Substances

Sangari Active Science, 2nd Edition

Student Lab Manual

Published by Sangari Active Science, 44 Amogerone Crossway #7862, Greenwich, CT 06830.

ISBN: 978-1-940901-44-2

Need help? Email us at support@sangariglobaled.com

For more information on our products and services, please visit us online at

http://www.sangariglobaled.com

The publisher of this book has used its best efforts in preparing this book.

The publisher makes no warranty of any kind, expressed or implied, with regard to the programs or documentation

contained in this book. The publisher shall not be liable in any event for incidental or consequential damages

in connection with, or arising out of, the furnishing, performance, or use of these programs.

Copyright © 2014 Sangari Active Science. All rights reserved. Printed in the United States of America.

SubstancesWork designed and produced by Sangari Research and Development Center

Substances

Dear Student,

You are about to learn using a science called chemistry. Chemists study substances. They study how substances behave and how they interact with each other. Different substances can behave in similar ways but have one characteristic that makes them very different. Or, two substances can have many different characteristics. The same substance can behave differently under different conditions. Why is this important? New materials are made by chemists who have fi gured out the properties and behaviors of substances. In this unit, you will investigate substances and mixtures, as well as their properties. You will learn more about what matters when making new materials.

Ask questions and try to discover answers as a chemist does!

The Sangari Active Science Team

OIL

Table of Contents11 Lesson 1

What Are Substances and Mixtures?

19 Lesson 2

What Can Water Dissolve?

27 Lesson 3

Why Do Some Mixtures Separate?

33 Lesson 4

How Are Diamonds, Charcoal, and Graphite Alike?

41 Lesson 5

Where Does Coal Come From?

47 Lesson 6

Is Air a Substance or a Mixture?

55 Lesson 7

What Is Important about Metals?

63 Lesson 8

How Can People Protect Earth’s Natural Resources?

70 Glossary

SafetySangari Active Science

Safety is important. During science activities, make sure to pay attention to the following safety symbols in your Student Lab Manual.

Follow these safety tips:1. Follow your teacher’s instructions.

2. Do not touch your face, eyes, nose, or mouth during investigations.

3. Do not mix things together to see what will happen.

4. Tie back long hair, and roll up sleeves before doing investigations.

5. Move everything out of the way that you do not need for science.

6. Tell your teacher right away if you have any accidents or spill anything.

CU

clean upDT

don’ttaste

SO

sharpobject

ES

energy source

WH

wash hands

PM

poisonous material

GO

weargoggles

10

LESSON 1

What Are Substances

and Mixtures?

How is it possible to know if a material is a substance or a mixture?

What are the names of some substances?

11

Lab ActivitySeparating Mixtures

How many ways can you think of to separate a mixture of objects? You are going to look at how you can use three different tools to separate seven types of materials.

Look at the objects in the bag.

● How many do you see?

● How might you separate these items into different categories?

Look at the tools you have to use. Line up the seven cups and place the objects in them as you separate the items by category. Determine with your team how you will use the tools and organize the items. Record your ideas in your Science Notebook.

12 Substances

1

Divide the tasks up evenly within your team. Listen to everyone’s ideas for sorting the materials and then decide on a plan.

Use note cards to label your groups of objects when you are finished separating them. Did you follow the plan you recorded in your Science Notebook? If you changed your ideas, make new notes in your Science Notebook.

Look at how other teams separated the objects.

● Were all objects separated?

● What differences do you see in the ways they were separated?

● What was the most effi cient method for separation?

What is the difference between a substance and a mixture? Discuss with your teammates. Record your ideas in your Science Notebook.

13Lesson 1 What Are Substances and Mixtures? 13

Learn MoreHow Do You Get Some of the Substances You Use?

Mixtures are made up of two or more substances. To get a substance out of a mixture, chemists use a process to separate the components of a mixture. A glass of water with sugar dissolved in it is one example. Two processes that can separate the sugar from the water are

crystallization and distillation.

Crystallization separates a solid from the liquid it is dissolved in. The substances can also be separated by evaporation or by boiling. These processes allow the water to leave the mixture, leaving the solid behind. Salt

Distillation uses the liquid’s melting point to separate it from a dissolved solid or from another liquid substance.

14 Substances

can be obtained by allowing ocean water to evaporate, leaving salt crystals behind.

Distillation also separates mixtures. Distillation can separate a solid from a liquid, or it can separate liquids that have different boiling points. First, the

mixture is heated until it reaches the boiling point of one of the substances. Some substances form more than one layer in a mixture. Other processes used to separate mixtures have names like fi ltering, decantation, magnetic separation, and fl otation.

