Chemistry Compounds Teacher

8/8/2019 Chemistry Compounds Teacher

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Compounds and Reactionsfrom the six-part

Elements of Chemistry Series

Produced by

Algonquin Educational Productions

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2003 Algonquin Educational Productions


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Table of Contents

The purchase of this program entitles the user to the right to reproduce or

duplicate, in whole or in part, this teachers guide and the blackline mas-

ter handouts that accompany it for the purpose of teaching in conjunction

with this program, Compounds and Reactions. This right is restricted

only for use with this program. Any reproduction or duplication in wholeor in part of this guide and the blackline master handouts for any purpose

other than for use with this program is prohibited.

This video is closed captioned.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Links to Curriculum Standards . . . . . . . . . . . . .1

Student Objectives . . . . . . . . . . . . . . . . . . . . . .1

Summary of the Program . . . . . . . . . . . . . . . . .3

Pre-Test and Post-Test . . . . . . . . . . . . . . . . . . .4

Teacher Preparation . . . . . . . . . . . . . . . . . . . . .4

Student Preparation . . . . . . . . . . . . . . . . . . . . . .5

Description of Blackline Masters . . . . . . . . . . .6

Answer Key . . . . . . . . . . . . . . . . . . . . . . . . . . .7

Discussion Questions . . . . . . . . . . . . . . . . . . . .9

Follow-Up Activities . . . . . . . . . . . . . . . . . . . .11

References . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

Script of Narration . . . . . . . . . . . . . . . . . . . . . .13


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Compounds and Reactions

from the six-partElements of Chemistry SeriesGrades 9 to 12

Viewing Time: 20 minutes

INTRODUCTIONCompounds and Reactions is part of theElements of Chemis-

try Series, a six-part series of programs to help students under-

stand the fundamental concepts of chemistry. The attractive

images and engaging narration of the program have been de-

signed by educators and filmmakers to help students understand

the sometimes complicated and obscure explanations of this

important branch of science.

Elements are able to bond together into compounds and it is

these compounds that make up the millions of unique sub-

stances that exist in the universe. There are two different types

of compounds: ionic bonds and covalent bonds. Chemical reac-

tions are the process in which elements bond together into

unique substances with different physical and chemical proper-

ties.

This program gives a practical explanation of the process of

bonding and explains different types of chemical reactions. It

provides a comprehensive introduction to this fascinating area

of science appropriate for high school students.

LINKS TO CURRICULUM STANDARDSThe Elements of Chemistry Series is based on the "National

Science Educational Standards" for "Physical Science," grades

9-12, (Content Standard B).

STUDENT OBJECTIVESAfter viewing the program and participating in the various fol-

low up activities, students should be able to:

Explain that the approximately 12 million substances that

chemists have discovered are all made from the 92 elements

found naturally in the universe.


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Describe the three types of changes in matter: nuclear, physi-

cal, and chemical changes.

Explain the difference between substances and mixtures.

Describe how valence electrons of atoms have the ability to

move.

Define a positive and a negative ion and explain how elements

become electropositive or electronegative.

Explain how ionic bonds are formed and held together.

Explain how covalent bonds are formed when electrons areshared between atoms in structures called molecules.

Define the principles behind the writing of molecular formu-

las.

Define and understand the Law of Constant Composition.

Explain how the octet rule can be used to understand how both

ionic and covalent bonds are formed.

Describe in a general way the importance of molecular shapesand the length of the bonds.

Describe the process of chemical reactions and the system

chemists use to write chemical equations.

Explain why chemical equations must balance.

Define oxidation and reduction and explain oxidation-reduc-

tion or redox reactions.

Give a general explanation of the redox reaction that occurs in

a voltaic cell battery.

Define anode and cathode and explain what is happening at

each of them when a battery is operating.


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SUMMARY OF THE PROGRAMThere are three different types of changes in matter: nuclear,

physical, and chemical changes. When chemical changes occur,

there is an actual change in the chemical composition of the

substances. The original atoms are preserved but they combine

in such a way that a new substance is created with a different

chemical composition.

In a chemical compound, the valence electrons are lost, gained,

or shared between the different atoms. These unions are called

chemical bonds. There are two basic kinds of bonds: ionic

bonds and covalent bonds.

Electrons have the ability to move between atoms. When a neu-

tral atom loses an electron, it becomes a positive ion and when

a neutral atom gains an electron it becomes a negative ion.

Frequently elements lose or gain electrons to other elements

and these ions are then attracted to each other because of their

opposite electrical charges. This is an ionic bond. There are

many examples of ionic bonds involving two or more elements

but one of the most common is sodium chloride, table salt.

Covalent bonds occur when electrons are shared between atoms

in structures called molecules. There are a vast number of sub-stances that have molecular structures including plastic, paper,

water, and all of the bonds in plants and animals. Molecules

can be made up with as few as two atoms or hundreds and even

a billion atoms. Molecular formulas are precise descriptions of

how many atoms there are in a single molecule.

