Matter and Chemical Change - Weebly

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U N I TU N I T

Matter andChemicalChange

Matter andChemicalChangePicture yourself sitting around a campfire after a day ofhiking. In this peaceful setting, chemical changes are takingplace all around you.

• The light and heat of the campfire are evidence of acommon chemical reaction.

• When you roast a marshmallow, the sugars in it reactwith oxygen to form a black and brittle carbon crust.

• When you eat the marshmallow, the chemical energy inthe sugars is transformed into other forms of energy.

• During the day, the evergreen trees use the Sun’senergy and carbon dioxide in the air to make food for themselves.

Your tent and camping gear are products of chemicalreactions. You likely got to the site in a motor vehicle that usedchemical reactions to move.

Chemical change is involved in every part of your dailylife. In this unit you will learn more about these chemicalchanges, and about the choices you can make to minimizechemical changes that damage the environment.

AA

2

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Matter and Chemical Change • MHR 3

Chapter 1Useful Chemistry

Chapter 2Common Reactions inOur Lives

Chapter 3Types of ChemicalReactions

Chapter 4Reactions and theEnvironment

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Over the past 100 years,advances in chemistry haveprovided many consumer productsthat have helped to change ourlives. These advances include theability to produce syntheticmaterials that have helped usreduce our need for naturalmaterials. Instead of wool fromsheep and fur from wild animals, wenow use nylon, polyester, and othersynthetic fibres. This has helpedreduce the risk of extinction formany fur-bearing species.

Synthetic dyes have made itpossible to produce dramatic coloursnot possible with natural dyes. Forexample, the orange colour used on hunting vests and clothing foremergency crews is synthetic. So aremost of the colours that were usedin making textiles during thetwentieth century.

Chemistry has also given usmany of the conveniences we takefor granted. Products like detergent,Teflon™, and margarine existbecause of what society has learnedabout chemistry.

4 MHR • Matter and Chemical Change

C H A P T E RC H A P T E R

Useful ChemistryUseful Chemistry1• How has chemistry made

life easier over the past100 years?

• What would gardening belike without fertilizers andpesticides?

• What do a bathing suit,fire extinguisher, andclimbing rope have incommon?

• What does a cake rising inthe oven have in commonwith a growing baby?

• How can you use chemicals safely?

The chemical paste in

a dry cell battery

conducts electricity

to power a flashlight.

Think of some other

chemical processes

that make useful

materials or energy.

How would life be

different without them?

Write your thoughts in

your Science Log.

These everyday products all have a chemical connection.

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Useful Chemistry • MHR 5

Starting Point

Chemicals have changed the way hair stylists work. Thishairdresser is using ceramic tube hair curlers to provide tight curls during the 1940s.

What You Will LearnYou Will LearnY

In this chapter you will learn:• how new materials have changed everyday life over the

past 100 years• about some chemical changes involved in cooking,

cleaning, and gardening• about the role of chemicals in the workplace• how to interpret safety information at work and home

Why It Is Important

Skills You Will Use

• Everyday life has changed a lot in the past 100 years.Many of the things we take for granted today wereunimaginable when your great-grandparents were yourage. Our growing knowledge of chemistry has mademany of these processes and products possible.

In this chapter you will:• investigate how modern chemicals and processes have

changed daily routines• investigate chemical changes involved in cooking,

cleaning, gardening, and cosmetics• read and interpret HHPS and WHMIS symbols• read and interpret an MSDS

Old-fashioned Ice CreamMake ice cream simulating a process that couldhave been used 100 years ago.

Safety Precautions

• Clean up the work area and wash yourhands thoroughly at the end of the activity.

• Never eat anything that has been made in ascience room or laboratory.

What You Need

2 resealable freezer bags (1 small, 1 large)

100 mL ice-cream mix

500 mL crushed ice

100 mL salt

thermometer

measuring cups

What to Do

1. Pour 100 mL of the ice-cream mix into asmall resealable freezer bag.

2. Squeeze the air out of the bag. Seal it.

3. Mix half the ice (250 mL) and half the salt(50 mL) together thoroughly in the largefreezer bag.Take the temperature.

4. Place the small freezer bag inside the bagwith salt and ice, and pack the ice-saltmixture around the smaller bag.

5. Add the rest of the ice and salt.

6. Seal the large freezer bag. Flip it every2 minutes for about 10–15 minutes or untilthe ice-cream mix has hardened.

7. Take the temperature of the ice-salt-watermixture.

8. Do the analysis provided by your teacher.

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Chemistry Then and Now

Chemistry on the FarmIf you had been alive in Canada 150 years ago, you probably would have beenliving on a farm. As well as feeding animals, shovelling manure, and driving ateam of horses, your jobs would have included pulling weeds and pickinginsects off the crops in your garden.

Today, only about 2.5 percent of people in Canada live on farms. Advancesin chemistry and technology enable modern farmers to produce a lot more foodwith less human labour. Many farms have automatic feeders and barn cleaners.Teams of horses have been replaced by tractors and other machinery that alloweach farmer to do the work of several people.

In addition, synthetic or human-made chemicals produced in a lab havereduced the amount of work farmers have to do. Instead of pulling weeds andkilling insects, farmers now use synthetic pesticides. There are two commonkinds of pesticides. Herbicides kill unwanted plants, and insecticides killunwanted insects.

The use of chemical pesticides and synthetic fertilizers means the land canproduce more food. Advances in technology and chemistry help the producesurvive the trip to the consumer. In addition, the produce lasts longer on thegrocery store shelves and in your cupboard.


1.1

Pesticides such asDursbanTM are commonlyused to control insects.DursbanTM is a form oforganophosphate. It works by interrupting theelectrochemical processthat nerves use tocommunicate withmuscles and with oneanother. A lethal dosekills insects. Farmers haveto handle the pesticidewith great care because it can also damage thehuman brain and centralnervous system.

How do chemists helpmodern farmers?

Figure 1.1 Farmers and gardeners in the nineteenth century used manure from their livestock to fertilizethe crops and gardens. Some modern farmers still use manure, but most use fertilizers produced in thechemical laboratory. Instead of relying on animal and plant waste of varying quality, chemists mix rawchemicals (such as potassium nitrate) together to make fertilizer. These manufactured fertilizers can bemore effective than natural ones because they are designed for specific crops and specific fieldconditions. On the other hand, manure returns valuable organic matter to the soil.

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Find Out

Chemistry for CleaningOne hundred years ago, farmers made their own soap using ashes from thecooking stove and natural fats from various animals living on the farm. Similarmethods have been used for thousands of years.

In the past, beef fat was usually used when making soap. Today, somemanufacturers have replaced some or all of the animal fat with plant oils. For example, coconut oil may be used to make a soap that has a nice scent andcleans very well. Other ingredients are sometimes added to provide more sudsor help soften skin.

Many cleaners include strong bases. Bases produce soap when they reactwith the fatty acids in grease. Soap consists of a two-ended molecule. One endof the molecule dissolves in grease and the other dissolves in water. This reactionenables us to wash away grease.


How Can YouMake Soapfrom NaturalSubstances?

Safety Precautions

• Lye is extremely corrosive. If you get it on you, hold the body part under coolrunning water for 10 minutes.Inform your teacher.

• Use tongs to handlehot glassware.

• Hot grease can causesevere burns.

• Clean up the work area and wash your handsthoroughly at the end of the activity.

What You Need

lye (NaOH(s)) lard or shortening

scale hot plate

2 beakers (250 mL) tongs

water plastic knife

50 mL graduated cylinder small plastic

stirring rod container with lid

What to Do

1. Measure 3.4 gof lye.

2. In one beaker,dissolve the lye in 15 mL of water. CAUTION:The mixture will heat up as you stir.

3. Allow the solution to cool while you measure23 g of lard or shortening.

4. Heat the lard or shortening in the secondbeaker on a hot plate set at medium.

5. Using tongs, carefully set the beaker of meltedlard or shortening aside until the contents areat room temperature but still liquid.

6. Slowly pour the dissolved lye into the lard orshortening.

7. Stir the mixture constantly for 15 minutes.Allow the mixture to stand, and then mix againevery 15 minutes until the mixture thickens.

8. Pour the mixture into a small plastic container.

9. Cover the container and set it aside overnight.

10. Carefully, use a knife or ruler to loosen theedges of the soap from the container.


S K I L L C H E C K

Performing and Recording

Analyzing and Interpreting

Communication and Teamwork

Initiating and Planning




How does modern soapdiffer from the soapmade 100 years ago?

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Chemistry and SyntheticsOne of the major changes in the past 100 years has been the development ofsynthetic fibres or threads. One hundred years ago, clothing was made fromnatural fibres such as cotton, flax, wool, and silk.

• The downy, white fibres found in the seed pod of the cotton plant areused to make cotton thread. This is woven into cotton material.

• The stems of the flax plant are processed into threads that are woven tomake linen.

• The woolly coats of animals such as sheep and goats are spun into wool.This is woven into woolen material.

• Fibres from the cocoons of silk worms are made into silk thread, which iswoven into silk cloth.

Today, we still use each of the natural forms of cloth. In addition, many newand exciting type of fibres have been developed in the chemistry laboratory.

The first of these synthetic fibres was nylon. Nylon is made from coal, water,and air. It was first discovered by Wallace Carothers in the 1930s. When nylonwas first made, scientists did not see any practical use for the material untilsome chemists at the company were playing games to see how far they couldstretch it. They found that the stretched nylon fibres were very strong andsilky. By 1939, nylon was used to make stockings.

Other synthetic fibres include polyester, Gore-Tex™, and Kevlar™.


Identify one naturaland one synthetic fibre.How is each made?

Use tweezers to obtain strands of each of the following materials: cotton, linen, wool, silk, nylon,polyester, Gore-Tex™. How are synthetic and natural fibres the same? How do they differ?

Polyester is a fibre thatbounces back into shapequickly and does notabsorb very muchmoisture. This material is used to make clothesthat dry quickly and donot need ironing.

oiled cotton

wood and canvas

Gore-Tex

Kevlar

canvas

polyester

wool

hemprope

nylon netnylon

Tm

Tm

Figure 1.2 Identify the natural andsynthetic materials in these pictures.Note which items might be made from polyester, Gore-Tex™, or Kevlar™.

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Check Your Understanding

1. How have chemicals made modern farming easier than it was 100 years ago?

2. How has the process of making soap changed over the past 100 years?

3. Name two synthetic and two natural fibres. Describe at least two advantagesof synthetic fibres.


Plastics, Polymers, and AlloysAnother major change over the past 100 years has been the development ofsynthetic polymers. Polymers are a type of compound that occurs in nature.For example, the silk in spider webs and the sap from rubber trees are twonatural polymers.

During the past 75 years, chemists have made synthetic polymers in thelaboratory. The great thing about synthetic polymers is that scientists candevelop different ones with physical characteristics that meet a particular need.You know many of these synthetic polymers as types of plastic.

Table 1.1 shows some synthetic polymers, their properties, and how they areused. Read the descriptions and identify ways that you use each of them.

Table 1.1 Synthetic Polymers and Their Uses

1.2

Synthetic polymers havechanged the way we live.Identify three that play arole in your daily life,and explain how youuse each one.

Synthetic polymers canhelp you see. Thelightweight lenses intoday’s glasses are madefrom polycarbonates.These lenses are muchlighter and can be mademuch thinner than old-fashioned glass lenses.

syntheticpesticidesherbicidesinsecticidessynthetic fibres

Key Terms

Polymer Significant Properties Uses

neoprene rubbery, porous, insulating, does not shoe soles, hoses, wet suitsreact readily with other chemicals

polyethylene can be easily formed into lightweight containers milk jugs

polystyrene does not absorb water, poor conductor styrofoam cups, insulation

polyurethane flexible, fibrous, does not absorb water upholstery, clothing

H

HH

H

H

H

H

H

HH

H

H

CC

CC

CC

polyethylene

Figure 1.3 A polymer is a giantmolecule made up of many smalland identical sub-molecules. Apolymer is put together like a stringof beads. In the case of polyethylene,each bead consists of two carbonatoms and four hydrogen atoms. Inthis visual, the circled areas showone unit of the polyethylene polymer.

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Find Out

Make Your Own PolymerIn this activity, you will make a synthetic polymerusing substances you can find at home.

Safety Precautions


What You Need

disposable cup

stirring rod

graduated cylinder

5 mL white glue

5 mL water

10 mL borax solution

What to Do

1. Mix 5 mL of water with 5 mL of white glue ina disposable cup.

2. Add 10 mL ofborax solutionto the gluemixture andstir for 2 min.

3. Roll the lump in your hands until it is notsticky anymore.

What Did You Find Out?

1. (a) Reshape the putty into at least three forms.(b) What happens when you try to bounce

or stretch the putty?(c) What else can you do with it?

2. How have the physical characteristics of thesubstances changed throughout the activity?

3. This product was around for a long timebefore anyone thought of using it as anythingexcept a toy. Suggest two or three otheruses for it.


S K I L L C H E C K







AlloysHave you ever wondered why stainless steel does not rust? In the past, cookingutensils were made of iron that eventually rusted. Modern kitchen utensils aremade from several metals mixed to look like one metal. This type of mixture isan alloy. Alloys have properties of the original metals that make up the alloy.

Figure 1.4 Many kitchenutensils are made of stainlesssteel. Stainless steel is amixture of iron, chromium,nickel, and carbon.

Explain what an alloy is.Give one example.

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Using AlloysMany of the products you use today — fromcars to jewellery — are made from alloys. Steelfor buildings is an alloy of iron and chromium.Cars made from steel in the early 1900s werevery strong, but they were heavy and prone torusting. The steel in today’s cars is also mixedwith chromium. This steel alloy has thestrength and durability of iron, pluschromium’s resistance to rusting.

A new type of steel has been developed calledsuperplastic or ultrahigh-carbon steel. This newsteel contains more carbon than was used inprevious steels. Ultrahigh-carbon steel can be stretched to 100 times its length withoutbreaking. Earlier forms of steel could bestretched to only 1.5 times their original length.

This new steel can be used to make structures that are light but still very strong.

Pure gold is very soft and gets damaged easily, so most jewellery is made withalloys. For example, 14k gold is actually an alloy of gold, silver, and copper.


1. What metals are found in stainless steel utensils? How would your life bedifferent if kitchen utensils were not made from stainless steel?

2. In the winter, you choose clothes with fabrics that will keep you warm.(a) What materials keep you warm today?(b) What materials would you have used 100 years ago?

3. Synthetic polymers are used in many products. Name three syntheticpolymers and briefly explain how they have changed daily life.


synthetic polymersalloy

Key Terms

www.mcgrawhill.ca/links/science.connect2Most jewellery is made from alloys. To learn about some of the alloys used in jewellery,go to the above web site. Then go to Internet Connects, Unit A, Chapter 1, and then toPrecious Metals.

Figure 1.5 Silver and copper in these gold rings provide strength.The gold jewellery you wear is actually a gold alloy — a mixture ofgold and another metal, such as silver, copper, zinc, or nickel.

How have alloys changedthe transportation industry?

Put a few drops of water on iron and on stainless steel. Wrap the items in damp paper towellingand leave overnight. Observe the surface of the materials. Describe any changes. What is theadvantage of stainless steel over iron?

Brass is an alloy madefrom copper and zinc.Musical instrumentssuch as trumpets, horns,and cymbals are usuallymade from brass.

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Chemistry at HomeChemicals in the CupboardIf you did a quick survey of the cupboards in your kitchen, bathroom, andlaundry room, you would probably find all-purpose cleaners, toilet-bowlcleaners, and a variety of other cleaning products. Cleaners usually containsubstances that are reactive. They start chemical changes that break down the dirt and make cleaning less strenuous.

Drain cleaners, for example, often contain highly corrosive substances suchas sodium hydroxide. Sodium hydroxide is a base used to make drain and ovencleaners. Bases like sodium hydroxide help clean clogged drains by breaking downthe proteins (such as skin cells and hair) and animal fats that cause the problem.Heat is given off, which helps melt the grease.

Table 1.2 names other common household cleaners and explains how eachworks.

Table 1.2 Common Chemicals and How They Clean


1.3

caution

warning

danger poisonous

flammable

explosive

corrosive

Figure 1.6 Many hazardoussubstances are found athome. Some of thesesubstances are stored ina cupboard to keep themaway from young children.Others are kept in specialcontainers that preventaccidental poisoning.Almost all of theseproducts have safetywarnings on their labels.Hazardous HouseholdProduct Symbols (HHPS)are designed to be easy tounderstand. The shapesthat outline the pictures are designed to look likeroad signs.

Chemical Where Found How It Cleans

muriatic acid • steam-iron cleaner reacts with lime (scaly buildup)(hydrochloric acid) to form a soluble product

acetone • nail polish remover dissolves nail polish so it can be wiped away

methanol (wood alcohol) • paint solvent dissolves the paint

Explain how one cleaneruses chemical changeto clean. What is thenegative side of thischemical change?

Many of today’s furniture polishes include hazardous substances. In the nineteenth century,people polished their furniture using products that were less hazardous. You can make your ownfurniture polish by mixing 20 mL of lemon juice with 1 L of mineral oil. Spray or wipe this mixtureonto wooden furniture and wipe it with a dry cloth.

The mineral oil will seep into the wood and help prevent dust from sticking to the wood.The lemon juice will help speed up the absorption.

When you pour hydrogen peroxideon a cut, it will start to foam. Thatis because the hydrogen peroxideturns into water and oxygen — achemical change. The foaming helpsremove small particles that couldenter the skin and cause infection.The chemical reaction also killsbacteria that enter the wound.

Figure 1.7

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Chemistry and CookingA knowledge of chemistry is important to chefs, bakers,and cooks. Knowing how different ingredients react allowsthem to control chemical reactions. For example, bakersmay use yeast to make bread. Yeast is a single-celledorganism that needs food, warmth, and moisture tothrive. It converts its food (sugar and starch) intocarbon dioxide and alcohol. Carbon dioxide bubblesmake baked goods rise.

A mixture of vinegar and baking soda will alsoproduce carbon dioxide gas. Sometimes bakers use thismixture to make baked goods rise. Sponge toffee, forexample, is a mixture of vinegar, baking soda, and sugar.


Describe one chemicalchange used in cooking.How is it used?

Cooking involves many other chemical reactions.For example, citrus fruits and rhubarb react withkitchen utensils made of aluminum. The acid in these foods reacts with the aluminum in theutensils and produces hydrogen gas. Thisreaction will cause the utensil to becomecorroded and no longer useful.

To avoid such a reaction, many chefs usekitchen utensils made from stainless steel.Stainless steel will not react with acid.

The inside of an aluminum soft-drink can doesnot react with the acid in the soft drink becausethe aluminum has been coated with a plasticpolymer that keeps the pop from coming intodirect contact with the aluminum.

Figure 1.9

In 1897, J.J. Thomson found that there were small electrons embedded in the atom like chocolatechips in a chocolate chip cookie or raisins in a plum pudding. Think & Link Investigation 1–A onpage 14 demonstrates something else chocolate chip cookies and chemistry have in common.

Figure 1.8 Yeast isresponsible for the chemicalreaction that makes breadrise. This knowledge helpsbakers produce differentkinds of bread.

Test whether yeast is active by dissolving15 mLof dried yeast and 5 mL of white sugar in 250 mLof warm water. Observe the mixture for severalminutes. What happens?

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Chemist’s Recipe forChocolate Chip CookiesCooks, chefs, and bakers use chemistry every day. They work with chemicalcompounds and polymers, use specialized tools to measure the volume andmass of ingredients, apply or remove thermal energy, and cause chemical andphysical changes to matter. In this activity, you will investigate the chemistryinvolved in baking chocolate chip cookies.


1–A1–A

Safety Precautions

• Never eat anything that has beenmade in a science room or laboratory.

• Be aware that some ingredients cancause allergic reactions in some people.

• Wash your hands and clean up thework area at the end of the activity.

Apparatusvolumetric measuring devices

(measuring spoons and cups)

2 reaction vessels (2 L) (mixing bowls)

wooden or plastic mixing utensils

metal reaction plate (cookie sheet)

device that will convert electricalenergy into thermal energy

cooling rack

MaterialsSee list on recipe card.

What to Do 1 Use the wooden mixing utensil to cream the

partially hydrogenated tallow triglyceride,4-hydroxy-3-methanoxybenzaldehyde, andboth types of C12H22O11(s) together in one ofthe reaction vessels.

2 Add the calcium carbonate encapsulated,avian-produced, albumen-coated protein,shells removed. Mix well.

3 In the second reaction vessel, combine themixture of 75 percent starch and 25 percentprotein, sodium chloride, and sodium hydrogencarbonate. Add to the creamed mixture.

4 Stir in the Theobroma cacao chips.

5 Spoon the final mixture onto a metal reaction plate.

6 To allow for the chemical reactions to takeplace, insert the metal reaction plate into thethermal energy producing device for 8 to 10minutes and bake at 463K (190˚C) until golden brown.

7 When complete, place the products of thechemical reactions on a cooling rack andallow the product to come to equilibrium.