Filtering, for example, is pouring a mixture through a material that holds the solids and lets the liquids pass through. Magnetic separation uses a magnet. The magnet attracts some types of metal, separating them from the other substances in the mixture.

1

15Lesson 1 What Are Substances and Mixtures? 15

Learn Even MoreA sieve can be used to separate solid particles of different sizes. The smaller solids pass through the sieve, but the larger solids do not.

Decantation involves pouring off part of a mixture, and leaving the other behind. A separating funnel is one way to do this. This funnel has a valve at the bottom. When it is opened, the densest liquid fl ows out. For a mixture of a

liquid and a solid, the solid, which is usually denser, can be left alone to settle at the bottom of a container. Then the liquid can be removed by pouring it off. This is another way to use decantation.

Flotation can also separate solid substances of different densities. A liquid is added to the mixture. The denser solid sinks and the less dense solid fl oats.

These processes are used to obtain products that you use every day. Sugar is one example. Sugar comes from sugarcane. The sugarcane stalks are squeezed. Squeezing produces juice. The juice goes through several crystallization stages and produces brown sugar. The brown sugar goes through a process to produce refi ned white sugar.

Sieve Process

16 Substances

Some wires contain copper, a natural mineral. Copper goes through several chemical reactions and other processes to become purifi ed copper, which gives it a characteristic brownish color.

Gold also occurs naturally in the ground. Water can be used to separate gold from the sand and rock found with it. The water washes away the less dense sand, so the denser gold stays behind.

This image shows part of the crystallization process.

1

17Lesson 1 What Are Substances and Mixtures? 17

18

LESSON 2

What Can Water

Dissolve?

How is water used?

What makes water so important?

19

Lab ActivityIs It Soluble?

What happens when a substance dissolves in water? Where does it go? Think of some examples of substances that can be dissolved in water. What are some substances that cannot be dissolved in water? Talk with your team about your ideas.

You are going to test four substances to check whether they are soluble in water.

A. Examine the four substances and, from their appearances, predict which ones will dissolve in water. Record your predictions in your Science Notebook.

B. Add the substance in Cup 1 to a cup of water. Use a straw to stir the substance. Watch what happens.

C. Repeat the process with the other three substances and the other three cups. Observe the results.

Can any substance dissolve in water?

20 Substances

2

Record results in your Science Notebook. Discuss these questions with your teammates:

● What did you do in this experiment?

● What happened to each one of the mixtures?

● What differences did you notice in each of the cups?

● What do you think might cause these differences?

CAUTION!Do not touch or taste the substances. If some substance falls on your hands, immediately wash your hands. Be careful and do not touch your eyes.

21Lesson 2 What Can Water Dissolve?

Learn MoreWater: A Precious Liquid

All living organisms—plants and animals—need water. Water makes up most of an organism’s weight. In humans, at least half of a person’s weight is water.

About 60% of a man’s weight consists of water.

About 70% of a baby’s weight is water.

About 50% of a woman’s weight is water.

Water in the Human Body

22 Substances

Some animals have even more water in their bodies. A toad is about 78% water. Plants range from 70-80% water.

Blood =83% Water

Muscles = 65% to 75% Water

Fat = 50% Water

Bones =22% Water

A jellyfi sh’s body is 98% water.

2

23Lesson 2 What Can Water Dissolve?

How Much Water Do You Need to Drink?Water is important. It dissolves many substances. It is called the universal solvent because of this property. Substances that dissolve in water are also called soluble in water.

Substances that do not dissolve in water are called insoluble in water. Many foods you eat are soluble in water. In your body, nutrients and salts that are important to keep you healthy dissolve in the water inside you. These substances are carried in your blood to cells in different parts of your body. This is why you need to drink water. To be healthy,

you should consume about two liters of water each day. You get water by drinking fruit juices, tea, coffee, and even while eating. Some foods contain a lot of water. An egg is 75% water, a slice of bread is 28%, and fruits and vegetables can be as much as 95% water. A lot of pure, clean water to drink, along with healthy foods, is very important for your body.

Learn Even More

Some foods are mostly water. Tomatoes are 95% water, and lettuce is 94% water.

24 Substances

How Much Fresh Water Is on Earth?Humans need water that is clean and safe to drink. The supply of clean and safe water is not endless. Most of Earth’s water is found in seas and oceans. It is salt water. Humans cannot live on salt water. Most of Earth’s fresh water is frozen. It is found in

the polar regions, in glaciers, or in underground reservoirs that are diffi cult to access. This illustration might be helpful: If all of Earth’s water could be placed in a one-liter jar, the amount of fresh water easily available from rivers, lakes, and reservoirs would fi ll only three spoons. Many people in the world suffer from lack of clean water. This is why it is so important to protect water sources by avoiding waste and pollution.