A chemical reaction is a process in which one or more sub-

stances are converted into new substances with different physi-

cal and chemical properties. An incredible number of chemical

reactions are going on around us at all times. Chemical equa-

tions are written to describe what happens in a chemical reac-tion.


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Electrochemistry is a special type of chemical reaction called

redox reactions. There are a wide variety of redox reactions,

from respiration in animals to the rusting of iron. One of the

most interesting is the production of electricity in a battery.

When chemists understood chemical bonding and how reac-

tions occur, they were able to explain how the millions of sub-

stances that exist could be formed from the 92 elements that are

found naturally in the universe.

PRE-TEST AND POST-TESTBlackline Master #1, Pre-Test, is an assessment tool intended

to gauge student comprehension prior to viewing the program.

Remind your students that these are key concepts upon which

they should focus while watching the program.

Blackline Master #7, Post-Test, can be compared to the results

of the Pre-Test to determine the changes in student comprehen-

sion after viewing the program and participation in the activi-

ties.

TEACHER PREPARATIONBefore presenting this program to your students, we suggest

that you preview the program and review this guide and accom-

panying Blackline Master activities in order to familiarize your-

self with the content. Feel free to duplicate any of the Blackline

Masters and distribute them to your students.

As you review the materials presented in this guide, you may

find it necessary to make some changes, additions, or deletions

to meet the specific needs of your class. We encourage you to

do this. Only by tailoring this program to your class will your

students obtain the maximum instructional benefits afforded by

the materials.

We suggest that you first show the program in its entirety to

your students. This is an introduction to the complex subject of


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modern chemistry, and at this stage it is helpful that students

gain an overview of the concepts and material in the program.

A number of lesson activities will grow out of the content of the

program and, therefore, the presentation should be a common

experience for all students.

After the introduction, the program is divided into chapters with

the following titles:

Changes in Matter

Ionic Bonds

Covalent Bonds

Chemical Reactions Electrochemistry

These chapters vary in length from three to five minutes. After

the students have seen the entire program, lessons could be

designed around these different chapters. A chapter could be

shown at the beginning of the class, and the balance of the class

time, and subsequent classes, could be spent examining the sub-

ject matter in the program in greater depth.

STUDENT PREPARATIONIt is important that students work through the material and

familiarize themselves with the vocabulary, concepts, and theo-

ries that scientists use to understand this field.

If the students have a textbook that they are following, assign

the relevant reading before the lesson. As students work

through the material, they will encounter a number of unfamil-

iar words and concepts. Most of these words are highlighted in

the program. An additional list of words is provided in Black-

line Masters #2a-c, Vocabulary Definitions and Activities.

The program concludes with a ten-question Video Quiz thatmay be used to gauge students' comprehension immediately

after the presentation of the program. Blackline Master #6,

Video Quiz, is a printed copy of the questions, which may be


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reproduced and distributed to the students. The answers to the

questions appear in the answer key of this Teacher's Guide.

DESCRIPTION OF BLACKLINE MASTERSBlackline Master #1, Pre-Test, should be given to students

before viewing the program. When these answers are compared

to the quiz results it will help you gauge student progress.

Blackline Master #2a, Vocabulary Definitions, will introduce

students to unfamiliar words and concepts used in this program.

Blackline Master #2b, Use the Right Word, and Blackline

Master #2c, Word Match, are activities designed to help rein-

force key concepts and vocabulary.

Blackline Master #3, Connected and Not Connected, will

help students identify their knowledge of key vocabulary terms

and the context in which they are used.

Blackline Master #4, Crossword Puzzle, reinforces key con-

cepts and vocabulary.

Blackline Master #5, Creative Writing Story Ideas, will

allow students to think creatively while incorporating scientific

principles and vocabulary covered in this program.

Blackline Master #6, Video Quiz, is a printed version of the

Video Quiz that appears at the end of the program.

Blackline Master #7, Post-Test, may be used to evaluate stu-

dent progress after completing this lesson.


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ANSWER KEYBlackline Master #1, Pre-Test1. False 6. True

2. True 7. True

3. True 8. False

4. False 9. True

5. False 10. False

Blackline Master #2b, Use the Right Word

1. nuclear change 6. molecular formulas

2. chemical reactions 7. polarity

3. ion 8. synthesis

4. octet rule 9. oxidation...reduction5. molecules 10. voltaic cell

Blackline Master #2c, Word Match

anode- where oxidation occurs

cathode- where reduction occurs

chemical reaction- change in chemical composition of sub-

stance

electrochemistry- study of chemical effects of electrical

action

element- an atom with a unique number of protons

ion- an atom with more or less protons than

electrons

molecule- covalent bond

oxidation- loss of electrons

polarity- molecules with a slight positive or nega-tive charge

reduction- the gain of electrons


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Blackline Master #3, Connected/Not Connected

1. fusion fission

2. changes in state chemical reactions

3. negative ions positive ions

4. mixtures compounds

5. electronegative electropositive

6. ionic covalent

7. negative positive

8. voltaic conventional

9. oxidation reduction

10. anode cathode

Blackline Master #4, Cross Word Puzzle

Blackline Master #6, Video Quiz

1. True 6. molecules

2. False 7. False3. reaction 8. True

4. ion 9. False

5. True 10. True

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Blackline Master #7, Post-Test

1. chemical reaction

2. ionic bond

3. molecules

4. anode

5. False. Nuclear changes are those changes that occur in the

nucleus of atoms.

