the weight of a sub-stance divided by its loss of weight in water.

Sedimentary rocks are rocks having grainspressed together by overlying beds and thencemented together.

Metamorphism is a process in which rocksbecome changed by heat and pressure; thischange alters their appearance and makesthem harder and more compact.

Humus is composed of decayed organicmatter from living things.

Sandy soil is more permeable than loamysoil, which is more permeable than clay soil.

pH is a measumment of acidity; the lowerthe pH, the greater the acidity.

3

INVESTIGATING THE HYDROSPHERE

The second sphere or layer of the Earth is thehydrosphere, or water layer. Water is vital inman's life. It is almost everywhere. It is in thefood he eats and the air he breathes. In addition,it is a major part of him as well as of other livingthings. It is used to carry waste materials fromhomes and factories, to water lawns, to washcars, and to aid the growth of the plants andanimals that people use for food. It producespower to turn generators, which make electricity.Water is necessary for all living things.

Children have many experiences with water,one of the most abundant substances on theEarth. They know something about its naturewhen they drink it, bathe in it, play in it, andswim in it. They may ask such questions as these:

"Is there really water in all our foods?" "Wheredoes the water in rivers and lakes come from?""How does water get into wells?" "Why does ittake longer to boil potatoes if you are on amountain than if you are at sea level?" "What is'hard' water?" "Why does water soak into somematerials and not into others?"

The following Activities suggest methods ofinvestigation. It is hoped that the children willhave a chance to try ideas of their own.

WHERE IS WATER FOUND?

Water is found in rivers, lakes, ponds, and oceans.

It is also present in soils, rocks, and living things.Water is present in air and can form clouds, fromwhich it can return to .the Earth as rain andsnow. The Activities in this section might best.be introduced by a discussion of the topic: Howmuch of our Earth really is water?

ACTIVITY 35 (x)

COMPARING THE AMOUNT OF THE EARTH'S WATER

AND LAND SURFACE

Purpose: To show that the largest part of the Earth'ssurface is covered by water

Concept to be developed: Water covers about 71% ofthe Earth's surface.

Materials needed:

Globe of the Earth

38

INTRODUCTION: How much water is there onthe Earth's surface? Which covers a greater area,land or sea? These are two questions you mightwrite on the blackboard and ask children to answer.Then place the globe on a table in front of the chil-dren and have them observe the different colors onthe globe.

What color represents the water? (Usually thecolor is blue.) What color represents land? (Us-ually colors other than blue or white.) If there isan area shown in white, what does it represent?(Snow and ice.) Where do you fmd the ice cover-ing? (At the North and South poles.) Whichcolor covers a greater area of the globe? (Theblue.) Is there more water, land, or ice covering

our Earth? (Water.) Ask the children to estimatewhat percentage of the Earth's surface is coveredby water. (About 71% .) Let them suggest waysto measure the area covered by the water.

Learning: (x) Water covers the greatest part ofthe Earth's surface. About 71% is water.

ACTIVITY 36 (x,y)

DETERMINING IF WATER IS IN THE FOOD WE EAT

Purpose: To show that water is found in most of thefoods we eat

Concept to be developed: The drying of foods is ac-companied by shrinkage and by loss of weight.

Materials needed:

ApplesPotatoesLettuceBreadCrackersHot plateTest tubeGlass plate

INTRODUCTION: Have the children talk aboutwhere they think water may be found. You mightmake a list of their ideas and chart them. From timeto time, the children may want to add to the chartas they get other ideas. Some children may suggestthat the food we eat contains water. Encourage themto give the reasons for their thinking. Then suggestthat there is a way to test their ideas. Ask them tobring small quantities of various kinds of foods toschool for testing.

Cooled glass plate

Test tube

Piece of food

Burner

Along with the foods they bring you might

want to have samples of the foods listed above.The names of the foods might be listed on theblackboard. Let children give their ideas abouthow to detect the presence of water in differentfoods. It may -be suggested that a piece of thefood be placed in a test tube and heated slowly.When a cool, square piece of glass is placed overthe mouth of the test tube, the children will seedroplets of water forming on its under surface.The amount of water present on the glass depends

upon the amount of water present in the food.It may be necessary to use a cool glass for eachtrial, so that the water vapor will condense into

water droplets.Some foods have very little moisture in them

(dried beans and rice, for example) and will show

little, if any, moisture on the glass surface. HowdoeS the food differ in appearance after beingheated? (It feels harder, or it may become dry

Piece of food

Piece of paper

Pencil tracingaround food


and powdery.) Why? (The moisture has beendriven out by the heat.) Were there any otherchanges? (Yes, a change in weight and possibleshrinkage from water loss.)

For another test the children can place piecesof food on a piece of paper, trace around thefood, and place the paper and food in a warmplace. After a day or so, they will observe thatthe food is shrinking from loss of moisture. Havethem weigh the food before and after beginningthis part of the Activity to see if there is a dif-

ference in weight.The children can also make a display of de-

hydrated foods. They may want to add water tosome of these foods to see what happens.

Learnings: (x) Water is found in most of thefood we eat. Foods such as raisins, dried apricots,beans, and dried milk have had most of the waterremoved. (x,y) The drying of foods is accom-panied by shrinkage and a loss of weight.

ACTIVITY 37 (x)

SHOWING THAT THERE IS MOISTURE IN A PERSON'S

BREATH

Purpose: To show that water vapor is present in theair that people exhale

Concept to be developed: In cold weather the watervapor in the air can be detected-when it condenses toform droplets of water.

Materials needed:

MirrorTest tube and test-tube holderWaterHot plate2-hole cork2 glass tubesCalcium chlorideGlass tubing

INTRODUCTION: Most children.have "seen theirbreath" on a cold day. Encourage them to de-scribe this and similar experiences. Perhaps somewill relate how sometimes their breath changes tofrost that they can see on their coat collars orscarves. This Activity will help the children to findout if, besides being present in foods, water existsin a person's breath.

Hair` e one of the children fill a test tube halffull of water. Using a test-tube holder, heat thetube over a hot plate. Point the open end of thetube tOward a mirror about an inch away. Whathappens? (The mirror becomes clouded.) Whatcauses this change? (Moisture adheres to the sur-face of the mirror.)

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Test tube holder

M irror

. Vapor

test tube

Water

N I

Hot plate

Dry the mirror and have a child hold it close tohis mouth and blow on it. What effect is ob-served? (The mirror again becomes clouded.)What causes this change? (Moisture from thechild's breath adheres to the mirror.) Suggestthat there is a way to remove the moisturefrom the breath before breathing against themirror. Encourage theories about this andthen point out that it can be done by blow-ing through a right-angle tube into a jar of achemical called calcium chloride. Set up the jaras illustrated; with another right-angle glass tubethrough which the dried air can be forced. Askthe children why the air coming from this jar doesnot cloud the mirror. What has the chemicaldone? (The calcium chloride acted as a dryingagent and removed the water vapor.)

The children may comment further on the"appearance" of breath. What happens in verycold weather? (A "cloudiness" can be seen whena person exhales, or breathes out.) Why? (Thewater vapor in his breath condenses to form tinydroplets of water and forms a small cloud.)

0: Breath Dry air

Two-hole stopper

Jar

Mirror

40

Calcium chloride

Learnings: (x) Water vapor is present in the airthat people exhale. It is this moisture that cloudsglass. (x,y) In cold weather this water vapor inthe breath can be seen as it condenses to formdroplets of water.

Summing Up Ideas: In this section the childrenwere introduced to the idea that water can befound in many places and in many things. Theylearned that water covered about 71% of theEarth's surface. They also learned that many'foods contain water. In addition, they learned thatthere is water in people's breath and that thiscan be seen under certain conditions.

WHAT ARE SOME OF THE CHARACTERISTICS OFWATER?

Water is a chemical compound composed of theelements hydrogen and oxygen. All compoundshave definite physical properties that can be ex-amined, such as boiling point, freezing point, andcolor. The following Activities will introduce thechildren to some of the important characteristicsof water.

ACTIVITY 38 (x)COMPARING THE FLOW OF WATER WITH THE FLOWOF OTHER LIQUIDS

Purpose: To show that water flows quite easily

Concept to be developed: All fluids have a propertycalled viscosity, a resistance to flow. The viscosity ofwater is very low, so water flows quite easily.

Materials needed:

WaterCane or maple syrupHoney4 test tubes with corksTesttube holderHot plate

INTRODUCTION: The children have learned thatwater is present in many unexpected places, suchas in foods and in people. Now they should beready to discover some of the characteristics ofwater, in order to understand its importance to theEarth.

Have some of the children fill one test tube halffull of water, another half full of cane or maplesyrup, and the third test tube half full of honey.Place a tight-fitting cork in each tube.

Ask the children to turn each test tube upsidedown and to observe what happens to each

Test tube holder

Test tube

Honey

Hot plate

liquid. (Each liquid moves to the other half ofthe test tube.) How did the liquids get to theother end? (They flowed to the other end of thetube.) Did each liquid flow at the same speed?(No.) Which liquid flowed to the other half ofthe tube most rapidly? (The water.) Which liquidflowed to the other half of the tube least rapidly?(The honey.) After the children have made theirobservations, develop the meaning of the wordviscosity.

Have a child place more honey in another testtube, filling it about half full. Have the childuse a test-tube holder and heat the honey over ahot plate. Caution: Be sure the test tube does nottouch the hot plate. After the honey has beenwarmed, have the child place a cork in the testtube and turn the test tube upside down. Askthe children to compare the rate of flow of thishoney with that of the honey that was notwarmed. What does heating do to the honey?(Heating makes it less viscous.) Ask the chil-dren if they have ever heard the expression "asslow as molasses in January." Is it appropriate?

Let the children speculate whether heatingwater will make it less viscous. How could theytest this?

Point out that the ability of water to flow isvery important, as this accounts for the forma-tion of streams and rivers and enables man todirect the passage of water to places of betteruse. Have the children guess what thc woddmight be like if water were as "thick" as honey.

Learnings: (x) Water has the ability to flow.(y,z) Some liquids flow with difficulty and arecalled viscous. Molasses and honey are examplesof these. (y,z) Heat can cause honey to lose someof its viscosity.


ACTIVITY 39 (x,y)

WEIGHING WATER

Purpose: To determine the density of water

Concept to be developed: The density of water can beexpressed as 1 gram per cubic centimeter, or 62.4pounds per cubic foot.

Materials needed:

Spring balance, calibrated in gramsTin can, 16-ounce capacityWaterWireGraduated cylinder, calibrated in cubic centimeters

(cc)

INTRODUCTION: The children have observed oneof the characteristics of waterits ability to flow.They can now investigate another of its charac-teristicsits density. This Activity will show themhow they can determine the density of water.

Have one of the children punch two holes inthe tin can and 'suspend it by a wire from thespring scale. Weigh the can and the wire andrecord the weight.. Have another child accuratelymeasure out 100 cc of water hi the graduatedcylinder and pour the water into the can. Havea child weigh the can of water and record theweight. The children will observe that the weightof the water is equal to the difference between

16-ouncetin can

100 ccof water

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,

the second weight recorded (water + can +wire) and the first weight recorded (can +wire). For example,

Weight of can, wire, and water = 150 grams-Weight of can and wire = 50 gramsWeight of 100 cc of water = 100 grams

Have the class estimate the weight of 200 cc ofwater. (200 grams.) What is the weight of 1 cc?Have the children measure out 1 cc of water anddetermine the weight. (Each cubic centimeterweighs I gram.)

Remind the children that density is weightper unit volume. Then ask them, What is thedensity of water? (One gram per cubic centi-meter.)

Some of the children may wish to work outmathematically the density of water in poundsper cubic foot. To do this, they will have to knowthe following relationships :

1 cubic foot = 28,322 cubic centimeters1 pound = 453. 59 grams

Knowing these two relationships, the childrenshould proceed in the following manner. If 1cubic foot of water is equal to 28,322 cubiccentimeters of water, and 1 cubic centimeterweighs 1 gram, then 1 cubic foot of water willweigh 28,322 grams. Since 1 pound is equalto 453.59 grams, then the weight of 1 cubic footof water (in pounds) will be equal to 28,322divided by 453.59, or 62.4 pounds. Therefore,the density of water can also be expressed as62.4 pounds per cubic foot.

Learning: (y,z) The density of water can beexpressed as either 1 gram per cubic centimeteror 62.4 pounds pa cubic foot.

ACTIVITY 40 (y,z)COMPARING THE DENSITY OF WATER WITH THAT OF

OTHER LIQWDS

Purpose: To show that the density of different liquidsvaries

Concept to be developed: The ratio of the density of asubstance to the density of water is called its specificgravity.

Materials needed:Graduated Cylinder, calibrated in cubic centimetersTin cans, 16-ounce capacitySpring balance, calibrated in gramsGlycerineWireAlcoholOther liquidsOlive jar

42

INTRODUCTION: Now that the children havedetermined the density of water, they can deter-mine the density of the other liquids and comparethese with water. In preparation for this Activityhelp the children make a string or wire support tohold an olive jar. Weigh the jar and support. Fillthe olive jar about three-quarters full of water. Sticka paper pointer on the jar to indicate the exactwater height. Weigh the jar and water in grams.Empty the water into a graduated cylinder andmeasure the amount of water. Subtract the weightof the jar and support from its weight with thewater. The weight in grams should equal the num-ber of cubic centimeters.

Have the children measure 100 cc of glycerineinto a tin can in the same manner as they didthe water in the preceding Activity. Then let themdetermine the weight of the glycerine as theydid that of water. What is the weight of 100 ccof glycerine? ( 126 grams.) What is the densityof glycerine? ( 1.26 grams per cubic centimeter.)Have the children repeat the Activity, usingalcohol in place of the glycerine. What is theweight of 100 cc of alcohol? (80 grams.) Whatis the density of alcohol? (0.8 grams per cubiccentimeter.) Which is more dense, glycerine orwater? (Glycerine.) Which is more dense, alcoholor water? ( Water. )

The children may wish to find the density ofsome other liqiuds. The following list gives thedensity, in grams per cubic centimeter, of somecommon liquids.

Liquid

benzenegasolinekerosenemilkcastor oillinseed oilolive oilvinegar

Density(in grams per cc)

0.900.670.821.030.970.940.921.05

Once the children have sem how the densitiesof some other liquids compare with the densityof water, they may be interested in learning therelationship between density and specific gravity.

Next have the children dry the glass arfill it to the mark with glycerine. How muglycerine is this? (The same as the measuredvolume of water.) Weigh the glycerine and the

jar. What is the weight of the glycerine? (Sub-tract the weight of jar from weight of glycerineand jar.) Divide the weight of the glycerine bythe weight of an equal amount of water. Thisgives the comparative weight of glycerine towater, or the specific gravity of glycerine. (Thechildren should note that the specific gravityis equal to the density if the density is measuredin grams per cubic centimeter.) Have the childrenreveat the procedure to fmd the specific gravityof other liquids, such as alcohol.

Learnings: (y) The density of liquids varies. (y)Water is used as a standard to compare thedensities of other substances. This comparisonis the specific gravity of a substance. Specificgravity is equal to the weight of a substancedivided by the weight of an equal volume ofwater. (y,z) A substance with a specific gravitygreater than 1 is more dense than water. Thegreater the specific gravity, the denser the sub-stance.

ACTIVITY 41 (y,z)

DETERMINING THE BOILING POINT OF WATER

Purpose: To show that the boiling point of water is100° Centigrade (212° Fahrenheit) at sea level

Concept to be developed: The boiling point of a sub-stance is the temperature at which it changes from theliquid state to the gaseous state.

Materials needed:Thermometer registering over 100° Centigrade or

212° FahrenheitBeaker of waterHot plate

INTRODUCTION: Discuss with the children thatmost substances exist in three statessolid, liquid,and gaseous.* Ask them whether they know howsubstances might be changed from one state toanother. Some may know due it is possible tochange a substance from one state to another bychanging the temperature. For example, water, aliquid, can be changed to a solid (ice) by freezing;or water can be changed to the gaseous state byheating. The point at which a liquid changes to agas is called the boiling point. The children willdiscover what the boiling point of water is in thefollowing Activity.

* For a further discussion of the three states of matter, seeAtoms and Molecules, by Seymour Trieger (InvestigatingScience with Children Series; Darien, Conn., TeachersPublishing Corporation, 1964).


Water boils at 212°F. or 100°C. when theair pressure is 14.7 pounds per square inch. Thisis the average pressure at sea level: a columnof air above a square inch of surface at sea levelweighs 14.7 pounds. As the air pressure is re-duced, water boils at a lower temperature. Waterboils at 90°C. when the pressure is 10.16 poundsper square inch and at 115°C. when the pres-sure is 24.55 pounds per square inch. In apressure cooker the increased pressure raisesthe boiling point of the water.

In this Activity, the children can determine theboiling point of water for their location. Have thechildren place some water in a beaker and boilit on a hot plate. Suspend a laboratory thermom-eter in the vapor, just above the boiling water.(A laboratory thermometer has the scale etchedon the glass and has a range of over 100°C. )Have the children read and record the tempera-ture. Why is the figure probably slightly under100 °C.? (Because the air pressure is probablyless than that at sea level-14.7 pounds persquare inch.) Would the temperature of boiling-water be higher or lower than 100°C. on amountain? (Lower than 100°C.) Would it takea longer or shorter time to cook potatoes on amountain? (Longer.) Why? (The water wouldnot become as hot before it boiled at the higheraltitude.) What is the principle of a pressurecooker? (It allows the water to become hotterbefore it begins to boil and thus cooks thingsmore rapidly.)

String

Thermometer

Vapor

Boiling water

Hot plate

I/

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Learnings: (y) The boiling point of a substanceis the temperature at which the liquid statechanges to the gaseous state. (y,z) The boilingpoint of water at sea level is 100°C. This boilingpoint will vary depending upon the pressure ex-erted above the water's surface. At high al-titudes the air pressure is lower and the boilingpoint is correspondingly lower.

ACTIVITY 42 (x,y)RAISING THE BOILING POINT OF WATER

Purpose: To show how the boiling point of water canbe raised

Concept to be developed: When table salt is dissolvedin water, the boiling point of the water is raised.

Materials needed:

Table saltBeaker of waterHot plateGraduated cylinderLaboratory thermometer registering over 100°C.

INTRODUCTION: In the preceding Activity, theclass determined that the boiling point of water wasabout 100°C. but varied with the pressure exertedupon it. Mention to them now that another factoraffecting the boiling point is the material dissolvedin the water. Tell the children that in this Activitythey will determine the boiling point of water thathas table salt dissolved in it. Ask them whether theythink the addition of salt will make a difference andhave them give their reasons.

Have a child pour 100 cc of water in a beaker.Then have him put the beaker over a hotplate and boil the water. Have the child readand record the temperature of the vapor justaboveThe boiling water.

Next have one of the children add enoughtable salt to the hot water to make a super-saturated salt solution ( a solution in whichno more salt will dissolve.) Then have himboil the solution. Have the child read andrecord the temperature at which the water nowboils. Compare the two temperature readings..Why does the. water now boil at a highertemperature? (Table salt is dissolved in thewater.) Explain that chemists use this principleof determining the raised boiling point of waterto determine how much salt is dissolved in a givenquantity of water.

Learnings: (x) When table salt is dissolved inwater, the boiling point is raised.

44

ACTIVITY 43 (y,z)LOWERING THE BOILING POINT OF WATER

Purpose: To show that the temperature at which waterwill buil can be lowered

Concept to be developed: Reducing the air pressureabove the surface of the water will cause it to boil at alower temperature.

Materials needed:

Pyrex flask with a 1-hole rubber stopperWaterTowelHot plateLaboratory thermometer

INTRODUCTION: Discuss with the class that theyhave determined the boiling point of water to be100°C. at normal atmospheric pressure of 14.7pounds per square inch. Point out that there areseveral ways used to reduce this weight of air, therebyenabling water to boil or to turn to a gas at a lowertemperature. Encourage them to give their ideas.Suggest that one way is to go to a higher elevation.Another way is to withdraw some of the air fromabove the water.

The children can reduce the pressure of 14.7pounds per square inch above the water in thefollowing way. Have some children pour waterinto the flask, about one-quarter full. Then havethem boil the water on a hot plate. Place athermometer in the vapor just above the boilingwater. Have the children read and record theboiling point of water.

Next have them carefully push a moistenedthermometer through the one-hole stopper.(Moistened glassware can be pushed throughrubber more easily.) The thermometer should bepushed far enough through to reach the pointjust above the surface of the boiling water. Care-fully remove the flask from the hot plate. What

Thermometer

One-hole stepper

Flask

Vapor

Boiling water

happens? (The water stops boiling.) Why?(There is no longer enough heat at that pressureto cause it to boil.) Have the children place thecork and thermometer into the mouth of the flask.Then have them place a towel that has beensoaked in cold water around the sides of theflask. What happens? (The water begins to boil.)Why? (The water vapor inside the flask con-densed to water again, creating a lower pressureabove the water. With the lessened pressure thewater will boil at the lower temperature.)