Each spoon contains 10 milliliters.

2

25Lesson 2 What Can Water Dissolve?

26

LESSON 3

Why Do Some

Mixtures Separate?

What happens to some mixtures when you shake them?

What are some mixtures you must shake before using?

27

Lab ActivityMixing Cornstarch

You are going to prepare a special mixture.

Water and Starch Mixture

A. Measure 75-100g of cornstarch and put it in a plastic container.

B. Pour 250-ml of water into a cup. Then slowly add it to the cornstarch, stirring as you pour. Observe what happens. Write your observations in your Science Notebook. ● What does the mixture look like?

● How does it fl ow? Is the mixture thin or thick?

● What happens when you touch it?

● Describe what you see happening.

Discuss the term viscosity with your teammates. Compare the viscosity of this new substance you have created with water and with honey.

A. Put a spoonful of mixture on newspaper. Wait a few minutes. What happens to the substance? Write your observations in your Science Notebook.

B. Touch the substance on the newspaper. How does it feel? Then put it back into the container. Wait a few minutes. What happens to the substance? Write your observations in your Science Notebook.

This diagram shows particles in a solid substance. What do you notice?

This diagram shows particles in a liquid substance. What do you notice?

28 Substances

3

C. Touch a fi nger to the mixture and press it down. Then, quickly remove it. What happens? Write your observations in your Science Notebook.

D. Stir the mixture again. Talk about how the mixture feels as you stir it.

Look at the water and salt mixture your teacher prepared. Write your observations in your Science Notebook. Draw an illustration that shows what happens.

Look at the water and sand mixture your teacher prepared. Write your observations in your Science Notebook. Draw an illustration that shows what happens.

Examine the cornstarch with a microscope.

A. Use a pipette to put a drop of mixture on a microscope slide.

B. Have a teammate put the slide on the microscope. Adjust the lens to focus the surface of the mixture clearly. Take turns observing what you see. Write your observations in your Science Notebook.

29Lesson 3 Why Do Some Mixtures Separate?

Learn MoreColloids and Other SubstancesIn this lesson, you investigated three examples of a solid mixed with a liquid. You have learned that the parts that make up a substance (the molecules) are held together less tightly in a liquid than they are in a solid. This means that molecules in

a liquid fl ow more easily. The fi rst mixture you made was cornstarch and water. When you stirred them together, they formed a thick, milky, white material. This material had unusual properties. It is called a colloidal mixture. When your teacher mixed sand and water, the sand particles were in suspension at fi rst. After the mixture sat for a while, it separated again. The sand particles sank through the water

particles, so the sand was on the bottom and the water was on the top. The sand and water formed a mixture. In a mixture, the substances it is made up of can be separated. In the salt and water mixture, the salt particles were not visible. But, if the water were allowed to evaporate, the process would separate the salt from the water. The water would evaporate, but the salt would still be in the container.

Types of Colloids

MILK

Foam

Colloidal Suspension of Butterfat in a Watery Liquid

30 Substances

Differences in the Behavior of Each SubstanceEach substance you investigated behaved differently.

Salt and WaterThe small particles of salt dissolved, so you could not see them. This is a homogeneous mixture. The particles are uniformly distributed throughout the mixture.

Sand and WaterThe particles of sand did not dissolve. They sank. This is a heterogeneous mixture. The particles are not uniformly distributed throughout the mixture.

Cornstarch and WaterOf the mixtures you investigated, only this one has particles that stay suspended. It is called a colloidal suspension.

3

Emulsion

Gel

Mixture

31Lesson 3 Why Do Some Mixtures Separate?

32

LESSON 4

How AreDiamonds,

Charcoal, andGraphite

Alike?

What are the different uses of diamonds, charcoal, and graphite?

What can you do with diamonds?33

Lab ActivityGraphite and Charcoal

Read the fi rst two paragraphs of the Learn More section to fi nd out about charcoal and the graphite used in black pencils.

● What has charcoal been used for in the past?

● What was charcoal used for in Ancient Egypt?

● What is graphite? Where did its name come from? How is it different than charcoal or diamonds?

● How do people use graphite?

How could you use each of the tools to observe a property of charcoal and graphite?

Drawing Paper

Well Slide Plastic Cup with Water

Magnifying Glass

Metal Plate

Microscope

34 Substances

4

Use the procedures you developed in the Prediction section of your Science Notebook. Use each tool and make observations of the charcoal and graphite. Complete the chart as you work.

Write with different-numbered graphite lead pencils. As you draw lines on paper, what do you notice about the hardness and softness of the graphite? What can you conclude?

Test the friction of the charcoal and the graphite and compare the scraped charcoal and graphite. Put a little of each material on the tip of your forefi nger and rub the material with your thumb.