8 Do the analysis your teacher provides.

Chemist's Chocolate Chip Cookies500 mL of a mixture of 75 percent starch and 25 percent protein (flour)5 mL NaHCO3(s) (sodium hydrogen carbonate or baking soda)5 mL NaCl(s) (sodium chloride or salt) 250 mL CH3(CH2)(16)COOH(s) (partially hydrogenated tallow triglyceride or butter)175 mL refined C12H22O11(s) (sucrose or white sugar)175 mL refined C12H22O11(s) (sucrose refined with molasses or brown sugar)5 mL C8H8O3(l) (4-hydroxy-3-methanoxybenzaldehyde or vanilla)2 medium calcium carbonate encapsulated avian-produced, albumen-coated protein,

shells removed (eggs)500 mL C12H22O11(s) Theobroma cacao chips (chocolate chips)

S K I L L C H E C K








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1. Many household cleaners rely on chemical changes to do their work. Whatchemical change occurs when you add drain cleaner to a clogged pipe?

2. Identify three chemicals commonly found in household cleaners anddescribe how each of these chemicals helps to clean.

3. (a) Yeast helps bread to rise. Explain the chemical change that yeastproduces and how this makes bread rise.

(b) If you wanted a flat bread, would you use more or less yeast? Explain.

Chemistry at WorkEven 100 years ago, chefs were using chemistry todo their work. So were blacksmiths and welders. Forexample, the welder in Figure 1.10 knows that piecesof steel must be heated to a very high temperature tomelt them. Only then can they be welded together.A chemical change involving acetylene gas andoxygen produces enough heat to melt steel.

In the early 1900s, blacksmiths served as bothmechanics and welders. When they were notshaping metal, they often experimented withdifferent ways to combine metal and other materials.

Today chemistry is used in every workplace.The list below provides some examples. Consider any place where you ormembers of your family work. What chemistry is involved?

Automotive Repair Shop — Paints, fillers, and cleaners all involvechemical reactions. Special car paint protects metal car bodies fromrusting. Waxes and polishes protect that paint. When the paint getsfaded by the Sun, special waxes may remove tiny amounts of paintto restore the shiny appearance.

Hair Salon — Just about everything but the scissors involves achemical change. This includes colorants, curling solutions,shampoos, and conditioners.

Office — Hazardous chemicals are common in inks, toner cartridges,correction fluid, and the fire retardants in paper, upholstery, and carpets.

Construction Site — Hazardous chemicals are found in demolitionexplosives, wood preservatives, paints for finishing, and solvents forcleaning up. Many solvents used to clean grease stains or washwindows include ammonia. Ammonia works by dissolving grease,wax, and window dirt.


1.4

HHPS

Key Terms

Figure 1.10 The acetylenetorch uses a chemicalreaction that producescarbon dioxide, water, andenough energy to melt steel.

Every workplace usessome type of chemicalreaction. Name onechemical reaction usedwhere you work part-timeor in your classroom.

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Cosmetic Chemistry

Before 1938, most people cleaned their hair with soap. Have you ever usedbar soap on your hair? It probably left your hair dull and rough — not reallythe look you wanted.

This happens because soap is a base that breaks down protein such as hair.Soap also reacts with calcium in water, leaving a scum layer on your hair. Thislayer makes hair dull and difficult to comb.

Even before 1938, hair stylists knew how to deal with this layer of scum.They used an acid rinse made from vinegar or lemon juice to dissolve thescum, making the hair shine again.

When you buy shampoo, you are buying a synthetic detergent that will helpwash oil and dirt from your hair. Dish detergents wash grease and dirt fromyour dishes. In the next activity, you will determine which detergents cleandishes best.


Soap will clean yourhair, but why won’tsoap make your hairshiny and smooth?

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

acids

acid rain

ant bites

purerainwater

blooddetergents

draincleaner

sea water

stomachacid

bases

neutral

Figure 1.12 This diagramshows the pH of somecommon substances.Where do the shampoosyou use in Design & DoInvestigation 1–B fit onthis scale?

Figure 1.11 Do you useshampoo that adds textureto your hair? If so, you areputting plastic in your hair.Such shampoos simplycover hair with plasticresins. The plastic resinsmake the hair thicker,which appears to improveits texture.

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Which Dish Detergent Is Best?Liquid dishwashing detergent has special ingredients intended to:• dissolve oil and grease from the surface of dishes: and• keep oil and grease suspended in the wash water.

In this activity, you will design an investigation that will determine which liquiddish detergent works the best.


1–B1–B

ChallengeDesign and construct an investigation that willexamine the ability of a liquid dishwashing detergentto remove grease from a clear plastic glass.

Safety Precautions

• Dish detergent can cause skin or respiratory irritation.

• Do not get dish detergent in your eyes. If you do, flush with water for 10 min.

• Clean up the work area and wash your handsthoroughly at the end of the investigation.

Apparatus4 large beakers

Materials4 different brands of liquid dish detergent

(approximately 1 mL of each)

4 clear plastic drinking glasses

4 mL tomato spaghetti sauce(or other source of grease)

Design CriteriaA. Test the four liquid dish detergents to see

which is best at removing grease from a plasticdrinking glass.

B. Develop a procedure that identifies: • one manipulated variable;• the responding variable: and• the other variables that you control.

C. Develop criteria to evaluate how well eachliquid dish detergent removes the grease froma plastic glass. For example, you might want tohold the glass up to the light and assess itscolour before and after washing.

Plan and Construct1 Identify what materials your group will need

to carry out this investigation.

2 Identify the manipulated variable, theresponding variable, and all of the othervariables you will control.

3 Write out all of the steps that you will followin this investigation. Include the safetyprecautions.

4 List the criteria you will use to evaluate thecleaning ability of the dish detergent. Thecriteria that you select should allow you torank the detergents from best to worst.

5 Create a data table to record your results.

6 Record your results and rank the detergentsbased on the tests your group performed.

S K I L L C H E C K








Evaluate1. Is there any difference between the

detergents tested?

2. Did your evaluation criteria help you rankthe detergents?

3. Which detergent worked best? Explainyour answer.

4. Why do dish detergents include an activeingredient that dissolves oil and grease andkeeps it suspended in water?

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Find Out

Make-up and Face CreamCosmetics have been around for thousands of years. Some of these cosmeticsare harmless, but others are not.

Many cosmetics are tested on animals before being used on people.Researchers study how much the animals are affected before allowing thematerial to be used on humans.

Today, many groups oppose the use of animals in testing cosmetics. As aresult, many manufacturers advertise that their products have not been testedon animals. Knowledge of chemistry helps manufacturers control chemicalreactions. Use the next activity to make your own skin cream.


Make a Skin Cream

In this activity, you will make a hand cream usingreadily available materials. As the skin ages, theouter layers become thinner and dryer. This tendsto exaggerate fine lines and wrinkles.

Various skin creams will help make the skin looksmoother by putting moisture back into the skinand creating a barrier to prevent evaporation. Ofcourse, the best way to make your skin look goodis to eat a proper diet and drink plenty of water.

Many skin creams are emulsions of oil, water, andwax. An emulsion is a mixture of two liquids, such asoil and water, that normally do not mix. If you shakeoil and water together, you get an emulsion that isunstable and will separate quickly.

An emulsifier can be used to make the emulsionmore stable. An emulsifier works by coating thedroplets of one liquid so they stay suspended inthe other liquid.

SafetyPrecautions


What You Need

60 mL distilled water

120 mL mineral oil

1 g borax

30 mL grated beeswax

hot plate and wire mesh screen

ice bath or access to a refrigerator

100 mL beaker

250 mL beaker

1000 mL beaker or small saucepan

100 mL graduated cylinder

stir stick or plastic spoon

What to Do

1. Use the graduated cylinder to add 60 mL ofdistilled water to the 100 mL beaker.

2. Dissolve the borax in the distilled water andset aside.

3. Use the graduated cylinder to add 120 mL ofmineral oil to the 250 mL beaker. Add thebeeswax to the mineral oil.

S K I L L C H E C K







Cosmetic manufacturing isbig business today. Eachyear, consumers spendbillions of dollars oneverything from creamsand oils to shampoos andshaving cream. Many ofthese products usechemical changes to keepyou looking good.

How is chemistry usefulin the development ofcosmetics? Explain.

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The Key to Chemical SafetyThe acid from a car battery will burn your skin. That is why people weargloves when handling a car battery.

How do you know what safety precautions to use when handling asubstance you have never used before? The best way is to read the label.

If the dangerous substance is found in a workplace — including a school,restaurant, or repair shop — you will find a WHMIS label on the container.WHMIS stands for Workplace Hazardous Materials Information System.It provides detailed information on how to store, handle, and dispose ofdangerous substances at work.

If you are working with hazardous materials, you should also check theMSDS or Material Safety Data Sheet. The MSDS provides detailedinformation that will not fit on the product label.


1. Choose two different workplaces and identify five hazardous substances youwould find in each one.

2. Why is it important for workers at a restaurant to understand WHMIS?

What do the initialsWHMIS stand for? Whyshould workers knowhow to use WHMIS?

WHMISMSDS

Key Terms

Figure 1.13 Look for theseWHMIS symbols on anyproduct you use at work.NaCl(s) is a substance you use every day. You even eat it!

NaCl(s), or table salt, can be hazardous because its dust causes respiratory irritation.People who work around salt dust wear a self-contained breathing apparatus. Becausesalt reacts dangerously with some classes of chemicals, large amounts of salt must bedisposed of as hazardous waste.

Compressed Gas

Oxidizing Material

Poisonous

Biohazardous

Flammable

Corrosive

Toxic

Reactive

4. Pour approximately 100 mL of tap water intothe 1000 mL beaker. Place this on the hotplate and gradually warm the water. This is thehot water bath.

5. Carefully place the 250 mL beaker of oil andwax mixture into the hot water bath. Heat themixture for approximately 10 minutes or untilthe beeswax melts. Describe the appearanceof this mixture.

6. Put on heat-proof gloves and carefully removethe melted oil-wax mixture from the hot waterbath. Remove the hot water bath from the hotplate. Let the hot plate cool down before doingthe next step.

7. Place the 100 mL beaker containing the boraxsolution on the hot plate and bring it almost toa boil. Describe the appearance of this mixture.

8. Slowly add the borax solution to the oil–waxmixture. Stir this mixture continuously.Describe the appearance of this mixture.

9. Cool the beaker containing the oil, wax,water, and borax mixture in an ice bath orthe refrigerator.

10. Check the beaker every 5 minutes for theremainder of the class. Record theappearance of the mixture.


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ReviewC H A P T E R

Key Terms


1syntheticpesticidesherbicides

insecticidessynthetic fibressynthetic polymers

alloyHHPS

WHMISMSDS

Reviewing Key TermsIf you need to review, the section numbers showwhere these terms were introduced.

1. What is a pesticide? How do pesticides helpcrops grow? (1.1)

2. Define synthetic. (1.1)

3. What do the substances in this drawing havein common? How are they different? (1.1)

4. Define synthetic polymer and give twoexamples. (1.2)

5. An alloy is an important type of mixture.Name an alloy and list the elements that makeit up. (1.2)

6. Many household products have HHPS ontheir labels. What does HHPS stand for? (1.3)

7. What three types of information would youfind on a WHMIS label? (1.3)

8. When it is used in a workplace, should tablesalt (NaCl(s)) have an MSDS? Explain why orwhy not. (1.4)

Understanding Key IdeasSection numbers are provided if you need to review.

9. Over the past 100 years, how has chemistrychanged the way gardening is done? (1.1)

10. Describe three ways in which synthetic fabricsbenefit your daily life. (1.1)

11. How does knowing about chemistry helpbakers? (1.2)

12. Explain why aluminum pots darken whenrhubarb is cooked in them. (1.3)

13. (a) Review the section on alloys and syntheticfibres. What do they have in common?

(b) What are the advantages of using alloysand synthetic fibres in commercialproducts? (1.2)

Developing Skills14. Use a table similar to the one shown here

to list two uses for each of the followingsynthetics and one natural substance that each replaced. (1.1)(a) nylon(b) Teflon™(c) Kevlar™

oiled cotton

Gore-TexTm

Synthetic Polymer Two Uses Natural Substance Replaced

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15. What safety equipment wouldyou wear when handling asubstance that had this WHMISsymbol on it? (1.4)

Problem Solving/Applying16. A farmer’s field is infested with weeds and

has poor soil. What two types of syntheticsubstances would help the farmer growcrops in this field? (1.1)

17. Describe the difference between natural andsynthetic medicines. (1.1)

18. Design a label for a new product people willuse in their homes. This product is highlyflammable and somewhat corrosive. Be sure toinclude the necessary HHPS. (1.3)

Critical Thinking19. Cars made in the early 1900s were made from

steel. Modern cars often contain polymers andalloys. What are some advantages of usingthese synthetics? (1.2)

20. Many cleaners contain hazardous substances.How could you minimize risk when storingcleaners at home? (1.3)


1. The use of chemicals and chemical processes has hadenormous effects on society. Some of these effects arepositive and some of them are negative. Use what youhave learned in this chapter to help you decide whethermodern synthetics have helped or hurt society more.Provide examples to support your answer.

2. Ceramic tiles are found on the space shuttle. The tileshelp protect the shuttle from burning up on re-entryinto Earth’s atmosphere. In a group, brainstorm otherproducts of chemistry that benefit society. Explain thebenefit of each product.

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Chemistry happens all aroundyou. Millions of chemical reactions(or chemical changes) occur all thetime, even though many of them areinvisible to you.

If you could see what happens tothe molecules in the flour, sugar, andother ingredients when you bake acake, you would observe some substances breaking down and othersforming. When you develop a roll offilm, chemical reactions turn theinformation stored on the film intopictures of friends and family. Whenyou shampoo, condition, and colouryour hair, you are taking advantageof chemical reactions.

Have you ever used silver polishto clean a favourite silver ring,necklace, or cup? All those swirls andpretty decorations make that job achallenging one — unless you knowa little chemistry!

In this chapter you will take acloser look at some everyday chemicalreactions and begin to appreciatetheir usefulness to you.



Common ReactionsCommon Reactions2• How can you use chemical

reactions to explore yourworld?

• How do chemical reactionsmake your life easier?

• Why must you take specialcare when dealing withcertain chemicals?

• How is energy involved inevery chemical reaction?

List some of the

chemical reactions

you encounter every

day. Try to name one

activity you are

involved in that does

not have a connection

to chemicals.

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Common Reactions in Our Lives • MHR 23

Starting Point

in Our Livesin Our Lives


In this chapter you will learn:• how chemical reactions are useful to you• how substances change during a chemical reaction• how to describe different types of chemical reactions • how to identify the evidence of a chemical reaction • that energy is absorbed or released by all chemical reactions

Why It Is Important

Skills You Will Use

• You breathe chemicals, eat chemicals, sleep on somethingmade of chemicals, and use chemicals to make your lifeeasier. Knowledge of chemical reactions can help youunderstand how substances can help or harm you. Thisknowledge can make you a wiser consumer and provideyou with a more comfortable lifestyle.

In this chapter you will:• carry out procedures and adapt those procedures

where needed• collect and organize information so it is easy to interpret• demonstrate a knowledge of WHMIS standards by

applying proper handling techniques• identify new questions or problems from what you

have learned• work co-operatively with team members to develop and

carry out a plan

Bottled SunshineHow do you know when a chemical reaction hasoccurred? This activity will help you find out.

Safety Precautions

• Clean up the work area and wash yourhands thoroughly at the end of the activity.

What You Need

balloon (medium–large size)

Erlenmeyer flask

measuring spoon

20 mL warm water

1 medicine dropper

cresol or phenol red solution

5 g calcium chloride

5 g sodium bicarbonate

What to Do

1. Pour 20 mL of warm water and two droppersof cresol red solution into the Erlenmeyerflask. Add the balloon to the mouth of theflask and gently move the solution aroundto mix it.

2. Add 5 g of calcium chloride to the solutionin the flask. Attach the balloon to the flaskand gently mix the solution. Do you notice achange in temperature? Describe the change.

3. Remove the balloon and quickly add 5 g ofbaking soda. Replace the balloon on theflask and gently mix the solution. Recordyour observations.

What Did You Discover?

1. Based on your observations, what do youbelieve is evidence of a chemical change?

2. How can you tell if energy was released?

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Useful Reactions

Almost everything you do involvesa chemical reaction. During achemical reaction, substances reactto produce new substances withdifferent properties from theoriginal substances. Some of thesereactions are simple, and some arecomplex. For example, launching aspace shuttle uses complicatedtechnology. A simple chemicalreaction makes it possible.

Hydrogen and oxygen combine during a chemical reaction to produceenergy and water. Energy powers the space shuttle, and water is a by-productof the reaction.

On the other hand, an everyday occurrence like taking an antacid to treatacid indigestion is based on a different type of chemical reaction. The antacidtablet contains a basic chemical called magnesium hydroxide. Magnesiumhydroxide reacts with the hydrochloric acid in your stomach to produce neutralmagnesium chloride and water.

How about an even more common chemical change? When you leave abanana on the kitchen counter for a few days, it turns from green to yellow to brown. It is obvious that changes are occurring, as shown in the flow chartthat follows.

Whitening WhitesHousehold bleach helps us keep white laundry looking bright and clean. Theactive component in some bleaches is hydrogen peroxide. Other bleachescontain sodium hypochlorite. Both of these key ingredients contain oxygen.Oxygen is responsible for the reaction that makes a coloured stain colourless.


2.1

Describe three everydaychemical reactions.

What element gives bleachits whitening power?

Take two green fruits.Place one in a bag with aripe banana and the otherin a bag alone. Comparethe time it takes for eachfruit to ripen.

Figure 2.2 Ripening bananas go through a chemical reaction. What tells you that areaction has occurred?

Figure 2.1 The space shuttlehas separate tanks of liquidhydrogen and liquid oxygen.When ignited, these producea chemical reaction that fuelsthe shuttle.

bananas release natural ripening gas known as ethylene ethylenetriggers enzyme production enzymes speed up chemical reactions

enzyme amylase breaks down starches into sugar

other enzymes trigger colour change and softening of fruit

enzymes break down large molecules into smaller ones thatevaporate in the air, providing the banana aroma

1

2

3

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Baking BreadIn Chapter 1, you learned about the role of yeast in making bread.Baking bread is a lot like working in a chemistry lab. A baker combinesflour, yeast, liquid, salt, and other flavourings in a bowl. The ingredientsare shaped into a dough that is left to rise, and then the dough is bakedin a hot oven to produce a tasty, nutritious loaf of bread.

Flour is made of cereal grains that release starch and proteins whenthey are milled. When flour is mixed with water and yeast, enzymes inthe yeast break down the starch into glucose. Other enzymes react withsome of the glucose molecules to produce carbon dioxide and ethanol,an alcohol. The carbon dioxide then bubbles up through the mixture,causing the dough to rise. Heat causes the pockets of gas in the dough to expand, giving the bread its airy texture. The alcohol burns off in thebaking process, leaving behind a delicious flavour.

Swimming Pool Scent

You have probably noticed that swimming pools smell distinctly of chlorine.When chlorine is added to water, it produces hypochlorous acid. Hypochlorousacid kills micro-organisms by destroying their cell membranes and inner enzymes.

Cleaners that include chlorine always have warning symbols. That is becausechlorine gas is dangerous when inhaled, and it can lead to unconsciousness oreven death. Protective rubber gloves and eye protection should be worn whenworking with chlorine.


Figure 2.3 A lot of chemistry goes intoevery loaf of freshly baked bread.

How is chemistry involved in baking bread?

Figure 2.4 Chemical reactions involving chlorine keep pools clean and disinfected for swimmers.

What substance isproduced when chlorineis added to water?

The digestion of food requires chemicalreactions. Digestive enzymes break downthe proteins, carbohydrates, and fats fromthe foods we eat and convert them toenergy for our cells to use. Digestionstarts in the mouth, where the enzymeamylase in the saliva breaks downstarches to simple sugars. In the stomach,the enzyme protease speeds up thebreakdown of proteins into amino acids.Partially digested foods are then carried tothe intestines where an enzyme calledlipase breaks down fats into glycerol andfatty acids.

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Identifying Common GasesMany chemical reactions produce oxygen, hydrogen, and carbon dioxidegases. Knowing how to test for these gases can explain what happened ina particular chemical reaction.


2–A2–A

ProblemHow do you determine the presence of hydrogen,oxygen, or carbon dioxide gases?

PredictionPart 1: What will happen to the limewater ifcarbon dioxide gas is produced?

Part 2: What will happen to the burning splint ifhydrogen gas is produced?

Part 3: What will happen to the glowing splint ifoxygen gas is produced?

Safety Precautions

• When testing for gases, point the mouth of the testtube away from yourself and other people.


Apparatus3 small test tubes

petri dish

medicine dropper

funnel

Materialsdistilled water

vinegar

5 g baking soda

50 mL limewater

20 mL hydrogen peroxide solution

10 grains dry yeast

manganese dioxide

2 wooden splints

matches

ProcedurePart 1: Carbon Dioxide Gas

1 Fill a small test tube half full with distilledwater. Add some vinegar until the liquidreaches just below the top of the test tube.

2 Fill the bottom of a petri dish half full withdistilled water.

3 Add 5 g of baking soda to the test tube.Immediately turn the test tube upside downand place it into the petri dish.

4 Observe what happens inside the test tube.Use your thumb to stopper the test tube andthen turn the test tube right side up again.

5 Using a medicine dropper, add a few drops oflimewater to the test tube. Limewater turnscloudy in the presence of carbon dioxide gas.

Part 2: Hydrogen Gas

1 Fill a clean test tube half full with distilledwater. Add hydrogen peroxide solution untilthe liquid reaches just below the top of thetest tube.

2 Fill the bottom of a clean petri dish half fullwith distilled water.

3 Add about 10 grains of dry yeast to the testtube. Immediately turn the test tube upsidedown and place it into the petri dish.