You may be able to borrow a vacuum pumpfrom the high school. By pumping air out of aflask containing hot water, the children may beable to reduce the air pressure enough to causethe water to boil.

Learning: (y) Reduced air pressure over the sur-face of water will lower the boiling point.

ACTIVITY 44 (y,z)

DETERMINING THE FREEZING POINT OF WATER

Purpose: To show that the freezing point of water is0° Centigrade (32° Fahrenheit) at sea level

Concept to be developed: The freezing point of a sub-stance is the temperature at which it changes from theliquid state to the solid state.

Materials needed:

Plastic bagRefrigeratorShallow panWaterLaboratory thermometerStringparaffinGlycerineDry iceOlive oilAlchoholMercury

INTRODUCTION: Tell the children that it is pos-sible to change the liquid state of water into the solidstate by lowering the temperature, and that thepoint at which the change occurs is called thefreezing point. Ask the children if they think thatall substances freeze at the same temperature. Pointout that the next Activity will give them an op-portunity to compare the freezing points of waterand other common substances. Have the childrencollect different kinds of liquids, such as thosementioned above.

Have the children place some water in a plasticbag, inserting a laboratory thermometer so thatthe bulb end is suspended in the water, and tie


Thermometer

Water

Mercury bulb

Plastic bag

a string around the top of the bag (the top endof the thermometer should be sticking out).Place this setup in a freezing compartment forseveral hours. When the water has frozen, re-move the bag from the freezing compartment.Read and record the thermometer reading. Howwould your class account fot the fact that thdreading might be below 0°C. or 32°F.? (Onceall the water has frozen, the ice can becomecooler if the freezer unit is set at a temperaturebelow 0°C.) Remove the plastic bag from aroundthe ice block and allow the block to stand in ashallow pan until it begins to melt. Read *thetemperature of the thermometer after the iceblock has been raised just to its melting point.What is the temperature reading now? (32°F.or 0° C. )

Some of the children might like to comparethe freezing point of water with that of otherliquids. If so, they should obtain and try someof the other liquids listed above. The followingtable gives the freezing points of these liquids.

liquidFreezing point

°Centigrade °Fahrenheit

alcohol -117 -179glycerine 17 63olive oil 2-6 35-43paraffin 55 131

mercury -30 -38

With some children you might want to com-pare the freezing point of water with the freezingpoint of paraffin. To do this, have them meltsome paraffin in a beaker over a hot plate, thenremove the paraffin from the hot plate and stir

45

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it with a glass rod until cooled but not hardened.When the paraffin is just forming a hardened sur-face, they should stir with the laboratory ther-mometer and record the temperature when theparaffin hardens. This is its freezing point. Whatis the reading? (About 131°F. or 55°C.) Howdoes frozen paraffin differ from liquid paraffin?(It does not flow.)

Some of the children might like to freeze some

mercury. Have them place a small 41 ofmercury in a paper cup and place v.t. a

mixture of alcohol and dry ice ( at .40°C.).(Use extreme caution in handling dry ice. Gloves

or tongs should always be used, for if dry ice

comes in contact with the skin, it may cause seri-ous skin injury.) Next, the children should break

Alcohol and

dry ice mixturePaper cup

with mercury

the chunks of ice with a hammer and place thechunks in a beaker half full of aim!' ol. Thealcohol is reduced to a temperature of 80°C.When the mercury reaches a temperature of39°C., the mercury freezes. How does frozenmercury differ from liquid mercury? (It is a solidand does not flow.)

Learnings: (y,z) Water freezes at 0° Centigradeor 32° Fahrenheit. Some liquids freeze abovethat temperature, and some other liquids freezebelow that temperature. Mercury freezes at atemperature of 39° C. Paraffin freezes at atemperature of 55°C.

ACTIVITY 45 (x,y)

LOWERING THE FREEZING POINT OF WATER

Purpose: To show that the freezing temperature ofwater can be lowered

Concept to be developed: The freezing point of watercan be lowered by dissolving certain substances in it.

MateriAls needed:

SaltLaboratory thermometerWaterPlastic bagStringRefrigeratorAlcoholShallow pan

46

INTRODUCTION: The children now know thatwater normally freezes at a temperature of 0°C.or 32°F., as they saw this happen in the precedingActivity. This Activity will show the children thatdissolving certain substances in water changes thefreezing point of the water.

The children should put enough salt into aplastic bag full of water to make a saturatedsolution. Have them place enough salt in thebag so that some crystals will not dissolve, butinstead will remain on the bottom of the plas-tic bag. Then have them place a thermometer inthe bag and tie the neck of the bag with a stringso that the thermometer is sticking out. Theyshould then place this setup in the freezing com-partment of a refrigerator. (The freezing unitmay have to be turned to its coldest position.)When the soludon has frozen, remove the plasticbag from the refrigerator. Let the block of icestand in a shallow pan until it begins to melt.The children should read and record the temp-erature of the mixture when it just reaches themelting point. Is there any difference betweenthis temperature and that of the frozen waterwithout salt? (Y es, the salt-water block of iceis at a lower temperature.) Why? (Adding saltto water lowers the freezing point.)

The children might like to discuss this conceptand its effect upon the oceans The oceans con-tain considerable salt and will thus have a freez-ing temperature lower than that of fresh water.Is this advantageous? Why?

Some children may want to mix certainamounts of alcohol and water together to see if

Thermometer

String

Plastic bag

Mercury bulb

Salt water

they can freeze the mixture using the 80°C.temperature of a mixture of dry ice and alcohol.(See Activity 44.)

To help children apply their learnings, youmight ask, Why does your father put alcoholor antifreeze in his car radiator during the winter-

time? (The alcohol or antifreeze lowers thefreezing point of the water. Therefore, the water

will not freeze and damage the radiator.)Encourage children to dissolve other sub-

stances in water to see how the freezing point is

affected.

Learnings: (x) When salt is dissolved in water,the freezing point of the water is lowered. (y) Amixture of alcohol and water also has a lowerfreezing point than that of pure water.

ACTIVITY 46 (y,z)

DEMONSTRATING THE COHESIVENESS OF WATER

Purpose: To show why water takes the shape of drops

Concept to be developed: Cohesion is the tendency of

substances to stick together.

Materials needed:

WaterMercuryWax paperMedicine dropperMagnifying glass

INTRODUCTION: Tell children that they are going

to discover another characteristic of liqiuds. First,discuss the word cohesion with them. Cohesionis the force of attraction of like substances.

Give each child a small square of waxpaper. Fill a medicine dropper with water and

place a few small drops on each piece of waxpaper. Do the drops make the paper wet? (No.)Have children push some of the drops together.What happens? (The water sticks together aslarger drops. ) What shape do the drops take?(They are ball-shaped.) Do they all have thesame shape? (No, the smaller ones are morespherical, the larger ones are flatter.) What hap-

pens when two small spherical drops are brought

together? (They form a larger and flatter drop.)

Let the children speculate about what would

happen if a larger, flatter drop were separated into

two smaller droplets. Have them try it.

The children might like to see if other liquids

exhibit cohesion, too. Have them repeat the

procedures, using some small drops of mercury


(or mineral oil) in place of the water. Caution:Do not let the children touch the mercurywith their bare fingers; it is poisonous if takeninternally. The children should use the tip of apencil or small stick to move the drops of mercuryacross the wax paper. Which is the more co-hesive, mercury or water? (Mercury.) How canyou tell? (The mercury forms larger, rounderdrops.) Perhaps some children might like tocompare the cohesive force of water with thatof other liquids, such as alcohol and glycerine.

Learning: (y,z) Cohesion is the tendency ofsubstances to stick together. Water shows a co-hesive force, but " 4s not as great as the forceexerted by many

ACTIVIT 47 (y)

STUDYING THE SURFACE TENSION OF WATER

Purpose: To demonstrate the phenomenon of surfacetension

Concept to be developed: The surface of water actsiike an elastic membrane; this elasticity of the surfaceis called surface tension.

Materials. needed:

RazorDish of waterNeedlePetroleum jelly

INTRODUCTION: Water has another interestingcharacteristic that the children may enjoy investigat-

ing. Perhaps they have observed water insectsskimming over the surface of the water. Theinsects' feet depress the surface, yet they do notbreak through the surface of the water.-There seemsto be an elastic membrane covering the top of the

water. Explain that this characteristic is surfacetension. It is caused by like particles (molecules)at the surface being pulled down more by waterparticles beneath than by like particles above. Theresult is a compacting of particles at the surface tobehave like a tough membrane.

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Needle

WaterDish

The children can observe this by gently placinga thin, double-edged razor blade on the surfaceof a dish of water. The same thing can be donewith a sewing needle. Id.ly the objects flat uponthe surface. (Smearing a I.;:tle petroleum jelly onthe metal will make it easier to perform theActivity.) What do the children observe? (Themetal makes a little depression in the water butdoes not break the surface.) Press on the bladeand needle. What happens now? (The water sur-face is broken, and the metals sink.) What doesthis show about the water surface? (The forcesacting on the surface particles must be differentfrom those acting on the particles in the interior. )

Learning: (y) The surface of water acts like anelastic membrane. This elasticity of the surfaceis called surface tension.

ACTIVITY 48 (z)

MAKING WATER RISE IN CAPILLARY TUBES

Purpose: To show why water rises in capillary tubes

Concept to be developed: Water rises in capillary tubesbecause of adhesion, the attraction between unlikeparticles.

Materials needed:WaterCapillary tubes or glass tubingBunsen burner2 pieces of glass about 2 x 2 inches

INTRODUCTION: Point out to the children thatthey have discovered that cohesion is the attractionthat like particles have for each other. Now theycan discover adhesion, which is the attraction un-like particles have for each other. Hold up a pieceof adhesive tape and discuss with the children thatit is a kind of tape that sticks well to other objects,such as the skin or gauze. Water and otherliquids show certain adhesive qualities. Explain thatwhenever unlike particles stick together, the forceis called adhesion. It is this adhesive characteristicof water that keeps soils moist. Explain to the chil-dren that they can discover the adhesive quality ofwater by performing the following Activity.

Fill a beaker about half full of water. Plasome capillary tubes in tlE. yeaker.tubes are glass tubes having inner diameters of

48

very small size. If you cannot get any, draw yourown glass tubing into thinner tubes. This is ac-complished by slowly rotating a glass tube in apropane or Bunsen flame while the tube is pulledat each end. The tube will stretch slowly to forma narrower tube. Remove it from the flame andbreak the tubing at convenient lengths with afile. The tubing can be broken easily after scratch-ing a deep line on the glass with a file. The tubebreaks when pressure is applied at the scratchmark.) What happens to .the water in the tubes?(It rises.) Why? (Water adheresis attractedto the sides of the tube.) In which tubes doesthe water rise the highest? (In the thinner tubes.)Why? (The amount of adhesion does not changewith smaller diameters, but the amount of waterit must act on is less. Therefore, the smalleramount of water can be pulled up higher.)

Bring out during the discussion that this ad-hesive quality of water is very important in plantlife, since it partially explains how water getsto the tops of tall trees. Plants such as trees andshrubs have tiny capillary tubes within the rootsand stems that carry the water up the plant.

Capillary tubes

Beaker

Water

Learnings: (z) Adhesion is the attraction that un-like particles have for each other. (z) The riseof water in capillary tubes illustrates this ad-

hesion.

ACTIVITY 49 (z)COMPARING THE ADHESIVE PROPERTIES OF WATERAND OTHER UQUIDS

Purpose: To show that the adhesive properties of dif-ferent liquids are different

Concept to be developed: INater does not adhere toall substances equally.

Materials needed:

Mercury2 glass platesRubber bandSyrupHoneySealing waxRulerBowlAlcohol

INTRODUCTION: Some children may want toinvestigate the adhesive properties of other liquidsand compare them with those of water. By aimingout the following Activity, they will make somevery interesting discoveries. They will find that notall liquids adhere to the same substance to thesame degree. In this Activity, the children canmeasure the adhesion of water to glass and com-pare this to their findings on the adhesion of otherliquids to glass; they can also compare the adhesionof water to substances other than glass.

Have a child fasten a rubber band to the centerof a 2 by 2-inch piece of glass with sealing waxand then place the glass on the surface of a bowlof water. He should stretch the rubber band,pulling the glass from the water. Measure thedistance the rubber band stretches before theadhesive force is disrupted. Record the distancein inches from the top of the rubber band tothe surface of the water when the glass is finallylifted from the water.

Try this same experimental setup usingsyrup, honey, and alcohol in place of the water.Observe and record tbe fmdings for each. Howdo the results compare? Which shows the great-est amount of adhesion to the glass? Which shows

the least?Some members of the class may want to com-

pare the adhesion of water to materials otherthan glassthey can try a piece of copper,wax paper,.or, plastic.


Ruler

Rubber band

Sealing wax

Glass plate

Water

B9Yil

Children can apply their findings as you asksuch questions as: Why are tentmakers concernedwith the adhesive qualities of their fabrics withwater? (They want a miOnum of adhesion, sothat the water will roll off the fabric.)

Learnings: (z) Water does not adhere equallyto all substances. (z) Different liquids show avariation in their adhesion to different materials.

ACTIVITY 50 (x,y)

COMPARING THE TRANSMISSION OF LIGHTTHROUGH WATER AND THROUGH OTHER LIQUIDS

Purpose: To show that water is transparent to light

Concept to be developed: A substance that transmitslight is transparent; a substance that does not transmitlight is opaque.

Materials needed:

WaterVinegarMercury4 test tubesNewspaper

INTRODUCTION: Review with the children thatwater, vinegar, mercury, and air are fluids. lf notheld within definite boundaries, such as in a testtube, they flow. Tell the children that they candiscover a characteristic of fluids in the followingway.

Have children fill ont; test tube with water,another with vinegar, a third with mercury, andleave the fourih containing only air. Place anewspaper in back of each test tube and have

49

EARTH

children read through the test tubes. Can theyread through each? (They can read throughthe water, vinegar, and air.) Why can they notread through the mercury? (Light is not trans-mitted through this fluid.)

From their observations, develop the meaningof the words transparent and opaque. (A sub-stance is transparent if light is transmitted readilythrough it, and opaque, if light cannot be trans-mitted through it.) Explain that it is this abilityof water to transmit light that enables plants tolive under the surface of the water. Light is ableto penetrate the water and give energy to thegrowing plants.

Learnings: (x) Transparency is the ability totransmit light readily. A substance is opaque ifit does not transmit light. (y) Water and air aretransparent fluids, but not all fluids are trans-parent.

Summing Up Ideas: In this section, children havediscovered some of the characteristics of water.They found the density of water and found outhow this density was used in comparison withthe density of other substances to determinespecific gravity. They performed Activities withthe boiling point and the freezing point of water,and they found out how to lower and raise theboiling point and how to lower the freezingpoint. They compared the boiling point andfreezing point of water to these points of otherliquids. They studied the cohesion and adhesionof water to other materials and .compared theseproperties with those of other liquids. Finally,the transparency of water was examined.

HOW DOES THE WATER CYCLE TAKE PLACE?

The water cycle starts in lakes, oceans, or otherbodies of surface water, and is one of the im-portant cycles in nature. Water is heated by thesun, causing the water to evaporate. When waterevaporates, it changes from a liquid to a gas, orvapor. The water vapor passes into the atmos-phere and becomes cooled. The cooled vaporcondenses, or comes together, forming dropsof water. The drops fall on the land as precipita-tion. Precipitation is the falling of water in theform of rain, hail, sleet, or snow. This cycle of

50

The Hydrologic Cycle

Rising air is cooled.

Cooled air condenseswater vapor, whichfalls as rain.

Warm air rises.

Water evaporates. CrfTh,

111111 111 I 4,H1111111111 --.)

evaporation (the changing of a liquid int(i a gas),condensation (the cooling of the gas formingcollected particles of matter), and precipitation(the falling of water particles as rain, hail, sleet,or snow) is called the hydrologic cycle, or watercycle.

ACTIVITY 51 (x)EVAPORATING WATER

Purpose: To investigate the meaning of the wordevaporation

Concept to be developed: Evaporation is the process ofa liquid turning into a vapor.

Materials needed:

WaterChalkboardSponge

INTRODUCTION: This Activity will help the chil-dren to investigate the meaning of the word evap-orate. Wet a sponge with water and have one ofthe children use it to wet the chalkboard in a largecircle. (The exact size of the circle is not important.)

Where is the water that was on the sponge?(Some of the water is on the chalkboard.) Howcan you tell that water is on the chalkboard?(The chalkboard looks wet.) Is the chalkboardwet? Have a child feel it.

Have the children observe what happens tothe water on the chalkboard. (The water dis-appears.) Does all of the water disappear at the

same time? (No, some particles go before theother particles.) Where do the particles go?(Most of them go into the airalthough someprobably go info the chalkboard.) Can you seethe particles in the air? (No.) Then how doyou know that they are in the air? (See Chapter4, which shows how to tell the relative humidity

in the air.) The water particles are called watervapor.

Learning (x) Evaporation is the process by

which a liquid changes into a vapor.

ACTIVITY 52 (x,y)

COMPARING THE EVAPORATION OF WATER AND

OTHER LIQUIDS

Purpose: To see if all liquids evaporate at the samerate

Concept to be developed: Some liquids evaporate morerapidly than others.

Materials needed:

Alcohol (from a drugstore)GlycerineTablespoonCrayons and paper4 saucersWaterMineral oil

INTRODUCTION: Write the names of the liquidLalcohol, glycerine, and mineral oilon the chalk-board and ask children whether they think theseliquids will evaporate just as water does. Suggestthat they try them and see.

Have a child measure one tablespoon of waterand place it in a saucer. Point out the importanceof having the same kind and size of saucers andthe same amount of each liquid in the saucers.Have a child use a crayon and a piece of paperto make the label "water" and place it in frontof the saucer containing water. Repeat the sameprocedure for each of the other liquids and makeappropriate labels. Let the saucers sit for 24hours at room temperature. At the end of thisperiod have the children observe the results.

Water Glycerine Mineral oil


(Only the alcohol and water have disappearedcompletely.) What has happened to these liquids?(They have evaporated into the air.) Are theyliquid when they are in the airthat is, can theparticles be seen and do they roll around, aswater rolls in a glass? (No, they are not liquids.)What are they in the air? (They have taken theform of an invisible vapor.)

What happened to the other two liquids?(A large portion of the glycerine and the mineraloil remained in the saucers.) Why did they notdisappear? (These liquids do not evaporate orturn into a gas as rapidly as alcohol and water.)Suggest to the children that they watch thesetwo liquids to discover how long it takes them toevaporate.

Some children may want to spread alcohol andwater onto the chalkboard (as in Activity 51)to see which evaporates more rapidly. (Thealcohol evaporates more rapidly.)

Learning (x,y) Some liquids turn into a gas,or evaporate, very rapidly; others evaporateslowly.

ACTIVITY 53 (x,y)

SEEING HOW AIR MOTION AFFECTS EVAPORATION

Purpose: To investigate the effect of air motion uponthe rate of evaporation of water

Concept to be deyeloped: When air moves over water,it increases the water's rate oi evaporation.

Materials needed:

Paper hand fanChalkboardWaterSpongeWatea with a second hand

INTRODUCTION: Now that the children haveobserved evaporation taking place, they may be in-terested in investigating some factors that mightchange the rate of evaporation. Some children willprobably mention that things dry faster in the wind.Tell them that they can test this in the following way.

Ask four children to go to the chalkboardand have each child make two chalk circles onthe board, each about as large as a dinner plate.Give each child a folded piece of constnictionpaperabout 8 by 8 inches. Have each child

wet the inside of both of his circles with a wetsponge. Then instruct the group to fan only oneof the circles with the paper fan to see which

51

EARTH

circle loses its water first. When the water disap-pears it is said to evaporate. Which circle of waterevaporates first? (The circle that is fanned.)Why? (Because fanning removes the moistair above the circle, replacing it with dry airinto which the water particles can "escape" moreeasily.) One child might act as a timer to recordthe thne it takes for evaporation to take place.He would begin timing with the first fanning andend when the circle is dry. Why do some circlestake longer to evaporate? (More water waspresent, or less fannft was done.) Where didthe water go? (It went into the air as an invisiblevapor.)

You may want to have another group of chil-dren go to the chalkboard, draw circles, and seewhether they can hasten evaporation by blowingon one of the circles.

Learnings: (x,y) Moving air over water in-creases the rate of evaporation. (x,y) Air overwater becomes moistened, making it more dif-ficult for evaporation to occur. Wind removesthis moist air and replaces it with drier air.