● What do you notice?

● Which material reduces friction best?

● How can you use the structure of the material to explain this?

What comparisons can you make between diamond, charcoal, and graphite? How are they similar? How are they different? Record your ideas in the Venn diagram in your Science Notebook.

35Lesson 4 How Are Diamonds, Charcoal, and Graphite Alike?

Learn MoreCharcoal, Graphite, and DiamondCharcoalPeople have used charcoal for thousands of years as a heat source to cook foods, to manufacture ceramic objects, and to melt metals. Many people still use charcoal for their cooking. You might use it for cooking on an outdoor grill. Charcoal can also be used as a remedy for digestive problems.

GraphiteFor nearly 600 years, people have used graphite mixed with clay to make pencil leads. The name comes from the Greek word grapho, which means writing. Graphite is widely used to protect surfaces. It is applied to the internal walls of tanks that contain corrosive substances that would “eat away” at other materials.

Graphite Ore of High Purity

Shavings of Graphite

Pencil leads are a mixture of powdered graphite and very fi ne clay. This mixture is pressed between two slices of wood to form the pencil used for writing.

36 Substances

DiamondDiamond is the hardest material found in nature. Because it is so hard, it is used to make saws and drills to work with rocks, steel, and concrete. Skilled workers can cut surfaces called facets on

diamonds. Faceted diamonds are much brighter than raw diamonds. Faceted diamonds are used in jewelry. Most diamonds that are mined are small and are used in industry.

These are diamonds before they are made into jewelry or parts of tools.

Cables with diamond particles are used to cut blocks of rock in stone quarries.

What Is Hardness?

Hardness is a property of a substance. Hardness is a measure of how diffi cult it is to make a mark on one substance with another one. For example, if you scratch quartz and ruby together, the one that scratches the other one is harder. In this case, ruby scratches quartz. Ruby is a harder material. Diamond is the hardest substance on Earth. It can scratch all other minerals.

4

37Lesson 4 How Are Diamonds, Charcoal, and Graphite Alike?

Learn Even MoreOne Element Forms Different Substances

Graphite, charcoal, and diamond are very different, but they are all made up of carbon. Carbon is an element. Currently scientists know of 117 elements that occur in nature. Elements are made up of only one type of atom.

Carbon is made up of only carbon atoms. Atoms from these 117 elements combine to form everything in the universe. They form every solid, liquid, and gas. How can the same carbon atoms make up graphite, charcoal,

Due to the random order of its atoms, charcoal breaks easily.

38 Substances

Arrangement of Carbon Atoms in Graphite

Arrangement of Carbon Atoms in a Diamond

and diamond, when those three substances are so different? Carbon is a special type of atom. It forms different substances when the atoms organize in different patterns. The carbon atoms in charcoal mix without any order. This makes charcoal a weak material. It breaks easily and

can turn into powder. The carbon atoms in diamond are arranged very precisely. The rigid, crystalline structure makes diamond extremely hard. Carbon atoms in graphite form in layers, one on top of the other. One layer can slide over another. This is why you can write with graphite.

When you are drawing on paper, a pencil leaves a layer of loosened graphite behind, making a mark. Carbon atoms arranged loosely make a softer material. Arranged in a more precise structure, those same atoms make a very hard material.

4

39Lesson 4 How Are Diamonds, Charcoal, and Graphite Alike?

40

LESSON 5

Where Does Coal Come

From?

How is coal used in the United States?

What are the characteristics of coal?

41

Lab ActivityCoal Study

What are some physical properties of the piece of coal? Use a magnifying glass to examine the coal. Discuss your observations with your team.

Now use your hands to examine the piece of coal. Gently tap it on your desk. Then feel it with your fi ngers.

● Does it feel hard or soft?

● Does it rub off onto your hands?

Draw pictures in your Science Notebook and describe what you see.

Coal

42 Substances

5

Use a paper clip to scratch the coal. What do you notice? Draw a picture of your piece of coal and label it in your Science Notebook. Write words to describe your particular piece of coal. Study your piece so that you would recognize it in a coal pile with many other pieces.

Before the dinosaurs, many giant plants died in swamps.

SWAMP300 million years ago

WATER100 million years ago

Over millions of years, the plants were buried under water and dirt.

Heat and pressure turned the dead plants into coal.

43Lesson 5 Where Does Coal Come From?