6. False. Electrons have the ability to move. When a neutral

atom loses or gains electrons, it becomes an ion. Negative ions

are attracted to positive ions because of their opposite electrical

charges. In the process, the ions form an ionic bond.

7. True

8. False. During a chemical reaction, atoms can form mole-cules; molecules can break apart or react with other molecules

and new bonds are formed.

9. False. Redox reactions occur when electrons are transferred

from the atom that is oxidized to the atom that is reduced.

10. Ions occur when neutral atoms lose or gain electrons. This

makes the ions electronegative or electropositive. The ions will

assemble into a pattern because positive and negative electrical

charges attract each other. This forms an ionic bond.

11. Electrons have the ability to move and often the electrons of

two or more elements join together in order to complete their

valence energy levels. These covalent bonds are molecules.12. A chemical reaction is a process in which one or more sub-

stances are converted into new substances with different physi-

cal and chemical properties.

DISCUSSION QUESTIONS1. We see change in the world all around us. Surely when

chemists claim that there are only three different types of

changenuclear, physical, and chemicalthey are exaggerating.

A chemist, like a physicist, focuses on the physical world.

Science has long demonstrated that matter cannot be created or

destroyed. The same amount of matter exists in the universetoday as existed when the Big Bang occurred some 15 billion

years ago. To a chemist, therefore, change can only occur at an

atomic level. There can be a change in the nucleus of atoms,


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called nuclear change. There can be a change of state as sub-

stances transform from a gas to a liquid or solid. This is almost

always induced by temperature or pressure changes. Or there

can be chemical changes, which occur when the original atoms

are preserved but they combine in such a way that a new sub-

stance is created with a different chemical composition than the

original.

2. What are the differences in the physical characteristics of

substances formed by ionic bonds and those formed by covalent

bonds?

Ionic bonds occur when electrons are transferred from one

atom to other atoms. What holds the ions together are their dif-fering electrical charges. Covalent bonds are a joining of atoms

into a molecular structure so that the valence electrons are

shared between the different atoms. Ionic bonds tend to be brit-

tle and make good conductors of electricity. Most have a high

melting point and dissolve in water. Covalent bonds tend to be

strong, they usually do not dissolve in water and most are not

good conductors of electricity.

3. Why are plants and animals made up of substances that have

molecular structures?

Of the 12 million substances that have been identified bychemists, the vast majority come from plants and animals.

Some of these molecular structures are very complex. The DNA

molecule in humans, for example, is made up of about one bil-

lion atoms. Living things have evolved for hundreds of millions

of years. As these organisms adapted to meet new conditions,

new molecular structures emerged to meet their needs.

4. Why must chemical equations that describe chemical reac-

tions always balance?

Matter cannot be created or destroyed, but it can change. A

chemical equation is a description of what happens in thatchange. Therefore, the same number of atoms must be on either

side of the equation.


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5. Why do batteries run down and electricity generated from

other sources does not run down?

Electric power in a battery is created by a chemical reaction.

Electrons are attracted from atoms and flow through a circuit

to create electricity. When the chemicals are exhausted, there

are no more electrons available and the battery is used up.

(Some batteries, like those in cars, can be recharged.) Virtually

all of the electricity that we use in homes, factories, and offices

comes from mechanical energy powered by steam, waterpower

or the wind. This mechanical power generates electricity by

turning a magnet in a coil of wire. As long as the magnet turns,

it will generate electricity.

FOLLOW-UP ACTIVITIESThe following activities and projects are designed to help stu-

dents understand compounds and reactions.

1. Research nuclear fusion and illustrate what happens as

hydrogen is converted into helium. How is it possible that ener-

gy is released in this process? Some scientists believe that

fusion will be a source of inexhaustible, inexpensive non-pol-

luting electrical power. What is the difficulty in reaching that

goal?

2. Visit a nuclear power plant, if there is one near your com-

munity, and discuss the safety precautions that are being taken

at the plant. Write a report explaining why the process of

nuclear fission is potentially so dangerous and give your esti-

mation about the plant's safety program.

3. Draw what happens at an atomic level when sodium chloride

is formed.

4. Draw a diagram explaining why ionic solutions are good

conductors of electricity.

5. Explain why the periodic table is able to predict when ionic

bonds are likely to be formed. Give three examples of bonds

that follow your predictions.


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6. Draw a diagram of a water molecule (H2O), and a methane

molecule (CH4). Label all of the atoms.

7. Research and write the molecular formula for the following

substances: water, table salt, a molecule of oxygen, propane,

octyne, and table sugar.

8. Research the history and use of the Lewis Dot method of

illustrating the valence electrons. What is the advantage of this

method?

9. Draw and label the important parts of a voltaic battery. Show

the flow of electrons.