ACTIVITY 54 (x)

SEEING HOW HEAT AFFECTS EVAPORATION

Purpose: To show that heat affects the rate of evapora-tion of water

Concept to be developed: Water evaporates morequickly when its temperature is raised.

Materials needed:

Hot plate or radiator2 beakers or Pyrex dishesStopwatchWaterTablespoon

52

Suggest to the children that there is anotherway to speed up the rate of evaporation of water.Have one of the children place a tablespoonfulof water in a beaker or Pyrex dish and place iton a hot plate or radiator. Have another childplace another dish containing the same amount ofwater on a table away from any source of heat.Have one child use a stopwatch and act as atimekeeper, recording the time the experimentbegan and the time that the water evaporatedfrom each of the dishes. From which dish didthe water evaporate first? (The dish that washeated.) Why? (Increasing the temperature ofthe water particles helps them to "escape." )Where did the water go? (It went into the air asan invisible vapor.)

Learning: (x) Heating water increases the rate ofevaporation.

ACTIVITY 55 (y,z)

DISTILLING WATER

Purpose: To demonstrate the process of distillation

Concept to be developed: Distillation is the process ofboiling a liquid, collecting its vapor, and then chang-ing the vapor back into a liquid by the process ofcondensation.

Materials needed:

250 milliliter (ml) flask1-hole stopperGlass tubingHot plateTest tubeGlassWaterClamp

INTRODUCTION: Review with the children thatthey have had a variety of experiences in whichthey have seen liquids evaporate, that is, change intoan invisible gas or vapor. This next Activity will helpthem discover how this vapor may, under certainconditions, change back into a liquid.

Show the children a carton or bottle labeled"distilled water," and tell them that perhaps theyhave seen such a container before, since someof their mothers may use distilled water in steamirons. Ask them if they know what distilled wateris. Suggest that they can make some in the fol-lowing way.

Pour some water into the 250-milliliter flask.Place a one-hole stopper, in which a glass tubewith two bends (as shown in the illustration)has been inserted, into the flask. Have the chil-

One-hole

stopper

Flask

Water

dren observe what happens when heat is appliedto the water in the flask. (The water boils, andthe liquid water turns into water vapor.) Canyou see this vapor? (No, not in the tube.) Canyou see anything in the glass tube? (Sometimesthe vapor will be cooled enough in the tube toturn back into droplets of water.)

What do the children observe coming out of theend of the tube? ( A white "cloud"some ofthe children may call this cloud "steam." Steam,however, is invisible and cannot be seen.) Whycan you see the white cloud outside the tubebut not inside it? (The vapor is cooled uponleaving the tube, and the little particles cometogether to form a "cloud," which is made upof groups of water particles.)

Direct the vapor into a test tube that is restingin a glass of cold water. Have the children ob-serve what collects on the bottom of. the testtube. Ask them what they think is forming in thebottom of the tube. (Water.) Why is more waterforming now than before the vapor was directed

into the test tube? (The vapor is cooled faster bythe cold water.) The water formed is distilledwater, which is pure water.

Learning: (y,z) Distillation is the process ofboiling a liquid, cooling the vapor, and thenchanging the vapor back into a liquid by theprocess of condensation.

ACTIVITY 56 (x,y)

MAKING WATER VAPOR PRECIPITATE

Purpose: To show why water vapor precipitates as rain

Concept to be developed: When water droplets ac-cumulate enough mass through the condensation oiwater vapor, they fall as raindrops.

Materials needed:

Glass or can of ice waterTeakettleHot plateWater


INTRODUCTION: Discuss with the children whatthey think makes rain. Elicit from them the factthat water falls as rain when moisture condensesinto particles that are denser than the air aroundthem. Explain that the falling of these denser par-ticles of water is called precipitation. Suggest that itis possible for them to make rain (precipitation).

Have them experiment with precipitation byboiling water in a teakettle over a hot plate.What do they see happening? (A cloudlike for-mation occurs as the water vapor coming out ofthe spout of the teakettle is cooled.) How is itcooled? (By coming in contact with the coolerair around it.) What happens to this coolervapor? (It turns into a cloudlike formation.)What happens to the cloud? (It disappears, andothers form from more cooled vapors.) Whatmakes the clopd disappear? (The particles sep-arate and dissipate into the air.)

Have the children place a glass or can full ofice water in front of the spout of the kettle.What happens now? (Water droplets form ontk° glass or can.) What happens to the droplets?(They get bigger until they are so large that theyfall as precipitation.)

Learning: (x,y) When water droplets accumulateenough mass through the condensation of watervapor, they fall as raindrops.

Cool can or beaker

KettleVapor

Hot plate

EARTH

ACTIVITY 57 (x,y)MAKING A SEALED TERRARIUM TO SHOW THEWATER CYCLE

Purpose: To illustrate the mechanism of the watercycle

Concept to be developed: The water cycle functionsthrough the evaporation, condensation, and precipita-tion of water.

Materials needed:

Gallon jars (paste, mustard, or milk) or aquariumsGarden soilSmall plantsCrushed limestoneLiving mossGlass covering

INTRODUCTION: Discuss the water cycle withthe children. During the discussion, bring out thechildren's concepts of evaporation and condensation.Suggest that they can discover the importance ofthese two processes in the water cycle and to plantlife.

Ask several children to bring to school a gallonjar with a large opening. (If gallon jars are un-obtainable, aquariums can be substituted.) Thenplace some crushed limestone rocks on the bottomof the jars. (Limestone helps keep the soil frombecoming too acid.) Have the children place3 inches of soil above the limesone and addsome living moss or small fern or other plantsthey may find in a wooded area or ferns obtainedfrom a florist. They should add enough water sothat the soil is moist, but not so much that thereare puddles of water showing. Finally, theyshould place a piece of glass over the top ofeach terrarium.

After several days, the children may observesome droplets of water clinging to the sides ofthe glass or hanging from the top glass. Wheredid the water come from? (From the mbistenedsoil and plants.) How did the water get up there?(It evaporated, and the vapor was cooled by the

Glass top,,..-.-------------------...\

Plants

54

.----___

Moistened soil

glass to form water droplets.) Must water beadded to the terrariums? (Not much, if any at all,as the moisture stays within the container.)

How does this experiment show the watercycle in nature? (It shows how water evaporatesfrom the ground and plants. The vapor cools andturns to rain.)

Learning: (x,y) A sealed terrarium can representthe water cycle in nature. Water evaporates andturns to vapor. When it is cooled, it condenses,forming particles of water.

Summing Up Ideas: In this section on the watercycle in nature the children had a variety of ex-periences which would help them gain an under-standing of three basic conceptsevaporation,condensation, and precipitation. To show theinterrelationship of these three ideas, childrenmade a terrarium and observed what the watercycle might be like in nature.

HOW IS WATER USED?

Water, in ponds and lakes, in rivers and streams,and in undPrground reservoirs, is vital to man'sexistence. Water is necessary to man for drinking.Water is important as a source of power andis useful as a cleansing agent. Water is alsoessential for all plant and animal life. Manyplants and animals cannot exist out of the water.In the following Activities children can investigatesome of the uses of water and see how water isnecessary to plant and animal life.

ACTIVITY 58 (x)FINDING PLANT LIFE IN SURFACE WATER

Purpose: To show that many forms of plant life canbe found on the surface of bodies of water

Concept to be developed: Some plant life depends uponlarge quantities of water to survive and cannot liveupon dry land.

Materials needed:

Pond waterMagnifying &assMicroscopeMicroscope slidesMedidne dropper

INTRODUCTION: The children might enjoy search-ing for some of the small forms of plant life foundin ponds and lakes. This miniature plant world canbe observed under the microscope.

":e" .

OEDOGONIUM

ULOTHR IX

VAUCHER IA

SPIROGYRA

Have a few children in the class collect somewater containing green scum from a pond, lake,

or stream. If there is no scum available, youwill probably find some on the sides of a fishaquarium that has been standing in the sunlight

for several months.First have the children use a magnifying glass

to examine the green plant life. Then have them

use a microscope to examine the green scum

more closely. What is the composition of thescum? (It is probably composed of tiny strands

or filaments of algae.) What color do they see inthe algae? (Green.) This green color is dzie to

the pigment chlorophyll. Chlorophyll is necessary

in the manufacture of food and the giving off

of oxygen into the water and air during the proc-

ess of photosynthesis.* How is the chlorophyll

distiibuted in the filaments? (In some it is inspiraling bands. In others it may be dotted.)

Children may discover other forms of plantlife, such as duckweed or Valisneria, in a pond

or lake. Some children may want to examinethe structure of these water plants. How arethey adapted to live in water?

Learnings: (x) Many forms of plant life arefound in water. (x) Some plant life is dependent

upon water and is not found on dry land. (x)Much of the plant life in lakes and ponds canbe seen only with the aid of a microscope.

*For a further discussion of photosynthesis, see Living

Things, by James Wailes (Investigating Science with Chil-

dren Series; Darien, Conn., Teachers Publishing Corpora-flan: 1964).


ACTIVITY 59 (x,y)

FINDING ANIMAL LIFE IN WATER

Purpose: To show that some forms of microscopicanimal life live in water

Concept to be developed: Many of the microscopicanimals that live in water serve as food for otherliving things.

Materials needed:

Pond waterMicroscope slideMedicine dropperMicroscope

INTRODUCTION: Discuss with the children thatthey have seen a variety of plants that live in thewater. However, point out that there are also animalsfound in water, but that they are so small that theycan be seen only with a microscope. The children

can discover what these animals look like if theyget some stagnant pond water in a jar. (If no stag-nant pond water is available, the children can createsome if they place a handful of dried grass, leaves,

or straw in a bowl of rain water .that has beenscooped from a puddle in dirt and allow the waterto stand in a warm, light room for about two weeks.)

Have a child use a medicine dropper to remove

a few drops of the water. Place the drops on amicroscope slide and have the children observethe water through a microscope. The children

may see some slipper-shaped, one-celled animals

called paramecia, some bell-shaped animals

called vorticellae, or some funnel-shaped

animals called stentors. There are many moreanimals, too, that may be seen. (Perhaps some

of the children would be interested in fmding

out what they are. You might encourage them

to do research in some of the references cited

in the Bibliography.) Explain to the children that

these aninials are eaten by larger aniMals and thus

eventually serve as food for man's use. Thuseven stagnant water is a "home" for living things.

Learning: (x) There are many forms of animal

life in stagnant water.

PARAMECIUM STENTOR VORTICELLA

55

EARTH

ACTIVITY 60 (x)PURIFYING WATER FOR DRINKING

Purpose: To show how water can be purified to makeit fit for drinking

Concept to be developed: Filtering the water will re-move many of the small plants and animals that maybe living in it.

Materials needed:

Pond waterFilter paperFunnelTest tubeMicroscopeMicroscope slideMedicine dropper

INTRODUCTION: Children are familiar with thefact that water is essential to man for drinking.Point out to them that man must first, however, makeit safe by removing organisms in it. Ask .he chil-dren how they think the water they drink is madesafe.. Where does their drinking water come from?Suggest that they can discover one way that wateris made safe for drinking.

Have the children bring some pond water tothe classroom or make some as was done in thepreceding Activity. Use the medicine dropperand place a few drops of pond water on a slide.Then have the children examine the drops ofwnter under the microscope. Do they see anyplant or animal life in the drop? (Your rhildrenmay see some protozoans or algaesee Ac-tivities 58 and 59.)

Now have a child take a piece of filter paper,fold it in half, then in half again, open it up toform a cone, and then place the cone in a moistfunnel. The end of the funnel should fit into atest tube. Pour some pond water into the filterpaper. What happens to the water? (It passesthrough the filter paper.) The filtered watercomes out and passes into the test tube. What isthe appearance of the water? (It looks clear.)

Have the children examine several drops ofthis water under the microscope. Do they seeany sign of life or any particles? (No.) Why not?Point out that water still might have some livingthings in it that are not visible through theordinary microscope, so water should be boiledor have chemicals added to it (iodine or chlorine)before it is used for drinking.

During *il discussion mention that insteadof using filter paper, cities like Chicago use largebeds of sand through which the water is strained

56

or filtered. Chicago uses filtered water from LakeMichigan and then adds chemicals to the waterto make it fit to drink. Encourage interestedchildren to find out other methods of purifyingwater, as used by other hrge cities. Have themreport their findings to 'lie class.

Learnings: (x) Filtering water helps to purifyit by removing dirt particles and tiny organisms.(x,y) Chemicals are usually added to water tomake it completely safe for drinking by killingany harmful things in it.

ACTIVITY 61 (x,y)MAKING A MODEL WELL

Purpose: To illustrate how a well works

Concept to be developed: A well is a hole sunk in thesoil to reach water. It must be deeper than the water-table level at that location.

Materials needed:

Aquarium, 5-gallon capacitySandWater8-inch glass chimney or drain pipe

INTRODUCTION: Discuss what the class knowsabout wells and well water. Perhaps various childrenmay recall times when they pumped water froma well while on a camping trip, or they may havevisited a farm where cattle drank well water. Somechildren who live in rural areas may get theirdrinking water from a well. After the children haverelated their experiences, they can make a modelof a well in the following way.

Have several children fill an aquarium withcoarse sand to represent soil. Add about onegallon of water to the aquarium. Can they seethe water as they look through the glass? (Yes,there is a water "line.") Explain that this waterlevel represents the ground water table that is

c2741)

Spoon

Glass chimney

Aquariurn

Water

Sand

present undt moist soil. The ground water tableis the level of the hydrosphere at a particularlocation on the Earth.

Push the glass chimney or pipe into the soil,all the way to the bottom. Have one of thechildren remove the sand in the pipe with along-handled spoon. How can he tell when hecomes to the water table? (The sand becomesquite wet and runny.) He should keep removingsand until there is a well of water. Where does-the water rise to in the well? (To about the samelevel as the water table in the aquarium.)How would the water be lifted up farther forman's use if this were an actual well? (Bybuckets or a pump.) Of what materials mightthe walls of the well be made? (Concrete, cement,stones, or metal. )

Have the children add more water to theaquarium. What happens? (The level of thewater table rises. The water in the well alsorises. ) Discuss with the children the effect ofweather on the water table under the groundand wafer in the well. What happens when thereis a long period of dry weather?

Learnings: (y) A well is a hole sunk in the soilto reach water. It must be deeper than the water-table level at its location. (x,y) The level ofthe water table will fluctuate in response toweather conditions. A lot of rain will cause thewater table to rise. (x,y) A lowered water tablemight cause wells to run dry.

ACTIVITY 62 (y,z)

MAKING A MODEL OF AN ARTESIAN WELL

Purpose: To illustrate how an artesian well works

Concept to be developed: Water flows from artesianwells because of the pressure of the water above thesurface of the well.

Materials needed:

Aquarium, 10-gallon capacitySand18-inch rubber tube with a Winch diameter

INTRODUCTION: The children may live in at-Aswhere water for drinking and irrigation comes fromartesian wells. They may be encouraged to discusstheir ideas about the differences between an artesianwell and the kind of well they made in the previousActivity. Suggest that they can make a model of anartesian well and compare the two types.


Water

Sand

(porous)

Tube

Aquarium

Sand(representingshale)

Water

Have the children fill an aquarium with sand;have the sand slope from one end of the aquariumdown to the other. This sand represents sand-stone, a rock through which water passes readily.A child should next place the rubber tube on thesand with the lower end coning straight up,being careful that the bend in the tube will notprevent water from flowing through it. Then heshould cover the tube with a different textureof sand to represent a layer of rock that willnot allow water to flow through it as easily(usually shale) .

Pour a quart of water on the exposed sandarea and into the tube. What happens to thewater at the other end of the tube? (The wateris forced out in a little stream.) Why is the waterforme out? (Because of the pressure exerted bythe water in back of it.)

Point out to the children that in nature thesand represents a porous rock like sandstone,which will allow water to pass through it. Theupright tube represents a pipe that might bedrilled through the shale into the water-carryingsandstone.

What happens if the well end of the tube israised to a height that is higher than the watersource? (The water will not come out of thewell.)

Learningsi (y,z) Water flows -along beds of rock,such as sandstone, that are very permeable towater. (y,z) Water flows from artesian wellsbecause of the pressure of .water above the sur-face of the well.

57

EARTH

ACTIVITY 63 (y,z)

SEEING HOW DEPTH AFFECTS WATER PRESSURE

Purpose: To demonstrate the effect of depth on waterpressure

Concept to be developed: The pressure of water ispartially determined by the height of the water aboveit.Materials needed:

No. 10 tin can or tall fruit juice canWaterNailHammerRulerSmall corks

INTRODUCTION: Have children describe someof their experiences when they felt or saw the forceof water: for example, the force of water comingfrom a garden hose direckd toward the earth; theforcelpressure) of waves as they break on a beach;the force of water coming from a faucet. Explainthat in most people's homes the pressure of watercan be controlled. This Activity can help the childrendiscover what factors affect water pressure andhow it can be controlled.

Explain to the children that one of the factorsinvolving pressure on liquids is depth. The effectof depth on the pressure of a liquid can bestudied as follows.

Have a child use a nail and hammer to makeone hole near the top of the can, one in the mid-dle, and one near the bottom. Plug each holewith a piece of cork. Fill the can with waterand have one of the children pull out the bottomplug. What happens? (The water comes out.)

58

Why? (Water is heavier than air and is pulleddown by gravity.) Measure with a ruler andrecord the horizontal distance from the can tothe point to which the water is forced. Replacethe plug. Have a child fill the can with water tothe same level as before and remove the middlecork. Children should then measure the horizontaldistance this stream of water is forced from thecan and record the measurement. Repeat withthe top cork and stream. What is observed? (Thelower the outlet, the greater the pressure andihe greater the distance the water is pushed.)Why is there greater pressure on the bottom?(The height of the water is greater above thebottom hole than it is above the top hole.) Youmay want the children to make a graph showingthe results based on their measurements. How issuch information meaningful in building a dam?(The dam must be thicker at the bottom to with-stand the greater pressure of water.)

Learning: (y,z) Pressure of water is partiallycontrolled by the height of the water above it.

ACTIVITY 64 (y,z)

MAKING A SIPHON

Purpose: To show how a siphon can be used to movewater from place to place

Concept to be developed: In order for a siphon to beused, the source of the supply of water must be at ahigher level, or altitude, than the outlet of the siphon.

Materials needed:

Aquarium or battery jarPlastic or rubber tubingBasin

INTRODUCTION: Perhaps in the classroom or athome the children may have an aquarium filledwith plant and animal life and wish to empty itscontents to replace it with clean water. Ask thechildren how they might do this. Let them give theirideas and try them. Suggest that one way of doingthis is by using a piece of rubber tubing and makinga siphon. In using rubber tubing to make a siphon,certain conditions are necessary to make it work.The chiklren might speculate about what these con-ditions are. Let them test their ideas.

Have one of the children place a 4-foot lengthof tubing completely into the aquarium full ofwater. What happens to the air in the tubing?(Air is forced out as the water fills the tubing.)Completely fill the tube with water. How doyou know when it is filled? (No more air will

Aquarium

Water

Shorter tube length

1

Longer tubelength

1- Basin

come out as the tube is moved in various positionsin the water.) Have a child press both ends of thetube closed so that no water can escape, andthen lift one end over the side of the aquariuminto the basin, while the other end is held in thebottom of the tank. Have him release both ends,but hold the higher end in the aquarium. Whathappens? (Water from the aquarium pours intothe basin.) Which column of the tube has thegreater depth of water in it? (The column out-side the aquarium.) Which columr. would there-fore have the greater pressure on it? (The longercolumn of water.) Why does the water go up theshorter column? (As the water goes down thelonger column, a lifting effect is produced onthe shorter column.) What causes this liftingeffect? (A partial vacuum resulting from themovement of water in the longer column.)

Have one of the children lift the longercolumn and have the class notice the effect onthe pressure. What is this effect? (Water doesnot come out with as great a force.) Why? (Thedepth of water in the column is not as great.)

Perhaps some of the children may want tomake a series of jars in a siphon arrangement,as shown in the illustration.

Upper siphon

Lower siphon

Lowest jar


Learning: (x,y,z) In a siphon the supply of watermust be higher than the outlet as the water isdirected through a tube from the supply to theoutlet. As the water leaves the longer column,it produces a lifting effect by creating a partialvacuum. This lifting effect brings the water upthe shorter column.

ACTIVITY 65 (x)COMPARING THE ACTION OF SOAP IN HARD ANDSOFT WATER

Purpose: To introduce the term hard water

Concept to be developed: Hard water is the result ofcertain materials being dissolvedin water.

Materials needed:

Epsom saltsWaterTable saltSoap solution2 test tubes or olive bottles

INTRODUCTION: Perhaps some of the childrenhave heard of "hard" water. Discuss the term viththem and ask if they know what it means. Explainthat hard water is the name given to water that hasa large concentration of calcium and magnesiumsalts. These salts react vith the soap and prevent itfrom doing its job. Bow do the children know ifwater is hard or soft?