4 Lift up the test tube and stopper it with your thumb.

5 Light a wooden splint.

S K I L L C H E C K








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Test for oxygen gas


6 Insert the burning wooden splint into the testtube as shown. If the gas suddenly causes asqueal or pop, this indicates the presence ofhydrogen gas.

Part 3: Oxygen Gas

1 Fill a clean test tube half full with distilledwater. Add hydrogen peroxide solution untilthe liquid reaches just below the top of thetest tube.

2 Fill the bottom of a clean petri dish half fullwith distilled water.

3 Add 1 g of manganese dioxide to the test tube.Immediately turn it upside down and place itinto the petri dish.

4 Lift up the test tube and stopper it with your thumb.

5 Light a wooden splint and blow out the flameso the splint is only glowing.

6 Insert the glowing wooden splint into the testtube. If the flame re-ignites, this indicates thepresence of oxygen gas.

Invert a cold beaker over a burningcandle. What happens? Why doesthis happen? What are the reactants?What are the products?

Figure 2.5 Identify thereactants and products.

Analyze

1. Summarize the three tests you used to testfor the presence of carbon dioxide,hydrogen, and oxygen gases.

2. How did the results of the threeinvestigations compare to the predictions?

Conclude and Apply

3. Problems may occur in the collection of gases from chemical reactions. What are some?

Extend Your Skills

4. A common product of chemical reactionsis water. Suggest a simple test that couldbe used to test for the presence of water asa result of a chemical reaction.

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1. Describe three chemical reactions that you read about in this section.

2. List two chemical reactions you did not read about in this section.

3. Liquid bleach is sometimes used as a disinfectant in kitchens. Predict whatgas might be formed as the sodium hypochlorite breaks down.

4. Sunlight can break down sodium hypochlorite. Observe the plasticcontainers used for bleach. Why will you never see a transparent bleachcontainer?

5. Reread the Try This! on page 27. How could you test for the presence ofgases resulting from this reaction?

The Changes That Occur


chemical reaction

Key Terms

2.2

Chemical reactions occur all around you. Some reactions,like those involved in cooking, require energy. Others, likethe demolition of a building, release energy.

In a chemical reaction, the substances you start with arenot the same as the substances you end up with. Substanceswith new properties are formed. This type of changecannot be reversed.

Reactants → ProductsThe substances that are there The substances that before a chemical reaction. form afterwards.

There are several indicators of chemical change. Onesign is the release or absorption of energy. Think aboutwhat happened during the Starting Point activity at thebeginning of this chapter (on page 23). During thisactivity, you likely felt an increase in temperature. Thisincrease indicated that energy was being released.

In some chemical reactions:• gases may be given off;• new solids may be formed; or• colour changes may occur.

Sometimes odours are also given off.

Figure 2.6 Carefully placed explosives can be used todemolish buildings. This photograph shows thedemolition of the Bow Valley Centre (formerly theCalgary General Hospital) in October, 1998.

Write definitions for theterms “reactant” and“product.”

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Combustion and NeutralizationConsider what happens when you light a candle. You bring a lit match or alighter close to the candle and ignite the wick. You then observe the wick burning, and feel heat and see light being given off.

Candle wax burns in the presence of oxygen to produce carbon dioxide andwater. This type of chemical reaction, in which a fuel burns in oxygen, isreferred to as a combustion reaction. Much of Alberta’s industry depends oncombustion reactions involving fossil fuels such as oil and natural gas.

Another group of chemical reactions are neutralization reactions. During thesereactions, an acid is added to a base to produce a compound and water. The pH of the product is more neutral (closer to 7) than the pH of either reactant.

Many neutralization reactions are involved in cooking. For example, anacid–base reaction between baking soda and an acid such as vinegar (containingacetic acid) or lemon juice (containing citric acid) produces carbon dioxidebubbles that make a cake rise.

In Section 2.1, you learned about a very common neutralization reaction —one that occurs when you take a antacid. You can describe this chemical reaction in one sentence.

Magnesium hydroxide reacts with hydrochloric acid to produce magnesiumchloride and water.

You can further simplify this using symbols. The result is known as a wordequation.

magnesium hydroxide � hydrochloric acid → magnesium chloride � water

Read the following Did You Know? to learn about some other examples ofchemical reactions. Chapter 3 will discuss word equations and other ways torepresent chemical reactions.


List the reactants incombustion reactions andin neutralization reactions.

Although toothpaste ingredients vary by brand, most contain some of the following common ingredients:

• a base such as aluminum hydroxide (Al(OH)3(s)) to neutralize the acids in your mouth that can causecavities

• sodium bicarbonate (baking soda) to help neutralize acids

• fluoride, which bonds to the enamel of your teeth to further protect them from the acids in your mouth

• abrasives, such as calcium carbonate, to help remove stains and plaque

• detergents to create the foaming action that keeps the toothpaste in your mouth, preventing it fromrunning out as you brush

• strong flavourings to cover the taste of detergent

• dyes or colourings to give toothpaste a more pleasing look. For example, titanium dioxide is often usedto make some toothpastes look bright white.

Do you know what is in your toothpaste?

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1. Give three examples of combustion reactions that you encounter in a day.List as many of the reactants and products as you can.

2. Explain one neutralization reaction that occurs in the kitchen.

3. Fishy odours on your hands are caused by a base and can be eliminatedwith lemon juice. Is this an example of a combustion or a neutralizationreaction? Why? What are the reactants?


Find Out

An Invisible Gas Made VisibleIn this activity, you will look at a common reactionthat results in a visible change.

Safety Precautions


What You Need

50 mL baking soda 250 mL Erlenmeyer flask

75 mL vinegar candle

100 mL graduated matchescylinder paper towel

What To Do

1. Use thegraduatedcylinder to measure out 50 mL of baking soda. Place it into the Erlenmeyer flask.

2. Slowly add 75 mL of vinegar to the bakingsoda in the flask. Cover the jar with paper.Wait about 30 s while the reaction proceeds.In this reaction a gas will be produced, asshown in the figure.

3. Light the candle.

4. Remove the paper from the top of the jar.Carefully pour the gas produced in the flaskover the candle flame. Take care not to pourout any of the liquid in the flask.


1. When have you mixed baking soda andvinegar before? What gas is produced?

2. What happened to the candle flame?

3. Why did this occur?

S K I L L C H E C K







www.mcgrawhill.ca/links/science.connect2Use the Internet to investigate the hydrogen fuel cell. The chemical reaction thatoccurs in the fuel cell is the same as the reaction used to launch a space shuttle.Could it also be useful for powering cars and reducing pollution? Go to the above website, then to Internet Connects, Unit A, Chapter 2, and then to Hydrogen Fuel Cell.

reactantsproductscombustionneutralization

Key Terms

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Chemicals in our environment change constantly. Sometimes wecause these changes. At other times, the changes occurspontaneously without human interference.

During Conduct an Investigation 2–B, you will study manychemical reactions. As you do, look for the evidence that achemical change has occurred.

Read the contents of the Off the Wall below to learn aboutvarious examples of chemical change.


Evidence That Change Has Occurred

2.3

Figure 2.7 Is it magic? No! Achemical change has occurred!

Read the Off the Wall, andthen explain two examplesof chemical change thatoccur in nature.

Figure 2.8 Bacteriaproduce methane gas inwet locations whereoxygen is scarce. Methane

gas is often referred to as “marsh gas” because it is present in marshes or bogs. Organic matter,a reactant, undergoes a chemical change thatproduces methane gas, a product. This chemicalreaction also occurs in the intestines of cattle and termites.

Methane gas is a greenhouse gas. In otherwords, it contributes to the greenhouse effect.

Water Treatment Plant Operator

Water treatment plant operators monitor and operate the equipment usedto purify and disinfect water for human consumption. They may workindoors or outdoors, and are usually employed at water, waste water, orsewage treatment plants in small towns or villages. Depending on the sizeand location of the treatment plant, some may deal directly with the publicto handle water quality complaints and emergencies.

The Northern Alberta Institute of Technology (NAIT) offers a one-yearWater and Wastewater Technician certificate program. The educationalrequirement for the program is a high school diploma. NAIT prefersstudents who have courses in mathematics, biology, chemistry, andphysics, but these are not mandatory. Unit C discusses what can happenif water treatment plant operators do not do their work properly.

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Investigating Chemical ReactionsIn this investigation you will learn to look for evidence of chemical change.


2–B2–B

ProblemWhat is the evidence that achemical change has occurred?

PredictionPredict what evidence ofchemical change you mightobserve for each reaction.

Safety Precautions

• Some of the chemicals you willuse in this investigation can burnyour skin and clothes. If you spillany on your skin or clothes, floodthe affected area immediately withplenty of cool water. Inform yourteacher.

• Never touch sodium hydroxidewith your bare hands.

• Dispose of all chemicals as theteacher directs.

• Clean up the work area and washyour hands thoroughly at the endof the investigation.

Apparatuswash bottles

waste containers

electrolysis apparatus

3 (50 mL) beakers

100 mL beaker

test tubes with stoppers

electronic balance

scoopula

graduated cylinder

thermometer

glass stirring rod

Materialscalcium chloride solid

distilled water

sodium carbonate solid

mossy zinc

1.0 mol/L hydrochloric acid solution

0.1 mol/L sodium hydroxide solution

Sani-Flush™ toilet bowl cleaner

0.1 mol/L hydrochloric acid solution

bromothymol blue pH indicatorsolution

Rolaids™ tablet or Tums™ tablet

paper towelling

manganese dioxide solid

blue litmus paper

Procedure Your teacher will set up this labin seven stations, numbered #1to #7. You will perform each stepin the procedure at a differentstation. As you move from station to station, take care toobserve the WHMIS symbolsand follow the precautions.Clean up each station beforeyou leave it, so it is ready to beused by the next group. All usedchemicals need to be put in thewaste containers provided.

1 At each station, record allevidence of chemical changeyou observe. Also record allreactants. Construct a tablesimilar to the one shown hereto record this information.Leave enough space torecord the following itemsfor each station:• What do the reactants

look like?• What is the evidence of

chemical change?• What do the products

look like?

2 Station 1: Add 50 mL of tapwater to a 100 mL beaker.Use a thermometer torecord the initialtemperature of the water.Carefully add 3 g of Sani-Flush™ to the water and stirwith a glass stirring rod.Describe any evidence ofchemical change.

S K I L L C H E C K








Reactants Products(colours, odours, (colours, odours,

Station and whether solid, Evidence of and whether solid, Number liquid, or gas) Chemical Change liquid, or gas)

1

2

3

4

5

6

7

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Analyze

1. List all the evidence ofchemical change youobserved in this lab.Include the number of the station(s) where you observed each of these changes.

2. Predict the gas that wasreleased by the chemicalreaction at Station 6.Describe a simple test thatyou could do in order toidentify this gas. Hint:Check out Conduct anInvestigation 2–A on pages 26–27.

3. Name the two gases produced in the reaction at Station 2.

Conclude and Apply

4. Can you imagine observinga colour change that is not caused by a chemicalreaction? Name one ifpossible.

5. Why does a reaction stop?Hint: Think back to thereactions at Station 1 andStation 6.

Extend Your Skills

6. It is important that youunderstand chemicalreactions in yourenvironment. Give an example of howrecognizing a chemicalreaction can help keep you safe.


3 Station 2: The illustrationshows an electrolysis apparatus similar to the one set up at this station.Electricity is used to drivethis reaction.

4 Station 3:(a) To make simulated

stomach acid, add 10 mLor 0.1 mol/L hydrochloricacid to a 50 mL beaker.Add 10 drops ofbromothymol blue pHindicator solution to theacid and record the initialcolour of this solution.

(b) Crush one Rolaids™ orone Tums™ antacidtablet on a paper toweland carefully add thecrushed antacid to thebeaker. Stir with a glassstirring rod and recordthe colour change.

5 Station 4:(a) Place 0.16 g of calcium

chloride solid into a testtube containing 5 mL ofdistilled water. Stopperand shake the tube untilthe solid is dissolved.Observe any temperaturechange.

(b) Put 0.15 g of sodiumcarbonate solid in asecond test tubecontaining 5 mL ofdistilled water. Stopperthe tube and shake to dissolve as before.

(c) Add the contents of onetest tube to the other.Observe the reaction forseveral minutes.

6 Station 5: Place a small pieceof mossy zinc on a watchglass. Add three drops of 1.0mol/L hydrochloric acidsolution. Observe anyreaction for several minutes.

7 Station 6: Add 5 mL of 3%hydrogen peroxide (H2O2(l))to a 50 mL beaker. Usebalance to obtain 0.5 g ofmanganese dioxide(MnO2(s)). Carefullysprinkle the manganesedioxide on to the surface ofthe hydrogen peroxide andrecord any evidence of achemical reaction.

8 Station 7: (a) Add 1 mL of dilute

hydrochloric acid to one50 mL beaker. Add 1 mLof dilute sodium hydroxidesolution (a base) solutionto the second beaker.

(b) Dip one piece of bluelitmus paper into the acidand record any colourchange. Dip a secondpiece of blue litmus paperinto the sodium hydroxidesolution and record anycolour change.

water

electrode6V DC source

+ –

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Evidence of Chemical ChangeHow can you tell when a chemical change hasoccurred? Look for some of the following evidence:

• A different colour is produced.• An odour can be detected.• Bubbles appear or a gas forms. • A solid that forms during a chemical reaction

is called a precipitate.• Energy is given off in some form — such as

light, heat, or sound — or absorbed.

Figure 2.10 shows one example of each.


A differentcolour isproduced.

An odourcan bedetected.

Bubblesappear.

Energy isgiven off.

In this chemical reaction, a solid has formed.This solid is called a precipitate.


1. List the five pieces of evidence that show a chemical reaction has occurred.Give an example of a chemical reaction for each piece of evidence.

2. Here are three word equations to represent chemical reactions. Pick out theone you observed in Investigation 2–B.

(a) hydrochloric acid reacts with sodium hydroxide to produce sodiumchloride and water

(b) hydrogen peroxide decomposes producing oxygen gas and water

(c) glucose reacts with oxygen to produce water and oxygen

Figure 2.10 Review the five pieces of evidence that indicate a chemical change has occurred.

Develop a list of questions you might ask yourself todetermine if a chemical change has occurred.

precipitate

Key Terms

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Chemical changes always involve energy changes. Some energy changes areobvious and some are unnoticeable. Fireworks are an example of an obviousenergy change. When fireworks explode, a huge amount of heat and light aregiven off.

Rusting is an example of a chemical reaction involving an unnoticeableenergy change. Would you believe that heat is released when metal rusts? The amount is so small that it takes very sensitive equipment to detect it.

Knowledge of energy and energy changes is important to society andindustry. For example, gasoline is burned in an automobile engine. Thischemical reaction results in forward motion and also produces heat. We needto know how much heat is produced so equipment such as a radiator can bedesigned to cool the engine. This way, the heat produced by the chemicalreaction does not damage the engine.

Gasoline working an engine illustrates an exothermic reaction because it releases energy into its surroundings. The breakdown (also called themetabolism) of fats and carbohydrates in the human body also releases heat and is exothermic.

Some chemical reactions, like photosynthesis, need to absorb energy in theform of heat or light. Plants need energy from the Sun to produce glucose andoxygen from carbon dioxide and water. Chemical reactions that absorb energyare called endothermic reactions.


2.4 Energy and Chemical Reactions

++——

lamp

battery

switch

To learn more aboutexothermic andendothermic reactionsand the evidence ofchemical change, loadthe student CD-ROMonto your computer.Launch the ChemicalReactions applet andfollow the instructions.

Disc

Figure 2.11 Batteries store chemical energy. When a battery isused, a chemical reaction releases electric energy. In thisdrawing, the electric energy flows through the light bulb, whichconverts the electric energy to light and heat.

chemical energy → electric energy → light energy and thermal energy

Figure 2.12 Cold packs are often used by athletes to treatinjuries. In cold packs, water and ammonium nitrate are held inseparate chambers until the pack is needed. When thechambers are broken, the ammonium nitrate dissolves in thewater and absorbs heat. This can make the pack as cold as 0ºC.This is an example of an endothermic reaction.

Explain the differencebetween exothermic andendothermic reactions.

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Hot Packs andCold PacksHot packs are very popular in our cold winters towarm up cold hands and feet. Cold packs areequally useful to relieve a sports injury such as atwisted ankle or bruised knee. Hot packs and coldpacks both rely on chemical reactions that involveenergy changes in the form of heat.

ChallengeDetermine which chemical makes the best hotpack, and which makes the best cold pack. Thereaction between the chemical and the water willeither absorb or release thermal energy.

Safety Precautions


Apparatusbeakers

glass stirring rod

thermometerwaterproof marker

Materialsresealable plastic bags

distilled water

calcium chloride

sodium chloride

sodium acetate

ammonium chloride

Design CriteriaA. The hot packs and cold packs must be made

inside resealable plastic bags. Hint: Label eachplastic bag with the name of the chemical youare using.

B. The only manipulated variable must be thechoice of chemical.

C. Data must be collected to show how effectiveeach hot pack and cold pack is.

Plan and Construct 1 With a group, write a procedure for how to

compare the chemicals provided. Be specificenough so someone else could duplicate yourinvestigation.

2 Get your teacher’s approval, and then performthe investigation.

3 Record all data in a data table.


2–C2–C

S K I L L C H E C K









Evaluate

1. Using a bar graph, compare the startingtemperature of each solution to the finishingtemperature of each solution.

2. Which chemical produced the most heat?Which absorbed the most heat?

3. Other considerations may influence your finalchoices for best hot pack and best cold pack.Evaluate the hot and cold packs you havedeveloped according to these criteria. (a) cost of chemical(b) danger of transporting the chosen

substance (Hint: Check the WHMISsymbols on the chemicals used.)

(c) duration of heat or cold production

4. Considering your answers to questions 1 and2 above, which chemical would you choosefor a hot pack? Which chemical would youchoose for a cold pack?

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Find Out


1. How do exothermic and endothermic reactions differ? How are they similar?

2. Some exothermic reactions can be quite dangerous. Give the reason behindthis statement.

3. Fossil fuel combustion reactions involve a fuel such as gasoline or propane.The fuel is combined with oxygen to produce carbon dioxide and water.We often think of these reactions as burning reactions. Are they exothermicor endothermic?

energy changesexothermic reactionendothermic reaction

Key Terms

A Light ReactionIn this activity, you will investigate an example ofan endothermic reaction that releases light energy.

Safety Precautions

• Do not bend activated glow sticks more thanonce. Excessive bending may break theplastic tube and spill the chemicals inside.

• The activated liquid is non-toxic, but maycontain tiny pieces of glass which may causeinjury if the light stick is punctured or split open.

• The liquid can permanently stain clothing orfurniture and can cause skin or eye irritation.

• Follow your teacher’s instructions fordisposing of the used glow stick.


What You Need

thermometer or computer temperature probe

watch

tap water

2 graduated cylinders (100 mL)

glow stick

What to Do

1. Construct a data table for your observations.

2. Read steps 3–6 and then predict what youthink will happen to the water temperature inthe experimental graduated cylinder.

3. Add 70 mL of tap water to the controlgraduated cylinder and 70 mL of tap water to the experimental graduated cylinder.

4. Use the thermometer to determine thetemperature of the water in both graduatedcylinders. Record the temperatures on yourdata chart.

5. Follow the instructions on the package toactivate the glow stick. Place the glow stick in the experimental graduated cylinder.

6. Take and record the temperature of the waterin both graduated cylinders at one-minuteintervals for at least five minutes.

7. Draw a line graph that includes both sets of data.



S K I L L C H E C K








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Key Terms


ReviewC H A P T E R

2chemical reactionreactantsproducts

combustionneutralization

precipitateenergy changes

exothermic reactionendothermic reaction


1. In your notebook, match each description incolumn A with a term in column B.


2. Describe a chemical reaction that you usedtoday. (2.1)

3. If you tested the gas produced in a chemicalreaction using a burning splint and heard apopping sound, what gas was produced? (2.1)

4. If you were testing a second gas and foundthat you could re-ignite a glowing splint in itspresence, what is the second gas? (2.1)

5. Use the words “reactants” and “products” todescribe a chemical reaction. (2.2)

6. In your notebook, make a table like the oneshown here. Complete the table using chemicalreactions discussed in this chapter. (2.2)

7. List the five pieces of evidence of a chemicalchange. (2.3)

8. All chemical changes are accompanied byenergy changes. Are these always obvious?Explain. (2.4)

9. Think of chemical reactions in your day. (2.4)

(a) Name one that requires energy to proceed.

(b) Name one that releases energy as it occurs.

