section 9.1 9.1 carbon compoundsmrbakerphysical.weebly.com/uploads/3/0/8/0/... · 262 chapter 9 u...

9.1 Carbon Compounds

Reading StrategyPreviewing Copy the table below. Beforeyou read, use the models in Figure 2 todescribe the arrangement of carbon atoms in each form of carbon.

Key ConceptsWhat are three formsof carbon?

What factors determinethe properties of a hydrocarbon?

What are the three types of unsaturatedhydrocarbons?

What are the three main fossil fuels and thetwo primary products of their combustion?

Vocabulary◆ organic compound◆ network solid◆ hydrocarbon◆ saturated

hydrocarbon◆ isomers◆ unsaturated

hydrocarbon◆ aromatic

hydrocarbons◆ fossil fuels

a. ?

b. ?

c. ?

Forms of Carbon Compounds

Diamond

Graphite

Buckminsterfullerene

262 Chapter 9

Until 1828, chemists divided compounds into compounds thatchemists could produce and compounds that only organisms couldproduce. The compounds produced by organisms were called organiccompounds. In 1828, a German chemist, Friedrich Wöhler, mixedsilver cyanate, AgOCN, with ammonium chloride, NH4Cl. He expectedto make ammonium cyanate. Instead, he produced urea, (NH2)2CO,which is a product of reactions that occur in the livers of many organ-isms. Wöhler had synthesized an organic compound.

An organic compound contains carbon and hydrogen, often com-bined with a few other elements such as oxygen and nitrogen. There aremillions of organic compounds—more than 90 percent of all knowncompounds. Remember that carbon has four valence electrons. So acarbon atom can form four single covalent bonds, or a double bondand two single bonds, or a triple bond and a single bond. Most of thebonds in organic compounds are carbon-to-carbon bonds or carbon-to-hydrogen bonds.

Figure 1 A whale’s survivaldepends on carbon compounds.Carbon compounds form thestructures of a whale’s cells andcontrol reactions that take placein those cells. The instructions forthese processes are stored inorganic compounds.

262 Chapter 9

FOCUS

Objectives9.1.1 Relate the structures of

three forms of carbon to their properties.

9.1.2 Explain why there are millionsof different organic compounds.

9.1.3 Relate the number andarrangement of carbon atoms in hydrocarbons to their properties.

9.1.4 Distinguish unsaturated fromsaturated hydrocarbons.

9.1.5 Classify hydrocarbons usingstructural formulas and names.

9.1.6 Describe the formation,composition, and uses of three types of fossil fuels.

9.1.7 Distinguish completecombustion from incompletecombustion of fossil fuels.

9.1.8 Describe the effects of someproducts of the combustion of fossil fuels.

Build VocabularyConcept Map Have students make aconcept map with the word hydrocarbonsas the starting point. The diagram shouldinclude the following terms: saturatedhydrocarbons, unsaturated hydrocarbons,alkanes, alkenes, alkynes, aromatic hydro-carbons, branched chain, straight chain,and rings.

Reading Strategya. Rigid three-dimensional networkb. Widely spaced layers c. Hollowspheres with a surface of carbon atomsarranged in alternating hexagons and pentagons

INSTRUCTBuild Reading LiteracyRelate Cause and Effect Refer topage 260D in this chapter, whichprovides the guidelines for relatingcause and effect.

Have students read p. 262. Ask, Whatcaused scientists to change thedefinition of an organic compound?(Wöhler synthesized urea, an organiccompound produced by many organisms.)Logical

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Reading Focus

1

Section 9.1

Print• Reading and Study Workbook With Math

Support, Section 9.1 and Math Skill: Balancing Equations forOrganic Reactions

• Transparencies, Chapter Pretest andSection 9.1

Technology • Interactive Textbook, Section 9.1• Presentation Pro CD-ROM, Chapter Pretest

and Section 9.1• Go Online, NSTA SciLinks, Fossil fuels

Section Resources

Forms of CarbonThe element carbon exists in several forms with different properties.

Diamond, graphite, and fullerenes are forms of carbon. In eachform, there is a different arrangement of bonded carbon atoms.

Diamond Cutting, grinding, and drilling tools are often coatedwith diamond because no substance is harder than diamond. Diamondis an example of a network solid. In a network solid, all the atoms arelinked by covalent bonds. A network solid is sometimes described as asingle molecule. Figure 2A shows how the carbon atoms are linked indiamond. Covalent bonds connect each carbon atom in diamond tofour other carbon atoms. The three-dimensional structure that resultsis rigid, compact, and strong. Diamond is harder than other substancesbecause cutting a diamond requires breaking many covalent bonds.