Learn MoreHow Was Coal Formed?Millions of years ago, large areas of Earth were covered with water. The water in swamps contained many types of plants. When the plants died, they were then covered by dirt and water. Usually, plants decay when they die. These plants did not decay. Trapped under dirt and water, there was not enough oxygen to support the organisms that cause living things to decay. As time went by, more dirt, rocks, and water covered the dead plants. Eventually, they were buried deep in the earth. The dirt and rock piled on top of them produced great pressure and hot temperatures. After millions of years, the dead plants turned into coal. Since coal is made of the remains of dead plants and animals, it is called a fossil fuel. Most coal is about 75% carbon. Carbon is the element that makes up the bodies of most plants and animals.

History of CoalThe Hopi Indians are the fi rst people known to use coal in North America. They used coal to bake clay pottery. These Native Americans still use this process today. The Hopi lived 700 years ago in the area of the United States now known as Arizona. People in Europe had used coal as a fuel for hundreds of years. When settlers arrived in North America in the 1600s, they found so many forests that they used mostly wood for fuel. They imported coal from England and Canada. Mostly, blacksmiths used coal to fuel their furnaces. More often, the settlers used waterwheels and wood for their energy needs.

In about 1750, coal mining started in Virginia. By the late 1700s, settlers mined coal from hillsides in Pennsylvania and other places. By the 1800s, many businesses used coal to run railroads and steamships. In 1882, Thomas Edison built a coal-fi red electric generating plant. The station supplied electricity to some places

in New York City. By the end of the1800s, more and more coal was used to make electricity.

During the early 1900s, coal was the primary source of energy. When automobiles were developed, coal became less desirable as a fuel, because cars needed gasoline. Petroleum became more and more important. Railroads quit using coal and changed to diesel fuel, which is made from petroleum. Homeowners started to heat their homes with gas or oil because they were cleaner than coal. Coal produces ash and black dust. By the 1950s, coal production was very low. It did not become popular again for many years.

Today, coal is an important resource. It supplies about 1/3 of U.S. energy needs. The U.S. uses a lot of coal. It also has huge coal reserves. Some people estimate that the U.S. has enough coal to last for more than 200 years. However, coal is a nonrenewable resource. Once the supply is gone, there is no way to make more.

44 Substances

Mining CoalThere are two ways to mine coal. Both ways rely on fi nding an area inside Earth with a lot of coal in it. This is called a coal seam. If the coal seam is close to the surface of Earth, it can be dug out with equipment called earthmovers. This process is called surface mining. Surface mining is less expensive, but it has negative consequences, too. Surface mining destroys the land and the forest growing above the coal. It also can release toxic chemicals in the area. A second way to mine coal is called deep shaft mining. Miners dig tunnels deep into the earth. Using tools and explosives, they extract the coal from rock and load it into carts. The carts haul the coal to the surface where it can be cleaned and sold. This type of mining is dangerous but important work.

5

45Lesson 5 Where Does Coal Come From?

46

LESSON 6

Is Air a Substance or

a Mixture?

What is in the air?

What makes air essential for life?

47

Lab ActivityWhat Is in the Air?

Chemical substances are represented by formulas. Look at some formulas of substances present in the air:

Nitrogen gas = N2

Oxygen gas = O2

Carbon Dioxide gas = CO2

Work with your team and make sure everyone gets a chance to participate. Using the molecular models, assemble the representations of these substances.

Read The Air section in the Learn More to fi nd out more about the composition of air.

48 Substances

6

Use a sheet of paper divided into 100 equal parts to demonstrate the composition of the air. This sheet is located in your Science Notebook. Choose a color to represent each one of the components of air.

A. Color the page in a way that represents the different gases present in the air, considering the quantity of each substance in the air as determined by scientists.

B. Create a key or legend to identify which color you are using for each gas.

Analyze what you did in Steps 1 through 3. Explain what you have learned about air and its composition.

49Lesson 6 Is Air a Substance or a Mixture?

Learn MoreThe AirThe air you breathe contains several gases. Air has much more nitrogen than any other gas. Scientists have measured the average proportion of each gas. As you inhale, oxygen, nitrogen, carbon dioxide, and water vapor get inside your body. Oxygen is used by your cells. Other gases, and some oxygen, go back into the air when you exhale.

The AtmosphereA thin layer of gases, the atmosphere, surround Earth.

Global Climate ChangeThe atmosphere allows some rays from the sun to get through to Earth. These rays supply light, and they heat the whole planet. This same layer of the atmosphere acts like a blanket. If it were not for the atmosphere, the difference in temperature between day and night would be much greater. As the amount of some gases that compose the air increase, especially carbon dioxide, it creates something known as the

greenhouse effect. The greenhouse effect maintains warm temperatures, leading to an elevated temperature, on average, across Earth. This phenomenon is called global warming, and the effect is called global climate change.

In every 100 parts of air there are:- 78 parts of nitrogen gas;- 21 parts of oxygen gas;- 1 part representing all of the other gases, including carbon dioxide.