10. Research different types of batteries. Draw diagrams ex-

plaining how each of them works and explain why different bat-

teries are appropriate for different uses.

REFERENCESThere are many excellent books and websites dealing with

compounds and reactions that are appropriate for students. The

following is a short list.

Books:

LeMay, Eugene, Karen M. Robblie, Herbert Beall, Douglas

Brower, Chemistry: Connections to Our Changing World,

Englewood Cliffs, New Jersey: Prentice Hall, 1996.

Jenkins, Frank, Hans van Kind, Lucille Davis, Olivier Lantz,

Patricia Thomas, Dick Tompkins, Chemistry II, Toronto:

Nielson, 2002.

McMurry, John, Robert C. Fay, Chemistry, Englewood Cliffs,

New Jersey, Prentice Hall, 1995.

Smoot, Robert C., Richard G. Smith, Jack Price, Chemistry,

Glencoe: McGraw Hill, 1998.


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Internet Sites:

www.molecularuniverse.com

http://highschoolhub.org/hub/chemistry.cfm

http://dir.yagoo.com/Science/Chemistry/

www.dist214.k12il.us/users/asanders/chemhome2.html

http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/elec-

trochem.html

http://www.howe.k12.ok.us/~jimaskew/creact.htm

http://www.ausetute.com.au/shapemol.html

http://dbhs.wvusd.k12.ca.us/Bonding/Electroneg-Bond-

Polarity.html

SCRIPT OF NARRATIONOnly 92 elements are found naturally in the universe and yetchemists have identified more than 12 million different andunique substances. How can this be possible? The secret lies inhow elements bond together into compounds. When chemistsunraveled the mysteries of compounds and reactions, they wereable to explain the fundamental nature of matter. This remark-able achievement lies at the very heart of modern chemistry.

CHANGES IN MATTERThere are only three different types of changes in matter:nuclear, physical, and chemical changes. Nuclear changes are

those that occur in the nucleus of atoms. Fusion occurs in thesun and stars when two hydrogen nuclei fuse together tobecome helium. In the process, enormous amounts of energyare released, which travels to us in the form of electromagneticradiation, or light.

Fission is a different type of nuclear process, created in nuclearbombs or nuclear power plants. In this process, the nuclei ofuranium atoms are broken apart and release energy. Radio-active decay is another form of nuclear change. In this process,the original nucleus of an atom decomposes to form a new

nucleus, releasing radiation in the process. But although nuclearchanges are vital in the universe, we tend not to be aware ofthem in our everyday life

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Physical changes in matter occur when a substance undergoeschange, but retains its chemical composition. Water can be inthe form of liquid, a solidice, or a gaswater vapor, but italways has the same chemical composition, H2O. Another termfor this is changes of state.

Chemical changes are significantly different and when theyoccur, there is an actual change in the chemical composition ofthe substances. The original atoms are preserved but they com-bine in such a way that a new substance is created with a dif-ferent chemical composition than the original. There are manyexamples of this. Metals can be melted together and form newalloys with a different chemical composition than the original.

Plastics are made by combining different types of elements. Inthe process, new substances with unique qualities are created.

Chemists make a distinction between pure substances and mix-tures. In a mixture, different substances are mixed together butdo not bond. Muddy water is a good example. The mud andthe water do not join together and if left to stand for a time, themud will settle to the bottom.

In a compound, however, the valence electrons of elements arelost, gained, or shared between the different atoms to create

substances with unique chemical properties. These unions arecalled chemical bonds. There are two basic kinds of bonds:ionic bonds and covalent bonds.

IONIC BONDSA neutral atom is made up of an equal number of positivelycharged protons and negatively charged electrons. Protons inthe nucleus of atoms rarely become free, but electrons have theability to move and it is the valence electronsthose electronsin the outer energy levelthat move and give the element itschemical characteristics.

When an atom loses an electron, or more than one electron, it becomes a positive ion, because it now has more positivelycharged protons than electrons. If an atom gains electrons, giv-ing it more electrons than protons, it becomes a negatively

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charged ion. These ions then attract each other because of theiropposite charges. The two elements do not merge; they lose orgain electrons.

The periodic table predicts when this type of bond is likely tohappen. Chlorine is in group 17 and all elements in this groupneed one more electron to fill their valence energy level. Allelements in this group strongly attract electrons. They are saidto be electronegative.

Sodium is in group 1 and all elements in this group have onlyone electron in their valence energy level. These elements areelectropositive, meaning that they are more likely to lose elec-

trons. Sodium is an element with only one valence electron inits outer energy level. Chlorine is an element with one electronmissing to complete its outer energy level and become stable.

When these two elements come close together, there is a natu-ral tendency for the lone valence electron of sodium to move tocomplete the valence energy level of chlorine. In the process,the two atoms become ions and form an ionic bond. As a resulteach of the elements becomes more stable. The new compoundformed is sodium chloride, a substance everyone knows as tablesalt.

This relationship is common in chemistry and has given rise tothe octet rule, which states that: "Atoms tend to gain, lose, orshare electrons in order to acquire a full set of valence elec-trons."