(a) chemicals presentbefore a chemicalreaction begins

(b) a fuel is burned inthe presence ofoxygen to producecarbon dioxide and water

(c) when energy isrequired for achemical reactionto occur

(d) a solid that forms ina chemical reaction

(e) energy, usuallythermal, produced ina chemical reaction

(f) chemicals present at the end of achemical reaction

(g) bubbles areproduced, light isemitted, colourchanges occur,energy is released or absorbed

(h) an acid and a basemake a compoundand water

i. combustion (2.2)ii. neutralization (2.2)iii. precipitate (2.3)iv. exothermic (2.4)v. endothermic (2.4)vi. evidence of chemical

reactions (2.2) vii. reactants (2.2)viii. products (2.2)

A B

Reactants Products

combustion reaction

neutralization reaction

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Developing Skills

10. An electrolysis apparatus demonstrates thebreakdown of water into hydrogen andoxygen gases. Combining hydrogen andoxygen gases, which is the opposite reaction,produces water and energy. Explain wherethis opposite reaction is useful. (2.1)

Problem Solving/Applying

11. When you convert ingredients such as flour,sugar, baking soda, eggs, baking powder, andwater into a cake, chemical changes occur.What indicators of chemical reactions canyou observe when you bake a cake? (2.2)

12. Liquid bleaches containing sodiumhypochlorite (NaClO(l)) are often sold indark plastic containers because sunlightcauses the compound to break down intooxygen gas (O2(g)) and sodium chloride(NaCl(s)). Explain whether you think that thebleach would be effective once the oxygengas had been released — and why you thinkthis way.(2.1)

13. Imagine you are a research chemist. Whymight you want to know whether a reactionwould require or absorb energy before youtry it in the laboratory? (2.4)

Critical Thinking

14. An industrial chemical process known as theHaber process converts gaseous nitrogen(N2(g)) from the air into gaseous ammonia(NH3(g)). The ammonia is then used in largequantities to fertilize crops. Look at thechemical formulas. One of the reactants isnitrogen. What is the second reactant? (2.2)


1. Go back to the beginning of the chapter to the GettingReady questions. How has your thinking changed? Howwould you answer these questions now that you haveinvestigated the topics in this chapter?

2. Stripping furniture of old paint involves chemicalreactions. How would you prepare for such a task,knowing what you have learned in this chapter?

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Chemical reactions can be sospectacular! Most of us enjoy acolourful show of fireworks. Anddid you ever have sparklers for aspecial party?

Some chemical reactions give offlight in a variety of colours; othersproduce sounds.

We use chemical reactions totreat and prevent disease, improveour food supply, purify water, andproduce a wide variety of consumergoods. The more we learn aboutsuch reactions, the easier it is to usethem with minimum risk.

It also helps to know how todescribe different reactions. Allchemical reactions involve changes inelements and compounds. This

chapter will explain how to recordwhat changes occur to elements andcompounds during a reaction.

Just as your friends and familyknow you by a given name — andoften by a nickname, too — mostchemical compounds have an officialname and a common one. Forexample, do you ever add sodium

hypochlorite to your laundry? Achemist knows the compound bythat name; you probably know it byits common name — bleach.

In this chapter you will investigatemany chemical reactions and learndifferent ways to describe them. Youwill also learn some of the universallanguage chemists use to describe whatoccurs during a chemical reaction.



Types of ChemicalTypes of Chemical3• Name one chemical

reaction you are familiarwith. What happensduring that reaction?

• What are some clues thata chemical reaction hasoccurred?

• Write one chemicalformula that you know.Explain what the symbolsmean.

• Why do chemists all overthe world understand theshort forms for variouselements?

Think back to some of

the chemical reactions

you have observed in

class. Pick several that

you remember. For

each of these, describe

in one sentence what

the reactants and

products were. As you

read this chapter, you

will see some different

ways to describe what

you saw.

C � O2 CO2

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Types of Chemical Reactions • MHR 41

Starting PointFlame TestsSafety Precautions

• Tie back long hair and secure any loose clothing.

• Do this investigation on a fire resistant surface.

• Clean up the work area and wash yourhands thoroughly at the end of activity.

What You Need

wooden splints 0.5 mol/L copper (II)

0.5 mol/L sodium nitrate solution

nitrate solution Bunsen burner

0.5 mol/L potassium tongsnitrate solution waste container safe

0.5 mol/L calcium for used splints

nitrate solution

What to Do

1. Set up and light a Bunsen burner asdemonstrated by your teacher

2. Use the tongs to remove one wooden splint that has been soaked in the sodiumnitrate solution.

3. Briefly place the soaked splint in the bluepart of the Bunsen burner flame. Caution:Do not leave the splint in the flame too longor it will start to burn.

4. Record the colour of light emitted by thesodium compound.

5. Place the used splint in the designatedwaste container.

6. Repeat steps 2 to 6 for the other solutions.

ReactionsReactions


In this chapter you will learn:• how to represent chemical equations using words and

chemical formulas• how to identify and describe different types of reactions• how to recognize chemical formulas for some commonly

occurring compounds• why scientists use balanced chemical equations• how the Law of Conservation of Mass applies to

chemical reactions

Why It Is Important

Skills You Will Use

• We live in an age of technology. Chemical reactions makemodern technologies possible. Learning how to expressand interpret the chemical reactions involved in commonprocesses will enable you to make wiser choices abouteverything from foods and household products totransportation.

In this chapter you will:• represent simple chemical reactions using word

equations• identify composition, decomposition, combustion, and

neutralization reactions• carry out procedures and adapt those procedures where

needed• demonstrate a knowledge of WHMIS standards by

applying proper handling techniques• name common compounds from chemical formulas• select and use appropriate methods of communication

for ideas, plans, and results

Sparklers use a chemical reaction.

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Word Equations


3.1

Here is a summary of what you have learned so far.

• Chemical reactions can be simple (like powering a space shuttle)or complex (like taking an antacid).

• Chemical changes can be obvious (like burning a candle) or lessnoticeable (like the reaction that makes a cake rise).

• They can occur immediately (like explosives) or more slowly (likethe ripening of a banana).

To describe these many different chemical reactions, chemists oftenuse a convenient method known as a word equation. A wordequation uses words to indicate what changed during the chemicalreaction and what is produced.

To learn more about representingsimple chemical reactions using wordequations, load the student CD-ROMonto your computer. Launch theChemical Reactions applet andfollow the instructions.

Disc

Word equations are a simple way for chemists to describe chemical changes.They also help us recognize patterns that many reactions have in common.

Writing Word EquationsWord equations are always written in the same format.

• The left side of the equation lists all the reactants.• The right side of the equation lists all the products.• An arrow points from the reactants to the products. It shows that

something is produced during the reaction.

all reactants → all products

All the reactants and all the products in a word equation are separated by aplus sign (+).

reactant 1 � reactant 2 → product 1 � product 2

Why do chemists useword equations torepresent chemicalreactions?

Describe the standardformat for word equations.

Figure 3.1 Limestone caves areformed when the calciumcarbonate in the stone combineswith acids in rainwater. Theproduct, calcium hydrogencarbonate, is washed away inwater. This leaves behind emptycaves. Read the next page to findthe word equation for this.

Zinc chloride solution isoften used to enhancethe detail in fingerprintanalysis. Fingerprintsdeveloped with regulardevelopment compoundsbecome fluorescentafter being treated withzinc chloride.

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Word Equations for Some Chemical ReactionsLet’s look at some commonly occurring chemical reactions.The first reaction takes place inside your body. It is the key toconverting the food you eat into the energy your body canuse. The word equation for this reaction is written as:

oxygen + food (glucose) → carbon dioxide + water + energy

The equation is read as:

Oxygen and food (glucose) produce carbondioxide and water and energy.

The second word equation describes a common chemicalreaction that produces limestone caves:


oxygen � glucose (food) → carbon dioxide � water � energyFigure 3.2 During cellular respiration, glucose or foodis broken down into water, carbon dioxide, and energyin a form that cells can use.

carbonic acid � calcium carbonate → calcium hydrogen carbonate

This equation is read as:

Carbonic acid and calcium carbonate produce calcium hydrogen carbonate.

In Conduct an Investigation 2–B (on page 32), you observed many differentchemical reactions. These chemical reactions can all be described using wordequations. For example, when you added hydrochloric acid to mossy zinc, youmay have noticed that the solution became warmer as the zinc dissolved, and agas was released. The equation for this reaction is written as:

zinc � hydrochloric acid → zinc chloride � hydrogen gas � energy

This equation is read as:

Zinc and hydrochloric acid produce zinc chloride and hydrogen gas and energy.


1. Copy each of the following word equations into your notebook. Besideeach, write what you would say as you read the equation.

(a) solid zinc � hydrochloric acid → hydrogen gas � zinc chloride

(b) ammonium nitrate � sodium hydroxide → ammonium hydroxide �sodium nitrate

(c) hydrochloric acid � sodium acetate → acetic acid � sodium chloride

Do you always needmore than one reactantor more than oneproduct to have achemical reaction?

word equation

Key Terms

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Types of ReactionsImagine you are preparing a cake from your favourite recipe, and you discoverthat you have run out of a few ingredients. If you know there are patterns inthe way some of the ingredients go together, you can make substitutions for themissing ingredients. For example, yogurt could be used instead of an egg toincrease the lightness of a cake.

In a similar way, chemists know there are patterns in the way certainelements and compounds go together. They use these patterns to groupdifferent types of chemical reactions. Grouping chemical reactions is useful forseveral reasons. First, it allows chemists to predict the product of an unknownchemical reaction. Second, it helps them to understand the behaviour ofsubstances in a chemical reaction. This section will deal with the four mostcommon reaction types.

Simple Composition ReactionsFigure 3.3 shows what happens when magnesium is ignited in the presence ofoxygen. During this reaction, there are two reactants. The first one is theelement magnesium. The other is the element oxygen.

If you held the magnesium in the flame, you might observe a reaction takingplace. The resulting product would be the compound magnesium oxide. Thereaction would also produce energy in the form of bright light. The wordequation for this reaction is:

magnesium � oxygen → magnesium oxide � light � thermal energy


3.2

Give two reasons why it is useful for chemists tounderstand reaction types.

www.mcgrawhill.ca/links/science.connect2Magnesium oxide is a compound with a veryhigh melting point. This makes it useful inthe manufacture of many industrial products.Research and report on some of the uses ofmagnesium oxide. Go to the above web site,then to Internet Connects, Unit A, Chapter 3,and then to Magnesium Oxide.

In a simple composition reaction, two or more simpleelements combine to form a compound. Whenever you seetwo elements as reactants, you know that the reaction is asimple composition reaction.

In a simple composition reaction, the product is always acompound. If we use the letters A and B to represent twodifferent elements, a simple composition reaction is writtenin this way:

Element1 � Element2 → CompoundA � B → AB

Most simple composition reactions are exothermic, meaning that some form of energy is released. It is wise to know about this type of chemical reaction before trying it in a laboratory.

Figure 3.3 When magnesiumburns, there is an obviouschemical reaction betweentwo elements. This is anexample of a simplecomposition reaction. What are the reactants?What are the products?

In your own words,define a simplecomposition reaction.

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Simple Decomposition ReactionsDuring electrolysis, water is broken down into hydrogen gas andoxygen gas. Electric energy is needed to drive this reaction. This makes it an endothermic reaction. The word equation for thisreaction is:

water � electric energy → hydrogen gas � oxygen gas


Most decomposition reactions are endothermic, meaning that energy isabsorbed.

You have learned about composition reactions, in which elements are “puttogether.” You also know something about decomposition reactions, in whichcompounds are “broken apart.” In Conduct an Investigation 3–A, you willinvestigate what happens to elements and compounds in these two reaction types.

O O O

+

+

simple composition reaction

simple decomposition reaction

2

O 2 OO

Figure 3.4 A simple composition reactioninvolves the combination of two elements.A simple decomposition reaction involvesthe breaking apart of a compound.

Figure 3.5 The process of electrolysis isan example of a simple decompositionreaction. Electric energy is required todrive this reaction, which also makes itan endothermic reaction.

A reaction that breaks a compoundinto its component elements is knownas a simple decomposition reaction.Whenever you see a compound as theonly reactant, you know the reaction isa simple decomposition reaction. In asimple decomposition reaction, theproducts are always elements. If we usethe letters C and D to represent twodifferent elements, a simpledecomposition reaction is written inthis way:

Compound → Element1 � Element2AB → A � B

In your own words,define a simpledecomposition reaction.

Knowing about reaction types makes it possible for scientists andtechnologists to predict the products of chemical reactions.Sophisticated lab equipment also helps to protect theinvestigating scientist.

In the past, experimenters sometimes endangered their healthby performing chemical reactions without any advance knowledgeof the chemicals that would be produced. English chemist SirHumphry Davy (1778–1829) frequently inhaled gaseouschemicals he produced in the lab. He experimented with breathingpure carbon dioxide gas, and nearly suffocated himself wheninhaling pure hydrogen gas. He also inhaled nitrous oxide gas,which has anaesthetic properties.

Figure 3.6 Sir Humphry Davy

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Making It and Tearing It Down: A Composition/DecompositionReaction — Teacher Demonstration In a decomposition chemical reaction, a compound is broken down into the elements thatmake it up. The electrolysis of water is one example of a decomposition reaction. Thechemical equation for this reaction is 2H2O(l) →2H2(g) � O2(g).

Hydrogen peroxide (H2O2(l)) is a commonly used disinfectant that can also bedecomposed into its elements. In Part 1 of this activity, you will investigate thedecomposition of this chemical compound.

Part 2 of this investigation demonstrates how chemistry can be used at home. Someteaspoons, especially ones made a number of years ago, are made of silver (Ag(s)). Silver tarnisheswhen exposed to hydrogen sulfide gas (H2S(g)), which is present in small amounts in air.

The black on a tarnished spoon is silver sulfide (Ag2S(s)). You can buy commercial tarnishremovers to remove this silver sulfide. In this activity, you will investigate how commonhousehold chemicals — aluminum foil, baking soda, and boiling water — can accomplishthe same task.


3–A3–A

Safety Precautions


• Clean up work area and wash your hands thoroughly atthe end of the investigation.

Apparatustest tube

test tube holder

graduated cylinder

scoopula

electric kettle

tarnished silver teaspoon

Styrofoam™ coffee cup

hot pads or oven mitts

equal arm or electronic balance

Materials2 mL 3% hydrogen peroxide solution

trace amount magnesium dioxide solid

wooden splint

matches

100 mL boiling water

aluminum foil 30 x 30 cm (enough to fit the coffee cup)

1 g of sodium bicarbonate (baking soda)

ProcedurePart 1: Decomposition Reaction

1 Set the test tube securely into the test tubeholder.

2 Use a graduated cylinder to add 2 mL of 3%hydrogen peroxide solution to the test tube.

3 Use the scoopula to add a trace amount ofmagnesium dioxide to the test tube. Recordyour observations.

4 Use the match to light the wooden splint.Insert the burning splint into the test tube.Record your observations.

S K I L L C H E C K







Test for oxygen gas.

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Conclude and Apply

1. What can you infer from your observationthat the glowing splint burst back intoflames?

2. Why is the chemical change in Part 1considered to be a decomposition reaction?

3. What evidence did you gather that wouldlead you to believe that a chemical reactionoccurred in Part 1 of this investigation?

4. The chemical and word equations for theremoval of tarnish are summarized below.Which product might account for thesmell that was produced by this chemicalreaction?

3Ag2S(s) � 2Al(s) → 6Ag(s) � Al2S3(s)silver sulfide � aluminum → silver � aluminum sulfide

5. Identify two pieces of evidence that wouldlead you to believe that a chemical reactionoccurred in Part 2 of this investigation.


5 Extinguish the flame but splint should still be“glowing.” Insert the glowing splint into thetest tube and record your observations.

6 Dispose of the used wooden splints as directedby your teacher.

Part 2: Household Chemical Reaction

7 Cut a 9 x 9 cm square of aluminum foil.Crumple it and place it in the bottom of aStyrofoam™ cup.

8 Boil approximately 100 mL of water in theelectric kettle.

9 Place 100 mL of boiling water into the coffee cup.

0 Mass 1 gram of sodium bicarbonate (bakingsoda) and add it to the boiling water.

! Place a tarnished silver spoon into the coffeecup. It must be touching the aluminum.

@ Record your observations, including the odourreleased by this chemical reaction.

# Dispose of the chemicals as directed by yourteacher.

Analyze

1. Which elements (gases) were formed whenhydrogen peroxide (H2O2(l)) was decomposed?

2. Describe what happened when you placed thetarnished spoon into the solution of boilingwater and baking soda.

3. Describe the odour that was released duringthe chemical reaction that removed the tarnishfrom the silver spoon.

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Combustion ReactionsWhen you light a candle, the candle wax burns in the presence of oxygen toproduce carbon dioxide and water. This is one example of a combustionreaction or burning. Combustion always occurs in the presence of oxygen.

Combustion also occurs when you burn fuel to power a car. The wordequation for the combustion of gasoline (octane) is:

gasoline (octane) � oxygen → carbon dioxide � water vapour � energy

The same type of reaction occurs when you light a butane lighter. The wordequation in this case is:

butane � oxygen → carbon dioxide � water vapour � energy

Oil and natural gas are fossil fuels. This means that they come from theaccumulated remains of plants and animals from prehistoric times. Fossil fuelsform very slowly, which is why many scientists believe we will run out of them.We use them up much more quickly than they can form.


Figure 3.7 Each of these items is a product of the petroleum industry.

Name another commonterm for a combustionreaction.

Neutralization ReactionsIn Chapter 2, you looked at some everyday chemical reactions, such as takingan antacid to relieve acid indigestion. This is an excellent example of aneutralization reaction. In a neutralization reaction, an acid reacts with a baseto produce a form of salt and water. The word equation for a neutralizationreaction is:

acid � base → salt � water

76 L of petroleum canprovide the gasoline todrive a vehicle 485 km, orit can produce 24 shirts,5 m2 of carpetingmaterial, 2 automobiletires, 30 m of 1.3 cmdiameter rope, 12windbreakers, 2 tents, 4 sleeping bags, 6 duffelbags, 1 blanket, 4sweaters, and 15 parkas!

Do one of the following.

1. Collect the itemsoutlined in the Did YouKnow? Measure thearea covered by all of these items.

2. Measure the distancefrom your school toOttawa. Assume thatyou are driving a smallcompact car that gets10 km/L of gas. Howmany litres of gasolinewould it take to drivefrom your school toParliament Hill? List the items that this number of litres of gasoline might also produce.

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When you take an antacid, the magnesiumhydroxide in the tablet reacts with the hydrochloricacid in your stomach. This neutralization reaction iswritten as:

hydrochloric acid � magnesium hydroxide →magnesium chloride� water

You may be surprised to know how manyneutralization reactions occur all around you everyday. They are involved in many natural, household,and industrial products and processes.



1. Read this list of chemical reactions. Identify the ones that show simplecomposition reactions.

(a) methane gas � oxygen gas → carbon dioxide � water

(b) solid calcium � oxygen gas → solid calcium oxide

(c) solid sodium chloride → solid sodium � chlorine gas

(d) solid sodium hydroxide � liquid acetic acid → sodium acetate (a salt) �water

(e) solid magnesium � oxygen gas → magnesium oxide

(f) hydrogen gas � oxygen gas → water

2. (a) Explain the following two equations.

A � B → AB

CD → C � D

(b) Which one shows the general format of a simple composition reaction?

(c) Which one shows a simple decomposition reaction?

Figure 3.8 Many acid–base reactions produce water and a form ofsalt. The white cloud of ammonium chloride seen here is a product ofthe reaction of hydrochloric acid and ammonia. What WHMISsymbols should be on these bottles?

In a neutralization reaction, an acid and a base react toform two products. Name the products.

simple compositionsimple decomposition

Key Terms

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Formulas for Common CompoundsWhat if you spoke a language that no one else could understand? How would youcommunicate with your friends? Scientists around the world faced this problemwhen they started sharing information about chemicals and chemical reactions.Because scientists speak many different languages, they created a commonlanguage that would allow them to communicate with one another. This commonlanguage became the basis of what you are learning about in this chapter.

Chemical Names and FormulasDuring a composition reaction you might add zinc powder to sulfur powder andthen apply heat. This composition reaction would produce a compound calledzinc sulfide. The word equation for this reaction is:

sulfur � zinc → zinc sulfide

When you write a word equation like this, you are using what is known asthe chemical name for each of the reactants and products. When you look atthe periodic table, you will see the chemical names of all the elements alongwith their chemical symbols. Each element has a symbol that consists of onecapital letter or one capital and one lower-case letter. In this example, you havesulfur (S) and zinc (Zn).


3.3

Most chemical compounds are named according to the majorelements they contain. Information about the chemicalcomposition and structure of a compound is given by itschemical formula. In the above example, the product is thecompound zinc sulfide, which has the chemical formula ZnS.

The rule for naming compounds like this is to name the metalfirst — zinc — followed by the name of the non-metal. Thename of the non-metal is changed to “ide”— sulfide.

You could now replace the names of the reactants with theirchemical symbols, and the product with its chemical formula.When writing formulas, remember to use a subscript to indicatethe state of the material. In this example, we are dealing withsolids, which are shown as (s). The chemical equation would looklike this:

S8(s) � 8Zn(s) → 8ZnS(s)

Substances can be in the form of asolid, liquid, or gas. These are known asphysical states or states of matter. Manyperiodic tables show a symbol called asubscript beside each element. Thissubscript indicates the state in which anelement is normally found. For example,the element zinc (Zn) would appear onthe periodic table with an (s), indicatingthat zinc is normally found as a solid.

science.connect 1 used the followingsubscripts:

• (s) to indicate a solid

• (l) to indicate a liquid

• (g) to indicate a gas

A fourth subscript — (aq) — is usedto indicate an aqueous solution, which isa substance dissolved in water.

Why do we need acommon internationallanguage when we talkabout chemical reactions?

Explain the difference between chemical names and chemical formulas.

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Common NamesNot everyone is a scientist, so many chemical compounds are often identifiedby a common name. These names are easier to use, and they have existedsince before the international naming system was created. You already knowmany chemicals by their common names. As a student of chemistry, you willlearn some chemical names. For instance, the common name for sodiumchloride (NaCl(s)) is salt. Water is the common name for dihydrogen monoxide(H2O(l)).