Bring out in discussion that some communitieshave water that has large amounts of mineral matterdissolved in it. When this is the case, it is quitedifficult to make suds in this water even though alarge quantity of soap is used. Such water is called"hard" water. Other communities have "soft" water.A small quantity of soap in this water will make alarge amount of suds.

The children may be interested in comparingthe effects of hard and soft water. Have somemembers of the class dissolve a teaspoonful ofEpsom salts in a quart of warm water. Canthe Epsom salts be seen? (No, the salts aredissolved.) How can it be proved that the saltsare still there? (Evaporate a tablespoonful ofthe solution in a Pyrex test tube by placing thetube over a hot plate. Note the white powderthat remains.)

Have children fill half of one test tube withthe solution and half of the other test tube withrain water. (Rain water is soft water, because

it is free of dissolved minerals.) Both liquidsshould be at the same temperature. Into eachtest tube a child should empty one-half a medicine

59

EARTH

Rain water Epsom salts Hard water

dropper of soap solution. The soap solution froma soap dispenser can be used, or a solution canbe made by chipping a cracker-size piece of soapinto a pint jar of rain water.

Have a child shake each test tube twenty times,while holding his thumb over the opening. Whathappens in each tube? (There are a few sudsin the test tube with the water containing Epsom

'saltrthe hard water. There are many suds inthe rest tube containing rain watersoft water.)

Learnings: (x,y) Hard water contains much dis-solved mineral matter. (x) Soap suds form withdifficulty in hard water.

ACTIVITY 66 (y,z)

MAKING HARD WATER SOFT

Purpose: To demonstrate how hard water can besoftened

Concept to be developed: Washing soda softens hardwater by reacting with the dissolved salts to precipitatethem.

MateriaIs needed:

BoraxEpsom saltsWaterSoap solutionBeakersWashing sodaCotton clothPetroleum jelly

INTRODUCTION: Discuss with the children theadvantage of having soft water. Children shouldbe able to state that suds are formed in muchgreater quantity in soft water than they are in hardwater. Explain to them that suds act as .emulsifyingagents, which help to remove grease from objectsby breaking up the grease particles and coatingthem with a film of soap. Ask the children if theythink it is possible to change hard water into softwater. List the ideas the children have and testthem. The following Activity will show how hardwater becomes soft.

To a quart of rain water have the childrenadd a teaspoonful of Epsom salts to make the

60

Washing soda Cloudy

tkiNgitgba9,Precipitate

water hard. Have them pour some of this hardwater into a beaker until it is half full and thenadd three medicine droppers of soap solutionto it. Next have them cut a 6-inch square ofcotton cloth. Let them rub petroleum jelly on thecloth and get the cloth dirty by rubbing it onthe floor. See that the dirt is equally distributedand then cut the cloth in half. Have them try towash one piece of the cloth in the beaker of hardwater that contains the soap.

Then have the children pour some hard waterinto a beaker so that it is about half full.Have them make a softening agent by mixingfive teaspoonfuls of washing soda in a glass ofwarm water. After allowing the mixture to settle,let them add the soda mixture to the hard water.What happens? (The mixture turns cloudy.)Allow it to settle overnight. What happens to thecloudy mixture? (It turns clear, and the precip-itate settles. The minerals have precipitated outof the solution.) Next have the children addthree medicine droppers of soap solution. Letthem attempt to wash the other half of the dirtycloth in this solution. Does the cloth get clean?(Much cleaner than when the hard water wasused.) Your class might want to try just rainwater and the soap solution to see how well thiscleans dirty cloths.

Learning: (y,z) Washing soda will soften hardwater by precipitating the minerals out of thesolution.

Summing Up Ideas: In this section the childrenwere introduced to some of the many uses ofwater. They learned of the plant and animal lifethat can be found in the lakes and ponds of thehydrosphere. They learned how the water table,which is the portion of the hydrosphere that isfound beneath the surface of the Earth, can betapped by wells to provide water for man's use.The children were also introduced to the ideaof hard and soft water and how hard water canbe made soft to make it easier to use for washing.



For the kindergarten, primary, and inter-mediate grade children, the kinds of ideaswith the most meaning and application arethese:

Water covers the greatest part of theEarth's surface; about 71% of the surfaceis covered by water.

The drying of foods is accompanied byshrinkage and loss of weight.

Water vapor is present in the air thatpeople exhale; it is this moisture that producesthe clouding of glass.

The density of liquids varies.r The boiling point of a substance is the

temperature at which the liquid state changes

to the gaseous state.When table salt is dissolved in water, the

boiling point is raised.When table salt is dissolved in water, the

freezing point is lowered.Water and air are transparent fluids, but

not all fluids are transparent.Evaporation is the pro:;ess by which a

liquid becomes a vapor.Moving air over the surface of water

increases the rate of evaporation.Heating water increases the rate of evap-

oration.When water droplets accumulate enough

mass through the condensation of water vapor,they fall as raindrops.

Many forms of plant and animal life arefound in water.

Filtering water helps to purify it by re-moving dirt particles and tiny organisms.

Hard water contains dissolved mineralmatter.

In the intermediate and upper grades, thechildren should be led to develop concepts thatare more complex and quantitative:

Some liquids are viscous, that is, theyflow with difficulty.

Heating viscous liquids causes them toflow more easily.

The density of water can be expressed aseither 1 gram per cubic centimeter or 62.4pounds per cubic foot.

The boiling point of water at sea levelis 100°C. or 212°F. The boiling point willvary depending upon the air pressure abovethe water's surfacethe lower the air pres-sure, the lower the boiling point.

The freezing point of water is 0°C. or32° F.

Cohesion is the tendency of similar par-ticles to stick together.

The surface of water acts as an elasticmembrane; this elasticity is called surfacetension.

Adhesion is the attraction that unlikeparticles have for each other; the rise of waterin capillary tubes illustrates adhesion.

A well is a hole sunk in the Earth's crustto reach water. It must be deeper than thewater-table level at the well's location.

Washing soda will softer hard water byprecipitating the dissolved n;nerals out ofsolution.

61'

4

INVESTIGATING THE ATMOSPHERE

What makes a cloud? Why do some winds blow

so fast? What makes it rain? How does a weather-man tell what it is going to be like tomorrow?These are a few of the questions the children mayhave asked about the atmosphere and about theweather. But just what is the atmosphere?

The atmosphere is the outermost sphere of theearth. Without it, life would be impossible. Theatmosphere contains oxygen for us to breathe.Rain and snow form in the atmosphere. Withoutan atmosphere there would be no winds, no fog,no clouds, or smog.

How thick is the atmosphere and what doesit consist of? The atmosphere is really a mixtureof several gases. Nitrogen is the most abundant,composing about 78% of the air. Oxygen isnext with 21% . There are small amounts ofother gases, including carbon dioxide (0.03% ).Water vapor is also present in the atmosphere,but in varying amounts.

It is believed that the very outer limit of ouratmosphere is about 600 miles above the Earth'ssurface. At this distance, however, the air isextremely thin. Most clouds occur at altitudes of

less than 7 miles.The atmosphere is divided into four layers:

the troposphere, the stratosphere, the iono-sphere, and the exosphere. The troposphere ex-tends from the ground up to the height at whichthe temperature stops becoming lower. Thisheight is about ten miles at the equator and thetemperature is about 100°F. At the poles thelow temperature of the troposphere is only50°F., and the height is only about 5 miles.The troposphere is the region of clouds andchanging weather conditions.

The stratosphere extends from the troposphereupward to about 50 miles. Ozone, which is aform of oxygen, is found concentrated in thiszone. Temperatures may rise to 90°F. or higherin this layer; thus, above the atmosphere thetemperature begins to rise. Powerful jet streams

62

of air sometimes reach speeds up to 300 milesper hour in the stratosphere, and the air thereis always clear and free of dust. Jet pilotsoften ride in the stratosphere to be above thestormy weather conditions of the troposphere.

The ionosphere extends from 50 to 300 milesabove the earth. This zone has in it electricallycharged particles of matter called ions. Becauseof the presence of these ions, the lower layer ofthe ionosphere has the ability to bounce radiowaves back to the earth and thus transmit themfor thousands of miles. The temperature in theionosphere rises steadily with increasing altitudeand may get as high as 4,000°F.

The exosphere is that part of our atmospherebeyond the ionosphere and extending out intospace. There is very little air in this zone andthus there is very little air resistance.*

In this chapter the children will carry on Ac-tivities concerned with the characteristics of airand air masses, the weather, the nature of clouds,and the types of precipitation.

WHAT ARE THE CHARACTERISTICS OF AIR?

Air is a material, or a form of matter. A materialis something that occupies space. There are threestates of matter: solids, liquids, and gases. Airis a gas and exerts a pressure, or a push, on ob-jects it comes in contact with. Special instrumentsmeasure the amount of pressure that air exerts.These instruments are called barometers. Air,being a material, offers resistance to other ma-terials that pass through it. Resistance is theopposition of movement that one substance has

toward another substance. Still another propertyof air is that it can be compressed, or squeezedtogether, into a smaller space.

*For a further discussion of the atmosphere, its layers,and its connection with space science and exploration, seeSpace, by Arthur Costa (Investigating Science with Chil-dren Series; Darien, Conn., Teachers Publishing Corpora-tion, 1964).

These characteristics or properties of air willbe illustrated in the following sedtion. Encouragethe children to formulate and test their ownideas. Have them work carefully and critically asthey make discoveries for themselves.

ACTIVITY 67 (x)

DISCOVERING THAT AIR OCCUPIES SPACE

Purpose: To show that air occupies space

Concept to be developed: Since all matter occupiesspace and air is matter, air occupies space.

Materials needed:Wide-mouthed gallon jar or battery jarBalloonWaterReceiving pan

INTRODUCTION: Discuss with the children whatthey think air is. Can they feel it? Does it affect them?How do they know? Suggest that they list their ideason a chart and use it as a reference as they carry outthe Activities given on these pages. Tell the childrenthat the following Activity will help them discoverone charixteristic of air.

Have one of the children fill the gallon jaror battery jar with water. Place this jar in a panthat will receive the overflow. Have anotherchild partially inflate a long balloon. Have himforce the balloon under water so that the entireballoon is under the water surface. Have thechildren observe what happens to the water inthe jar. ( It overflows into the pan.) Why didthe water overflow? (The balloon took up spaceand forced the water out. )

Have the balloon inflated still further andsubmerge the balloon again. What happens thistime? (Even more water overflows.) Why did

Inflatedballoon

Jar fullof water

Pan


more water overflow? ( More air was added to theballoon. ) What does this show about air? (Airtakes up space.)

Learning: (x) Air occupies space.

ACTIVITY 68 (y)

CHANGING THE-VOLUME OF AIR BY CHANGING ITS

TEMPERATURE

Purpose: To show that the volume occupied by a givenamount of air varies with its temperature

Concept to be developed: A given amount of air takesup more space when it is warmed 'and less space whenit is cooled.

Materiais needed:

Glass tube1-hole stopperFlaskThermometerHot and coid waterBeakerDye or blue inkRing stand and clamp (not essential)

INTRODUCTION: Tell the children that they can-discover another characteristic of air. Have one of thechildren set up the equipment as shown in theillustration, using a flask, one-hole stopper, glasstube, and beaker. The water in the beaker shouldbe colored with a dye or with a drop of ink A ringstand and clamp is helpful to support the flask.

Have one of the children pour some hot water

on the inverted flask while the end of the glass

tube is submerged in the beaker of water. Whathappened? (Bubbles came out of the glass tube.)

Flask

--1-hole stopper

Glass tube

1 Beaker:

Colored water

\

63

I

EARTH

What were these bubbles? (Air that was in theflask.) Why did air come out? (It was warmedby the hot water and took up more space.)

Allow the apparatus to stand for several min-utes. Do not pour any more hot water over theflask. Have a child make certain that the endof the tube is still under the water surface. Discuss

the new change that occurs. (Water rises in theglass tube.) Why? (As the air cools in the flask,

it takes up less room. The air pressure on thewater in the beaker, which is now greater than

the air pressure in the flask, forced the water up

the tube.)The children might speculate about what would

happen if they placed some cold water on theflask. Let them try it and see. They might want

to measure the number of inches the water noes

when they use water of different temperatures.

Learning: (y) Air takes up more space when itis heated and less space when it is cooled.

ACTIVITY 69 (x,y)

OBSERVING THAT AIR HAS WEIGHT

Purpose: To show that air has weight

Concept to be developed: One of the properties ofmatter is that its weight can be measured. Since airis matter, its weight can be measured.

Materials needed:

Coat hanger2 balloons2 paper clipsStringThumbtack

INTRODUCTION: Have the children discuss thecharat.eristics that they have discovered about air.Let them check these with the original list. Thefollowing Activity will help children to discover thatair has weight.

Stretch out a metal coat hanger so that it isone piece of straight wire. Have the children make

a balance out of this wire by suspending it with

a piece of string tacked to a doorway or bulletin

board with a thumbtack. Suspend a balloon fromeach end of the wire by means of a paper clip.Have one of the children make certain that theballoons have a designated spot on the wire byfastening a piece of scotch tape to the wire tomark the designated spot. (If either balloon ismoved from its spot, the system will no longer

64

A

String support

Balloon

Inflated balloon

be in balance.) What does this equal balanceshow? (That the weight on each side of thebalance is the same, or equal.)

Now have another one of the children removeone of the balloons and inflate it. He shouldreplace the paper clip so that the balloon willremain inflated and replace the balloon on thesame spot on the hanger. What is the appearanceof the balloon? (It is more fully inflaied.) Whatis now inside the balloon? (More air than therewas before.) What happens to the arm of thewire having the inflated balloon on it? (It islowered.) Why? (With more air in it, the balloonhas gained in weight. )

Learning: (x,y) Air has weight.

ACTIVITY 70 (y,z)

SEEING THAT WARM AIR WEIGHS LESS THAN COLD

AIR

Purpose: To show that warm air weighs less than anequal volume of cold air

Concept to be developed: There is less matter in agiven volume of warm air than there is in an equalvolume of cold air; therefore, the volume of warm airwill weigh less.

Materials needed:

Two balloonsGlass tube1-gallon jar half full of waterBeaker of hot waterPaper clipsCoat hangerThumbtackString

INTRODUCTION: Now that the children haveseen that air has weight, ask them if they think thatequal volumes of air always have the same weight.Remind the children of the Activity they have justfinished. Tell them that there is another Activitythat will enable them to determine if equal volumesof air always have the same weight.

Suspend the coat hanger in the doorway oron the bulletin board as in Activity 69. Thenblow up two balloons to about the same size

(about one-half total capacity). Place these onthe coat-hanger "balance." Do the equal volumesof air have the same weights? (Yes.) How do thechildren know this? ( The balloons balance onthe coat hanger.) Next have the children takethe balloons off the balance (after marking the

Air bubbles


spots where they were placed) and slip a lengthof glass tubing into the opening of one balloon.(Caution the children to be careful that they donot dislodge the paper clip that is holding theair in the balloon.) Have them place the oppositeend of the glass tube into a one-gallon jar thatis half full of water and then pour hot waterover the balloon. What happens? (The balloonbecomes larger.) Why? (The air the balloonexpands when it is warmed by the water.) Havethe children remove the tube and attach bothballoons to the coat-hanger "balance" in theiroriginal positions. Are the weights of the twoballoons still equal? (Yes.) Why? (Althoughone balloon has become larger, the amount of airinside it has not changed. Since both balloonscontain the same amount of air, their weightsare equal.)

Next have the children remove the balloonsfrom the coat hanger, reinsert the glass tube intothe larger balloon, place the tube in the jar ofwater, and pour warm water over the balloononce again. When the balloon has enlarged toabout twice the size of the smaller one, havethem remove the paper clip. What happens? (Airleaves the balloon.) How do the children knowthis? (They can see the bubbles rising from thebottom of the glass tube through the water in thejar.) When the heated balloon has reached theiize of the smaller balloon, have a child replacethe paper clip and attach the two balloons to thecoat-hanger "balance" once again. Is the weightof the two balloons equal? (No.) How do thechildren know this? (The balloons do not bal-

ance.) Which balloon is heavier? (The one inwhich the air was not warmed.) Are the volume:,

of the balloons the same? (Yes, since they arethe same size.) How can the volumes be thesame but the weights different? (Since the air wasseen to leave the heated balloon, the childrenknow that there is less air in this balloon thanin the other, even though the two balloons areof the same volume. Therefore, since air hasweight, and since there is less of it in the balloonthat was heated, this balloon weighs less.)

Learning: (y,z) Warm air Weighs less than anequal volume of cooler air. Equal volumes ofair weigh the same amount only if their tempera-tures are equal.

65

EARTH

ACTIVITY 71 (x,y)

DISCOVERING AIR PRESSURE

Purpose: To show some of the things that air pressurecan do

Concept to be developed: Air pressure can force waterout of a tube or can hold it in under specific conditions.

Materials needed:

Glass of waterGlass tube

INTRODUCTION: Point out to the children thatmany interesting discoveries can be made aboutthe effects of air pressure by using just a glass tubeand eiglass of water.

Give the children some clean glass tubes andlet them discover different things they can dowith the tube and a glass of water. Here are afew possibilities:

Blow bubbles in the water. Air can beforced into the tube and can rise through thewater as bubbles.

Air can be forced part way down the tubeand held at that point if the pressure is maintainedby blocking the passage of air (the top of thetube) with a finger or the tongue, or sustaininghi some other way the pressure that forced theair down.

Water enters the tube and rises to the heightof the water in the beaker if the top of the tubeis left open. Why? (Air pressure lorces water upthe tube.) Perhaps the level of the water in thetube is slightly higher because of adhesion ofwater to the sides of the tube.

Water will remain in the tube if the upperend of the tube is blocked by a fmger and thetube is lifted from the water. The air pressureon the bottom of the tube holds the.water in place.

Beaker of

water

66

Finger overtop of tubu

Water

Water

If the finger is withdrawn, the water flows out.This happens because the air pressure is nowequalized on both ends of the tube, so theweight of the water forces the water out.

Water can be forced to rise in the tube if airis withdrawn from the tube. The pressure of theair pushing down on the surface of the water,being greater than the reduced pressure in thetube, forces water up the tube.

Learning: ( x,y) Air pressure can force water outof a tube or can hold it in the tube when specificconditions are provided.

ACTIVITY 72 (x,y,z)

MAKING A MINERAL OIL BAROMETER

Purpose: To construct a simple barometer

Concept to be developed: Differences in air pressureaffect the position of a liquid in a tube sealed at oneend.

Materials needed:

Flask1-hole stopperMineral oilMedicine dropperS-shaped glass tube

INTRODUCTION: Show the children a barometerand ask them if they can explain how it works. Writethe word barometer on the chalkboard. Encouragetheir ideas. Bring out in the discussion that a bar-ometer is an instrument that measures the pressureof the atmosphere. Suggest that some children mightlike to make their own barometer and compare itsperformance with that of a commercial barometerto verify its accuracy. The following Activity showsa way to make one.

Have some of the children set up the equip-ment as shown in the illustration. Insert a one-hole stopper into a flask or jar. Place an S-shapedtube into the stopper. (The S-shaped tube can be

1-hole stopper

Flask

Marked tube

Mineral oil

easily made by heating a stiaight glass tube in

a propane burner flame and applying pressure

with a tweezer.) Have one of the chiklren dropenough mineral oil into a portion of the tube

so that about It2 inch of oil is "trapped" in thetube. Suggest that they mark off the position of

the oil. Have a child blow into the tube withonly slight pressure. What happens to the oil?

(It moves toward the flask.) Why? (The pres-syre on one side of the oil has become greater

than the pressure on the other.) Then have himwithdraw a little air from the tube. What happens

to the oil now? (It moves toward the child.)

Why? (The pressure on the other side of the oil

is now greater.)Allow the apparatus to remain for several

days. Have the children observe the effect ofchanging air pressure on the position of the oiland keep a record of their observation. Stress the

importance of making careful observations. Doesihe outside pressure increase or decrease during

stormy days? During clear dayi? ( On stormy days

the outside pressure is likely to be less, and thedrop of oil will be nearer the outside end of the


tube. On clear days the outside pressure islikely to be more, and the drop of oil will befarther from the outside end of the tube.)

Children should plan how to record theirobservations. The chart below shows one kindof record they might keep. Help them to sum-marize their findings. Why are there differencesin the position of the oil? What causes thesedifferences? How does the kind of weather con-dition outside affect the position of the oil?

Learnings: (x,y,z) Differences in air pressuieaffect the position of a liquid in a tube that issealed at one end. Sealing the 'tube keeps the airpressure at this end constant. Movement of theliquid demonstrates that the pressure of atmos-phere changes from day to day. (x,y) Stormyweather is usually associated with a lowered

atmospheric pressure.