When ions are close together, they assemble into a pattern. Ne-gative and positive electrical charges attract each other. Forexample, in sodium chloride, or table salt, the sodium ions aresurrounded by the chloride ions, which in turn are surroundedby the sodium ions and so on. They are arranged in this way tomaximize the electrical attraction among them.

There are many examples of ionic bonds. Some, like calciumcarbonate, involve more than two elements. Ionic compoundsshare a number of similar properties. They have high melting

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points and tend to be brittle. Most dissolve in water, which sep-arates the ions and makes the water a good conductor of elec-tricity.

COVALENT BONDSIonic bonds occur when electrons are transferred betweenatoms, but there are many substances formed when electronsare shared between atoms in covalent bonds in structures calledmolecules.

A vast number of substances have molecular structures, includ-ing plastic, paper, all plant life, water, most of the air we breathe, and every tissue in the bodies of animals such as

humans. Molecules can be made up of as few as two atoms orhundreds of them. The DNA molecules that provide the hered-itary code in every cell of our bodies are made up of about one billion atoms. It is the ability of atoms to join together intocovalent bonds that result in the millions of substances that wefind in the world.

To describe the composition of molecules, chemists use molec-ular formulas, which precisely describe how many atoms thereare in a single molecule. O2, for example, is a molecule of oxy-gen, which is in the air we breathe and flows through our blood-

stream. O is the symbol for oxygen, and 2 indicates that thereare two oxygen atoms in the molecule.

This is the molecular formula for ordinary table sugar:(C12H22O11). It is a complicated molecule but it is possible to seeits composition at a glance. The molecule is made up of 12 car-bon atoms, 22 hydrogen atoms, and 11 oxygen atoms.

Molecules always arrange themselves in the same proportions because the atoms bond together in a predictable way. Thechemical formula of a substance reflects these proportions.This is called the Law of Constant Composition, which states"A given compound always contains the same elements in thesame proportion by mass." Pure water, H2O, for example, isalways 88.9% oxygen and 11.1% hydrogen by mass.

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The principle that influences covalent bonding is the octet rule,the same rule that influences ionic bonds. In a molecule ofwater, H2O, the oxygen atom has 8 electrons, 6 of which are inits valence energy level. As this Lewis Dot drawing shows,when the oxygen joins with hydrogen, the two electrons fromthe hydrogen atoms complete the valence energy level of theoxygen atom and satisfy the octet rule. The molecule also com-pletes the valence energy level of the hydrogen atoms.

Although the octet rule predicts the structural formulas for mil-lions of molecules, there are many exceptions. Some atoms,particularly those elements that are beyond the second row inthe periodic table, often form bonds that have an irregular num-

ber of electrons in the valence energy level. This is true ofphosphorous and sulfur.

Molecules have different shapes and sizes. Some have a linearshapethe centers of the atoms fall in a straight line. Othershave a triangular shape, and still others have the shape of tetra-hedrons. The reason atoms arrange themselves in this way isbecause of the attraction and repulsion of the electrical chargesbetween the atoms.

The length of the bonds varies and many molecules have slightnegative and positive charges. This is called polarity and results

from unequal distribution of the electrical charges.

CHEMICAL REACTIONSWhen we crack an egg into a hot pan, it changes from a semi-liquid, runny goop into a fried egg, ready to eat. The egg can'tbe uncooked and put back into the eggshell. It has undergone achemical reaction.

A chemical reaction is a process in which one or more sub-stances are converted into new substances with different physi-cal and chemical properties. During a chemical reaction, atomscan form molecules, molecules can break apart, or react withother molecules and new bonds are formed. Some substancesreadily go through chemical reactions, but others do not be-cause of the arrangement of the electrons in the atoms and mol-ecules.

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There are an incredible number of chemical reactions going onaround us all of the time. All life processesrespiration, diges-tion, and reproductionare chemical reactions, as are the com-bustion of gasoline in car engines, the rusting of metal, and thedecomposing of plants.

Chemists categorize reactions to describe what is happening ata molecular level. A synthesis is a union of substances into anew molecular structure, in this case, a polymer. A singlereplacement reaction is one in which one element displacesanother. Here we see sodium-displacing hydrogen from water.And a double replacement reaction is an exchange of elementsto form new compounds. Potassium leaves iodine behind and

bonds with nitrate, and lead breaks its connection to nitrate andbonds with iodine. The rate of these reactions can be affectedby temperature and the presence of a catalyst.

Chemical equations are written to describe what happens in achemical reaction. This is magnesium, quite a reactive element.When it reacts with hydrochloric acid, hydrogen gas is pro-duced. It can be written magnesium plus hydrochloric acidproduces magnesium chloride plus hydrogen gas: Mg + HC1MgCl2 + H2. The arrow means yields or produces.