Look at Table 3.1 to see how many more common and chemical names youalready know.


Common Name Chemical Name Chemical Formula

alcohol ethanol C2H5OH(l)

antifreeze ethylene glycol CH2H6O2(l)

baking soda sodium bicarbonate NaHCO3(s)

chalk, limestone, marble calcium carbonate CaCO3(s)

club soda carbonic acid H2CO3(l)

Epsom salt magnesium sulfate MgSO4(s)

laughing gas dinitrogen monoxide N2O(g)

lye or caustic soda sodium hydroxide NaOH(s)

natural gas methane CH4(g)

quartz silicon dioxide SiO2(s)

rubbing alcohol isopropyl alcohol C3H7OH(l)

table salt sodium chloride NaCl(s)

salt substitute potassium chloride KCl(s)

sugar glucose C6H12O6(s)

sucrose (table sugar) C12H22O11(s)

water dihydrogen oxide H2O(l)

Table 3.1 Chemical Names and Formulas of Some Common Chemicals


1. Investigate one of the chemicals below. Use your periodic table, Table 3.1,and other chemistry textbooks to describe the chemical as thoroughly aspossible.• Where might it be used?• How many different elements does it contain? How many atoms of each?

How many atoms in total?• Should it be labelled with a WHMIS symbol? If so, which one(s)?• What is its common name? Its chemical name?

(a) CaCO3(s)

(b) SiO2(s)

(c) C2H5OH(l)

(d) CH4(g)

(e) C12H22O11(s)

www.mcgrawhill.ca/links/science.connect2Use the Internet to find out about otherchemical names and formulas. Go to the aboveweb site, then to Internet Connects, Unit A,Chapter 3, and then to Molecule of the Month.

chemical namechemical formulacommon name

Key Terms

Copy down the chemical formulas for five ofthe chemical compounds listed in Table 3.1.Beside each, list the elements contained in thechemical along with their chemical symbols.

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Chemical EquationsThink back to some of the chemical reactions you have seen in this chapter andthe previous one. During the activities, you observed colours changing, bubblesappearing, and precipitates forming. You may also have detected odours beinggiven off and energy being released in the form of light or heat.

In some chemical reactions, matter may appear to be destroyed. Is it really?What happens to the masses of the reactants and the products during achemical reaction? That is what a French chemist named Antoine Lavoisierasked more than 200 years ago.

The Law of Conservation of MassIn the 1700s, Antoine Lavoisier (1743–1794) placed a carefully measured massof solid mercury (II) oxide into a sealed flask. When heated, the compoundproduced liquid mercury and oxygen gas. When this chemical reaction wasfinished, Lavoisier measured the mass of each of the products. He found thatthe total mass of the two products was identical to the mass of the reactants.The following word equation shows this reaction. The masses of the reactantand products are shown below the word equation:

solid mercury (II) oxide → oxygen gas � liquid mercury10.0 g 0.7 g 9.3 g

Lavoisier concluded that the atoms in achemical reaction were just rearranged, notdestroyed. This conclusion is known as theLaw of Conservation of Mass, which states:

In a chemical reaction, matter is notcreated or destroyed. If you start areaction with 10 g of reactants, youwill end up with 10 g of products.


3.4

Figure 3.9 Antoine Lavoisier used precise balances for his investigations.This led to the Law of Conservation of Mass.

Why did Antoine Lavoisieruse a sealed flask for hisinvestigation?

Develop an activity during which you repeat AntoineLavoisier’s investigation. Use safe chemicals such asbaking soda and vinegar. Allow the gas to escape. Checkthe mass of the chemicals before and after. What do yourresults suggest about the mass of carbon dioxide thatwas released?

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Staying BalancedWhen chemists write chemical equations, they do not usually use wordequations. When dealing with chemicals, this method is not exact enough.Using a word equation would be like writing a word equation to explain how tobuild a house.

energy � wood � concrete � steel � metal → house

The builder of such a house would soon have many questions. How much ofeach material would she need?

Chemists feel the same way. They need to know the exact quantities ofchemicals to use when chemical reactions are used in technological processes.Word equations do not state the quantities of the substances needed. They alsodo not reveal the types of atoms involved. Compare these two equations:

vinegar � baking soda → sodium acetate � water � carbon dioxide gasCH3COOH(aq) + NaHCO3(s) → NaC2H3O2(l) + H2O(l) + CO2(g)

When the chemical formulas of the reactants and products are used, thenyou can determine exactly what atoms make up the reactants and products. TheMath Connect on this page and the one on the next page will help you learn toanalyze such equations.


To learn more aboutbalancing equations, loadthe student CD-ROM ontoyour computer. Launch theChemical Reaction appletand follow the instructions.If possible, do either thisapplet or the Find Outactivity on page 55 beforeworking on the MathConnects that follow.

Disc

Checking the Balance of Simple EquationsA balanced chemical equation has the sameelements and the same number of atoms of eachelement on both sides.Sample Problem

The equation that follows shows what happenswhen carbon and oxygen gas go through achemical reaction. Is the equation balanced?

C(s) + O2(g) → CO2(g)

Steps in Solving It1. What elements are on the reactant side?

The letters shown are C and O. If you cannotremember what these stand for, check a copyof the periodic table. C is the element carbon.O is the element oxygen.

2. How many atoms of each element are on thereactant side? There is no subscript beside carbon. Thismeans that there is only one atom of carbon.

The subscript 2 (2) beside oxygen tells youthere are 2 atoms of oxygen.

3. What elements are on the product side? Again, there is a C and an O.

4. How many atoms of each element are on theproduct side? There is no subscript with C, so there is onlyone atom of carbon. O has a subscript — 2. So there are two atoms of oxygen.

5. Is this equation balanced?reactant side = 1 atom of carbon, 2 of oxygen

product side = 1 atom of carbon, 2 of oxygen

Yes, the equation is balanced.

Solve These

Use the example above to help you checkwhether the following equations are balanced. Be sure to show your thinking and calculations.

1. Cl2(g) � H2(g) → 2HCl(g)

2. FeO(s) → Fe(s) � O2(g)

What is the advantage ofusing equations withformulas instead ofsimple word equations?

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Checking the Balance ofComplex EquationsWater electrolysis is anexample of a simpledecomposition reaction. You observed such a reaction during Conduct anInvestigation 2–B on page 32.Although the reaction issimple, the equation thatrepresents it is not so simple.This Math Connect will showyou how to read and checkthe balance of such equations.

The equation for showing the decompositionof water is 2H2O(l) → O2(g) � 2H2(g). In suchequations, the numbers in front of the chemicalformulas are called coefficients. Coefficientsare used to balance those individual atoms. In2H2O(l) → O2(g)� 2H2(g), the 2 in front of the H is a coefficient. It tells how many H2 moleculesare present.

Sample Problem

Read the equation. Identify and count the atomson each side. Is it balanced?

2H2O(l) → O2(g) � 2H2(g)

Steps in Solving It1. What elements are on the reactant side?

The letters shown are H and O. If you cannotremember what they stand for, check a copy of the periodic table. They are hydrogen and oxygen.

2. How many atoms of each element are on thereactant side?The 2 in front of H2O(l) makes this tricky. Thelarge 2 means that there are 2 H2 and 2 O.Let’s deal with each one separately.

2H2 � H2 � H2

The subscript 2 (2) beside hydrogen tells thatthere are two hydrogen atoms in each H2molecule.

H2 � H � H

And there are two of these in the chemicalname. So

2H2 � H � H � H � H � 4 hydrogen atoms

2O � O � O � 2 oxygen atoms

3. What elements are on the product side? Again, you see H and O. These are hydrogenand oxygen.

4. How many atoms of each element are on theproduct side?

O2 � O � O

The 2 in front of H2(g) makes this tricky. Thelarge 2 means that there are 2 H2(g). Let’s dealwith each one separately.

2H2 � H2 � H2

The subscript 2 ((2)) beside hydrogen tells thatthere are two hydrogen atoms in each H2molecule.

H2 � H � H

And there are two of these in the chemicalname. So

2H2 � H � H � H � H � 4 hydrogen atoms

5. Is this equation balanced?reactant side � 2 oxygen atoms, 4 hydrogen atoms

product side � 2 oxygen atoms, 4 hydrogen atoms

Yes, the equation is balanced.

Solve These

Use the example above to help you checkwhether the following equations are balanced. Be sure to show your thinking and calculations.

1. 2Mg(s) � O2(g) → 2MgO(s)

2. 2Al(s) � 3I2(s) → 2AlI3(s)

3. CH4(g) � 2O2(g) → CO2(g) � 2H2O(g)

H

H

O

This molecular model ofa water molecule(H2O(l)) clearly showsthere are two hydrogen(H) atoms and oneoxygen (O) atom ineach molecule of water.

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1. Look carefully at the equations below. Which ones are balanced? Showyour thinking and any calculations.

(a) Cl2(g) � 2KI(g) → 2KCl(g) � I2(s)

(b) 3Li(s) � 2H2O(l) → 2LiOH(l) � H2(g)

(c) Zn(s) � H2SO4(l) → ZnSO4(s) � H2(g)

2. In your own words, explain why equations must be balanced. Compare abalanced chemical equation to what actually happens during the reaction.

3. Look back at the four reactions in the Find Out activity above. Classifyeach reaction as a composition reaction, decomposition reaction,combustion reaction, or neutralization reaction.


Find Out

Working with Chemical Compounds In this activity, you will build models of reactantsand products to see how they are affected bychemical reactions.

Safety Precautions


What You Need

molecular model kit

orfoam balls (different sizes and/or colours)

toothpicks

What to Do

1. Word equations for four different chemicalreactions are shown here. For each reaction,use the molecular model kit or foam balls andtoothpicks to build models of the reactantsand products. Refer to the molecular model ofa water molecule shown earlier in this section.This will help you get started on your model.

Reaction 12H2O(l) → O2(g) � 2H2(g)

Reaction 2CH4(g) � O2(g) → CO2(g) � H2O(g)

Reaction 3N2(g) � O2(g) → 2NO(g)

Reaction 42HgO(g) → Hg(s) � O2(g)

2. Start with Reaction 1. Build a model of thereactant(s) in the equation.

3. Take apart your model of the reactant(s). Now,use the same balls and toothpicks to createthe products of that reaction.

4. Repeat Steps 2 and 3 for each of thereactions listed.


1. Which reactions are not balanced? How doyou know?

2. Explain in your own words how this activityillustrates the Law of Conservation of Mass.

S K I L L C H E C K









Law of Conservationof Mass

balanced chemicalequation

coefficients

Key Terms

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Key Terms


ReviewC H A P T E R

3word equationsimple compositionsimple decomposition

chemical namechemical formulacommon name

Law of Conservation of Massbalanced chemical equationcoefficients


1. In your notebook, write the correct term orterms to complete each of the followingsentences.

(a) Although two or more are needed for a simple compositionreaction, only one product results. (3.2)

(b) Simple reactions producea compound, while simple

reactions break downcompounds. (3.2)

(c) Reactions follow patterns. Studying thesehelps a

chemist know what to expect. (3.2)

(d) If a chemical appears on the periodic table,it is a(n) . (3.2)

(e) Chemicals represented by symbols arecalled . (3.3)

(f) Chemicals are not created or destroyed ina chemical reaction. This is known as the

(5 words). It was firstproposed by . (3.4)


2. This chapter examines simple composition,simple decomposition, combustion, andneutralization reactions. Copy the data tableshown here into your notebook. Fill it in todescribe all four types of reactions. (3.2)

3. Give the chemical names and chemicalformulas for the following compounds. (3.3)

(a) salt

(b) water

(c) sugar

(d) baking soda

(e) chalk

(f) marble

4. Write down a word equation for one chemicalreaction in this chapter. Then list:

(a) the reactants

(b) the products (3.1)

5. In your own words, explain the Law ofConservation of Mass. (3.4)

6. Explain how a chemical equation can bewritten in a universal language understandableby chemists around the world. (3.4)

Developing Skills

7. Why is it important to balance a chemicalequation? (3.4)

Reaction Type Reactant(s) Product(s) Energy Released(exothermic) orEnergy Required(endothermic)

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8. Classify each of the following chemicalreactions as a simple composition or simpledecomposition reaction. (3.2)

(a) X � Y → XY

(b) CD → C � D

(c) Energy in the form of heat, electricity, orlight must usually be added to this type ofreaction.

(d) Two or more elements combine to form acompound in this reaction type.

(e) A chemical is broken down into itscomponent elements.

(f) Oxygen in the air combines with iron toform rust.

(g) Heat or light are often given off in thistype of reaction.

(h) Water breaks down into hydrogen andoxygen gases.


9. Think of an analogy to explain simplecomposition and decomposition reactions toyour younger sibling or friend. For example,these two reaction types can be compared todancing. A simple composition reaction is liketwo people coming together to dance. Asimple decomposition reaction occurs whenthe song ends and the two people return totheir seats. Now you think of one. (3.2)

10. Is the following equation balanced? Explainyour answer. (3.4)

Mg(s) � 2HCl(l) → MgCl2(s) � H2(g)

Critical Thinking

11. The mass of the reactants in a chemicalreaction will equal the mass of the products.Is the same always true for the volumes ofthe reactants and the products? (3.4)

12. In the reaction of carbon with oxygen, onecarbon atom reacts with one oxygenmolecule. If 20 billion atoms of carbon reactwith 30 billion molecules of oxygen, will allthe reactants be used up? Explain. (3.4)

13. Why are composition reactions mostlyexothermic? Why are decompositionreactions mostly endothermic? Investigatethis question in your school library. (3.2)


1. Review how you answered the Getting Ready questions atthe beginning of the chapter. How has your thinkingchanged? How would you answer these questions nowthat you have investigated the topics in this chapter?

2. Now that you know much more about chemical reactions,how does this affect your thinking about the products youuse every day? How will your new knowledge change theway you choose these products?

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What do these pictures haveto do with the study of chemistry?

To answer, examine thephotograph of the cars and trucksdriving over the steel bridge.Chemistry has allowed us to harnessthe energy stored in oil, natural gas,and other fossil fuels to power ourvehicles and industries.

Chemistry also plays an importantrole in the steel bridge. Chemicalreactions are used to make the steel.Chemical reactions that form rustare also at work trying to weaken the structure.

Even something as natural as rainhas a chemical connection. In someparts of Canada, pollution from

combustion reactions has createdacid deposition. The picture at thetop left of page 59 shows a forestdamaged in this way.

In this chapter, you will explorechemical reactions between acids andbases and learn how we use thisknowledge to combat acid deposition.

You will also investigate howcombustion reactions lead to globalclimate change and acid deposition,and you will demonstrate theenvironmental conditions that causethe corrosion of steel. In addition,you will identify technologies that protect steel against corrosion.



Reactions and theReactions and the4• Why are coal, oil,

and natural gas called“fossil fuels”?

• Name the type of reactionthat gives off heat or light.

• What are some clues thata combustion reaction has occurred?

• What type of chemicalreaction occurs when you mix vinegar andbaking soda?

List 10 chemical

reactions that you

encounter on a regular

basis. Describe the role

each reaction plays in

your life. As you read

this chapter, you will

learn about some

common chemical

reactions that you may

not normally notice.

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Starting Point

Reactions and the Environment • MHR 59

The Halifax Explosion

An explosion in Halifax on December 6, 1917,was one of largest, most violent human-made,energy-releasing chemical reactions in history.This chemical reaction killed nearly 2000 peopleand injured about 9000 others. In this activity,you will do research to uncover the cause ofthe explosion.

What to Do

1. Read the Internet Connect below and follow the links to start your investigation.

2. Present your findings in a series of diagramsor a flowchart that shows the disaster as asequence of events. Include captions orbrief descriptions about what happened atdifferent points during the disaster.



EnvironmentEnvironment


In this chapter you will learn:• how to describe changes to reactants and products in

fossil fuel combustion reactions• how the products of fossil fuel combustion affect

our environment• how to explain common acid–base neutralization reactions• how technologies can reduce the emissions that affect

our environment• how to describe changes to reactants and products in

rusting reactions

Why It Is Important

Skills You Will Use

• Some of the products and conveniences you enjoy cannegatively affect the environment. What if you had togive up some of the conveniences you have come todepend on? Knowing more about chemical reactionshelps you make choices that are good for you — and for the environment.

In this chapter you will:• plan investigations of questions, ideas, problems,

and issues• carry out procedures using a broad range of tools

and techniques• demonstrate a knowledge of WHMIS standards by

handling chemicals and other materials properly• compile, analyze, and display information in a variety

of formats• work as part of a team to address problems and

communicate information

www.mcgrawhill.ca/links/science.connect2Use the Internet to investigate the cause, thechemistry, and the consequences of the Halifaxexplosion. Go to the above web site, then toInternet Connects, Unit A, Chapter 4, and then toThe Halifax Explosion.

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Fossil Fuel Combustion

How many of the following things do you do each day?• switch on a light bulb or use an electric hair dryer• drive a car or get a ride on a bus• heat your home with a natural gas furnace• use natural gas to heat the water for your shower or bath

If you do any or all of these, you are relying on the combustion or burningof fossil fuels.

Chapter 3 discussed that fossil fuels are energy resources from the decayedremains of ancient plants and animals. (Chapter 8 discusses the formation offossil fuels in more detail.)

In most cases, the energy stored in fossil fuels must be transformed intoother forms of energy before it can be used. Combustion, or burning, is themost common way to transform this stored energy.

During a combustion reaction, a fossil fuel reacts rapidly with oxygen gas.The products of this combustion reaction are carbon dioxide gas (CO2(g)) andwater vapour (H2O(g)).

Like all exothermic reactions, the combustion of fossil fuels gives off energy.In a car engine, some of the chemical energy released is transformed intokinetic energy to turn the wheels of the car. If you feel a car hood after a longtrip, you will know what most of the energy is given off as heat.

The following chemical equation describes the combustion of octane, a component of gasoline:

2C8H18(l) � 25O2(g) → 16CO2(g) + 18H2O(g) � energy

The word equation for this reaction is:

octane � oxygen → carbon dioxide � water vapour � energy

In the following activity, you will investigate changes to the reactants andproducts in a common fossil fuel combustion reaction.


4.1

Name the products of acombustion reaction.

Figure 4.1 Fossil fuels provide theenergy to power cars, and provideheat to appliances such as this gasstove burner.

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Find Out


Evidence of a Combustion ReactionWhen you light a candle, you observe fossil fuelcombustion as the candle wax (made from fossilfuels) burns. In this activity, you will identify more evidence of fossil fuel combustion.

Safety Precautions


• Clean up the work area and wash your hands thoroughly at the end of the activity.

What You Need

small ball of modelling claycandlepie plate with high sidesmatchesglass jarwaterfood colouringruler

What to Do Part 11. Use the modelling clay to anchor the candle in

the bottom of the pie plate.

2. Light the candlewith a match.

3. Place the glass jar over top of the burning candle.

4. Carefully observe the candle as well as theglass jar. Record any evidence that acombustion reaction occurred in the glass jar.

Part 25. Remove the glass jar from over the candle.

6. Add enough coloured water to cover thebottom of the pie plate to a depth of 1 cm.

7. Light the candle.

8. Place the glass jar over top of the burningcandle.

9. Make sure you observe the candle as well asthe events that occur in the glass jar. Recordany evidence that a combustion reactionoccurred in the glass jar.



Incomplete CombustionIf fossil fuels do not burn completely, they undergo a chemical reaction calledincomplete combustion. Incomplete combustion occurs when there is notenough oxygen available. For example, it may occur in a blocked chimney, aninefficient furnace, or a car engine running in a closed garage.

Complete combustion produces three products: carbon dioxide (CO2(g)),water vapour (H2O(g)), and energy. Incomplete combustion produces fiveproducts: carbon monoxide (CO(g)), carbon (C(s)), carbon dioxide, watervapour, and energy.

Carbon monoxide is an odourless, colourless gas that is extremely poisonous.It combines with blood in the bloodstream to starve the body of oxygen,causing death. The carbon produced in an incomplete combustion reactioncauses the black coating (soot) you see in fireplaces. How does this relate toyour observations from the Find Out activity you just performed?

List the five products of an incomplete combustion reaction.

S K I L L C H E C K








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Greenhouse Gases


Figure 4.2 A greenhouse preventsheat from escaping into theatmosphere. Greenhouse gaseswork the same way to trap heat inEarth’s atmosphere.

Name some naturalgreenhouse gases.

In your own words,explain global climatechange.

We use fossil fuels to heat homes, provide energy for industry, and generateelectric energy. Our cars and trucks burn millions of litres of gasoline daily. Allof these combustion reactions release millions of tonnes of carbon dioxide intothe atmosphere. What effect does all this extra carbon dioxide have on Earth’satmosphere?

Most scientists agree that carbon dioxide is important to life on Earth. All living creatures, including plants, produce it naturally. In fact, all livingthings produce carbon dioxide, water vapour, and methane. These are known asnatural greenhouse gases.

Greenhouse gases trap heat in Earth’s atmosphere and prevent heat fromescaping into space. They also help to maintain the average global temperature of�15°C. Without them, the average global temperature would be much colder —about �18°C!

Global Climate ChangeThroughout Earth’s history, there have been intervals of warming and cooling.Scientists are concerned about the current long-term trend toward globalwarming. Accompanying this trend is a dramatic increase in extreme climaticevents. Glaciers are melting. Sea levels are rising. Climate zones are shifting.