ACTIVITY 73 (y,z)

MAKING A CARTESIAN DIVER

Purpose: To show that air can be compressed by apply-ing pressure to it and expanded by releasing thatpressure

Concept to be developed: Compressed air exerts agric ter pressure on water than does noncompressed

Materials needed:

Olive bottleWaterMedicine dropperBalloon and string

INTRODUCTION: The following Activity will helpchildren gain further understanding of the charac-teristics of air. They can discover more about thepressure; or force, that air exerts.

Have one of the children remove the rubberbulb of a medicine dropper and fill the dropperwith enough water so that it will just barelyfloat in an olive bottle filled to within 1 inchof the top with Water. (Seal the wide endof the dropper with wax from a meltedcandle. It may also be necessary to weight thelower end of the dropper with the melted wax tomake the dropper remain in a vertical position.)Stretch a heavy balloon over the olive bottk andsecure it with string.

Have the child apply pressure on the balloonwith his finger. What happens to the medicinedropper? (lt fills with more water and sinks to

67

EARTH

Olive bottle

Candle wax

seal

Medicine dropperpartially filled

with water

Candle wax

weighting

the bottom of the jar.) Why does it sink? (It be-came more dense because water was forced intothe dropper.) What forced the water into thedropper? (The increased pressure on the balloonincreased the pressure of the air above the water;thus, the pressure of the air outside the dropperbecame greater than the pressure of the air insidethe dropper and water was forced in.)

Have the child release the pressure on the bal-loon and have him explain the results. (Thedropper rises because the pressure is released.The air in the dropper is able to expand againstthe lowered air pressure in the jar and the wateris forced out of the dropper. This reduces thedropper's density, so the dropper rises.) -

Learnings: (y) Air can be compressed by theincrease of pressure and expanded by the releaseof pressure. (y,z) Compressed air exerts a greaterpressure on water than noncompressed air.

ACTIVITY 74 (y,z)

COMPRESSING AND EXPANDING AIR WITH A PUMP

Purpose: To observe some of the effects of the ex-pansion and compression of air

Concept to be developed: Air becomes warmer as it iscompressed and cooler as it expands.

Materials needed:Bicycle pump or ball pump

1NTiODUCTION: Bicycle and ball pumps arefamiliar objects to most children. Discuss this type ofpump with them. What does it do? They should be

68

able to state that it is used to force air into aspace already, occupied by some air. Have severaldifferent pumps brought into the classroom. Youmay want to have the children examine one and takeit apart. They should notice on preliminary ob-servation that each has a handle attached to a rod.At the end of the rod there is a disk that allows airto move only in the direction of the hose (a "needle"in the case of the ball pump).

Now have the children examine the pump tosee why air can move only in one direction.(Have them examine the movement of the washersurrounding the disk.) Discuss their hypotheses,and test these as the children examine the waythe pump works.

Have them work the pump to compress air.What happens to the air as the disk pushes downupon the air column inside the pump? (The airis compressed and is- forced out of the smallerexit.) What happens to the temperature of the airinside the pump? (The temperature rises.) Howdo you know? (The pump barrel gets warmer.)

What happens to the warmed air as it is forcedout of the smaller end? (As it is released it ex-pands and feels cooler.)

Learning: (y,z) Air becomes warmer as it iscompressed and cooler as it expands.

Summing Up Ideas: The class has performed Ac-tivities to learn about the characteristics of airas a form of matter. They found out that airoccupies space and that the volume of air in-creases and decreases with changes of tempera-ture. They performed Activities involving weigh-ing air as a material substance. They discoveredthat air exerts a pressure and can also flow as acurrent. In addition, they found that air offersresistance and can be compressed.

WHAT ARE THE CHARACTERISTICS OF AIR

MASSES?

A knowledge and understanding of air masses isessential in the study of weather. Air masses arehuge assemblages of air with definite charac-teristics# that can be measured with variousinstruments. Certain air masses are termed con-tinental air masses; these form over land. Mari-time air masses are those that form over water.An arctic air mass farms over arctic regions. Apolar air mass originates in the polar regions anda tropical mass originates near equatorial latitude.

The surface over which air masses rest hascertain characteristics it gives to the air massesover it. These characteristics involve the majordifferences of temperature and water content. Awarm body of water may give the air mass overit the characteristics of warmth and moisture. Adry, warm land area may give the air mass over itthe characteristics of a warm, dry air mass. Airmasses, likewise, could be cold and dry or cold

and moist. As air masses remain over the landor water surface for a longer time, they tend toassume to a greater degree the characteristicsof the surface features.

ACTIVITY 75 (x,y,z)

POSTING DAILY WEATHER MAPS

Purpose: To familiarize the children with weather maps

Concept to be developed: Knowledge of existing weatherConditions is important in weather predictions.

Materials needed:Daily weather map from the newspaper


Have a member of the class collect and posta daily weather map from the newspaper. Havehim point out the changes each day. Some ofthe changes would involve the following:

Movement of highs and lows: these are areaswhere the air masses have high pressures or rela-tively low pressures. They generally move fromwest to east.

Movement of winds: these are generally in-

dicated by arrows showing the dire:fion ofthe wind. What is the movement around a high?(Clockwise.) Around a low? (Counterclockwise.)

Sky condition: a clear circle or area representsa clear sky and a shaded circle or area representsan overcast (cloudy) sky.

Areas of precipitation: shaded areas indicaterain. Dotted areas indicate snow.

Cold and warm fronts: fronts are indicated bya single or double line with the temperature con-dition generally printed behind the front. Arrowsoften indicate the direction the front is moving.

Have several members of the class predict4.

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CI latairsR CI FOG 0 MISSING

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a 11St1110210S

7:00 P.M. E.S.T. 30.0DMECTION OF WIND

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69

EARTH

what the general conditions of weather will betbe next day, based upon a study of several dailymaps. Have them write out and "post" theirpredictions. Check the predictions the next dayto see how many were correct.

Learnings: (x,y,z) Weather maps indicate at-mospheric conditions including temperature,pressure, sky conditions, precipitation, winds,and location and movement of cold and warm airmasses. (x,y,z) Knowledge of weather conditionsis important in weather predictions.

ACTIVITY 76 (y,Z)PRODUCING A MINIATURE COLD AIR MASS

Purpose: To show that a cold air mass flows down-ward and underneath a warm air mass

Concept to be developed: A cold air mass takes thetemperature characteristics from the surface it flowsover.

Materials needed:

Dry iceTableJar of waterThermometerHammer

INTRODUCTION: From their study of weathermaps, children will discover the term air mass. En-courage them to guess how they think warm andcold air masses are formed. Explain that cold airmasses in nature are produced over extremely coldland areas or over ice:covered fields. The areas arecold because the angle of the sun's rays is very lowor because the sun's rays do not strike them forlong periods of time.

In the following Activity the children will pro-

Cold air mass

Movement ofcold air mass

70

Jar

Water anddry ice

duce their own miniature air mass which wid take onthe characteristics of the surface it rests over.

Have the class prepare a cold area by crushinga piece of dry ice with a hammer and placing afew chips in a jar of water. (Caution: Wrap thedry ice in newspaper before breaking it. Its tem-perature is 80°C. and direct contact maycause serious skin injury. You and the chil-dren should use gloves or tongs in handling thedry ice.) The children should observe what hap-pens over a period of time to the air above thejar. (The air is cooled and the moisture condensesinto "clouds." ) Where is the air mass the highest?(Just over the cold jar.) What happens to the airas it cools? (It flows down over the table top andflows off the edge toward the floor.) To Whattool might the edge of the cold front be com-pared? (To a wedge as it flows along under thewarmer air.) Which is denser, warm air or coolair? (Cool air.) How do the children know this?(In Activity 70, the children discovered that avolume of warm air weighed less than an equalvolume of cold air. Since density is weight perunit volume, the cold air must be the denser ofthe two.) Why does the cold air sink beneath thewarm air? (Because it is more dense.)

Have one of the children measure the tempera-ture of the cold air mass. Also have him measurethe temperature of the warmer air mass aboveit. What is the difference in temperature?

Learnings: (y,z) A cold air mass takes its char-acteristics of temperature from the surface itforms over. (y,z) A cold air mass flows down-ward and underneath a warm air mass.

ACTIVITY 77 (y,z)

LEARNING ABOUT COLD FRONTS AND WARM FRONTS

Purpose: To demonstrate that a denser fluid tends tosink downward and act as a wedge to shove a iighterfluid upward

Concept to be developed: Cold fronts are denser thanwarm fronts and tend to move down, prshing thewarmer air up over the top of the colder air.

Materials needed:

Quart bottle (A flat one with a cork is preferable.)Pint of heavy motor oilWater

INTRODUCTION: Point out that the children mayhave seen the word front on the weather maps theystudied. In this Activity, the class will make a sim-

ulated cold and warm front to give meaning to theterm. Explain that a front is the boundary betweentwo different air masses.

Have one of the children fill a .quart bottle halffull of heavy motor oil and half full of water.Which liquid is the denser of the two? (Thewater.) How can the children tell? (The oil risesabove the water. ) Point out that the water rep-resents the heavier and colder air.

Have the child cork the bottle and slowly turnthe bottle on its side. How does the denser fluidmove? (As if it were a wedge shoving up the lessdense fluid.) What is the final position of thedenser fluid? ( Again, it is on the bottom.) Showthe relationship to warm and cold fronts by ask-

Bottle

Oil

Water

ing, If the denser fluid moves toward a less densefluid, would the leading edge of the denser fluidbe at the ground or above the ground? ( At thegroundit acts as a wedge.) If the less densefluid moves towards a denser fluid, would theleading edge of the less dense fluid be at theground or above ground section? (Above theground.)

Learnings: (y,z) A denser fluid tends to sinkdownward and will act as a wedge shoving thelighter fluid upward. (y,z) Cold fronts are denserthan warm fronts and tend to move down,pushing the warm air up over the top of thecolder air.

ACTIVITY 78 (y,z)

MAKING AN AIR-CURRENT BOX

Purpose: To show how air currents move

Concept to be developed: Winds are caused by themovement of air as warm air rises and cool air sinks.

Materials needed:

Small box (wood or cardboard)2 glass chimneysPane of glass to fit open side of box2 candlesMatch


INTRODUCTION: Tell the children that they canalso experiment with movement of gases to lemon-strate the movement of cold and warm air fronts.Obtain a small box similar to a chalk box. Bore twoholes on one of the long sides of the box, one neareach end. The holes should be about 1 inch in diam-eter. Place a glass chimney over each hole. Coverthe front of the box with the pane of glass, asshown in the illustration.

Discuss with the children the comparison be-tween the box and outdoor conditions. The heatfrom the candle represents the heatej (by thesun) land conditions.

Have the children place a snioking candle overthe chimney that is not above the candle in thebox. What happens? (The smoke above the burn-ing candle inside the box goes up; the smokeabove the other chimney goes down into thebox. ) Why does the smoke go into the box? (Asthe burning candle in the box- warms the airaround it, the warm air rises up the nearest chim-ney and a current of air is produced. This cur-rent of air corresponds to a wind.) Why does oneair current go down? (The cool air, which ismore dense, flows down to replace the warm airthat is !lowing up; when air goes up in one area,other air must come down to replace it.) This isa circulation of air called a convection current.W arm air rises and cold air bames down to takeits place, since the cold air is more dense.

The children may like to guess which wouldbe the most effective way -of heating a roomby having a heater on the floor level or a heater

Smoking candle

Glass chimney

1-inch hole

Box withglass front

71

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hung at the level of the ceiling. Why? (It wouldbe best at the floor level, for then the warmedair would rise and the cold air would sink downto the heater to be warmed. This would also re-sult in a better circulation and mixing of the air.)

Perhaps some children would like to try a can-dle having a very short wick giving a small flame,and a candle having a long wick giving a largerflame inside the box. Some children might like totry the experiment without chimneys or with evenlonger chimneys made of cardboard.

Learnings: (y,z) Air currents move because ofvariable densities of air. (y,z) Heated air is lessdense and tends to rise. Cool air is more denseand will sink. (y,z) Winds are caused by con-vection currents.

ACTIVITY 79 (x,y)

DETERMINING WIND DIRECTION

Purpose: To demonstrate the use of a wind vane

Concept to be developed: Winds are named for thedirection from which they are coming.

Materials needed:

Dowel rodDrillNailSupport rodTin canTin snips

INTRODUCTION: Suggest to the children that sincethey have already made a barometer, they may wantto make their own weather station and keep arecord of their observations. Here is another in-.strument they might add to their station, a wind vane.

The children can make the wind vane in thefollowing way. Have them use a tin snips to cuta triangle and tail fin out of a tin can. Have thechildren insert these into a 12-inch dowel rod,which is separated at each end to receive themetal parts. Next, have them drill a small verticalhole at the balance point of the rod the ful-crum. Have the children place the wind vane ona nail protruding from a support rod. The rodshould be high enough to be in the path of un-obstructed winds. The vane should be able toswing freely around the nail.

Have them indicate the compass readings ofnorth, south, east, and west below the wind vaneas shown in the illustration.

72

12-i_nchdowel

Metal tip section

Metal tail section

NailI

Support rod

If the wind comes from the north, it is a northwind; if the wind comes from between the northand east it is a northeast wind and the vane pointsin that direction. The vane points in the directionfrom which the wind is coming, and that is thename given to the wind. The children shouldmake a chart indicating the wind direction at agiven time each day for several weeks. Havethem compare their fmdings with the official winddirection as printed in the local newspaper.

Learnings: (x) A wind vane indicates the direc-tion from which the wind is coming. (x) Windsare named for the direction that the windscome from.

ACTIVITY 80 (x)DETERMINING WIND VELOCITY

Purpose: To introduce the children to the BeaufortScale

Concept to be developed: The velocity of the wind canbe estimated by seeing how it affects certain objects.

Materials needed:

Chart paper

Have the children prepare a chart showing thewind velocity at a certain time each day, Theymay want to use the Beaufort Scale (named afterAdmiral Beaufort, who introduced it into theEnglish navy about 1805) in determining thevelocity of the wind in their school area.

Encourage the children to make their own ob-servations of other land indications. (The degreeto which a flag might wave could indicate thevelocity of the wind.) How does the velocity theyestimate compare with the wind velocity givenin the newspaper for the locality?


MEASURING WIND VELOCITY

Beaufort Scalenumber

Velocity(in m.p.t)

Wind name Land indication

0

1

2

3

4rJ6

7

8

9

10

11

12

less than 1

1-3

4-78-12

13-18

19-24

25-31

32-38

39-46

47-54

55-63

64-75

Above 75

calm

light air

slight breeze

gentle breeze

moderate breeze

fresh breeze

strong breeze

high wind

gale

strong gale

whole gale

storm

hurricane

smoke rises vertically

smoke drifts

leaves rustle

small twigs in motion

small branches in motion

small trees sway

large branches move

whole trees move

twigs break off

loose shingles tear off

some trees uproot

severe damage

widespread destruction

Learnings: (x) The velocity of the wind can beestimated by observing how certain things move.Winds over 60 miles per hour usually result inconsiderable damage to trees and buildings.

ACTIVITY 81 (x,y,z)

STUDYING WIND DIRECTION AROUND PRESSURE

CENTERS

Purpose: To show the direction of wind flow aroundair masses

Concept to be developed: The wind travels clockwisearound high-pressure areas and counterclockwisearound low-pressure areas.

Materials needed:Daily weather maps

Have the class study a collection of severalweeks of daily weather maps. Have them discussthe following questions: How can you tell wherehigh-pressure centers and low-pressure centersare located? (The words high and low are indi-cated on the maps.) In what direction do thesecenters generally move? (Generally from west toeast.) How many days does it take them to move

across the country? (It takes generally about five

to seven.days, although some centers may remainin the country for several weeks.)

In what direction do the win& move in a high-

pressure area? (They move around it in a clock-

wise direction, the direction in which the handsof a clock move.) How do the winds around alow move? (They ?rove in a counterclockwisedirection.) If a high is approaching, what kind ofwinds would probably be approaching? (North-

erly winds.) Would you expect warmer or cooler

weather from that direction? (Cooler.) If a lowis approaching, what kind of winds would prob-ably be approaching? (Southerly winds.) Wouldyou expect warmer or cooler weather from thatdirection? ( Warmer.)

Learnings: (x,y,z) Wind spins are clockwise

around a high and counterclockwise around alow. (x,y,z) Highs and lows usually move from

west to east across the country.

ACTIVITY 82 (x,y)

COMPARING AIR TEMPERATURE AND GROUND

TEMPERATURE

Purpose: To establish that there is a difference be-tween air temperature and ground temperature

Concept to be developed; The Earth heats up first andthen warms the air around it.

Materials needed:

2 thermometersChart paper

INTRODUCTION: Suggest the thermometer asanother instrument the children might add to theirweather station. The Activities that follow will helpthe children to expand their understanding of tem-perature and its relation to movements of air.

Have the children push a thermometer into

the ground. Another thermometer should beplaced so that it is about 5 feet above the ground.Have the class take and record the readings onthe two thermometers at one-hour intervals. The

73

EARTH

day should be a clear day. You might have themgraph the difference between the two readings athourly intervals.

Which thermometer indicates the higher tem-perature? (The ground thermometer.) Why?(The atmosphere is heated mostly by the Earth.The atmosphere absorbs only about one sixthof the radiation from the sun; the Earth's surfaceabsorbs about one half of the radiation. The at-mosphere is heated as the Earth radiates heat.)

Learnings: (x,y) There is a difference betweenground temperature and air temperature. (x,y)The Earth heats up first and then warms the air.

ACTIVITY 83 (x,y)

COMPARING WATER, SOIL, AND AIR TEMPERATURE;

Purpose: To demonstrate that the lithosphere warmsfaster than the hydrosphere, and that both of thesewarm faster than the atmosphere

Concept to be developed: Sunlight warms a water sur-face much more slowly than it does a land surface.

Materials needed:

4 thermometers2 ceramic bowls of identical sizeWaterSoilString

INTRODUCTION: Review with the children thatlight from the sun warms the soil, which in turnwarms the air above it. In the preceding Activity thechildren observed that the soil warms up first. Nowsuggea: that the children compare the heating ofsoil and water with that of air.

74

:MinriPioNevionwonerierMts,rE7r2117.1""fr:

Have the children place some dry soil in oneceramic bowl and some water in the other. Makesure that the soil and water both come up to thesame level in the bowls. Place a thermometerin the dry soil, another in the water, and suspendthe other two in the air just above the soil andthe water. Allow the series to remain in a shadedpart of the room until all the thermometers regis-ter approximately the same temperature.

Then have the children place both of thesetups in the sun. Have them take and recordthe temperatures at one-hour intervals. Theymight like to make a graph of the temperatures,as they did in Activity 82.

Which heats the fastest? ( The soil.) Whichheats most slowly? (The air.) Why is the waterheated more slowly than the soil? (More heat isneeded to warm water than to warm almost anyother substance. Soil is opaque and absorbs sun-light at the surface. Water is partially transparentand absorbs only a small part of the solar radia-tion. Heated water is moved and circulated bywater currents. Water conducts heat downwardmore rapidly than does soil. In addition, heatfrom the sun causes water to evaporate, andevaporation is a cooling process.)

The children may 'want to discuss the effect alarge body of water has upon the air above it.Why is it cooler at the ocean in the summer thanit is inland? (The ocean does not get as hot asthe land and therefore does not heat the air up asmuch.) Why is it warmer at the ocean in thewinter than it is inland? (The water heats upslowly, but it also cools down slowly. The waterremains warmer in the winter than the soil andso tends to keep the air above it warmer also.)

Learning: (x,y) Sunlight warms a water surfacemuch more slowly than a land surface.

Summing Up Ideas: In this section the childrenwere introduced to some of the characteristics ofair masses. They learned how air masses are re-corded on weather maps and what other types ofinformation can be found on these maps. Theyworked with hot and cold air masses, saw howthese caused convection currents (winds) in theatmosphere, and learned about wind directionand velocity They also saw how the temperature

of the atmosphere was affected by the tempera-ture of the lithosphere and by the temperatureof the hydrosphere.

HOW DOES MOISTURE GET INTO THE

ATMOSPHERE?

The children are aware that there is moisture inthe air. In the preceding section they saw how thismoisture was recorded on weather maps when itleft the atmosphere in the form of rain and snow.The Activities in this section will help them an-swer the question: How does moisture get intothe atmosphere?

ACTIVITY 84 (x)

MEASURING WATER LOSS BY EVAPORATION

Purpose: To show that water can escape into the air

Concept to be developed: Any wet object will evaporatewater into the air.

Materials needed:

SpongeWaterSpring balance

Have the children determine and record theweight of a dry sponge by tying a thread aroundit and suspending it on a spring balance. (Theweight of the thread is negligible.) Then havethem soak the sponge in water and allow it todrip until no more drops fall from it. Have themreweigh the sponge and record the weight of thesponge and water. (Some sponges may weigh al-most ten times their original weight when theyare filled with water.)