The key to understanding chemical equations is that they mustbalance. Matter can never be created or destroyed. There mustbe the same number of atoms on each side of the equation. Isthis chemical reaction written correctly? No! On the right-handside of the equation, there is one magnesium atom, two chlorineatoms and two hydrogen atoms. The equation does not balance.In order to make both sides of the equation balance, there must be 2 molecules of hydrochloric acid. This is now the properequation: Mg + 2HC1Mg Cl2 + H2.

The system that chemists have developed for writing the equa-tions for chemical reactions and the formulas for compoundsare precise ways of describing the structure and reactions ofelements at an atomic level.

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ELECTROCHEMISTRYOne special type of chemical reaction is called oxidation-re-duction, or redox reaction. Oxidation refers to the loss of elec-trons, while reduction refers to the gain of electrons.Oxidation-reduction reactions occur when electrons are trans-ferred from the atom that is oxidized to the atom that is reduced.

There are a wide variety of redox reactions that occur in naturefrom the rusting of iron, to breathing in animals, to the func-tioning of muscles.

An important class of oxidation-reduction reactions is used toprovide electric current in voltaic cell batteries. This is a sim-

plified drawing of a voltaic cell battery. These types of batter-ies can be created using any two different metals since metalsdiffer in their tendency to lose electrons. We take advantage ofthis by connecting two such metals with a wire to allow elec-trons to flow from one to the other. This is electric current.

In this example, zinc is placed in a zinc-salt solution, zinc sul-fate, and copper is in a copper-salt solution, copper sulfate.Oxidation takes place at the electrode we call the anode andreduction occurs at the cathode.

Zinc atoms of the anode are oxidized, providing two electrons,which flow through the external wire from the anode to thecathode. This causes the electric current to light the bulb. Intheir oxidation, the zinc atoms have become positive ionsbecause they have given up electrons, and they go into the solu-tion.

On the copper side, when the two electrons are received, theyreduce a copper ion in the copper-sulfate solution into a neutralcopper atom, which attaches itself to the cathode. As this pro-cess continues, an imbalance of charge is very quickly built up

in the battery, as positive charges are generated on the left andnegative charges accumulate on the right. For the voltaic cell tocontinue to produce an external electric current and power thelight bulb, there must be a movement of sulfate ions in solution

19


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from the right to the left, to balance the electron flow in theexternal circuit wire.

This is an oxidation-reduction process. At the anode, oxidation or loss of electronsoccurs, and at the cathodereduc-tionor gain of electrons occurs.

When scientists came to understand how elements bonded tobecome compounds, they were able to explain one of the greatriddles that has puzzled us since the beginning of human civi-lization: what is the makeup of matter?

20


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Name ____________

Directions: This will help you discover what you know about compounds and reactions before you begin

this lesson. Answer the following True or False.

1. Matter can never change.

T_______ F_______

2. Chemical reactions occur when there is a change in the chemical composition of substances.

T_______ F_______

3. In a mixture, substances do not bond.

T_______ F_______

4. In an ionic bond, the protons in the nucleus attach themselves to other atoms.

T_______ F_______

5. An electropositive element is one that has a tendency to attract electrons.

T_______ F_______

6. Molecules are covalent bonds.

T_______ F_______

7. A molecular formula precisely describes how many atoms there are in a single molecule.

T_______ F_______

8. A molecule of water, H2O, has two oxygen atoms and one hydrogen atom.

T_______ F_______

9. All life processeslike respiration, digestion, and reproductionare chemical processes.

T_______ F_______

10. A battery produces electricity by passing electrons back and forth from the anode to the cathode.

T_______ F_______

1

2003 Algonquin Educational Productions Published and Distributed by United LearningAll rights to print materials cleared for classroom duplication and distribution.

COMPOUNDS AND REACTIONS from theElements of Chemistry Serie

Pre-Test


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2a

Name ____________



Vocabulary Definitions

anode - Where oxidation, or the giving up ofelectrons, occurs.

atom - The fundamental unit of matter in the

universe, made up of a nucleus of protons

and neutrons and orbiting electrons

atomic number - The number of an element

determined by the number of protons in its

nucleus.

atomic mass - The mass of the element.

cathode - Where reduction, or the gain of

electrons, occurs.

change of state - Most substances can

undergo changes from a gas, to a liquid, to a

solid, but still retain their chemical composi-

tion. This is sometimes called physical

change.

chemical bonds - When valence electrons

of elements are lost, gained, or shared

between different atoms to create substances

with unique chemical properties.

chemical equations - Descriptions of what

happens in a chemical reaction using chemi-cal symbols.

chemical reaction - A change in the che-

mical composition of a substance.

compounds - When valence electrons of

elements are lost gained or shared between

different atoms to create substances with

unique chemical properties.

covalent bonds - When electrons are shared

between atoms, they are called covalent

bonds, or molecules.

double replacement - An exchange of ele-

ments to form a new compound.

electrochemistry - The study of the chemi-

cal effects of electrical action.

electron - Negatively charged particles that

orbit the nucleus of atoms.

electronegative elements - Those elements

that tend to attract electrons. They are on the

right-hand side of the periodic table.

electropositive elements - Those elementsthat tend to lose electrons. They are on the

left-hand side of the periodic table.

element - An atom with a unique number of

protons.

energy levels - Electrons orbit the nucleus

of atoms with different levels of energy.