The real threat is the rate at which climate change is occurring. Climatesare changing much faster than in Earth’s past. Scientists point out that manyspecies of organisms will not be able to adapt to such fast changes. Theseorganisms may become extinct.

Some people believe that climate change is a natural phenomenon. Theynote that Earth has gone through many ice ages with shorter periods ofwarming between the ice ages. The Earth and its species will adjust.

In the following investigation, you will consider both sides of the globalwarming issue.

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Analyze1. As a group, compare the information that

you found supporting and refuting thescientific view that human activity isresponsible for the rapid increase in globaltemperatures. Use a chart or other tool toorganize the data that you collect.

Climate Change:What is YourPosition?Think About ItThere is abundant evidence that the globalclimate has warmed significantly during the lastcentury. Scientists point out that this is due to theincrease of two greenhouse gases: carbon dioxideand methane.• The burning of fossil fuels such as coal and

gasoline has released tremendous amounts ofcarbon dioxide.

• Human activities such as burning vegetation,landfilling garbage, growing rice in large paddies,and keeping large amounts of cattle together infeedlots release large quantities of methane.

The level of these and other greenhouse gasesreleased by human activities appears to be causingthe current rapid global warming.

The Earth has experienced natural variations inclimate throughout its history. In fact, thegreenhouse effect maintains the temperature ofthe Earth at a level suitable for life to exist.

Natural climate changes occur over a relativelylong period of time. Because the change isgradual, organisms adapt to the new temperatureand precipitation patterns.

Today, many scientists are concerned about therate of change. Global temperatures are changingmuch faster than in the past. Will species haveenough time to adapt to the new climate?

Some skeptics argue that there is nothing toworry about. Warmer temperatures will makeEarth more hospitable for humans and otherorganisms. They also question the reliability ofthe climate models that scientists use to makepredictions about climate change. What do youthink?

What to Do 1 Work in teams of three or four students.

2 Each member of the group should use anapproved search engine to locate:• one web site that supports the scientific

viewpoint that human activities are directlyrelated to climate change; and

• one web site that refutes the scientificviewpoint that human activities are directlyrelated to climate change.

3 Evaluate and summarize the informationfound on each web site.


4–A4–A

S K I L L C H E C K









Glacier high above Peru in the Andes Mountains, 1978 The same glacier, 2000

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Air PollutionCarbon dioxide is not the only chemical substance that human activities add to the air. Many other chemicals in the air cause harm to living things or theenvironment. These chemicals are called pollutants.

Air pollutants can cause problems such as asthma, headaches, and irritation ofthe eyes, nose, and throat. They can also aggravate heart and lung conditions.

Even worse, air pollutants can combine with each other to produce acidprecipitation or rainwater that has become more acidic. The more accurateterm for this phenomenon is acid deposition since dry matter, as well asprecipitation, causes acids. Study Figure 4.3 and identify the different sources of pollutants that contribute to acid deposition. Notice the chemical reactions involved.


SO2(g)

NO2(g)

acid precipitation

sulfur dioxide gas + water sulfurous acid nitrogen dioxide gas + water nitric acid + nitrogen monoxide gas

SO2(g) + H2O(l) H2SO3(aq) 3NO2(g) + H2O(l) 2HNO3(aq) + NO(g)

When volcanoes erupt, they release carbon dioxide and water vapour. They also release sulfur dioxide (SO2(g)) and nitrous oxides (NOx(g)) into the atmosphere. These gases mix with water vapour in the clouds to form diluted sulfurous and nitric acids.

Forest fires release carbon dioxide and water vapour. The burning of wood also releases nitrogen dioxide (NO2(g)) and some sulfur dioxide (SO2(g)) into the atmosphere. Both of these gases react with rainwater to make acid deposition.

NO2(g) SO2(g)

In your own words,explain how aciddeposition is produced.

Figure 4.3A Natural Formation of Acid Deposition.

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1. List three natural greenhouse gases.

2. Describe three negative effects of global climate change.

3. What are the major contributors to acid deposition?

4. Name two gas emissions that are linked to acid deposition.


NO2(g)

NO2(g)SO2(g)

sulfur dioxide gas + water sulfurous acid

SO2(g) + H2O(l) H2SO3(aq)

acid precipitation

In a similar way, nitrogen oxides emitted from car exhaust react with rainwater to form nitric acid.

Industrial smokestacks release sulfur dioxide and nitrogen oxides, which react with rainwater to make acid deposition.

nitrogen dioxide gas + water nitric acid + nitrogen monoxide gas

3NO2(g) + H2O(l) 2HNO3(aq) + NO(g)

greenhouse gasesglobal warmingclimate changepollutantsacid precipitation acid depositionsulfur dioxide

(SO2(g))nitrous oxides

(NOx(g))

Key Terms

Figure 4.3B Human Contribution to Acid DepositionLike air pollutants, acid deposition comes from both natural sources andhuman activities. Study the illustrations here and on page 64 to identify bothnatural and human-made causes of acid deposition.

For more information about acid precipitation andother forms of acid deposition, load the student CD-ROM onto your computer. Launch the AcidDeposition applet and follow the instructions.

Disc

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Acid–Base ReactionsChapter 3 discussed what happens when an acid and a base are combined. Thisproduces a neutralization reaction. During this neutralization reaction, the acidand base react together to form two new chemical compounds: a salt and water.

Neutralization reactions do not just happen in labs. They also happen inyour body. Study Figure 4.4 — read both the caption and labels — to see howyour digestive system uses neutralization reactions.

Acids and Bases in the EnvironmentNatural limestone (CaCo3(s)) is a base used by industry. Thisbase is also used to neutralize lakes that have been acidifiedby acid precipitation. This technique is called liming.

During liming, calcium carbonate (CaCO3(s)) is added tothe waters of an acid lake. The calcium carbonate neutralizesthe acidic water, thus raising the pH of the lake water.

Study Figure 4.6 (on page 67) to see what happens to thepH of acidic water during the neutralization process. Alsostudy the equations showing this chemical reaction.


4.2

Figure 4.5 Calcium carbonate is released into a lakeaffected by acid precipitation. This neutralizes thelake water. Such liming is not a permanent solutionto the effects of acid precipitation. Why do you thinkthis is so?

Explain the benefit of adding lime to lakes.

Explain a neutralizationreaction that occurs inyour digestive system.

pancreas

smallintestine

Cells in the stomach release hydrochloricacid to help digest food. Hydrochloric acid isso strong that it could literally eat away thelining of your digestive tract. In order toprevent this, other cells in your stomachcontinually release mucous. Mucous containsa base that neutralizes any acid that comesinto contact with the wall of the stomach. Thisexplains why the stomach does not digest itself.

The pancreas produces sodium bicarbonatesolution that is dumped into the small intestine.

After leaving your stomach, the acidic foodenters the small intestine. Sodium bicarbonatefrom the pancreas and from cells in the smallintestine neutralizes the acid.

stomach

Figure 4.4 The following equations show what happens during the neutralizationreaction in your digestive system. What product does this reaction produce?

HCl(aq) � NaHCO3(aq) → NaCl(aq) � H2O(l) � CO2(g)

hydrochloric acid + sodium bicarbonate → sodium chloride + water + carbon dioxide

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Reducing EmissionsA better way to reduce acid deposition is to prevent it from forming. In Figure 4.3on page 64–65, you learned that sulfur and nitrogen oxides are responsible forthe high levels of acid deposition. Sulfur dioxide is a major by-product ofindustrial processes. It is also a product in the combustion of fossil fuels likenatural gas.

One way to reduce sulfur emissions is toremove the sulfur from the fuel before thefuel is burned. Figure 4.7 shows one placein Alberta where this is done. Turn thepage to learn how it is done.


acids neutrals bases

batteryacid

0

lemonjuice2.0

apples3.0

vinegar 2.2acid lake water

4.5

neutralized lake water6.0

calcium carbonate9.8

tomatoes4.2

normalrain5.6

milk6.6

humanblood

7.4

normalGreat Lakes

water8.5

ammonia11.1

ovencleaner

14.0bakingsoda8.2

milk ofmagnesia

10.5

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Figure 4.6 The pH scale tells you how acidic or basic a substance is. Identify the pH levels of an acidlake, calcium carbonate, and a neutralized lake. The liming process is represented by the followingword and chemical equations:

sulfuric acid � solid calcium carbonate → solid calcium sulfate � carbon dioxide gas � water

H2SO4(aq) � CaCO3(s) → CaSO4(s) � CO2(g) � H2O(l)

Add drops of vinegar to 100 mL of water until a test with universal pHindicator paper shows the solution has a pH of about 4.5. Slowly addlime (calcium carbonate) to the solution, testing with universal pHindicator until a pH of 6.0 is reached. What reaction did you just create?

www.mcgrawhill.ca/links/science.connect2Use the Internet to investigate how liming raisesthe pH of acidified lakes. Go to the above website, then to Internet Connects, Unit A, Chapter 4,and then to Liming Acid Lakes.

Name two sources of sulfur dioxide emissions.

Figure 4.7 At gas plants such as this one in Waterton,Alberta, hydrogen sulfide has been removed from naturalgas. The by-product of this chemical reaction is sulfur.

The coal mined in Alberta is valuedfor its low sulfur content.

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Removing Sulfur from FuelMost scientists agree that using sweet natural gas is one way to reduce emissionsthat produce acid precipitation. You may have noticed large yellow piles of sulfur at some natural gas plants in Alberta. This sulfur has been removed fromsour natural gas before it is sent to consumers. Since sulfur emissions are one of the main causes of acid precipitation, removing sulfur from the fuel beforeburning it will reduce acid precipitation.

Sulfur ScrubbingThe coal produced in some areas of the country contains sulfur. When this coalis burned, the sulfurous emissions can return to Earth as acid precipitation. Tohelp prevent this, a device known as a scrubber is installed on the smokestacksof many industrial plants that burn coal.

Scrubbing is a chemical and physical process that removes sulfur compoundsformed during the combustion of coal. Look at Figure 4.8 to see how this isdone. Scrubbers remove the sulfur from the smokestack before it reaches theatmosphere. Study the equations in the figure and trace what happens to thecoal, limestone, and air that enter the furnace.


1. Write out the general chemical equation for a neutralization chemical reaction.

2. Describe how driving a car contributes to the problem of acid precipitation.

3. Explain how liming can raise the pH of a lake affected by acid precipitation.

4. Why is it important to remove sulfur from coal and natural gas before theyare burned?


limestone CaCO3(s) tosmokestack

scrubber

furnace wet slurryof CaSO3(s)

coal (C(s)+S(s))

air

CO2(g) + SO2(g)

CO2(g) + CaO(s)SO2(g) + CaO(s)

O2(g) CO2(g)

CO2(g)

CaSO3(s)

water + CaO(s)

Figure 4.8 In the final stages of scrubbing, calcium oxide (CaO(s)) is injected. It reacts with sulfur dioxide gas (SO2(g)) to form a wet slurry of calcium sulfite (CaSO3(s)). Calcium sulfite forms the sludgethat is washed away with water. Using this method, scrubbers can remove more than 95 percent of thesulfur dioxide from smokestack emissions.

limingscrubber

Key Terms

Explain in your ownwords how sulfur scrubbing works.

Explain why sulfur isremoved from natural gas.

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Corrosion of Iron4.3

Figure 4.9 Iron and steel will rust when exposed to oxygen and moisture.

Figure 4.10 Rusting is an example of a simple compositionchemical reaction. Check the information on page 44 in Chapter 3to review this reaction type.

Corrosion refers to any process that chemically breaks down or degrades metal.The best-known case of corrosion is the rusting of iron. Most metals will rust, butthe corrosion of iron and steel is a serious problem because these metals are widelyused. As rust flakes off an iron structure, more metal is exposed to the environment.The structure is weakened over time, as more and more metal is exposed.

Have you ever left a metal tool or toy outside and found that it rusted andbroke? If so, you might think rust is a decomposition reaction. In fact, rusting isa simple composition reaction.

Examine the chemical reaction for the corrosion of iron, shown below. Ironis reacting with oxygen to produce iron oxide, which is commonly called rust.Although it is not included in this chemical equation, water is also required forrusting to occur.

4Fe(s) � 3O2(g) → 2Fe2O3(s)

solid iron � oxygen gas → iron (III) oxide

To see how acid deposition might accelerate the corrosion anddestruction of building materials, place an egg in a small beaker. Addenough vinegar to cover half the egg. Leave the beaker undisturbedfor a few days and observe the effects of the acid.

Explain how rusting is asimple composition reaction. What are thereactants? What is theproduct?

Gold is one metal thatdoes not corrode. This isone reason why manygold objects have survivedfor thousands of years.

Scientists and engineers are concernedabout the corrosion of steel. Unless rustingis prevented, it will weaken an iron or steelstructure. The rusting of the steel used toreinforce concrete in bridges and buildingscan cause these structures to fail andcollapse. Repairing or replacing thesestructures costs millions of dollars.

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Corrosion of IronIn this investigation you will model the factors that cause the corrosion (or rusting) of steel wool, which is made mainly from iron.

ProblemWhat factors cause the corrosion (rusting) of iron?

PredictionWhat environmental factor do you think is responsible for the rusting of iron?


4–B4–B

Safety Precautions

• Read the procedure carefully before starting thisinvestigation.


Apparatus3 test tubes of equal size and small enough

to fit into a graduated cylinder

3 graduated cylinders (100 mL)

3 test tube clamps and stands

electronic balance

small beaker

Materials1 g steel wool

water

Procedure 1 Obtain 1 g steel wool and divide it into two

equal pieces. Roll the steel wool into tiny spheresthat will fit into the test tubes but will not fallout if you turn the test tubes upside down.

2 Add some tap water to the small beaker andsoak one of the steel wool spheres for aboutfive minutes. Leave the other sphere of steelwool dry.

3 Squeeze the excess water from the first sphereand place this piece of steel wool in thebottom of one test tube.

4 Place the dry steel wool in the bottom of thesecond test tube.

5 Leave the third test tube empty.

6 Add approximately 40 mL of water to each ofthe three graduated cylinders.

7 Set up the three test tubes as shown in thefigure. Remember, one test tube will be empty.

S K I L L C H E C K








wet steel wool controldry steel wool

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8 Make a table like the one shown here in yournotebook. Use it to record the volume of thewater level in each test tube.

9 Leave the apparatus set up for at least 24 hours.

0 Record the level of water in each test tubeafter 24 hours.

! Calculate and record the change in the waterlevel in each test tube.

Water Level Water Level Water Levelin the test tube in the test tube in the control

with the wet with the dry (empty)steel wool (mL) steel wool (mL) test tube (mL)

Start

After 24 hours

change in water level


1. Write out the word and the chemical equations for the corrosion of iron.

2. List the two environmental factors that must be present in order for iron to rust.

3. Why is the combustion of steel wool similar to the corrosion of steel wool?

The rusting of steel is similar to the combustion of fossilfuels. Both reactions require oxygen. Remove one thread ofsteel wool. Use tongs to hold the steel wool — do not useyour fingers! Hold the thread of steel wool in the flame of aburning candle. What happens to the steel wool?

Before doing this activity, list the safety equipment needed.Get your teacher’s approval, and use the necessary safety equipment.

corrosionrusting

Key Terms

Analyze

1. Describe what happened to the amount ofwater in the test tube that had:

(a) the wet steel wool

(b) the dry steel wool

(c) the control

2. If rusting requires oxygen, oxygen wouldbe used up in the chemical reaction. Waterwould move into the test tube to replacethe oxygen. Which test tubes showed thatoxygen was consumed in this reaction?

3. Explain which test tube demonstrated thatwater speeds up the process of rusting.

Conclude and Apply

4. Did the evidence you gathered support orreject your original prediction? Explainyour answer.

5. Using the equation on page 69 as a guide,write out the chemical equation and theword equation for the rusting of steel.

6. How do you think you could prevent the rusting of metal such as steel wool?

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Solving the Problem of Corrosion


4.4

Have you ever noticed that metal parts of a car that have been damaged in acollision are more susceptible to rusting? Why would some metal parts of the car rust while others remain rust free? The answer is in the way metals are protected.

Painting — One way to protect metals is to give them a protectivecoating of paint. Painting over the metal prevents oxygen and waterfrom reaching the surface of the metal. This explains why steelbeams used in office buildings or on bridges are often painted withred paint.

Painting, however, may not be the best way to permanentlyprotect iron or steel. Once the paint chips off, water and oxygen arefree to attack the steel, and rust blisters grow rapidly.

Galvanizing — Another way to protect steel or iron is to use a processcalled galvanization. Galvanization is the process of applying a zinccoating to iron or steel. This involves immersing the metal in a bathcontaining molten zinc. This process coats the metal with a layer ofzinc that provides a protective barrier between the metal and theenvironment. The galvanized coating adheres to the base metal andresists chipping and cracking. In fact, the zinc coating actuallybecomes part of the surface of the steel.

Some galvanized nails also have a polymer coating to increase theprotection. Chapter 1 discusses how polymers can be developed forspecial needs. In this case, polymers help protect metal from rusting.

Figure 4.12 Paint can protect steel from corrosion. This bridge has been cleaned with high-pressure jets of water toremove loose paint, rust, and other loose debris. The cleanedsurface was then given a fresh coat of protective paint.

Figure 4.11 When oxygen and water contact the surface, metals such as iron and steel will rust.

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Sacrificial Metal — A third method of protecting iron involves the useof a sacrificial metal. If you could look closely at an undergroundoil pipeline, you would notice bars or ingots of a second metal, suchas magnesium, buried with the pipeline. The magnesium willcorrode but the pipeline will not. In this case the magnesium issacrificed in order to protect the pipeline.

The equation for this is:

2Mg(s) � O2(g) → 2MgO(s)

It is much easier and cheaper to replace the bars of magnesiumthan it is to repair a ruptured pipeline.



1. Explain why the chemical reaction for the rusting of steel is similar to thechemical reaction for the combustion of a fossil fuel.

2. How does painting a steel beam protect it from rusting?

3. How does dipping nails into molten zinc help prevent them from corroding?

base metal

galvanized coating

polymer coating

connected insulated wire

magnesium

buried steel pipe

Figure 4.13 Galvanized nails resistrust for many years.

Figure 4.14 Magnesium (Mg(s)) is sacrificed to protectsteel pipelines that contain iron (Fe(s)). Magnesium, zinc,and aluminum are commonly used as sacrificial metals.

galvanizationsacrificial metal

Key Terms

Describe three methodsof protecting metals fromcorrosion.

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Key Terms


ReviewC H A P T E R

4greenhouse gasesglobal warmingclimate changepollutants

acid precipitation acid depositionsulfur dioxide (SO2(g))nitrous oxides (NOx(g))

limingscrubbercorrosion

rustinggalvanizationsacrificial metal


1. All of the following statements are false. Asyou rewrite each statement in your notebook,change one or two words to make it true.

(a) The two reactants of the combustion ofgasoline are carbon dioxide gas and watervapour. (4.1)

(b) Combustion reactions release energy andare classified as endothermic. (4.1)

(c) The release of excess carbon dioxide gasinto the atmosphere is thought to be associated with acid precipitation. (4.1)

(d) Pollutants released into the atmosphere donot usually bother people with asthma andother medical conditions. (4.1)

(e) The pH of normal rainwater is 4.0. (4.2)

(f) Sulfurous acid is associated with globalwarming (4.1)

(g) The products of a neutralization reactionare an acid and a base. (4.2)

(h) A scrubber is a technology that helpsreduce the gases associated with globalwarming. (4.2)

(i) The brown material flaking off the side ofan old car is a fossil fuel. (4.3)

(j) Iron nails can be protected from rusting bydipping them in an acid. (4.4)

(k) Global warming concerns many scientistsbecause many species may not be able to adapt at the rate temperatures arecurrently changing.

(l) Acid precipitation includes both dry matterand precipitation.


2. Write out the word and chemical equationsfor one of the combustion reactions describedin the first section of this chapter. (4.1)

3. Use both word and chemical equations todescribe how sulfur dioxide gas (SO2(g)) isturned into an acid in the atmosphere. (4.1)

4. List three health problems that may be aggravated by air pollutants. (4.1)

5. Identify three naturally occurring greenhousegases. (4.1)

6. Why do some people take antacid tabletswhen they have heartburn? (4.2)

7. Why is lime added to lakes in some parts ofeastern Canada? (4.2)

8. How is a combustion reaction similar to thecorrosion of iron? (4.3)

9. Why is the steel used in a building coatedwith red paint? (4.4)

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Developing Skills

10. Look at the photograph of the burning candle. What evidence is there that this is a combustion reaction? (4.1)

11. Describe the procedure that you could followto determine if a new coating will preventthe corrosion of a iron nail. (4.4)


12. Identify one technology that can be used toreduce the amount of sulfur dioxide enteringthe atmosphere. Use chemical equations andword equations to explain how this technologyworks. (4.1)

13. An unknown tablet was found to contain thechemical aluminum carbonate. When dissolvedin distilled water, the pH of the mixture wasapproximately 8.0. Describe a simple investigation you could do to determine if thiscompound would make a good ingredient inan antacid tablet. (4.2)

14. Describe the connection between thegreenhouse gas carbon dioxide and concernsabout global warming. (4.1)

Critical Thinking

15. It is cheaper to paint a car than it is to producethe galvanized steel needed to make a new car.When you are shopping for a new car, you havea choice between a car made with galvanizedsteel and one made with ordinary steel. The carmade with galvanized steel costs $1000.00more. The manufacturer’s warrantee for therusting lasts nearly twice as long for the carmade with galvanized steel. Would you spendthe extra $1000.00 to purchase the car madewith galvanized steel? Why or why not? (4.4)


1. The chemical industry and the combustion of fossil fuelshave provided our society with many of the benefits weenjoy today. However, these same products andprocesses have created many environmental concerns.What changes to your lifestyle would you be willing tomake to reduce the environmental damage caused bythese products or the chemical reactions associated withthese materials?