Have the children allow the sponge to remainsuspended in the air and reweigh it at two-hourintervals. Suggest that they make a graph show-ing the loss of weight. Discuss why there is thisloss of weight. It is the result of the evaporationof the water into the atmosphere. What is theweight of the sponge in 24 hours? (It should bethe same as the original weight.) What does thisshow? (That all the water has evaporated.)

Learnings: (x,y) A sponge may absorb severaltimes its weight in water. (x) The sponge loses

its water through evaporation into the air. (x)Any wet object will evaporate water into the air.


ACTIVITY 85 (x,y)

MEASURING THE WATER LOSS FROM SOIL

Purpose: To show that soils evaporate moisture intothe atmosphere

Concept to be developed: Soils lose water to the airthrough the process of evaporation.

Materials needed:

Flower potSoilBalance scale

Have the children fill a flower pot full of gardensoil. Have them feel the texture of the soil. (Thesoil should feel moist.) What is the color of thesoil? (It should look dark in color.)

Have, them weigh the flower pot full of soiland record the weight. This is most easily doneon a balance.

In 24 hours have them weigh and record theweight again. How does this weight differ fromthe first one recorded? (it is much lighter.) Whyis the soil lighter? (Because of the water loss.)How was the water lost? (Through the liquidwater's being turned into a vaporthe processof evaporation.)

Perhaps the children will think of weighing the

soil daily for a week to note any further loss.They might graph this water loss.

What is the texture of the top soil in the flower

pot after several days of standing? (It lookslighter in color and feels dryer.) Dig unaer thetop layer and make further observations. (Thesoil looks more moist farther down.) Where did

more evaporation occur? (In the upper layers ofthe soil.)

Learnings: (x) Soil loses moisture to the airthrough the process of evaporation. (x,y,z) Mostof the evaporation occurs in the upper layers of

the soil.

ACTIVITY 86 (x,y)

DETECTING THE MOISTURE LOSS FROM PLANTS

Purpose: To show that planfi lose water to the at-mosphere

Concept to be developed: Plants lose water throughtheir leaves; this water enters the air as water vapor.

Materials needed:

Bean plant in potCellophane bagRubber sheeting (from a balloon)Large beaker or jar

75

EARTH

INTRODUCTION: Discuss wtth the children someof the ways that they have observed that moisturegets into the atmosphere. Can they think of any otherways? This Activity will show them another way.

Have the children tie a cellophane bag overone of the leaves of the bean plant. Have themnote the bag at the beginning of the Activityand then again after several hours. (The bagshould have condensed moisture within it.) Youmay want to discuss where the moisture camefrom and why the moisture condensed on thesides of the bag.

Next have one of the children cover the soilarea of the pot by placing a piece of rubbersheeting over the soil and the pot. This might beaccomplished by slitting the sheeting to the centerand then running it close to and around the stemof the plant, and 'overlapping both ends as illus-trated. Cover the plant with a clean, dry glass jaror large beaker and after several hours note whathas happened. (Moisture should have formed onthe side of the glass.) Where does the plant getits water from? (From the soil, by means of itsroots.)

76

Cellophane

bag

Stem

Rubber sheetingcoveri ng soi I

4/ Overlap ofsplit sheeting

Learnings: (x,y) Plants lose water through theirleaves. This water enters the atmosphere in theform of water vapor. (x,y) Plants can influencethe amount of moisture in the air.

ACTIVITY 87 (x,y)

DETECTING MOISTURE PRODUCED IN CERTAINCHEMICAL CHANGES

Purpose: To show still another way moisture entersthe atmosphere

Concept to be developed: Certain chemical changesproduce water as a product of the reaction, and thiswater may enter the atmosphere as water vapor.

Materials needed:

CandleGlassMatch

INTRODUCTION: In this Activity the children willlearn how moisture gets into the air through certainchemical changes. Explain to them that when acandle burns, energy in the form of light and heatis given off and new substances are formed. Whena new substance is formed, a chemical change is saidto have taken place.

Have one of the children light a candle witha match. Discuss with the class the many changesthat they see. What visible energy is now givenoff by the burning of the candle? (Light energy isgiven off.) Why is there a difference in tempera-ture near the candle? (Heat energy is given off.)How does the solid wax of the candle change?(It melts and becomes a liquid.) Where does theliquid wax go? (It goes up the wick throughcapillary attraction.) What happens to the liquidwax? (It turns to a gas.) Blow out the flame andquickly bring a lighted match near the wick.What happens? (The flame ignites the candleagain.) What does this show? (That there is agas that burns in the wick.)

Place a cold glass over the candle. What hap-pens inside the glass? (A film of moisture ap-pears.) Where did it come from? (from theburning wax and possibly from the burningwick.) Why does the moisture go away from theglass after several minutes? (The condensedmoisture evaporates.) Try placing a hot glassover the candle. Is the result the same? (Thevapor does not condense as rapidly.)

Learning: (y,z) When a candle burns, there aremany changes that take place. The productionof water is one.


RELATIVE HUMIDITY IN PERCENTAGES

Dry-bulb

temperature(degrees

Fahrenheit)

Difference between wet-bulb and dry-bulb readings

222426283032343638404244464850525456586062646668707274

1 2 3 4 5 6 7

86 71 .58 44 31 17 487 73 60 47 35 22 1087 75 63 51 39 27 1688 76 65 54 43 32 2189 78 67 56 46 36 2689 79 69 59 49 39 3090 81 71 62 52 43 3491 82 73 64 55 46 3891 83 75 66 58 50 4292 83 75 68 60 52 4592 85 71 69 62 55 4793 85 78 71 63 56 4993 86 79 72 65 58 5293 86 79 73 66 60 5493 87 80 74 67 61 5594 87 81 75 69 63 5794 88 82 76 70 64 5994 88 82 76 71 65 6094 88 83 77 72 66 61

94 89 83 78 73 68 6394 89 84 79 74 69 6495 90 84 79 74 70 6595 90 85 80 75 71 6695 90 85 80 76 71 6795 90 86 81 77 72 6895 91 86 82 77 73 6995 91 86 82 78 74 69

8 9 10 10 12 13 14 15 16 18 20 22 24 26 28 30 32 34 36 38

41016 620 11 225 1629 21 13 A33 25 17 3.4 237 29 22 ;0 740 33 26 ;0 1243 36 30 21 1645 39 32 .0 2047 41. 35 9. 2349 43 38 2751 46 400 2953 48 4211 3255 40 4410 3456 51 4641 3758 53 480 3959 54 500 4160 56 5114 4361 57 531.4 4462 58 54 4664 59 5541 4865.61 57M4965 61 58a50

511i

78 9C91..87 ROW67;'::.6: .66 56 5380 96 91 87 83 79 75 72 68 64 61 57 5482 96 92 88 84 80 76 72. 69 65 61 58 5584 96 92 88 '84 80 76 73 69 66 62 59 5686 96 92 88 84 81 77 73 70 66 63 60 5788 96 92 88 85 81 77 74 70 67 64 61 5790 96 92 89 85 81 78 74 71 68 65 61 5892 96 92 89 85 82 78 75 72 68 65 62 5994 96 93 89 85 82 79 75 72 69 66 63 6096 96 93 89 86 82 79 76 73 69 66 63 61

510 414 8 218 12 7 1

21 16 10 524 19 14 927 22 17 12. 330 25' 20 16 732 27 23 18 10 1

34 30 2621 13 536 32 28 24 16 838 34 30 26 18 11

40 36 32 29 21 1442 38 34 31 23 1644 40 36 33 25 19'45 42 38 34 28 2147 43 39 36 29 2348 44 41 38 31 2549'46 43 39 33 2750 47 44 41 35 2951 48 45 42 36 3052 49 46 43 37 3253 50 47 44 39 3354 51 48 46 40 3555 52 49 47 41 3656 53 50 48 42 3757 54 51 49 43 3858 55 52 50 44 39

Using the Table: Read thedry-bulb and the wet-bulb ther-mometers. Determine the dif-ference between the readings.

In the left-hand column findthe reading of the dry-bulbthermometer. Then read acrossuntil you reach the columnrepresenting the differencesbetween the wet-bulb and dry-bulb readings. The number youfind is the relative humidityexpressed as a percentage.

For example, if your readingon the dry-bulb thermometer is76'F, and on the wet-bulb is65'F, the difference betweenthe readings is 11, and therelative humidity is 55%.

1

47

10 3

12 615 9 3

17 11 519 13 8 321 16 10 523 18 12 7 325 20 14 10 526 21 16 12 7 328 23 18 14 9 5 1

30 25 20 15 11 7 331 26 22 17 13 9 5 1

32 28 23 19 15 11 7 3

33 29 24 20 16 12 9 5 1

35 3( 26 22 18 14 10 7 3

ACTIVITY 88 (y,z)

DETERMINING RELATIVE HUMIDITY

Purpose: To introduce the concept of relative humidity

Concept to be developed: Relative humidity is theamount of moisture in the air compared to the amountof moisture it could hold at that temperature.

Materials needed:

2 thermometersClothWater

INTRODUCTION: Tell the children that now thatthey have studied about how moisture enters theatmosphere, there is a way actually to determine howmuch moisture there is in it. This Activity will showthem one way. It may also suggest another instru-ment they might make and add to their weatherstation.

Explain to the children that relative humidity isthe amount of moisture present in the air comparedwith the maximum amount of moisture that the air at

a particular temperature could hold. In order todetermine the relative humidity, the class must firstdetermine the moisture content of the air. Point outto them that on a dry day much moisture can evap-orate into the air. As they know, evaporation causesa cooling effect, which can be measured using athermometer. On the other hand, .on a humid daymoisture cannot evaporate into the air as quickly.This effect of little evaporation causes little coolingas measured by a thermometer.

Have the children tie one wrapping of clotharound the bulb end of a laboratory thermometerand mark it A. Place another thermometer,marked B, beside A. Have the children observeand record the temperature of each. (Theyshould be the same.) Have them then wet thecloth and fan both thermometers. Have them ob-

serve the readings on both. (The temperature ofA should be lower than that of B.) Why is thetemperature of A lower? (Evaporation causes a

77

EARTH

cooling effect.) Why would there be more of acooling effect on a drier day? (There would be agreater loss of water.) Why would there be lesscooling on a more humid day? (Less moisturecan evaporate into a humid air mass.)

The relative humidity can be determiricd ona chart, such as the one shown here, if the dry-bulb reading is known and the difference be-tween the two readings is known. Some childrenmight like to graph the relative humidity dailyfor several weeks. (The humidity in a class-room should also be compared with the humidityoutside.)

Learnings: (x,y,z) Relative humidity is a factorthat varies daily and can be measured. (y,z)When the air is humid, evaporation takes placewith difficulty and objects tend to remain damp.When air is dry, water evaporates very rapidly.(y,z) Relative humidity is the amount of mois-ture in the air compared with the amount it couldhold at that temperature.

Summing Up Ideas: In this section the childrenwere introduced to some of the ways water vaporenters the atmosphere. They learned of evapora-tion from soils and plants, and of the productionof water vapor in some chemical reactions. Theywere also introduced to the concept of relativehumidity and shown how it could be measured.

WHAT ARE THE CHARACTERISTICS OFDIFFERENT FORMS OF PRECIPITATION?

In this section the class will discover some of thecharacteristics of various forms of precipitation.They will also determine how these forms precip-

78

itate from the atmosphere. When a chemist talksabout precipitation, he generally refers to a sub-stance being separated from a solution. Whena meteorologist or weatherman refers to the term,he is speaking of how a form of water is con-densed and falls to the ground. In order forcondensation to occur there must be sufficientmoisture, a cooling effect, and particles for themoisture to condense on.

A cloud is a mass of condensed water vapor.The condensed vapor may be in the form ofdroplets, ice crystals, or both, depending uponthe temperature. There are three major typesof clouds: cirrus, stratus, and cumulus. The prefixalto means high, and the prefix nimbo or suffixnimbus means stormy. The following chart maybe useful in discussing cloud types.

Height of Clouds Name Symbol

18,000-40,000 ft.

6,000-18,000 ft.

Below 6,000 ft.

cirrus Ci

cirrocumulus Cc

cirrostratus Cx

altocumulus Ac

altostratus As

nimbostratus Ns

stratus St

stratocumulus Sc

cumulus Cu

cumulonimbus Cb

ACTIVITY 89 (y,z)DETERMINING THE DEW POINT

Purpose: To illustrate the meaning of dew point

Concept to be developed: The dew point of the at-mosphere is the temperature at which moisture beginsto condense.

Materials needed:

Shiny metal cupThermometerIceWaterHot plateKettle

INTRODUCTION: Discuss with the children theidea that there is a temperature at which water vaporcondenses. This Activity will help them to discoverwhat this temperature is.

Have a member of the class fill a shiny metalcup (a shiny empty tin can will work satisfac-torily) half full of water and stir the water witha laboratory thermometer. Have him observe andrecord the temperature of the water. Have him

place a few pieces of ice into the water, stir con-stantly, and note when moisture appears on theoutside of the container. A cloudy film of mois-ture will dull the surface. Have the children re-cord the temperature at which tIPP moisture forms.Develop the idea of dew point, bringing out thatit is the temperature at which the moisturecondenses on the tin can. Then :ask: If there werea great deal of moisture in the air, would .1iewater have to be cooled a great deal or just alittle? (Just a little.) Why? (Because the manyparticles of water in the air would condense orcome together more easily because of their num-ber with just a little cooling.)

Suggest that some children can make a chartshowing the dew point of the atmosphere at acertain time each day for a period of several days.The dew point may vary from day to day, de-pending upon the amount of moisture in themosphere at that particular time.

Perhaps some children would like to try asimilar Activity using other liquids. (Suggestalcohol, salt water, or sugar water.) Other chil-dren might try cooling the water with anothercooling agent, like dry ice. (Caution the childrenon the use of dry ice.)

To extend the Activity, a group of the childrenmight compare the dew point of the air in a dryroom and in a humid room.

Select a small room, such as a storeroom,which is relatively free from moisture. Have thechildren determine the dew point as before, byfilling the shiny cup half full of ice and room-temperature water and noting ,the temperature ofthe water when moisture condenses on the out-side of the container.

Next, have the children boil a quart of waterin a kettle placed on a hot plate in the storeroom.This should give a great deal of moisture to thelimited amount of atmosphere in the small room.Repeat the procedure of finding the dew point.(The children should start with room-tempera-ture water to which ice has been added.) Havethe children discuss why the dew point is nowmuch higher in the same room. (The atmosphereis laden with moisture and needs to be cooledrelatively little before the moisture condenses onthe metal can.)

Bring out in your discussion of the dew pointthat dew often forms outside during the night.


Thermometer

Ice and water

Shiny metal cup

Why? (Because the temperature drops belowthat of the dew point and the water condensesinto liquid droplets.)

Learnings: (x,y,z) The dew point of the atmos-phere can be measured by determining the tem-perature at which moisture condenses on a sur-face. (y,z) The dew point is higher in anatmosphere of high moisture content.

ACTIVITY 90 (x,y)

MAKING MODELS OF CLOUD TYPES

Purpose: To familiarize the children with the shapesof some cloud types

Concept to be developed: The names of clouds arebased on each cloud's shape, height, and composition.

Materials needed:

Blue construction paperCottonGlue

Take the class outside for a look at the clouds.They may see several of the cloud types men-tioned on page 78. From their observations ofclouds have them tear cotton into forms repre-senting what they saw and glue these pieces onblue construction paper. Small tufts can representthe cirrus clouds, which are high clouds com-posed of ice crystals. Flat layers can representthe low stratus clouds. Large fluffy masses canrepresent the cumulus clouds. The children mightsee the tall and towering cumulonimbus clouds.

You may wish to write to the United StatesDepartment of Documents, Washington, D.C.,and ask them to send you the Cloud-type Chart.

79

EARTH

This chart gives pictures of cloud types alongwith their symbols.

Suggest that some children might represent theclouds from the chart on blue construction paper.Other children might like to show how cloudschange shape as the clouds get smaller or buildup. Several pieces of cotton would represent thestages in cloud formation. What might causeclouds to build up? (Further condensation ofmoisture particles.) What makes the claudsmove? (Moving air currentswinds.) Whatmakes them get smaller? (They might move intoa drier area and evaporate.)

Learnings: (x) Clouds are formed from con-densation of water vapor. (x,y) Their names arebased upon their shape, height, and composition.(x,y,z) Clouds can change shape because ofchanging atmospheric conditions such as moreor less condensation. (x,y) Clouds move becauseof air currents, or wind.

ACTIVITY 91 (y,z)

OBSERVING HOW CLOUDS ARE FORMED

Purpose: To demonstrate how clouds are formed

Concept to be developed: Clouds are formed by thecondensation of water vapor.

Materials needed:

1/2-gallon milk bottleWaterMatch

Have a child pour a cupful of water into thehalf-gallon milk bottle, shake the water around,and pour it out. This procedure nearly saturatesthe air inside the bottle with moisture. Have himblow hard into the bottle while pressing his lipstightly against it. Point out that air is warmedthrough compression. Then have him release thepressure-, suddenly and have children note thelittle, if any, cloud formation that. occurs. Havethe child repeat the process of adding water,shaking it, and pouring it out. But this time havehim blow smoke, from a smoking match or can-dle held near the neck of the bottle, into the bot-tle. Have him blow into the bottle and then re-lease the pressure suddenly. Have your classnotite the production of a cloud this time.

Ask the following questions: What three thingswere necessary in the cloud formation? (Mois-ture, cooling effect, and particles on which the

80

moisture could condense.) How did the moistureget in the bottle? (From the water placed in thebottle and from the child's breath.) How was acooling effect produced? (By a sudden release ofpressure.) Where did the small particles comefrom? (From the match or candle smoke.)

Why is the Activity more effective if the firstpart (without adding the smoke) is performed?(To show that without the smoke there would belittle cloud formation.) Why might there havebeen some cloud formation without smoke?(The air always contains some dust particlesaround which moisture can condense.) Whymight a cloud have been produced even if water

LI

Milk bottle

.Cloud

had not been poured into the bottle first? Havesomeone try this with a dry bottle. (Some mois-ture is always present in the air; in addition, agreat deal of moisture is present in the breath.)

Learning: (y,z) A cloud is produced when mois-ture is cooled sufficiently and condenses on smallparticles in the atmosphere.

ACTIVITY 92 (x,y,z)

OBSERVING HOW IT RAINS

Purpose: To demonstrate how precipitation takes place

Concept to be developed: Precipitation takes placewhen enough water vapor has condensed around aparticle in the atmosphere to make it dense enoughto fall.

Materials needed:

BeakerWaterIceThermometerHot plateTransparent custard cup

INTRODUCTION: Ask the children how they thinkrain is formed. Suggest that they can discover howto produce precipitation (rain) under controlled set-tings in the classroom. Have them set up the equip-ment as illustrated, with the custard cup on top ofthe beaker of water, which rests on the hot plate.

Have the children take and record the temper-atures of the water in the beaker and the waterin the custard cup before the hot plate is turnedon and before the ice is added to the cup. Whatare their findings? (They should be the sametemperature.)

Have the children turn on the hot plate andadd ice to the custard cup. Have them wait afew minutes, then take and record the tempera-tures again. How do the temperatures differ now?(The water in the beaker is warmer and the waterin the cup is cooler than before.) As the water inthe beaker becomes warmer and the water in thecup becomes cooler, have the children observewhat forms on the bottom of the cup. (Waterdroplets form.) Why do the droplets form? (Thewater evaporates from the beaker and turns tovapor. The vapor is cooled by the cold cup andcondenses upon it.) What happens to the drop-lets? ( When enough form they come together anddrop back into the water.)

Suggest that some children try the experimentagain, but without heating the water. They might


also try it without adding ice to the cup. Doescondensation occur? (It might if there is enoughmoisture in the beaker and if the water in thecup is cool enough.) Why is there not as muchcondensation as there was in the first experiment?(The necessary conditions of enough moistureand cooling are not being met as well.)

Learning: (x,y,z) Condensation occurs whenwater vapor is cooled sufficiently. Precipitationoccurs when enough condensation takes placearound a particular particle to make it denseenough to fall.

ACTIVITY 93 (y,z)

PRODUCING FROST ON A SURFACE

Purpose: To illustrate the formation of frost

Concept to be developed: When water vapor is cooledsufficiently, the vapor crystallizes to form ice.

Materials needed:

Dry iceMetal cupAlcoholWaterTongs

INTRODUCTION: Mention that the children haveprobably seen frost form on the insides of refrigera-tors and freezers or on streets and sidewalks when theweather is cold enough. In thii Activity the childrencan make frost form on the outside surface of ametal container.