These energy levels are sometimes called

shells or levels. The energy levels corre-

spond to the periods of the periodic table.

fission - When the nucleus of atoms are split

apart releasing energy. This is the energy ofnuclear bombs and nuclear reactors.

fusion - When two hydrogen atoms fuse

under extreme heat, energy is released.

Fusion is the energy of the sun and stars.

groups - Vertical columns of the periodic

table.

ions - Atoms with more electrons than pro-

tons or fewer electrons than protons are

called ions.

ionic bonds - Two or more ions held to-

gether by the electrical attractions be-tweenthem.

Law of Constant Composition - A given

compound always contains the same ele-

ments in the same proportion by mass.

Lewis Dot drawings - Representations of

elements by showing the valence electrons

as dots around the nucleus.

matter - Material that makes up objects.

Matter cannot be created or destroyed.

mass - The total quantity of an object's mat-ter.

mixtures - When substances are mixed but

do not chemically bond.

molecules - When electrons are shared

between atoms. Molecules are covalent

bonds.

molecular formula - The precise descrip-

tion of the type and number of atoms in a

single molecule.

negative ion - An ion that has more elec-trons than protons.

neutral atom - When an atom has an

equal number of protons and electrons, its

electrical charges are balanced and the

atom has a neutral electrical charge

neutron - Particles in the nucleus of atoms

that have no electrical charge.

nuclear change - A change that occurs in

the nucleus of atoms.

octet rule - Atoms tend to gain, lose, or

share electrons in order to acquire a full set

of valence electrons.

physical change - When a substance under-

goes change but retains its chemical compo-

sition. This is sometimes called change of

state.

polarity - Molecules with slight negative or

positive charges.

positive ion - An ion that has fewer elec-

trons than protons.

proton - Positively charged part of thenucleus of atoms.

Quantum Theory - The theory that ex-

plains matter and energy at atomic and sub-

atomic levels.

radiation - When the nucleus of an atom

decomposes to form a new nucleus, it re-

leases radiation in the process.

reduction - The gain of electrons.

single replacement - When an element

replaces another element.

synthesis - A union of substances into a new

molecular structure.

valence electrons - The outer ring of elec-

trons of an element.

Volta, Alessandro (1745-1827) - Italian

physicist best known as the developer of the

voltaic battery, which is named after him.

voltaic cell battery - A devise for producing

an electric current by the action of two plates

of different metals in an electrolyte.

The following words and terms used in the program may be unfamiliar to you. Try to listen for these terms whileviewing the program, pay close attention so you can later include them in your scientific descriptions, observa-tions, and creative writing assignment activities.


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Name ____________

2b


Directions: Find the right word from the vocabulary list that completes the following sentences.

1. Fusion is an example of ____________ ____________ because it is the change in the nucleus of atoms.

2. ___________ ____________ occurs when there is an actual change in the chemical composition of sub-

stances.

3. An ____________ is an atom that has more or less protons than electrons.

4. "Atoms tend to gain, lose or share electrons in order to acquire a full set of valence electrons," is called

the ____________ ____________.

5. Substances formed when electrons are shared between atoms in covalent bonds are called __________.

6. ____________ ____________ are precise descriptions of the number and type of elements in a single

molecule.

7. Many molecules have slight negative or positive electrical charges. This is called ____________.

8. A union of substances into a new molecular structure is called a ____________.

9. ____________ refers to the loss of electrons, while ____________ refers to the gain of electrons.

10. A device for producing an electrical current by the action of two plates of different metals in an elec-

trolyte is called a ____________ ____________ battery.


Use the Right Word


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2c

Name ____________



Word Match

Directions: Connect the word with the proper definition.

anode an atom with more or less protons than electrons

cathode molecules with a slight positive or negative charge

chemical reaction change in chemical composition of substance

electrochemistry the gain of electrons

element where oxidation occurs

ion where reduction occurs

molecule an atom with a unique number of protons

oxidation study of chemical effects of electrical action

polarity covalent bond

reduction loss of electrons


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Name ____________

3



Connected/Not Connected

Directions: Place the following words in the proper sentences.

fusion positive ions ionic conventional

fission mixtures covalent oxidation

changes in state compounds negative reduction

chemical reactions electronegative positive anode

negative ions electropositive voltaic cathode

1. ____________ is connected to ____________ because both are nuclear charges.

2. ____________ are NOT connected to ____________ because a substance undergoes change in one while

in the other there is a change in the chemical composition of the substance.

3. ____________ are connected to ____________ because the opposite electrical charges holds them togeth-

er.

4. ____________ are NOT connected to ____________ because in one the substances do not bond and in

the other there is a chemical bond of the substances.

5. ____________ elements are connected to ____________ elements because one tends to lose electrons

and the other tends to gain electrons.

6. ____________ bonds are NOT connected to ____________ bonds because the electrons in one type of

bond are lost or gained between the elements and the electrons in the other type of bond are shared betweenthe elements.