2. Go back to the beginning of the chapter (on page 58).Check your answers to the Getting Ready questions. Howhas your thinking changed? How would you change youranswers now that you have investigated the concepts inthis chapter?

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A n I s s u e to A n a l y z e

A P U B L I C F O R U M

"Not in My Backyard"

U N I T AU N I T A


S K I L L C H E C K









Throughout this unit you have learned to identifyand classify chemical reactions that occur allaround you. You have learned how chemicalchanges occur, and how chemistry is used toimprove your standard of living. You nowunderstand the chemistry behind many commonindustrial processes. In this activity you will usewhat you have learned to evaluate how chemicalchange affects the world around you.

Think About ItAmmonia (NH3(g)) is a colourless, strong-smelling gas at room temperature. Ammonia can be fatal if inhaled. One of its compounds,ammonium nitrate (NH4NO3(s)), is used to make fertilizers and explosives.

Commercially, ammonia is produced by reactingnitrogen with hydrogen at high temperatures and pressures.

The following equations show this chemicalreaction:

N2(g) � 3H2(g) → 2NH3(g)

nitrogen gas � hydrogen gas → ammonia gas

BackgroundIn this activity you will role-play what might happen in a small rural community where the following events are planned.

• The president of a new company wants tobuild a chemical plant near the community.This plant will process ammonia to produceammonium nitrate for fertilizer and explosives.

• The company plans to purchase land nearthe edge of town. The property they want isclose to a marsh that is a favourite restingplace for migrating ducks.

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Unit A Issue Analysis • MHR 77

• The company expects to employ up to 150local residents, mostly in manufacturing jobs.There will also be openings for engineersand chemists. Local farmers expect tobenefit from reduced fertilizer costs.

Many townspeople are happy about the company’s plans. Some expect to get jobs in theplant. Others hope the plant will boost the localeconomy. This would mean their children may beable to find jobs locally when they finish school.Local business owners look to the new plant as apotential customer.

Some people, however, are concerned aboutthe risks to the environment and human health.In particular, they are worried about the effects of fumes, gaseous emissions, potential spills, and explosions.

The company president is aware of theseconcerns and has assured the mayor that the plant will be equipped with pollution controltechnologies. As well, the president claims thatevery effort will be made to minimize spills and leaks.

The company’s proposal includes an actionplan that explains what the company will do if aspill or leak occurs. This action plan will bedelivered to every home.

During this activity, you will participate in atown hall meeting to discuss the various concernsabout the company’s plans. The meeting will bechaired by the town’s mayor, who wants to hearwhat local people think about the issues beforemaking a decision. During this town meeting,representatives from a number of special interestgroups will make presentations. Communitymembers will be invited to ask questions andvoice their concerns.

The following people will speak at the meeting:

Representatives of Special Interest Groups• an area farmer• a member of an environmental

advocacy group

• a chemist who lives in the community• a town resident who has asthma, a

respiratory illness

Company Representatives• the president of the company• the architect who will design the plant• a chemical engineer

What to Do 1. Briefly outline what you think each person’s

point of view will be before the meetingtakes place. This will help to prepare you for the forum.

2. Your teacher will give your group the role ofone of the people listed above. As a group,• discuss the issue,• gather information about how such a plant

might affect a rural community, and• formulate a point of view for the person

your group is representing.

3. When the forum takes place, your group willhave three minutes to state your case. Theother members of the class will representcommunity residents. They will be invited toask questions and state their concerns.

4. As a class, your task is to assess thepresentations made at the meeting andevaluate the possible risks of the new chemicalcompany. You will make a recommendation tothe mayor about whether to accept or rejectthe company’s application.

www.mcgrawhill.ca/links/science.connect2Use the Internet to gather information about how sucha plant might affect a rural community. Go to the aboveweb site, then to Internet Connects, Unit A Project, andthen to “Not in My Backyard”.

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306 MHR • Glossary

science.connect™ 2 glossary

acid deposition acidic materials(liquids or solids that contain sulfuricor nitric acid) that are deposited onEarth (pp. 64, 148)

acid precipitation sometimesreferred to as acid rain; rain, snow,fog, or dew that has become moreacidic; see acid deposition (p. 64)

acquired immunity body’s immunityto pathogens developed throughoutlife by natural exposure or vaccina-tion; see active immunity and passiveimmunity (p. 199)

active immunity body’s process ofdeveloping antibodies against certaindiseases; see acquired immunity (p. 199)

air bag inflatable bag instantlyreleased from a vehicle’s steeringwheel or dashboard in a collision inorder to restrain the occupant andlessen chance of serious injury (p. 298)

air bag, first generation first air bagdesign; inflated too quickly and toomuch, often causing injury; see airbag (p. 298)

air bag, second generationimprovement on early air bag design;inflates more slowly without over-inflating; see air bag and air bag,first generation (p. 298)

air bag, third generation furtherimprovement in air bag design;senses both mass of the occupant andforce of collision; adjusts the infla-tion accordingly; see air bag andair bag, second generation (p. 298)

alloy two or more metals mixedtogether; looks like one metal (p. 10)

amniocentesis procedure used todetermine the chromosomal make-up of a fetus and to check forabnormalities (p. 223)

antibiotic drug that fights bacterialinfections by either killing bacteriaor preventing them from reproducing(p. 204)

antibodies protein compoundsreleased by white blood cells to reactwith and destroy antigens (p. 197)

antigens structures attached to allcells; they help the body’s immunesystem identify pathogens (p. 197)

aseptic free of pathogens (p. 170)

BAC Blood Alcohol Concentration;measure of the amount of alcohol inthe bloodstream; usually measured inmilligrams of alcohol per millilitreof blood (p. 241)

bacteria microscopic, one-celledorganisms; may be beneficial,harmful, or neither (p. 159)

balanced chemical equationreaction equation that has the samenumber of atoms of each elementon both sides of the equation (p. 53)

booster seats vehicle safety seatsdesigned to raise a child enough tofit the seat belt properly; allow theseat belt to restrain the child duringa collision (p. 297)

botulism form of food poisoningcaused by bacteria (p. 163)

braking force applied by brakes tostop a vehicle (p. 272)

braking distance distance a vehicletravels between when the driverapplies the brakes and when thevehicle comes to a stop; see alsostopping distance (p. 254)

carbohydrate main source of energyfor the human body; usually in theform of glucose (p. 125)

cellular respiration process used byall plant and animal cells to obtainenergy from food (p. 119)

chemical energy energy in chemi-cals; for example, potential energyfrom food converts to chemical energyduring digestion and chemical energyin fireworks ingredients is transformedto light, sound, and heat energy whenthe fireworks are set off (p. 87)

chemical formula standard scientificsymbol by which each chemical ele-ment or compound is known (p. 50)

chemical name standard scientificname by which each element or com-pound is known; established by aninternationally recognized namingsystem (p. 50)

chemical reaction transformationthat occurs when two or more sub-stances react together, producing oneor more new substances with differ-ent properties from the originalsubstances (p. 24)

child seat vehicle safety seatdesigned to restrain a child (p. 297)

chlorophyll green enzyme in plantcells that enables photosynthesis(p. 118)

chloroplasts special parts of greenplants that capture solar energy(p. 118)

chromosomes found in the nucleusof a cell; they contain DNA (p. 212)

climate change natural process ofEarth’s warming and cooling intervals;see also global climate change (p. 62)

coal see fossil fuels (p. 137)

coefficients numbers placed in frontof chemical formulas to balance thenumber of atoms on either side ofthe equal sign in a chemicalequation (p. 54)

combustion chemical reaction inwhich a substance combines withoxygen to produce heat and light;burning (pp. 28, 144)

common name name by which acommon chemical is referred to insociety; varies from region to region;existed long before an internationalnaming system was created (p. 51)

communicable diseases illnessesthat can be spread from one organismto another (p. 163)

Conservation of Energy, Law ofenergy cannot be created ordestroyed, only converted from oneform to another; input energy isequal to output energy (p. 92)

Conservation of Mass, Law ofmatter can be neither created nordestroyed (p. 52)

C

B

A

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Glossary • MHR 307

Conservation of Momentum, Lawof total momentum of collidingobjects stays the same after thecollision (p. 280)

converter system in which energyis changed from one form intoanother (p. 86)

convertible child seats vehiclesafety seat designed to restrain achild (from newborn to a mass of18 kg) during a collision (p. 297)

corrosion process that chemicallybreaks down or degrades metal(p. 69)

crash cushion road feature designedto decrease the force of a collision byslowing the impulse; barrels of wateror sand; see also road safety featuresand guardrails (p. 291)

crash test dummies manikinsdesigned to behave like the humanbody during a collision; fitted withsensors to record data (p. 288)

crude oil petroleum; see fossil fuels(p. 137)

crumple zones parts of a vehicledesigned to crush when hit, absorb-ing much of the energy in a collision;include hood, trunk, and fenders(p. 288)

depressant substance that slowsreactions, lowers co-ordination,and increases drowsiness (p. 240)

disease illness; something thatprevents the normal functioning ofthe body (p. 158)

distance change in position (p. 252)

distance/time graphs graphic repre-sentations of speed (velocity) (p. 256)

distillation process by which a sub-stance (such as crude oil) is separatedinto its component parts by boiling itand then condensing the resultingvapours (p. 141)

distraction anything that takesattention away from a task (p. 237)

DNA complex molecule that con-tains genetic information; appearsas long strands in the nucleus ofeach cell (p. 212)

dominant inherited traits/genes thatappear in offspring; tend to coverrecessive traits; see also recessive (p. 216)

drink practical guide for monitoringalcohol consumption that defines astandard drink as either 45 mL ofhard liquor (40% alcohol), 150 mLof wine (11% alcohol), or 350 mLof beer (4% alcohol) (p. 241)

efficiency measure of how wellenergy is converted to accomplishthe intended task (p. 112)

endothermic reaction any chemicalreaction that absorbs heat (thermalenergy) (p. 35)

energy ability to do work (p. 82)

energy change obvious or unnotice-able production or absorption of aform of energy (e.g., sound, light,heat) as part of a chemical change(p. 35)

epidemics diseases that spreadthrough the population faster andmore widely than would normallybe expected; not as widespread aspandemics (p. 176)

exothermic reaction any chemicalreaction that releases heat (thermalenergy) (p. 35)

fat source of energy and energystorage in animals; see also saturatedfats and unsaturated fats (p. 126)

first generation air bags see air bag,first generation (p. 298)

following distance distance(measured in seconds) at which itis considered safe to follow anothervehicle under good driving condi-tions; generally accepted to betwo seconds (p. 265)

force any push or pull on an object(p. 270)

fossil fuels formed from the remainsof swamp vegetation and/or animalsthat lived about 300 million yearsago; include coal, crude oil (petro-leum), and natural gas (p. 136)

friction force resisting motion,caused by substances rubbingtogether; rubbing (p. 272)

fungi organisms that live off deadand decaying organisms or are para-sitic on living organisms; see alsoparasites (singular � fungus) (p. 162)

galvanization process of applyinga zinc coating to iron or steel toprovide a protective barrier (againstrust) between the metal and theenvironment (p. 72)

generator device that makes electric-ity (p. 100)

genes basic building blocks of inher-ited traits that form segments thatmake up DNA; see also DNA (p. 212)

genetic disorders diseases or ill-nesses caused by alterations to genesthat affect their normal functioning(p. 220)

genetic engineering transferringgenes from one organism or type oforganism to another (p. 223)

genetics scientific study of howcharacteristics or traits are passedfrom parents to offspring (p. 212)

genotype letter code for the combi-nation of genes that an organismhas for each trait (p. 217)

geothermal energy heat producedwithin Earth (from geothermal activ-ity) that comes close to the surface;can be used for heating or toproduce electricity (p. 84)

global climate change formerlycalled global warming; during thisprocess, some places on Earth mayget much warmer while others mayget cooler; see climate change (p. 149)

global warming long-term trendtoward warmer temperatures accom-panied by extreme climatic eventsand shifting of the climatic zones;more correctly called global climatechange; see global climate change (p. 62)

glycogen starch-like carbohydrate inwhich the body stores glucose forfuture use (p. 125)

greenhouse effect phenomenoncaused by an insulating layer ofcarbon dioxide and other gasesaround Earth; lets radiation in butkeeps heat from escaping (p. 62)

G

F

E

D



greenhouse gases compounds(such as carbon dioxide, water, andmethane) that trap heat in Earth’satmosphere (p. 62)

grief feelings of regret, sadness, orloss (p. 244)

guardrails road features designedto keep vehicles on the road and todecrease the force of a collision byslowing the impulse and thus absorb-ing the force of the collision; seecrash cushion and road safety features(p. 291)

herbicide chemical that kills particu-lar plants (p. 6)

heredity passing of characteristicsfrom parents to offspring (p. 216)

HHPS Hazardous HouseholdProduct Symbols; safety symbolsplaced on hazardous products tohelp consumers safely use, store,and dispose of them (p. 12)

homeostasis state of equilibrium orbalance; regulation of the body’sinternal environment (p. 123)

hybrid organism with both thedominant and recessive gene fora trait (p. 216)

hydrocarbons group of fossil fuelsso named because they are made upof carbon and hydrogen (p. 144)

hydro-electric kinetic energy ofmoving water converted intoelectric energy (page 102)

immune system body’s third lineof defence against disease; targetsspecific pathogens (p. 195)

immunization catalyst for the bodyto begin producing antibodies;see vaccination (p. 201)

impaired unable to functionnormally (p. 240)

impaired driving legal term forthe offence of driving with a bloodalcohol concentration of more than0.08; may be applied to other formsof impairment (p. 241)

impulse force that changes momen-tum; force applied over time (p. 274)

infant-only seats vehicle safety seatsdesigned to restrain an infant duringa collision and transfer the force of acrash to the infant’s back (p. 297)

inflammatory response tissueswelling and increased blood flow;the body’s second line of defenceagainst further damage when thephysical barrier of the skin isbreached (p. 195)

inherited immunity resistance thatorganisms have to most diseases;passed on genetically (p. 199)

input energy energy that entersthe system (p. 86)

insecticide chemical that killsparticular insects (p. 6)

Kelvin standard scientific scale usedto measure temperature (p. 15)

kilowatt hour kW•h; 1000 watts perhour (p. 110)

kinetic energy energy due to motion(p. 82)

kW•h see kilowatt hour (p. 110)

lap belts 2-point seat belts; vehicleseat belts designed to hold the occu-pant in place by securing the personto the seat with a strap placed acrossthe pelvis (p. 292)

lift pump working component in anoil well located deep underground;lifts oil hundreds of metres to thesurface (p. 141)

liming process of adding naturallimestone to lake water to neutralizelakes that have been acidified by aciddeposition; neutralizing means bring-ing the pH of lake water closer tonormal (p. 66)

macrophages specialized whiteblood cells of the immune systemthat surround and destroy damagedcells, foreign protein, and pathogens(p. 195)

maintenance continual care thatensures proper functioning (p. 245)

manipulated variable aspect of aninvestigation that the researcherchanges; see also variable andresponding variable (p. 256)

metabolic needs body’s needs forenergy (p. 130)

metabolism rate at which a humanbody uses energy (p. 123)

microbes micro-organisms (p. 158)

momentum measure of an object’smotion and likelihood that the objectwill remain in motion (p. 270)

MSDS Material Safety Data Sheet;provides detailed information (thatwill not fit on the product label)about chemicals found in theproduct (p. 19)

mutagens environmental factors(anything outside the body) thatcause mutation (p. 220)

mutation change in genetic informa-tion because of an abnormal gene(change may be beneficial, harmful,or neither) (p. 220)

natural gas see fossil fuels (p. 137)

neutralization type of reaction duringwhich an acid and a base produce a saltcompound and water; the pH of theseproducts is more neutral (closer to 7)than the pH of either reactant (p. 29)

newton N; unit of measure for force;force applied over distance (p. 108)

nitrous oxides NOx(g); naturallyproduced acidic gases that mix withwater vapour in clouds to form acidprecipitation (p. 64)

non-communicable diseasesillnesses that are not caused bypathogens and so cannot be spreadfrom one organism to another (p. 163)

non-renewable useable only once;will not form again in nature in theforeseeable future (p. 147)

operational features parts of a vehi-cle that operate all the time to keepoccupants safe; include headlights,rear-view and side-view mirrors, tailand signal lights, brakes, etc. (p. 289)

O

N

M

L

K

I

H


Glossary • MHR 309

output energy energy that leaves thesystem (p. 86)

over-the-counter drugs medica-tions sold without a doctor’sprescription (p. 204)

pandemics diseases that affect alarge proportion of the populationin many countries; farther-reachingthan epidemics (p. 176)

parasites living organisms that gettheir nourishment from a host organ-ism; cannot live independently (p. 162)

passive immunity antibodiesintroduced into the body to createimmunity; see also acquiredimmunity (p. 199)

pasteurization process in which afood is heated to kill the microbesthat make it spoil (p. 158)

pathogens disease-causing agentssuch as bacteria, viruses, fungi, andprotists (p. 159)

pedigree family tree; diagram usedby geneticists to show the history ofa trait passed from generation togeneration (p. 218)

pesticides substances that use chem-icals to kill plants or animals (p. 6)

petroleum crude oil; see fossil fuels(p. 137)

photosynthesis process by whichplants use chlorophyll and sunlightto convert carbon dioxide and waterinto glucose and oxygen (p. 118)

physical defences body’s physicalbarriers against pathogens; includethe skin and secretions such asmucus (p. 194)

pollutants chemicals in the air,water, or soil that cause harmto living things or to the environ-ment (p. 64)

potential energy stored energythat can be converted into otherforms (p. 82)

poverty circumstance in which basicneeds for food, water, health care,and education are not met due toeconomic conditions (p. 166)

power rate at which energy is trans-ferred or work is done (p. 108)

precipitate solid that forms becauseof a chemical change (p. 34)

products substances present after achemical reaction (p. 28)

protein building block and sourceof energy for the body (p. 127)

protists single-celled organisms thatshare some characteristics with bothanimals and plants; some cause seri-ous disease, such as malaria; see alsopathogens (p. 162)

public health government and otheragencies working together to developand maintain healthy communities(p. 180)

pump jack working component in anoil well; lifts oil located deep under-ground hundreds of metres to thesurface (p. 141)

Punnett square tool used by geneti-cists to predict the probability ofoffspring inheriting certain traits(p. 217)

purebred organism with identicalgenes for each trait; for example, thesame two genes for tallness — TTor tt (p. 216)

quarantine isolate sick people, oftenin special facilities; place where suchpeople are isolated (page 180)

reactants substances present before achemical reaction (p. 28)

reaction time time it takes to recog-nize a situation and act on it (p. 237)

recessive inherited traits/genes thatdo not appear in offspring exceptwhen both parents possess the trait;are covered by dominant traits;see also dominant (p. 216)

reservoir rock porous rock contain-ing tiny droplets of oil forced thereby changes in Earth’s crust (p. 140)

responding variable aspect of aninvestigation that the researchermeasures as it changes; see also vari-able and manipulated variable (p. 256)

restraining features hold occupantin place; prevent occupant from hit-ting the dashboard, windshield, sides,or roof of the car, or from being

thrown out of the vehicle during acollision; include seat belts, air bags,headrests, and child seats (p. 289)

rise difference in vertical position ona graph; shows the distance intervalbetween two points on a distance/time graph (p. 260)

road safety features traits of a roadthat are designed to decrease theforce of a collision by slowing theimpulse; see crash cushion andguardrails (p. 291)

run difference in horizontal positionon a graph; shows the time intervalbetween two points on a distance/time graph (p. 260)

rusting one type of corrosion (p. 69)

sacrificial metal a metal used toprotect a nearby metal that is morereactive; it “draws” the corrosion;magnesium is a common sacrificialmetal (p. 73)

salmonellosis form of food poison-ing caused by bacteria (p. 163)

sanitary maintaining clean, germ-free conditions to help preventdisease (p. 164)

saturated fats animal fats and someoils; associated with an increased riskof heart disease (p. 126)

scrubber device installed in industrialsmokestacks to remove sulfur and otherpollutants formed during the com-bustion of coal, for example (p. 68)

second generation design see airbag, second generation (p. 298)

seismic survey method used bygeologists to determine the locationof potential oil and natural gasreservoirs by sending shock wavesthrough the layers of Earth’s crustthat reflect off rock; the printoutfrom this survey shows the under-ground rock formations; see reservoirrock (p. 140)

shoulder harness 3-point seat belt;vehicle seat belt designed to hold theoccupant in place by securing theperson to the seat with one strapplaced across the pelvis and anotherstrap placed across the chest frompelvis to shoulder (p. 292)