Have the children put the dry ice in a clean,shiny metal container, using gloves or tongs.(Caution: Dry ice has a temperature of 80°C.and may cause severe damage if touched di-rectly.) Then have them pour enouth alcoholinto the container to fill it half full.

Have the children notice the frost that formson the side of the cup. Ask where the crystals ofice came from. (From the water vapor in the air.)

Hot plate

Cup

Beaker

Water

81

EARTH

What made the vapor particles crystallize? (Thecooling effect of the dry ice.) Why does frost notform on all surface areas of the cup? (The upperportion is not as cold as the lower portion.) Howcan they find out how long the frost will reniainon the cup? (By allowing the cup of alcohol anddry ice to stand in the same position for a longtime and observing it at regular intervals.) Sug-gest that some of the children try the experimentusing water instead of alcohol with the dry ice.

During your discussion with the class, empha-size how frost forms out-of-doors: what condi-tions are necessary, what harm it can do to crops,and how it is controlled by smudge pots.

Ask the children what they think happens ifthe temperature in the atmosphere becomes socold that the water droplets crystallize (freeze)before they fall to the ground. (The water drop-lets precipitate as crystals, and they are calledsnow. If the temperature is very cold and the crys-tals become very large, then they are called hail. Ifthe temperature is so cold that some of the water

droplets crystallize before they reach the groundbut warm enough so that some of them can stillprecipitate as rain, the mixture is called sleet.)

Learnings: (y,z) When water vapor is cooledsufficiently, it crystallizes to form frost. (x,y,z)Snow, hail, and sleet are forms of precipitationin which the water droplets have crystallized be-fore reaching the surface of the Earth.

Summing Up Ideas: In this section the childrenbecame familiar with the various forms of precip-itation. They should have become aware of whyclouds form, and of the names and shapes of cloudtypes. They were introduced to the idea thatprecipitation is the result of condensation of thewater vapor around particles in the atmosphere,forming water droplets that fall when they be-come too dense. They were also shown that snow,hail, and sleet are forms of precipitation causedby the crystallization of water droplets whilethey were still in the atmosphere.


For the kindergarten, primary, and inter-mediate grade children, the ideas with the mostmeaning and application are the following:

Air occupies space.Air takes up more space when it is heated

and less space when it is cooled.Air has weight.Air pressure can force water out of a Aube

or hold it in the tube when the conditions areright.

A barometer measures air pressure.Winds are named for the direction that

they come from.Winds move clockwise around a high-

pressure area and counterclockwise around alow-pressure area.

The Earth heats up first and then warmsthe air above it.

Any wet object will evaporate water intothe air.

Relative humidity is a factor that variesdaily.

The dew point of the atmosphere can bemeasured by determining the temperature atwhich moisture condenses on a surface.

Clouds are formed by the condensation ofwater vapor.

Clouds move because of air currents, orwind.

Snow, hail, and sleet are forms of pre-

cipitation in which the water droplets havecrystallized (frozen) before reaching the sur-face of the Earth.

In the intermediate and upper grades, thechildren should be led to develop conceptsthat are more complex and quantitative:

Warm air weighs less than equal volumesof cooler air that are at the same pressure.

Equal volumes of air have the sameveightonly when they are at the same temperatureand pressure.

Air can be compressed by increased pres-sure and expanded by the release of pressure.

Air becomes warmer when it is com-pressed and cooler as it expands.

An air mass takes its characteristics oftemperature from the surface over which itforms.

A denser fluid tends to move downwardbeneath a less dense one.

Cold fronts are denser than warm frontsand tend to move downward, pushing the warmair up over the top of the colder air.

Winds are caused by convection currents.Relative humidity is the amount of mois-

ture in the air at a particular moment com-pared to the amount of water the air couldhold at that tempeature.

A cloud is formed when moisture iscooled sufficiently and condenses on smallparticles present in the atmosphere.

82

5

INVESTIGATING THE WAYS THE EARTH

CHANGES

Did the Earth always look the same as it doestoday?

It did not always have mountains and valleys,and the oceans once covered much of the land.

The Earth's surface is constantly changing,because it is constantly being acted upon by vari-ous physical and chemical forces. Most of thechanges are hardly noticed from year to year.However, a few are very noticeable at the timethey take place, such as those changes caused byearthquakes and erupting volcanoes.

The three spheres of the Earth interact withone another to bring about changes. Weather,which originates in the atmosphere, greatly altersthe lithosphere, or rock surface. Likewise, thehydrosphere also alters the rockseach year,pounding oceans and rushing streams weardown more and more land; as the streams slowdown, they deposit this material, forming deltasand other deposits. It is the atmosphere that helpsto form the hydrosphere, and the two spherescontinuously interact with each other, as is evi-denced in the hydrologic, or water, cycle.

But what are some of the changes that occuron the Earth and what are some of the forcescausing them? Maybe the children have askedsome of these questions concerning these changes:What makes mountains and valleys? Why aresome mountains really high and steep whileothers are only small rounded hills? Why dosome places have no mountains at all? Whatmakes earthquakes? Why do volcanoes erupt?What is a glacier? Is there going to be anotherearthquake sometime in the future? What makesthe sand on the beach? Where do fossils comefrom? .

The Earth is being changed by many forces.Gravity may cause rocks to fall down slopes andmud to creep and flow. Rivers continually wearaway the land, making valleys and canyons.Oceans pound upon the shore, breaking the rocks

and changing the shoreline. Winds blow sandand dirt into dunes. Ice and snow carve outmountains and valleys and produce gouges andscratches in the rocks. Earthquakes may causesudden movement in the Earth's crust and erupt-ing volcanoes can even produce mountains over-night And how do we know about all this? Fos-sils have been one of the main clues telling usabout the history of the Earth.

In this chapter, Activities are presented thatwill show how some of these forces can changethe Earth's surface.

WHAT IS EROSION?

Erosion is the wearing away of the Earth's crustby water, wind, or ice. The rocks and soil of thelithosphere are carried from one place to anotherduring erosive processes, eUriching the land inone place while deteriorating it in another. Run-ning water dissolves tiny particles of the materialit flows over, carrying these particles with it overgreat distances and then depositing them in newlocations. The wind blows the soil from one loca-tion to another, carrying it the way the waterdoes, to change the composition of the Earth'scrust at a particular location. And during the iceage large ice sheets tore up the Earth's crust andmoved large volumes of soil and rock.

In the following Activities, the children will beintroduced to erosion and learn some of the waysit affects the Earth.

ACTIVITY 94 (x,y)

CREATING A SMALL LANDSLIDE

Purpose: To show how landslides can be caused

Concept to be developed: Landslides are rapid falls ofdirt and rocks often caused by streams undercuttingtheir banks.

Materials needed:

ShovelGarden hose connected to water outlet

83

EARTH

Hose

INTRODUCTION: Perhaps the children have seenrocks, mud, and debris on a road or highway aftera rain. Discuss with the children how this materialmight have arrived there. Explain to them that gravitypulls objects downward. Perhaps the children knowthat when rocks weather and loosen on the top of aslope, they will tend to tumble down to the bottomof the hill. These sudden movements of large quan-tities of rock down mountainsides .are called land-slides. The movements of mud down steep slopesare called mudflows. These occur after hard rainsin areas where there is little or no vegetation to holdthe soil. A slow movement of soil down a slope, avery common occurrence on most soil-covered hills.is called soil creep.

Have the children build a mound of dirt about1 or 2 feet high. Turn the water on gently andaim the hose at the base of the dirt mound alongone of the edges. As the stream of water under-cuts the mountain of dirt, what happens? (Thedirt begins to slump or slide down.) Why? (Gra-vitational attraction pulls it toward the groundwhen the base has been undercut.)

Explain to the children that the stream of waterfrom the hose could be compared with a streamin nature. As the stream undercuts its bank,material from above "landslides" down into thevalley where the stream is flowing. Suggest thatthe children may want to find evidences of land-slides ox soil creep around them. Mention thattilted telephone poles and fences are resultsof slow soil movements. So are the small terracesor cracks seen on slopes.

Learnings: (x) Gravity can cause changes in theEarth's surface. (x,y) Landslides are rapid fallsof rock and dirt often caused by streams under-cutting banks. (x,y,z) Soil creep is a very slow,imperceptible movement of soil down a slope.

84

ACTIVITY 95 (x,y,z)MAKING AN EROSION TABLE

Purpose: To show how running water causes erosion

Concept to be developed: Rivers carry much debris anddirt with them as they travel downstream.

Materiab needed:

3 foot x 5 foot x 6 inch wood boxHose for water outletPlastic cloth 4 x 6 feetHose for water inletSandy soilWood for support

INTRODUCTION: Mention to the children thatstreams are very important in altering the surface ofthe Earth. Can the children tell why? Perhaps theywill realize that streams help to carve the Earth'ssurface into mountains and valleys, canyons andgorges. Explain that every year tons of debris areremoved from the mountains and highlands anddumped in the lowlands or oceans, forming alluvialfans or deltas. Alluvial fans are fan-shaped depositsof debris formed at the base of mountains; deltas aretriangular deposits formed where rivers enter the

Suggest that a group of the children build an ero-sion table using-a metal sand box or a wood box,as shown in the illustration.

Have them lay the plastic cloth in the box tomake it waterproof. A drain might be made byuse of a metal tube placed in a hole in the woodat the lower end. Pack the sandy soil tightly intothe box. Have the children elevate one end of the

Plastic sheet

Water outlet pipe

Water inlet

Hose

Soil

Elevation

INVESTIGATING THE WAYS THE EARTH CHANGES

erosion table to a height of about 10 inches. Al-low water to flow in through the inlet hose at theelevated end and out the drain. The children canobserve "streams" being formed in the sandy soil.These could be related to the streams beingformed out-of-doors and a map could be used toshow how they drain into lakes or rivers.

Are the streams clear or muddy? (They aremuddy and laden with debris.) Erosion is the re-moval of soil from the surface of the land bymeans of running water. Erosion, then, can beseen taking place on this table.

Where are the soil and debris being deposited?

(At the end of the stream.) Why? (Because thestream slows down and can no longer carry theload.)

What kind of course does the stream take?

(A winding or twisting course.) This curving iscalled meandering and is typical of all streamsand rivers. You might show the children mapsthat illustrate the courses followed by streamsor rivers to demonstrate this typical meanderingcharacteristic.

Suggest that another chance to observe excel-

lent streams-in-miniature would be after a rain-storm. Have the children observe some of the tinyrivulets that develop on open soil and note thetypical meandering, or winding, of the streamsand that they cross in a peculiar interbraiding pat-

tern. This same braided pattern of streams can beobserved on the beaches of oceans or large lakesafter the water has been washed up and is justreturning to the body of water after the breaking

of a wave.Ask the children if they can discover what

happens to the surface of the Earth after thelittle streams have formed. (Little valleys develop

where the streams travel.) Explain that it isstreams that carve out valleys in the Earth's sur-face. Most valleys are the result of streams thatonce traveled through them.

Learnings: (x) Erosion is the removal of soil anddebris from the surface of the land. Erosionusually occurs after a rain, especially when thesoil is exposed. (y,z) Rivers carry much debrisand dirt with them as they travel downstream.They will deposit this debris at the end of theircourse when they slow down and can no longercarry it. (y,z) All streams have a typical me-andering, or winding, pattern. This is caused by

chance altering of the course because of tinyobjects in the way. (y,z) As they flow, streams cutout valleys by cutting downward. They widenthe valley by undercutting the banks. (y,z) Manystreams traveling together usually produce a typ-ical pattern that has a braided appearance. Thisis most often observed when streams are neartheir end, for example, the lower portion of theMississippi River.

ACTIVITY 96 (x,y)

DEMONSTRATING THE EFFECT OF PLANTS UPON

EROSION

Purpose: To show the effect plants have upon erosion

Concept to be developed: Plants have a holding effectupon the soil and help to prevent erosion.

Materials needed:

3 foot x 5 foot x 6 inch wooden boxHose for outletPlastic cloth, 4 x 6 feetHose for water inletSandy soilGrass seedWood for support

INTRODUCTION: If possible, take the children toobserve an area where the soil has eroded becauseof lack of plant cover. Discuss what they see andhave them give their ideas about why the area looksas it does. What might stop the soil from blowingor washing away? Can they demonstrate their ideas?

The children will be able to discover the effectthat plants have upon erosion, or removal of thesoil, in this Activity. Have the children plantgrass seed in a section of the sandy soil in theerosion table set up in the preceding Activity.When the grass has a network of roots, try thesame Activity with the hose and erosion table asbefore. Do the roots have any holding effect onthe soil? (Yes.) Pull up some of the sproutinggrass and have your children change the amountof water coming out of the hose by regulatingthe water valve. Have the force of the waterchanged by regulating the opening of the outlet.What are the effects upon erosion? (The greaterthe force of the water, the greater the erosion.)

Learnings: (x) Plants have a considerable holdingeffect upon the soil and help to prevent erosion.(x,y) The harder the force of the water, thegreater the amount of erosion. Flash floods,therefore, would be more destructive than gentle

rains.

85

<

ACTIVITY 97 (x,y)

MAKING A SPLASH STICK

Purpose: To emphasize themagnitude of erosion

Concept to be developed: Theinfluences the quantity of soil

Materials needed:

Several yardsticksChart paperRubber bandBrick

effect of force upon the

force of the water directlyit can erode.

This is another Activity in which the childrencan observe the effect of water upon soil. Have thechildren paint several yardsticks white (so thatmud splashes will show up plainly) and place thewhite sticks outdoors in various areas. Supporteach stick with a brick and rubber band as shownin the illustration. After a rainstorm, have thechildren observe the height to which mudsplashed on each stick. Make a chart showingthe height to which mud splashed on a stick ina grassy area, a sandy area, a garden area, andother locations you might think of.

Why did the mud splash less in the grassy area?(Grass roots hold the soil in place.) Why wasthere a greater splashing of mud in certain loca-tions? (Wherever the mud was free to move,there was a greater amount of splashing.)

You could try this Activity using a nozzle andhose for your "rain" supply.

Do all rainstorms produce the same effect inthe same location? Have the children repeat theActivity during different rainstorms or by usingdifferent forces of water from the hose.

'ts

( -1t..

\\\ \\\

\

\ )

86

Learning: (x,y,z) Movement of soil is partiallydependent upon the type of soil and the coveringof the soil. It is also partially dependent uponthe strength or the amount of the rainfall.

ACTIVITY 98 (x,y)

COMPRESSING SNOW CRYSTALS TO FORM ICE

Purpose: To illustrate the way glaciers are formed

Concept to be developed: Ice can be formed by thecompacting of snow.

Materiel needed:4 mik cartonsSn.rv or ice shavings

od blockMagnifying glassScissorsRulerBalance scale

Have the children fill the four milk cartons withsnow or very fine ice shavings. Put one cartonaside. Have a child use a block of wood andpress down the snow in the remaining three car-tons until there is half the volume of snow and

Snow Milk cartonPressure

put one of these three aside. Have him continuepressure on the snow in the third and fourthcartons until the third has less volume than thesecond and the fourth has less volume than thethird, as shown in the illustration.

Cut away one side of each carton with scissorsand examine the contents with a magnifyingglass. What differences do you notice in the fourcolumns? (The snow was packed more closelytogether as pressure was increased.) How doesthe one look that had the most pressure placedupon the column of snow? (Its contents lookmore like ice.)

Now develop with the children the followingdefinitions: A glacier is a huge mass of compact


snow and ice that covers the land. There are twomain types of glaciers. One is called a mountainglacier and is found on the higher mountains es-pecially in the north. The second type of glacieris called a continental glacier and covers wholecontinents. At present there are only a few rem-nants of the continental glaciers that oncecovered much of the Northern Hemisphere. Onesuch remnant is the glacier on Greenland.

Learning: (x,y) Compacting snow can cause theformation of ice. The,greater the pressure appliedto the snow, the more compact the ice.

ACTIVITY 99 (x,y)OBSERVING A GLACIAL EFFECT

Purpose: To show how glaciers can cause erosion

Concept to be developed: As glaciers move downslopes, they scratch the surfaces of rocks and gougeaway the land.

Materials needed:

SandAluminum foilWaterRefrigeratorClay or plasterboard

INTRODUCTION: As the children will realize bynow, glaciers have had a considerable effect in erod-ing and wearing away the land. The following Activ-ity will demonstrate the wearing action of a glacier,or block of ice.

Form a 12-inch square of aluminum foil intoa box about 2 inches high. Place fine sand in thebottom of the box, fill it with water, and placethe box in a refrigerator until the water is frozen.Remove the foil and have the children feel thebottom surface of the ice block. How does it feel?(It feels rough.) Have a child rub this block oversome clay or plasterboard. Have the children ob-serve the rubbed surface of the clay closely. Whatdoes the ice block do? (It scratches lines on theclay. The lines are parallel to each other.)

Repeat the Activity, but do not add any sand.Does the ice block without sand scratch the clay?(No.)

Suggest to the children that the ice block withsand could represent a glacier. Glaciers usuallyhave much sand, rock, and debris trapped withinthe ice. As a glacier moves, it scratches rock andwears away soil.

Learnings: (x) Glaciers are huge masses of icethat carry large amounts of sand and debris.(x,y) As glaciers move down slopes, they scratchthe surfaces of rocks and gouge away the land.

ACTIVITY 100 (x,y,z)OBSERVING HOW WIND CHANGES THE APPEARANCEOF THE SOIL

Purpose: To demonstrate how the wind causes soilerosion

Concept to be developed: Wind blows sand into dunesand ridges.

Materials needed:

1 quart of fine, moist sand1 quart of fine, dry sand1 quart of flourFanChart paperYardstick3 pie tins

INTRODUCTION: Review with the children thatthey have seen the effects of water and ice upon theEarth's surface. Wind can have a considerable effectin changing the Earth's surface. Ask the children ifthey have ever felt the effects of strong wind. Whathappens? (Dry sand, dust, and soil can be Slown intosmall ridges and dunes.) The following Activity willdemonstrate to the class how the wind can alter theEarth's surface.

Have the children fill one pie tin with a quartof moist sand, the second with dry sand, and thethird with flour. Then have them place the tins25 feet from the fan, which is directed to blowtoward the tins. Where is the force of wind thegreatest? (Near the fan.) Move each pan towardthe blowing fan until there is the slightest move-ment in the pile of material.

On a chart indicate the three materials and thedistance at which each showed movement as aresult of the "wind." Which moves at the farthestdistance? (The flour.) Which moves at the leastdistance? (The moist sand.) Why? (The sandis heavy and thus requires more force to move it.The flour is very light and thus needs less forceto move it.) The children may notice a pattern inthe way the materials have blown. The lightest isthe farthest away and the heaviest is the closest.Many mixtures of particles are separated in thisway. Explain that this is called sorting, and it is afrequent occurrence in nature.

Suggest that the children try to create smallsand dunes by using the fan and the dry sand.

87

EARTH

Are they able to create any patterns of ridges inthe sand? What causes sand dunes in nature? Ifa sandy area is available, the children might en-joy studying this for any evidence of wind form-

ing dunes or ridges.

Learnings: (x) The degree to which wind canmove objects depends upon the objects and the

force of the wind. (y,Z) The arrangement of

particles by winds, that is, the piling of the lighterparticles together and the heavier particles to-gether, is known as sorting. (x,y,z) Vegetationhas a holding effect upon the sand and soil, andtends to prevent movement. (x) Wind blowssand into dunes and ridges.

Summing Up Ideas: In this section the childrenwere introduced to erosion as a means of chang-ing the surface features of the Earth. Theylearned how erosion can undercut portions of theEarth's crust to cause landslides, how runningwater and moving ice wear away rocks and soil,and how winds blow sand and soil from one place

to another. They also learned of the sand dunesand deltas and the meanderings and mudslidesthat alter the appearance of the Earth's surface.

HOW DO CHEMICAL CHANGES AFFECT THE

EARTH?

In certain areas of the country the rocks of thecrust are largely limestone. These areas frequentlyhave underground caverns and large sunken areas

or depressions called sinks. Both of these featuresresult from the dissolving of the rocks. Perhapsthe children are curious as to how such a process

can occur. The following Activities will help todemonstrate this important process and also toshow how chemical changes alter the atmosphere.

ACTIVITY 101 (x,y)

CHANGING THE APPEARANCE OF LIMESTONE WITH

AN ACID

Purpose: To show how limestone can be dissolved

Concept la be developed: Underground caves areformed when dilute acids dissolve underground lime-stone formations.

Materials needed:

LimestoneDilute acid, such as hydrochloricBeakerBlue litmus paperWater

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Some of the children may be interested in test-ing a liquid to see if it is an acid. An acid will turnblue litmus paper red. Have the children placesome blue litmus paper in water. What happens?(There is no color change because water is notan acid.) Have them dip one end of the litmuspaper into vinegar or some dilute hydrochloricacid. What color does the paper turn? (Red.)