50 Substances

Acid RainWhen humans burn fossil fuels, such as petroleum and coal, gases and other substances are released into the atmosphere. Some of them undergo chemical reactions. They combine with water in the air to form harmful acids. The acids fall back to Earth as something called acid rain. Acid rain contaminates lakes, destroys forests and crops, gets into the soil, and corrodes metal roofs, outdoor sculptures, and other metal structures.

This photograph shows trees destroyed by the combination of acid rain with other types of contaminants.

6

51Lesson 6 Is Air a Substance or a Mixture?

The Ozone LayerOne of the gases in the atmosphere is ozone. Ozone gas forms a layer that protects the earth. Ultraviolet radiation from the sun can be very dangerous, but the ozone layer protects humans from being exposed to radiation. Ultraviolet radiation, for example, can cause skin cancer. The atmosphere also contains gases that do not exist in nature. Humans accidentally created new gases, often in industrial processes. The most common gases are some of the most dangerous. Chlorofl uorocarbons (CFCs) are an example. CFCs were used in refrigerators, air conditioners, and many products that spray from a can (aerosols) contain CFCs.

Gas under pressure is used in many spray containers. As you press the button on a can of aerosol, the gas sprays out and carries with it drops of liquid such as deodorant, paint, or room spray. The CFCs react in the atmosphere and reduce the amount of ozone.

In this picture of Earth, as seen from space, the blue stain over the Antarctic region is the hole that the CFCs have caused in the ozone layer.

Learn Even More

52 Substances

SmogIndustrial processes and motor vehicles (cars, trucks, buses, and motorcycles) burn fossil fuels for their energy. Burning fossil fuel releases many substances into the air. These include carbon monoxide, nitrogen oxide, and hydrocarbons. Radiation from the sun causes changes in some of these, forming new toxic substances called smog. The word smog combines smoke and fog. Smog can cause breathing problems for people who must breathe polluted air. These substances can make the sky appear gray, yellowish, or green.

Smog in the City of Santo André, Brazil

6

53Lesson 6 Is Air a Substance or a Mixture?

54

LESSON 7

What Is Important

about Metals?

What are some reasons that cranes are made of steel?

What else could cranes be made of?

55

Lab ActivityMetal Study

Think about these four objects: paper clip, stapler, soda can, and penny. Describe their characteristics. Why are these objects made of this particular type of metal rather than a different type? Talk with your team and decide which metal they could be made of. Record your ideas in your Science Notebook.

Cut two slits in a piece of paper. Label them with the letters A–D. Sort the wires according to their flexibility, from the least flexible (#1) to the most flexible (#4). Label each wire with its fl exibility number and record this information in the Properties of Metal Samples chart in your Science Notebook.

Label the metal plates 1–4. Then, wearing gloves and safety glasses, clean the metals with the steel wool and observe their colors. How do they look clean as compared to dirty? Record your observations of each metal in your Science Notebook.

56 Substances

7

Place the magnet close to each sample. Record which samples were attracted and which were not.

Look at the samples your teacher prepared with copper sulfate solution. Write in your Science Notebook which of the samples reacted to the solution.

Look at the Properties of Metal Samples table in your Science Notebook. Use your notes and the table to try to identify each metal sample—the wires and the plates. Discuss the properties of metals with the class.

57Lesson 7 What Is Important about Metals?

Learn MoreMetals have characteristics such as their color, strength, brilliance, ability to conduct electric current, fl exibility, ability to be stretched into wires, and ability to conduct heat. These are also properties of each metal. Metals were once used mainly as raw material for weapons and tools. Gold and silver were

used to make coins and jewelry. Jewelers continue to use these metals to make jewelry because gold and silver are fl exible, shiny, and beautifully colored. Gold, the most fl exible metal in its natural state, can be pounded into sheets so thin that people can see through them! The thin plates are used in the

Jewelry is usually made with an alloy of gold and copper.

Roman Weapons from the 3rd to the 1st Centuries B.C.

58 Substances

visors on astronauts’ helmets and in the glass of airplane cabins to provide protection from dangerous rays from the sun. Gold and silver are also used in computers, as they conduct electricity and do not corrode. The ability to conduct electricity is a property that allows metals to be used for wire. Copper is most often

used for this purpose. Silver is also a good conductor, but it is much more expensive than copper.

Astronauts’ helmets contain thin sheets of gold.

Copper, which has high electrical conductivity, is widely used for transmitting electric power.

7

59Lesson 7 What Is Important about Metals?