S

R

Q

P



simple composition reaction inwhich two or more elements com-bine to form a compound (p. 44)

simple decomposition reaction thatbreaks a compound into the elementsthat make it up (p. 45)

slope steepness of the line on agraph; measured by dividing riseby run (p. 260)

solar cells items that convert lightenergy (usually energy from the Sun)into electricity (p. 107)

solar energy energy from the Sun(p. 84)

staph bacteria staphylococcus; causeof food poisoning (p. 168)

staphylococcus see staph bacteria(p. 168)

statistics numerical facts gatheredand analyzed in an effort to identifypatterns (p. 234)

sterilization process that uses steamto destroy microscopic organismssuch as bacteria (p. 170)

stimulant substance that increasesheart rate and speeds up reactiontime; at high doses, can impairreaction time because it makes itmore difficult for the person tofocus (p. 240)

stopping distance distance that avehicle travels during reaction time(until the vehicle stops); see alsobraking distance (p. 264)

structural features parts of a vehiclethat protect the people inside;include crumple zones and rigid fea-tures such as heavy frame, roll cage,and side-impact beams that will notcrumple or break under extremepressure; see crumple zones (p. 289)

sulfur dioxide SO2(g); acidic gas thatmixes with water vapour in clouds toform acid precipitation (p. 64)

synthetic human-made substance(p. 6)

synthetic fibres human-made fibres(such as cloth or thread) made in thelaboratory using raw chemicals (p. 8)

synthetic polymers human-madematerials consisting of long chains ofmolecules; often spun into thread tomake fabrics or moulded to formplastics (p. 9)

therapy medical treatment that doesnot involve surgery or drugs (p. 244)

thermal energy heat (p. 84)

thermo-electric chemical energystored in a fossil fuel and convertedinto thermal energy, then to kineticenergy, then to electric energy (p. 102)

thermonuclear thermal energyreleased when atoms are split that isused to produce electricity (p. 102)

third generation air bags see airbag, third generation (p. 298)

3-point seat belt see shoulder harness(p. 292)

time interval between events (p. 252)

total momentum sum of momentumof colliding objects; see Conservationof Momentum, Law of (p. 281)

trauma physical and emotional stressor injury resulting from an accident(p. 243)

turbine sets of blades put at an angleso they can collect energy from fast-moving water, steam, or wind (p. 102)

2-point seat belts see lap belts (p. 292)

unsaturated fats most vegetable oils;associated with a lowered risk ofheart disease (p. 126)

vaccination injection of vaccine; anantigen; see vaccine (pp. 182, 201)

vaccine antigen injected into thebody as a catalyst for the body tobegin producing antibodies; see alsovaccination and immunization (p. 201)

variable aspect of an investigationthat changes because it is manipu-lated or because it responds tomanipulation; see also manipulatedvariable and responding variable (p. 256)

velocity speed; distance travelledduring a specific time interval (p. 252)

viruses microscopic, non-cellulardisease-causing agents; see alsopathogens (p. 159)

W•h see watt hour (p. 109)

watt W; international unit represent-ing one joule of energy per second(p. 108)

watt hour W•h; one watt of powerper hour; see kW•h (p. 109)

whiplash injury caused by musclesand ligaments of the neck beingstretched or compressed too much(p. 243)

WHMIS Workplace HazardousMaterials Information System; pro-vides detailed information on how tostore, handle, and dispose of danger-ous substances at work (p. 19)

wind energy kinetic energy capturedby windmills (p. 84)

word equation symbolic representa-tion of a chemical reaction that useswords to indicate reactants andproducts (p. 42)

W

V

U

T


Index • MHR 311

Index

Abrasives, 29Accident, aftermath of, 244actAcetic acid, 29Acetone, 12Acid deposition, 64, 69, 148Acid precipitation, 64, 148

reducing emissions, 67Acid-base reaction, 29, 66Acquired immunity, 199Active immunity, 199Adenoids, 194AIDS, 159, 163, 175, 176, 177inv,

179, 184, 204Air bags, 245, 298

first generation, 298second generation, 298simulation, 299invthird generation, 301

Air pollution, 64Air quality, 182Albino, 217Alcohol, 51Allergies, 202, 203actAlloy, 10

using, 11Aluminum hydroxide, 29Alzheimer’s disease, 225Ammonia, 15, 76Ammonium nitrate, 76Amniocentesis, 223Amoeba, 162Amylase, 24, 25Antacid, 24, 29, 48, 49Anthrax, 158, 164actAnti-lock braking systems, 245Antibiotics, 154, 204

problems with, 205safe use, 206

Antibodies, 130, 197, 199Antifreeze, 51Antigens, 197Antiseptics and microbes, 171invAntitoxin, 201Aqueducts, 181Aqueous solution, 50Arthritis, 163Aseptic, 170Aspirin, 204Athlete’s foot, 162

BAC (blood alcohol concentration),241, 242act

Bacteria, 159conditions for growth,

160–161invgrowth of, 196actpublic health, 188inv

Baking soda, 13, 29, 51Balanced chemical equation, 53act,

54actBenedict’s solution, 117Biological terrorism, 164actBituminous coal, 137Bleach, 24, 40Blood transfusions, 200invBlood types, 200invBody temperature, daily changes,

124invBoil-water advisories, 185Booster seat, 297Botulism, 163, 168Braking, 272Braking distance, 264Brass, 11Bread, 25Breast cancer, 223Bubonic plague, 178Bunsen, Robert, 137Butane, 48

Calcium carbonate, 42, 43, 51, 66Calcium hydrogen carbonate, 42, 43Calories, 125Cancer, 163CANDU reactors, 106Carbohydrate, 118, 125Carbon, 61Carbon dioxide, 43, 61

combustion, 144identifying, 26–27inv

Carbon monoxide, 61combustion, 144

Carbonic acid, 43, 51Carothers, Wallace, 8Caustic soda, 51Cellular respiration, 117, 118, 119

combustion, 146energy sources, 125simulating, 120–121inv

Chemical compounds, 50working with, 55act

Chemical energy, 87, 118Chemical equations, 52

balancing, 53

coefficients, 54combustion, 60

Chemical formulas, 50coefficients, 54

Chemical names, 50Chemical reactions, 23act, 24,

41act, 59actbaking bread, 25digestion, 25energy, 35energy conversion, 88–89invevidence of chemical changes,

32–33inv, 34household, 47invprecipitate, 34products, 28reactants, 28safety, 25swimming pools, 25types of. See Acid-base reaction;

Combustion reaction;Neutralization reaction; Simple composition; Simple decomposition

word equation, 42, 43working with, 55act

Chemicalsapplications, for cleaning, 7applications, in cooking, 14invenvironment, in the, 31soap, 7

Chemistryapplications, fibres, 8applications, in cooking, 13applications, in cosmetics, 16applications, in metalworking, 15applications, in the home, 12applications, on the farm, 6safety, 19

Chicken pox, 197Child restraints, 297Child seat, 297Chlorophyll, 118Chloroplasts, 118, 119Chromosomes, 212, 217

DNA, 213gender, 213number of, 213

Citric acid, 29Climate change, 62, 63invCloning, 224inv, 225Coal, 136, 137

Boldface entries are defined terms; italicized inv and act are investigations and activities, respectively.

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312 MHR • Index

extracting, 138mining, 138

Coefficients, 54Cold packs, 36invCollisions, 233act

distraction, 238–239invinjuries, 243Law of Conservation of

Momentum, 281momentum, 282invreaction time, 238–239invsafety systems, 287actseat belts, 246invvelocity, 279inv

Combustion, 29, 144carbon dioxide, 144carbon monoxide, 144cellular respiration, 146chemical equation, 60examining, 145invfossil fuels, 60–61, 144gasoline, 60incomplete, 61octane, 60propane, 144

Combustion reaction, 48evidence of, 61act

Common cold, 163Common name, 51Communicable diseases, 163Composition/decomposition

reaction, 46–47invCompounds, 50

working with, 55actConservation of Energy, Law of, 92Conservation of Mass, Law of, 52Conservation of Momentum,

Law of, 280Converter, 86Convertible child seats, 297Corrosion, 69

solving problem of, 72–73Cosmetics, 16, 18Coste, Eugene, 143Cowpox, 201Crash barrier, 291Crash cushion, 291Crash statistics, 233actCrash test dummies, 288, 304–305Crude oil, 136, 137Crumple zones, 245, 288, 289, 301Cystic fibrosis, 223

Davy, Sir Humphry, 45, 100Death, causes of, 234–235actDepressant, 240Depression, 163

Detergent, 17invDiabetes, 163Dihydrogen oxide, 51Dinitrogen monoxide, 51Diphtheria, 182, 201Disease, 154, 158

preventing, 168risk factors, 166society, affect on, 176–180treating, 204–208

Disinfectants, 170microbes, 171inv

Distance, 252calculating, 262reaction time, 264–265

Distance/time graph, 256calculating distance, 262velocity, 260

Distillationoil, 143soft drink, 142inv

Distraction, 237collisions, 238–239inv

DNA, 212chromosomes, 213structure of, 212

Dominant trait, 216Drink, 241Drug reactions, 206Drugs and reaction time, 240Dynamics cart, 269actDynamos, 101Dysentery, 163

E. coli, 163Ear, 194Efficiency, 112

calculating, 112actenergy, 111–113environmental benefits, 113

Electric energy, 80, 82, 85, 108Canadian generation of, 103invdistributing, 102–107generating, 100–101, 102–107power, 108solar cells, from, 107inv

Electricity, 99actdistributing, 106generating, 101solar cells, from, 107inv

Electrolysis, 45Elements, 44Emissions, reducing, 67Emulsifier, 18Emulsion, 18Endothermic reaction, 35

light energy, 37act

simple decomposition reaction, 45Energy, 82

chemical conversion, 87chemical reactions, 35conservation of, 92–93efficiency, 111–113glucose, 117acthuman needs, 130–131need for, 123pendulum, 81actsnack foods, in, 128–129invsources of, 125–129transformation device, 152world consumption, 148inv

Energy changes, 35Energy conversion, 86, 90inv, 101,

119chemical reactions, 88–89invnature, in, 118plants to animals, 122

Energy conversion system, 94input energy, 95invoutput energy, 95inv

Energy pyramid, 122Environment and genetics, 221invEnzyme, 24Epidemic, 178, 179Epsom salt™, 51Ethanol, 51Ethics, 225Ethylene, 24Ethylene glycol, 51Exothermic reaction, 35, 60

simple composition reaction, 44Eyelashes, 194Eyelids, 194

Face cream, 18Family tree, 218Faraday, Michael, 100Fatigue and reaction time, 240Fats, 126Fertilizers, 6Fetus and energy needs, 130Fibres, 8First generation air bags, 298First law of motion, 270Flame tests, 41actFleming, Sir Alexander, 204Flu, 163, 175actFluoride, 29Following distance, 265Food poisoning, preventing, 168Food preservation, 168Food recalls, 185Food safety, 169invForce, 108, 270

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Index • MHR 313

calculating, 278friction, 273actimpulse, 275momentum, 274

Fossil fuels, 48, 134, 136combustion, 60–61, 144

Friction, 272force, 273actmass, 273actmomentum, 280stopping, 273act

Fungi, 159, 162

Galvanization, 72Galvanometer, 100Gas, 50

identifying common, 26–27invinvisible, 30act

Gasoline, 48combustion, 60

Gender and chromosomes, 213Generator, 100, 102Genes, 212Genetic disorders, 220

mutagens, 222Genetic engineering, 223Genetic research

concerns regarding, 225issues in, 223–224

Geneticist, 218Genetics, 211act, 212

changes, 220–222dominant trait, 216environment, 221invhybrids, 216inheritance, 216–219offspring, 219invpaternity, 214–215invrecessive trait, 216

Genotypes, 217Geothermal energy, 84, 85Germs, 158

public health, 188invGiardia, 154, 162Gingivitis, 159Global climate change, 62, 149Global warming, 62Glucose, 43, 51, 118, 119, 146

energy, 117actGlycogen, 125Gold, 11

corrosion, 69Gore-Tex™, 8Greenhouse gases/effect, 62, 63inv,

149Grief, 244Guardrails, 291

Hair, 194Halifax explosion, 59actHazardous Household Product

Symbols (HHPS), 12Health challenge game, 228–229Health warnings, 185Heat of light bulbs, 111actHepatitis, 182Herbicides, 6Heredity, 216HHPS, 12HIV, 159, 179Homeostasis, 123Horsepower, 108Hot packs, 36invHuntington’s disease, 220Hybrids, 216Hydrocarbons, 144Hydrochloric acid, 12, 24, 29, 43Hydro-electric energy, making,

105invHydro-electric plants, 102, 105Hydrogen, identifying, 26–27invHydrogen peroxide, 12, 24, 46Hydrogen sulfide, 46Hypochlorous acid, 25

Ice cream, 5actImmune system, 195, 197

operation of, 198Immunity, 197

types of, 199Immunization, 201

reasons for, 202Impaired, 240Impaired driving, 241Impulse, 274

calculating, 275force, 275measuring, 274

Incomplete combustion, 61Infant-only child seats, 297Infection

detecting, 198acttreating, 204–208

Inflammatory response, 195Influenza, 163Inheritance

genetic disorders, 220genetics, 216–219

Inherited characteristics, 211actInherited immunity, 199Injuries, 236

collisions, 243Input energy, 86, 92, 94

energy conversion system, 95invInsecticides, 6

Ironcorrosion, 70–71invrusting, 69, 70–71inv

Irradiation, 168Isopropyl alcohol, 51

Jenner, Edward, 201Joule, 108

Kelvin, 15Kerner’s disease, 168Kevlar™, 8Kilowatt hour (kW.h), 110

calculating, 110actKinetic energy, 82, 83inv, 85, 87, 92Koch, Robert, 158, 170

Lactic acid, 119Lactobacillus acidophilus, 160–161invLap belts, 292Lavoisier, Antoine, 52Law of Conservation of Energy,

92, 94pendulum, 93act

Law of Conservation of Mass, 52Law of Conservation of Momentum,

280collisions, 281

Lift pump, 141model, 141act

Light energy, 85, 92endothermic reaction, 37act

Lignite, 137Limestone, 51Liming, 66Liquid, 50Lister, Joseph, 170Lye, 51

Macrophages, 195Magnesium as sacrificial metal, 73Magnesium chloride, 24, 29Magnesium hydroxide, 24, 29Magnesium oxide, 44Magnesium sulfate, 51Maintenance, 245Make-up, 18Manipulated variable, 256Marble, 51Marsh gas, 31Mass, 270

friction, 273actMaterial Safety Data Sheet (MSDS),

298Measles, 182, 201Mendel, Gregor, 216, 217Meningitis, 163, 182

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314 MHR • Index

Mercury oxide, 52Metabolic needs, 130Metabolism, 123

determinants of, 131Methane, 31, 51, 146Methanol, 12Microbes, 158

antiseptics, 171invdisinfectants, 171invspreading, 157act

Mitochondria, 119Molds, 162Momentum, 270

calculating, 271collisions, 282invconservation of, 280final, 283force, 274formula for, 271friction, 280slowing, 272stopping, 277velocity, 276act

Mothers Against Drunk Driving(MADD), 244

Motion, 270graphing, 258–259inv

Mousetraps, 83invMSDS, 19Multimedia, xiiMultiple sclerosis, 163Mumps, 182, 201Muriatic acid, 12Mushrooms, 162Mutagens, 220

effects of, 222genetic disorders, 222types of, 222

Mutation, 220

Natural gas, 48, 51, 136, 137, 143Neoprene, 9Neutralization, 29Neutralization reaction, 48, 49, 66Newton, Isaac, 270, 274Newtons (N), 108Nightingale, Florence, 170Nitrous oxides, 64Non-communicable disease, 163, 165Non-renewable, 147Nose, 194Nylon, 8

Octane, 48combustion, 60

Oil, 48, 135act, 136distillation, 143

drilling for, 141extracting, 139, 140refining, 143

Oil sands, 139Oil spills, 147Open-pit mining, 138Operational features, 289Output energy, 86, 92, 94

energy conversion system, 95invOver-the-counter drugs, 204, 207inv

choosing, 206safe use, 206

Oxygen, identifying, 26–27inv

Pandemic, 176, 179Paramecium, 162Parasites, 162Passive immunity, 199Pasteur, Louis, 158Pasteurization, 158, 168Paternity, 214–215invPathogens, 158, 159

defences against, 194immune system, 195inflammatory response, 195

Pedigree, 218interpreting, 218act

Pelletier, David, 80Pendulum and energy, 81actPenicillium notatum, 204Perspiration, 123Pesticides, 6Petroleum, 137pH, 16, 29, 67Photosynthesis, 35, 118Physical defences, 194Polio, 182, 201Pollutants, 64Polyester, 8Polyethylene, 9Polymer, 10actPolystyrene, 9Polyurethane, 9Potassium chloride, 51Potential energy, 82, 83inv, 85, 87Poverty, 166Power, 108

electric energy, 108Precipitate, 34Products, 28

word equation, 42Propane, combustion, 144Protease, 25Protein, 127Protists, 159, 162Public health programs, 175act,

180, 181–183

factors affecting, 184guidelines, 187health warnings, 185protecting the public, 184

Pump jack, 141Punnett square, 217Purebred, 216

Quarantine, 178Quartz, 51

Rabies, 202Reactants, 28

word equation, 42Reaction time, 237

collisions, 238–239invdistance, 264–265drugs, 240fatigue, 240

Recessive trait, 216Regional Health Authority, 181–183Reservoir rock, 140Responding variable, 256Restraining features, 289Reyes syndrome, 204Rigid features, 289Ringworm, 162Rise, 260Road safety, 185Road safety features, 291Rubbing alcohol, 51Rubella, 182, 201Run, 260Rusting, 69

Sacrificial metal, 73Safe roads, 247Safe vehicles, 245Safety, 236inv

chemical reactions, 25chemistry, 19

Safety features, 245, 290Safety precautions, xivSafety systems and collisions,

287actSafety technology of the future,

300invSale, Jamie, 80Salk, Jonas, 202Salmonellosis, 163, 164Salt, 51Sanitary, 164SARS, 184Saturated fats, 126Science log

chemical paste, 4chemical reactions, 22, 40, 58

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collision, 232common chemical reactions, 58driving decisions, 268energy transfer flowchart, 80food safety, 156fossil fuels, 134genetic research, 210power outages, 98products, 40public health programs, 174reactants, 40roller coaster, 250safety, 286solar energy, 116speed, 250traffic accident, 232vaccinations, 192vehicle safety, 286

Scrubbers, 68, 104Seat belts, 292act

children, for, 296invproper use of, 295retractor units, 293study, 294–295invwebbing, 293

Second generation air bags, 298Seismic survey, 140, 141Sewage treatment plants, 182Sexually transmitted diseases, 163Shoulder harness, 292Sickle cell anemia, 220Side impact beams, 245Silicon dioxide, 51Silver sulfide, 46Simple composition reaction, 44

exothermic reaction, 44Simple decomposition reaction, 45

endothermic reaction, 45Sinuses, 194Skin, 194

role of, 193actSkin cream, 18actSlope, 260Smallpox, 176, 184, 201Soap, 7act, 16Sodium azide, 298Sodium bicarbonate, 29, 51Sodium chloride, 19, 51Sodium hydroxide, 12, 51Sodium hypochlorite, 24, 40Soft drink, distillation, 142invSolar cells, 107Solar energy, 84, 85, 118, 119

quantity, 103Solid, 50Sound energy, 80, 85, 92

Spanish flu epidemic, 179, 181Speed, 251actStaph bacteria, 168Staphylococcus bacteria, 168States of matter, 50Statistics, 234STDs, 163Steel, 11

corrosion, 69Stem cells, 225Sterilization, 170Stimulant, 240Stomach, 194Stopping

friction, 273actmomentum, 277

Stopping distance, 264Strep throat, 203Structural features, 289Students Against Drunk Driving

(SADD), 244Sub-bituminous coal, 137Sucrose, 51Sugar, 51Sulfur dioxide, 64Sulfur scrubbing, 68Superplastic steel, 11Synthetic chemicals, 6Synthetic fibres, 8Synthetic polymers, 9, 10act

Table salt, 19, 51Tears, 194Tetanus, 182, 201Therapy, 244Thermal energy, 80, 84, 85, 87, 92

light bulbs, 111actwasting, 91

Thermo-electric plants, 102, 104Thermonuclear plants, 102, 106Third generation air bags, 301Thomson, J. J., 13Three-point belts, 292Time, 252Tonsils, 194Total momentum, 281Traits, 217Trauma, 243Triclosin, 170Tuberculosis epidemic, 178Turbines, 102Two-point belts, 292Typhoid fever, 182Typhoid Mary, 163

Ultrahigh-carbon steel, 11Unsaturated fats, 126

Vaccinations, 182, 185, 197, 201Vaccine, 201Variables, 256Vehicle maintenance, 245Vehicle safety, 288Velocity, 252

calculating, 254changing, 257collisions, 279invconstant, 257distance/time graph, 260formula for, 254graphing, 256–261, 258–259invmeasuring, 253invmomentum, 276actplotting, 257act

Viruses, 159mutation, 204

Walkerton’s water tragedy, 186invWater, 51

quality testing, 186invWater and Wastewater Technician,

31Water quality, 181Water treatment plant operator, 31Watt, 108Watt hour (W.h), 109Watt, James, 108Whiplash, 243White blood cells, 195WHMIS, 19Whooping cough, 182, 201Willson, Thomas, 101Wind energy, 84Wood alcohol, 12Word equation, 42

chemical reactions, 42, 43products, 42reactants, 42

Work, 82, 108Workplace Hazardous Materials

Information System (WHMIS), 19

Yeast, 13, 25, 162digestion, 25

Yellow fever, 182Yogurt, 160–161inv

Zinc chloride, 42, 43Zinc sulfide, 50

Index • MHR 315

SC2-18/Index 5/21/03 11:21 AM Page 315

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