Have the children drop a piece of limestonethe size of a kernel of corn into a beaker of di-lute hydrochloric acid. Have them observe whathappens. (Bubbles come from the limestone,which eventually dissolves in the acid.)

Apply these observations to the study of theEarth's surface. Limestone rock covers much ofthe United States. In these areas it is possible fordilute acids to dissolve parts of the limestone.Underground caves and caverns are examplesof this dissolving of rocks. Have the childrenfind some pictures of limestone caves.

Learnings: (x,y) Dilute acids will dissolve lime-

stone. (x,y) Underground caves are formed bydilute acids dissolving limestone deposits.

ACTIVITY 102 (x,y,z)

CHANGING WATER INTO AN ACID

Purpose: To demonstrate how acids can be formed innature

Concept to be developed: The air we exhale containssomething (carbon dioxide) that turns water into anacid.

Materials needed:

Blue litmus paper2 beakersStrawWater

INTRODUCTION.. This Activity will help the chil-dren gain a better understanding of the source of theacid and the chemical action on the rocks in theformation of underground caves.

Have ti,z; children place similar strips of bluelitmus paper in each of two similar beakers and

put a teaspoonful of .water in each beaker. Useone as a control and set it aside. Have one ofthe children blow through a straw into the waterof the other beaker. He should blow about tendeep long breaths or more. Does the litmus paperchange color? (The paper turns a pink or reddishcolor.) Why? (The exhaled air turned the waterinto an acid.)

Blue litmus

,

CONTROL APPARATUS

.INVESTIGATING THE WAYS THE EARTH CHANGES

TEST APPARATUS

Some of the children might be interested indoing research to find out what it is in the airthey exhale that turns water into an acid. Theywill find that exhaled air is a mixture of severalgases, among them oxygen, nitrogen, water vapor,and carbon dioxide. Only carbon dioxide, of allthe gases present in the atmosphere, can turnwater into an acid. The carbon dioxide combineswith the water to form carbonic acid. It is thisacid that can slowly dissolve limestone rock.

Learnings: (x,y) Something in the air we exhalecan cause water to become an acid. (y,z) Carbondioxide dissolved in water forms a dilute acid,called carbonic acid. Carbonic acid occurs in na-ture and can dissolve limestone.

ACTIVITY 103 (y,z)

OBSERVING HOW LIMESTONE CAN FORM IN WATER

Purpose: To show how chemical reactions can helpbuild up the Earth

Concept to be developed: The addition of carbon dioxideto water that contains dissolved lime may cause theprecipitation of limestone.

Materials needed:

St rawBeaker of waterLi mewater ta b let sFilter paperFunnel

INTRODUCTION: Show the children a piece oflimestone. Have them tell what they think it is madeof. (Limestone is made of the chemical compoundcalcium carbonate. This substance can be formedin water if conditions are favorable.)

Now show the children a limewater tablet anddissolve it in water. Stir until the solution be-comes clear. You may have to pour the waterthrough filter paper to strain out the larger par-ticles. Fold the circular paper into a funnel-shaped cone and put it in a funnel. Pour the lime-water through the cone and collect the clearsolution.

Divide the solution into two equal parts in twodifferent test tubes. One part acts as a control.Have a child blow through a straw into the sec-ond tube. What happens? (The clear solutionturns cloudy.) Why? (The cloudiness is due tothe presence of calcium carbonate, finely dividedlimestone, which is produced by the action of thecarbon dioxide in the child's breath on the limedissolved in the limewater.)

Now relate the children's fmdings to the actionof water on limestone. Explain that water contain-ing considerable lime forms limestone when car-bon dioxide is added. The limestone is insolublein the water and precipitates. Limestone depositscan form in nature under these conditions. Manyof the cave deposits, such as stalactites and stalag-mites, are examples of limestone deposits. Lime-stone rock can also be formed by precipitationof lime from water.

Learning: (y,z) The addition of carbon dioxideto water containing dissolved lime may cause theprecipitation of limestone.

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EARTH

ACTIVITY 104 (y,z)

TESTING AIR FOR CARBON DIOXIDE

Purpose: To show how chemical reactions can affectthe composition of the atmosphere

Concept to be developed: A burning substance will addcarbon dioxide to the atmosphere.

Materials needed:

LimewaterCandleJar with cap

INTRODUCTION: To help the children becomeaware of the presence of carbon dioxide in the air,have them perform the following Activity. Tell thechildren the purpose of this Activity is to test oneof the gases present in the air. The Activity is use-ful in pointing out the value of a control and thevalue of a known test. The test for carbon dioxide isthe white substance (calcium carbonate) produced inthe presence of limewater and the gas carbon di-oxide (see Activity 103).

Have a child place a teaspoonful of limewaterin the jar. Have him cap the jar and shake it.Why is there no change in the appearance of thelimewater? (There was no large amount of car-bon dioxide in the air.) Have another child placean unlit candle into the jar, cap the jar, and letit stand for several minutes. Then have him re-move the candle, recap the jar, and shake it.Does the limewater turn cloudy? (No.) Next,have a third child place a lighted candle in a jarcontaining a teaspoonful of limewater. Have him

cap the jar and let the candle burn until it goes

Cap

Jar

Candle

-- Clear limewater

90

out. Then have him quickly remove the candle,recap the jar, and shake it. What is the appear-ance of the limewater now? (It is milky.) Why?(It contains a large amount of carbon dioxidewhich reacted with the limewater.) In what waydid the two jars differ? (One jar had a burningcandle in it.) What does this show? (Th.... theburning candle introduced carbon dioxide intothe air.)

Learning: (y,z) Carbon dioxide is naturally pres-ent in the air. A burning substance, such as acandle, will add additional carbon dioxide to theatmosphere.

Summing Up Ideas: In this section the childrenlearned of some of the ways chemical changesalter the Earth. They saw how limestone reactedwith acids and learned that this was a way under-ground caves could be formed. They saw how thehydrosphere could absorb carbon dioxide fromthe atmosphere to form a weak acid, carbonicacid. And they saw how the .composition of theatmosphere could be altered by chemical change.

HOW DO EARTHQUAKES CHANGE THE EARTH?

One of the most spectacular changes of the fea-tures of ele Earth is an earthquake. Becausethey can oe observed as they take place and be-cause they often cause much destruction, theseevents receive a large amount of newspaperspace and public attention. In the Activities inthis section the children will be given experiencesthat will help them to develop understanding ofthese violent changes.

ACTIVITY 105 (x,y,z)DEMONSTRATING THE ACTION OF AN EARTHQUAKE

Purpose: To illustrate the cause of earthquakes

Concept to be developed: Earthquakes are produced bya long-continued strain on the Earth's crust, whichfinally gives way and fractures, or snaps.

Materials needed:

Table surfaceDry stick

INTRODUCTION: Some of the children may haveexperienced an earthquake and have asked whatcaused it. Earthquakes are caused by a suddenbreaking of the rocks in the Earth's crust. The fol-lowing Activity will help to demonstrate to yourchildren how and why earthquakes occur.


Place a dry stick upon a table top so that halfof it hangs over the edge. Have one of the chil-dren support the end firmly on the table top. Letanother child press down on the stick gently,

causing it to bend. Have him continue pressingdown. What eventually happens? (The sticksnaps in two.) What happens when the sticksnaps? (The stick vibrates back and forth.) Ex-plain to the children that earthquakes are causedwhen rocks of the Earth's crust are under con-tinued strain. Eventually the rocks snap, relieving

the pressur ben this happens, a certainamount of mk... talent usually occurs. When thereis breakage, considerable vibration of the Earth'scrust occurs. This is transm lied along the surfaceof the Earth and through the underlying rocksby means of earthquake waves.* It is these earth-quake waves that the seismograph (an instrumentused to detect earthquakes) picks up and records.

Point out that the intensity of earthquakesvaries considerably. The effectS are more intensetoward the center of the earthquake. Mention tothe children that a scale has been established toindicate the intensity of earthquakes in numbersfrom 1 to 12. The scale is known as the ModifiedMercalli Scale. The children might be interestedin knowing what the scale is and trying to simu-

late the intensities on model buildings on a tabletop. You may want to put the scale on a chart,which the children can use as a reference as they

make their investigations.Modified MercalF Scale

L Rarely felt by anyone.2. Felt by a few persons at rest on upper floors.

Delicately suspended objects may swing.

3. Vibrations like those caused by a passingtruck.

4. Sensation like that of a heavy truck strik-ing the building. Dishes and windows may be

disturbed.5. Some dishes and windows broken. Some

cracked plaster; unstable objects overturned.

6. Ikavy furniture moved. Many peoplefrightened. Fallen plaster and damaged chimneys.

7. Well-constructed buildings slightly dam-aged. Chimneys broken and poorly constructedbuildings damaged.* For a fuller discussion of waves and how they travel seeEnergy in Waves, by Louis Cox (Investigating Science

with Children Series; Darien, Conn., Teachers PublishingCorporation, 1964).

8. Falling factory stacks, chimneys, and col-umns. Panel walls thrown out.

9. Damage considerable even in well-con-structed buildings. Ground cracked. Pipes broken.

10. Landslides in riverbanks and watersloshed over the banks. Ground badly cracked.Foundations and frame structures destroyed.

11. No structures remain standing. Under-ground pipelines completely out of service.

Bridges destroyed.12. Objects thrown into the air. Total damage.

Learnings: (x,y,z) Earthquakes are produced bylong-continued strain on the rocks of the Earth'scrust, which finally give 'way and fracture, orsnap. Accompanying ihis breakage is consider-able vibration, which can be measured by seismo-graphs. (y,z) The intensity of the earthquakevaries with the closeneSs to the 'disturbance andthe original intensity of the earthquake. Areasthat are farthest away will suffer the least amountof damage. (x,y,z) Earthquakes are usually ac-companied by dislocations in the Earth's crust.(x,y,z) Earthquake waves travel along the sur-face of the Earth and under the surface.

ACTIVITY 106 (z)

MAKING SEISMOGRAPH MODELS TO RECORD

"EARTHQUAKE" WAVES

Purpose: To show how a seismograph can be used todetect earthquake waves

Concept to be developed: Earthquake waves can be

detected by a seismograph.

Materials needed:

For the horizontal recording seismograph(dimensions are approximate)Base board, 1 x 12 x 24 inchesBrick supports:

2 sides, 1 x 2 x 24 inches1 top, 1 x 2 x 12 inches1 top diagonal, 1 x 2 x 18 inches2 side braces, 1 x 2 x 18 inches

Pivot block, 2 x 4 x 6 inchesRound oatmeal box or fruit juice canBrickSoda strawStraight pinl/2.-inch pencil leadLump of plastic clayCement (Pliobond or Duco)StringCoat hangerUstaples (16)11/2 - or 2-inch thin nails (24)TapeSawHammerWire-cutting pliers

91

EARTH

For the vertical recording seismographSame as above except add rubby bands or springs

to support brick. Brick-support sides can be lessthan 24 inches. Experiment to see how far therubber bands or springs stretch. Diagonal on topof brick support can be omitted if support ismade lower.

INTRODUCTION: Sometimes great forces build

up in the Earth's crust because of erosion thatlightens one section and is accompanied by deposition

of millions of tons of sediment on another section.

When the forces become great enough, the crust may

break suddenly along its weakest line and the sec-

tions on either side of the break quickly slip to nett;

positions, relieving the forces. Earthquake waves areproduced at the break and move outward through

the Earth, as the solid crust "twangs" after thebreak. Earthquake waves, including the artificial

ones made by explosives, are recorded by seismo-

graphs. Geologists use these records to learn moreabout the interior of the Earth.

Help a small group of children Obtain materials

and construct models of two kinds of seismo-

graphs as shown in the illustrations. The models

will recOrd transverse and longitudinal waves of

"tablequakes" the children can produce.

In the horizontal recording seismograph model

the brick suspended by the long strings tends to

remain stationary when the Earth (table) shakes

in the north-south direction marked on the base.

The base shakes with the Earth, so the stylus

U staplesand stringto supportbrick

Straight-pin pivot

Soda straw

Sharp pencil-lead styluscemented to soda straw.

Oatmeal box orfruit juicecan (whitepaper tapedto drum)

92

Pull stringslowly tomake drumturn

Brick(free toswing)

1 Baseboard

Plastic clayconnectingbrick and\ soda straw

Wood block

j staples

Coat-hangerwire axleand supports

Plastic clayconnecting brickand soda straw

Oatmepl box orfruit juice can(white papertaped todrum)

Sharppencil-leadstyluscemented tosoda straw

U staples

Pull stringslowly to makedrum turn

U staples andsprings or rubberbands tosupport brick

Straight-pinpivot

Wood blockSoda straw

Coat-hanger wireaxle and stand

draws a shaky line on the turning drum. At leasttwo seismographs are needed to record quakesfrom all directions, one set north-south and One

set east-west.To record a "tablequake," help the children

adjust the soda straw on the pivot pin and in theclay so the stylus presses firmly on the drum.Have one child begin to pull the string wrappedaround the drum so it turns very slowly. Thenhave another child jar the table gently in thenorth or south direction marked on the base.Children can see the "quake" recording made bythe stylus on the drum. In the vertical recordingseismograph model, the brick is suspended bysprings or rubber bands and tends to remain sta-tionary when the Earth (table) shakes up anddown. The base shakes with the Earth so thestylus draws a shaky line on the turning drum.

To record a "tablequake," again help the chil-dren adjust the stylus so it presses against thedrum and place the end of a yardstick under thetable leg. Have one child pull the string slowly toturn the drum. Then remove the yardstick so thatthe table leg drops to the floor and a vertical shockis recorded on the drum.

Learnings: (x) Earthquakes cause waves totravel through the rocks of the Earth. (x) Earth-quake waves can be recorded on a seismograph.

Summing Up Ideas: In this section the childrenlearned how earthquakes affect the surface Lea-


tures of the Earth. An earthquake is caused bythe shifting of the Earth's surface under stress.When the surface shifts, earthquake waves areproduced that travel through the lithosphere and

can be recorded on seismographs.

WHAT CAN FOSSILS TELL US ABOUT THE EARTH

AND CHANGE?

What are fossils? Fossils are evidences of prehis-

toric plants or animals preserved in the rocks.The fossil might be an evidence of life, such as aburrow, or hole, of a marine worm. The fossilmight be part of the original preserved shell oranimal, such as some of the mammal remainspreserved in ice for millions of years in Siberia.The fossil might be an impression of a plant oranimal, such as a fern or shell imprint.

What does a fossil tell us? Fossils tell us of the

kinds of plants and animals that lived millions ofyears ago. Fossils also tell us about the conditions

at the thne the rocks were formed. Many rocksthat contain fossils of fish or other marine or-ganisms must have been deposited and formedunder water, even if they are no longer near anybody of water. Why are the rocks no longer un-der water? Changes have occurred in the Earth'scrust. Certain areas that were once covered withseas may have been uplifted high above the ocean.

Again, fossils of tropical plants and animalshave been found at the South Pole, which is nowcompletely covered with ice and snow. What hashappened? We know that millions of years agothe climate of the South Pole must have beendifferent from what it is now. The climate atthat time must have closely resembled the climate

of South Africa or Australia. The Earth, then,has not always been the same as it is today.

The following Activities with fossils will help

your children gain some understanding of howfossils are formed and what they indicate.

ACTIVITY 107 (x)

MAKING A "FOSSIL"

Purpose: To introduce the topic of fossils

Concept to be develord: Fossil impressions are madeby plant or animal remains being pressed upon softsediments that later harden.

Materials needed:

ClayFern or animal shell

Have the children mold a small block of clayinto a rectangular shape about one-half inchthick and slightly larger than the object you wish

to fossilize. Be sure that the surface is withoutbumps or impressions. Next, have the childrenpress the object they wish to make the "fossil"

with on the smooth surface of the clay, as shown

in the illustration. Have them press the objectdown firmly until it makes an impression on theclay. Now allow the clay to harden by baking itin the sun. What is the result? (A preserved im-print in the baked clay of the plant or animal.)What was necessary to make the fossil? (The fol-lowing things were needed: a soft sediment, theclay; a hard part of a plant or animal, a shell orleaf for example; and the sediment had to beturned into rock by t:z)me means without toomuch heat or pressure that might disturb thefossil imprint.)

These are the conditions that are also neces-

sary for the formation of fossils in nature. We do

not have many fossil remains of animals that didnot have hard parts Juch as skeletons or shells.Let the children speculate on the possibility ofgetting a fossil of a jellyfish. Likewise, fossils are

found only in sedimentary rocks, since metamor-phic and igneous rocks are formed under ex-tremes of temperature and pressure that couldnot preserve the fossil imprint.

Learnings: (x) Fossil impressions are made byplant or animal remains being pressed upon softsediments that later harden. (x) Hard parts ofthe plant or animal are necessary for preserva-

tion.93

EARTH

ACTIVITY 108 (x,y)

MAKING A CAST FROM A FOSSIL IMPRINT

Purpose: To show how to make a cast of a fossil im-print

Concept to be developed: The cast of a fossil imprinthas the same shape as the plant or animal remainsthat made the imprint.

Materials needed:

Fossil imprintWater-base clayTempera colorTalcum powderFine brush

INTRODUCTION: Perhaps some child has a fossilimprint, or perhaps you could obtain one from a localmuseum. The imprint is just the opposite shape ofthe living thing that made it up. A cast is the shapeof the original plant or animal.

To make a cast, have one of the children dustthe imprint with talcum powder using a finebrush. The powder makes the clay easy to re-move from the fossil. Then have the child gentlybut firmly press the clay into the imprint Havehim pull the clay from the imprint and trim offany excess clay. After the clay has air-dried, havethe children paint the cast or the border withtempera color for contrast.

Clay cast

Imprint

Clay cast

What do the children notice about the shapeof the cast as compared to the shape of the im-print? (The cast is reversed, like a mirror image.)The cast is the same shape as the original livingpart. The imprint was the negative impressionfrom the living part.

Learning: (x,y) The cast of a fossil imprint hasthe same shape as the plant or animal remainsthat made the imprint.

Summing Up Ideas: In this section the childrenwere introduced to the existence of fossils. Fossilsare the imprints made by animal or plant remainsin rocks. They are used by geolowists to deter-mine the changes that have occurred since theEarth was first formed.


For the kindergarten, primary, and inter-mediate grade children, the kinds of ideaswith the most meaning and application arethe following:

Gravity can cause changes in the ap-pearance of the Earth's surface.

Erosion refers to the movement of soiland debris from one place to another.

Plants have a considerable holding effecton the soil and help to prevent erosion.

The movement of soil is partially depen-dent upon the type of the soil and the coveringof the soil. It is also partially dependent uponthe strength or amount of rainfall.

Compacting snow can cause the formationof ice; this is how glaciers are formed.

Glaciers are huge masses of ice thatcarry large amounts of sand and debris.

Wind blows sand into dunes and ridges.The degree to which the wind can move

objects depends upon the kinds of objectsmoved and the force of the wind.

Underground caves are formed by diluteacids dissolving limestone deposits.

Earthquakes are produced by long-con-tinued strain on the rocks of the Earth'scrust.

Earthquake waves travel through thelithosphere and can be recorded on seis-mographs.

Fossil impressions are made by plant andanimal remains being pressed upon softsediments that later harden.

The study of fossils is very important indetermining the ways the Earth has changedsince it was formed.

In the intermediate and upper grades, thechildren should be led to develop concepts thatare more complex, such as the following:

Rivers carry much debris and dirt withthem as they travel downstream. They depositthis debris at the end of the course when theyslow down and can no longer support it.

Streams cut out valleys as they flow bycutting downward.

The arrangement of particles by winds,that is, the piling of the lighter particlestogether and the heavier particles together,is called sorting.

Carbon dioxide dissolves in water to formcarbonic acid.

Burning a substance, such as a candle,will add carbon dioxide to the atmosphere.

94

BIBLIOGRAPHY

American Geological Institute. Geology and Earth Sciences Sourcebook for

Elementary and Secondary School. New York: Holt, Rinehart, andWmston, Inc., 1962. An excellent sourcebook in geologyx with a largebibliography, list of filmstrip, and reference materials.

The Earth. Life Nature Library. New York: Time, Inc., 1962.

Emmons, William H., et al. Geology. 5th ed. New York: McGraw Hill

Book Co., Inc., 1960. A well-written, easy-to-read, and very complete

college text.

Fenton, Carroll. Our Amazing Earth. New York: Doubleday & Company,

Inc., 1945.

Namowitz, Samuel N., and Stone, Donald B. Earth Science: The World

We Live In. 2nd ed. Princeton, N. J.: Van Nostrand Company, Inc.,

1960.

Shinier, John A. This Sculptured Earth: The Landscape of America. New

York: Columbia University Press, 1959. An excellent book of geology

for the layman.

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