Learn Even MoreMetal objects can be the same size, yet have very different masses. That is because their densities are different. Density is another property of substances. If two objects are the same size, but one is much heavier, the heavier one is denser. Some metals are denser than others. It doesn’t matter what object they are made into, different metals are more or less dense. Old bicycles were much heavier than bicycles today. Bicycles were once made of steel. Steel has a high percentage of iron, and iron has a much higher density than the aluminum that many of today’s bicycles are made from.

Two bicycles can have very different weights depending on the metal from which they are made – steel or aluminum or even plastics!

60 Substances

Some of the fi rst airplanes were made of wood covered with cloth. Airplanes today are made from aluminum and plastic. An airplane made from lead would be too heavy to fl y without changes like more powerful engines. Lead is not as strong as aluminum, so it would be more likely to bend.

Metals can be mixed with other metals to form alloys. Brass is an alloy formed from zinc and copper. Brass is used to make musical instruments and many decorative objects. Steel is a strong alloy of iron and carbon. When strength is needed, steel is often used. Machines, tools, and the frameworks of tall buildings are made of steel. Bronze is a mixture of copper and tin.

7

Airplane fuselages are often made of aluminum – a strong and light metal.

The trumpet is a wind musical instrument made of brass.

61Lesson 7 What Is Important about Metals?

62

LESSON 8

How Can People Protect Earth’s Natural

Resources?

What are natural resources?

How can you conserve them?

63

Lab ActivityIt’s Natural

What are natural resources? You will make a poster about a natural resource. Your teacher will help you decide which natural resource to research.

Your poster should be informative, telling the audience something important. It should also be persuasive, making the reader want to do something positive to protect and preserve the environment. Brainstorm with your teammates. Decide what images you want to show on your poster and how you will display them. See how much information you can use that you learned in this unit. Research in the library and on the Internet. Look in books and magazines for information and images that support your topic.

Decide what task each team member will do. Create your poster. Be sure to include at least two actions people can take to protect and conserve natural resources. Make illustrations of what you discuss. Be colorful and persuasive!

64 Substances

8

The conservation of natural resources is the fundamental problem. Unless we solve that problem, it will avail us little to solve all others.

- Theodore Roosevelt, Address to the Deep Waterway Convention, Memphis, TN, 4 October 1907

When we try to pick out anything by itself, we fi nd it hitched to the universe.

- John Muir, Naturalist

65Lesson 8 How Can People Protect Earth’s Natural Resources?

Learn MoreNatural ResourcesThe United States has many natural resources. Every day you use air, water, land, oil, petroleum, and minerals. Plants and animals can also be thought of as natural resources. They exist in the environment and are not “made” by humans. Even though it might seem like natural resources are unlimited, that is not true. For example, many people think Earth could never run out of water, but they do not realize that most of Earth’s water is salt water. It cannot be used for agriculture or

for drinking. Only a small amount of water on Earth is usable as it is. Another example is coal. The Earth has enough coal to last for about 200 years. Then the supply will be used up. There is no way to make more natural resources. Although there is enough petroleum to last for many years, one day it will be used up. If trees are cut down faster than new trees are planted and can grow, this natural resource will be used up (depleted). Even fi sh are being eaten more quickly than they reproduce. People can learn about the environment and how it is affected by their activity.

When trees are cut down to make wood and paper products, this action affects the soil, the environment, and all living things. If the soil erodes, plants cannot grow. Soil can travel to lakes and rivers and from there to oceans. The soil could sink to the bottom of the ocean, and cover fi sh and plants. Some people believe there should be rules about how natural resources are used in order to protect them for the future. But, some people do not think it is necessary to make laws about natural resources. What do you think?

Forests are one of our natural resources. There are only a few old-growth forests left in the United States.

66 Substances

The Importance of ConservationThe idea of conservation goes back to people from long ago. Native Americans lived in America before people started to arrive from Europe. The Native people used only what they needed. They wasted very little. Their population was small, so they did not do much damage to the environment. The exception is that they killed many large animals that no longer existed by the time Europeans arrived. When Europeans came, most natural resources were still plentiful. Most of America was covered with forests. As people spread out across the land, they cut trees to create farmland and to build. They used ore and more natural resources. One of the fi rst people to notice

and to speak out about using up natural resources was John Muir. Muir’s family arrived in the United States in 1838. As a boy, Muir worked on his family’s farm. Later, he studied science in college. In 1867, he travelled throughout the United States, which deepened his love of nature. He visited a beautiful place which later became Yosemite National Park. He became an advocate for protecting and conserving the park. He understood that natural resources were limited. Part of the region was already protected, but after years of hard work, Yosemite became a national park in 1890. Then, even more laws protected this natural resource, and they still do today. In 1892, Muir helped create the Sierra Club. It continues today to preserve natural areas around the world.

8

67Lesson 8 How Can People Protect Earth’s Natural Resources?