7. Molecules with a slight ____________ charge and molecules with a slight ____________ charge are con-

nected because they tend to attract each other.

8. A ____________ cell battery is NOT connected to ____________ electric power because in one the elec-

tricity is the result of a chemical reaction and in the other the electricity is generated by mechanical energy

when a magnet is spun in a coil of wire.

9. ____________ is connected to ____________ because one refers to the loss of electrons and the other

refers to the gain of electrons.

10. An ____________ is NOT connected to a ____________ because one electrode is where oxidation occurs

and the other is where reduction occurs.


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Name ____________

4



Crossword Puzzle

1 2

3

4 5 6

7

8 9

10 11

12

13

14

15

Across

3. Atoms with greater or fewer protons than electrons.

4. Where reduction occurs.

7. When substances mix, but do not bond.

8. Release of energy when a nucleus decomposes.

11. Positively charged particles in the nucleus of

atoms.12. _____ cell battery.

13. Covalent bonds.

14. Union of substances into new molecular structures.

15. The gain of electrons.

Down

1. Molecules with slight negative or positive char

2. Negatively charged particle.

5. The loss of electrons.

6. The study of the chemical effects of electrical

action.

9. Where oxidation occurs.10. The rule of how elements gain, lose, or share

electrons.


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5

Name ____________

5



Creative Writing Story Ideas

Directions: Choose from one of the ideas listed below and write a story or dramatization. Include plot

lines that follow scientific principles and key vocabulary terms.

1. You have been asked by a prominent politician to write a speech advocating the expenditure of several bil-

lions of dollars to research fusion techniques for the generation of electricity. What is the text of the speech?

2. Chemists working in a private company have synthesized a new group of substances that are resistant to

the effects of heat, light, water, organic pests, and radiation. The company president has asked them to come

up with some ideas about how these new products might be commercialized. Write a story that dramatically

illustrates how they come to their conclusions.

3. Four university chemists have collaborated to analyze the chemical structures of a group of newly discov-

ered substances. Some have worked very hard at the project and made major contributions while others have

done little or nothing, but all four are very anxious to be recognized because those given credit for theachievement will gain enormous prestige and their careers will be greatly enhanced. Write a short story

describing what happens when the association of chemists meets to give rewards and credit for the work.

4. Write a film script with a story line that involves four high students in a chemistry lab trying to understand

the molecular structures of various substances. A little humorous dialogue might lighten up the story.

5. Write a story that explores the reaction that people in the early nineteenth century might have had when

they saw how a voltaic cell battery actually worked. Perhaps the Italian physicist, Alessendro Volta, could be

in the story demonstrating this startling new technology.


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6

Name ____________


Video Quiz

Directions: Answer the following either true or false, or fill in the blank with the correct word to

make it true.

1. There are only 92 elements that are found naturally in the universe.

T_______ F_______

2. The process when atoms are broken apart to release energy is called fusion.

T_______ F_______.

3. When there is a change in the chemical composition of a substance, it is called a chemical __________.

4. When an atom loses or gains one or more electron, it becomes an ____________.

5. The octet rule states that atoms tend to gain, lose, or share electrons in order to acquire a full set of

valence electrons.

T_______ F_______

6. When electrons are shared between atoms in covalent bonds, they are called ____________.

7. Molecules never arrange themselves in the same way.

T_______ F_______

8. A chemical reaction is a process in which one or more substances are converted into new substances

with different physical and chemical properties.T_______ F_______

9. Chemical equations do not need to balance. There can be different numbers of atoms on each side of

the equation.

T_______ F_______

10. The electric power in a battery is generated by a chemical reaction.

T_______ F_______



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7

Name ____________

7COMPOUNDS AND REACTIONS from theElements of Chemistry Serie

Post-Test

Directions: Fill in the blank with the appropriate term from the list below.

anode electron mixtures polarity

cathode element molecules protonchemical reaction ionic bond orbitals radiationelectrochemistry mass oxidation reduction

1. When there is a change in the chemical composition of a substance, it is called a ____________.

2. When two or more ions are held together by the electrical attractions between them it is called an

____________.

3. A covalent bond is when electrons are shared between atoms. These bonds are usually called

____________.

4. In a battery, the place where oxidation, or the giving up of electrons, occurs is called the ____________.

True or False

Directions: Fill in the blank with True or False. If the statement is false, change it to make the state-

ment true. Rewrite the true statement in the space provided.

5. __________ Nuclear changes occur when electrons move from atom to atom.

6. __________ Ionic bonds occur when the electrons of one atom merge with the electrons of another atom.

7. __________ When electrons are shared between atoms, they form covalent bonds, or molecules.

8. __________ A chemical reaction only occurs when molecules are formed.

9. __________ Oxidation-reduction, or redox reactions, occur when molecules merge.

Essay Section

Directions: Answer the following questions in complete sentences. Use the back of this page or a sep-

arate sheet of paper to complete your answers.

10. Explain how ionic bonds are formed.

11. Explain how covalent bonds are formed.

Documents

Chemistry Compounds Teacher