John Muir’s LegacyThrough the years, many people have helped to change how others interact with nature.

Rachel CarsonMany people think of Rachel Carson as the person who started the environmental movement. She wrote a book called Silent Spring. In it, she warned people about chemicals (pesticides) in food.

Anne LaBastilleAnne LaBastille lived in New York. She was an environmentalist and a photographer. In 1965, she built a cabin in the wilderness where she lived for 35 years. She studied the natural world and wrote many books and articles about her experiences.

Ansel AdamsJohn Muir and Ansel Adams were close friends. Adams was a photographer and conservationist. Adams lived near Yosemite Park. He took many photos in the park, and worked hard to capture the beauty of the land in his photographs.

Marjory Stoneman DouglasMarjory Stoneman Douglas lived in Florida for over 100 years. She was a journalist and conservationist. She fought to protect and preserve the Everglades. She wrote a book called, The Everglades: River of Grass. It helped people understand the importance of the Everglades as a natural resource. She said, “If we can save the Everglades, maybe we can save the planet.”

Learn Even More

68 Substances

The Everglades is a wetland ecosystem in Florida.

8

The Adirondack Mountains are in upstate New York.

69Lesson 8 How Can People Protect Earth’s Natural Resources?

70

acid rain – rain that has become polluted, mostly from burning fossil fuels

alloy – a mixture of metals

atmosphere – very thin zone of gas that surrounds a body in space, such as a planet

atom – smallest unit of an element that retains the chemical properties of the element

biodegradable – something that can be broken down naturally

carbon – a chemical element found in coal as well as in all plants and animals

chemist – a scientist who studies substances and how they interact with each other

charcoal – a black, carbon-based material used as a fuel, fi lter, or absorbent

colloidal suspension – a mixture in which one substance is evenly suspended in another substance

conductor – a substance that allows heat or electricity to fl ow through it

conservation – protection of natural resources

crystal – a solid with a highly regular physical structure

deplete – to empty or to use up

derivative – something that comes from something else; such as from another substance

diamond – very hard, usually clear crystal made of carbon

Glossary

70 Substances

disinfection – killing bacteria and other harmful organisms

dissolve – when a solid mixes into a liquid to form a uniform mixture throughout

edible – something that can be safely eaten

element – a basic type of matter that is made of just one type of atom

erosion – the wearing away of land or rock by water or wind

ethanol – a renewable fuel made from corn, sugar beets, sunfl owers, wheat, and other crops

extract – to take out, to remove

fat – a solid, oily substance found in animals and some plants, such as nuts and avocados

fermentation – the process of turning sugar into alcohol

fi lter – a device that removes substances from a mixture

fl exible – able to bend without breaking

freshwater – water that has only a small amount of salt

friction – resistance between one moving object and another

fuel – a substance that is used for heating or energy, such as coal, gasoline, natural gas, wood, or charcoal

global climate change – disruptions in Earth’s temperatures and climate patterns

graphite – soft black or gray substance made of carbon

gravity – the force of attraction that causes objects to fall to Earth

71Glossary

heterogeneous mixture – a mixture of two or more substances that are not evenly dispersed

homogenous mixture – a mixture of two or more substances that are evenly dispersed (for example, a solution)

lake – a large body of freshwater surrounded by land

lubricant – oil or grease that reduces friction between moving parts

marine – related to the sea

material – two or more materials combined, but not chemically bound, together

mine – a place underground or on Earth’s surface from which workers extract materials, such as coal

mixture – two or more materials together, but not chemically bound together

molecule – small, organized particles that make up most ordinary substances except metals and crystals

natural resource – a material found in nature that people use, such as wood, land, water, or minerals

nonrenewable – can be used up; limited supply of

oil – a greasy, liquid substance used in cooking; found in olive, sesame, and sunfl ower plants, among others; fats that are liquid at room temperature

ozone layer – a layer above Earth’s surface that blocks some of the sun’s harmful rays

particle – a very small piece of something

petroleum – dark, oily, natural substance that does not mix with water

pond – a small body of freshwater surrounded by land

potable water – water that is safe for drinking

72 Substances

preserve – sustain; protect a place or substance we want to keep in its natural state

river – freshwater that fl ows into a lake or an ocean

saline – containing salt

separate – to take something apart or divide it

smog – a mixture of smoke and fog that results from air pollution

soluble – able to be dissolved

solvent – a material, usually a liquid that can dissolve another substance

stream – a small body of fl owing freshwater, usually ending in a river

substance – material from which something is made

synthetic – made artifi cially

trans fat – unhealthy, solid fat made by humans and used to make food last longer

viscosity – a measure of a fl uid’s resistance to fl owing

73Glossary

Substances