Graphite A second form of carbon, graphite, has very differentproperties from diamond. It is extremely soft and slippery. Figure 2Bshows how the carbon atoms in graphite are arranged in widely spacedlayers. Within each layer, each carbon atom forms strong covalentbonds with three other carbon atoms. Between graphite layers thebonds are weak, which allows the layers to slide easily past one another.Because graphite is soft and slippery, it is a good lubricant for movingmetal parts in machinery. Pencil “lead” is a mixture of graphite andclay. The layered structure of graphite explains why you can makepencil marks on paper and why the marks can be erased easily.

Fullerenes In 1985, researchers discovered a third form of carbonin the soot produced when some carbon compounds burn. Fullerenesare large hollow spheres, or cages, of carbon. These cages have sincebeen found in meteorites. Figure 2C shows a model of a cage made from60 carbon atoms. On the surface of the cage, the atoms form alternat-ing hexagons and pentagons, like a soccer ball cover. The C60 moleculeis called buckminsterfullerene after Buckminster Fuller, an architectwho designed domes with similar geometric patterns.

Figure 2 There are several formsof carbon. A In diamond, carbonatoms are arranged in a rigid,three-dimensional network. B Ingraphite, the atoms are arrangedin layers. C In fullerenes, carbonatoms are arranged in hollowspheres. Predicting Are theproperties of fullerenes more likethose of diamond or of graphite?Give a reason for your choice.

Carbon Chemistry 263

Diamond Graphite

A B

Buckminsterfullerene

C

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Forms of CarbonUse VisualsFigure 2 Emphasize that the structuresshown in A, B, and C all contain onlycarbon atoms. Ask, What are thedifferences between the three formsof carbon? (Diamond has a rigid three-dimensional structure, graphite containswidely spaced layers, and fullerenes arehollow cages.) What types of bondshold carbon atoms together in allthree forms of carbon? (Covalent bonds)Visual

When students are asked why amethane molecule has the formula CH4, a typical response is that carbonneeds four bonds. Encourage them toconsider a less anthropomorphic view.Have students recall that carbon hasfour valence electrons and that neon haseight valence electrons. When carbonatoms form four single covalent bonds,as in methane, they achieve the stableelectron configuration of neon. Logical

FYICharcoal, carbon black, and lamp blackare classified as amorphous carbonbecause they do not have a regularcrystalline structure.

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Customize for English Language Learners

List-Group-LabelEncourage students to work independently or in groups to brainstorm words that makethem think of the following forms of carbon:diamond, graphite, and fullerenes. Then, askstudents to review the list of words and groupthem into logical categories (structure: rigid,

hollow, layers; properties: slippery, hard, soft;uses: writing, cutting, jewelry). There must beat least three words in each group. Studentscan include a word in more than one group.They should label the groups to show how the words are related.

Answer to . . .

Figure 2 Students may predict thatfullerenes are likely to have propertiesmore like diamond because of theirthree-dimensional structures. Or, theymay (correctly) predict that fullereneshave properties more like graphitebecause their hollow structures are not rigid.

IPLS

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Students can interact with three-dimensional models of the differentforms of elemental carbon.

0260_hsps09te_Ch09.qxp 4/18/07 1:56 PM 63

264 Chapter 9

Saturated HydrocarbonsGrass contains a compound called cellulose. Most organisms,including the grazing cows in Figure 3, cannot digest cellulose.However, microorganisms in cows’ stomachs break down cellu-lose into smaller molecules that cows can digest. One of theproducts of this process is methane, CH4, which is a hydrocar-bon. A hydrocarbon is an organic compound that contains onlythe elements hydrogen and carbon. Methane is a saturated hydro-carbon. In a saturated hydrocarbon, all of the bonds are singlebonds. A saturated hydrocarbon contains the maximum possiblenumber of hydrogen atoms for each carbon atom. Another namefor a saturated hydrocarbon is an alkane. Names of alkane com-pounds end in –ane, as in methane and propane.

Factors that determine the properties of a hydrocarbon arethe number of carbon atoms and how the atoms are arranged. Ahydrocarbon molecule can contain one carbon atom, as in methane,or more than 30 carbon atoms, as in asphalt. The carbon atoms can bearranged in a straight chain, a branched chain, or a ring.

Straight Chains Figure 4 lists the names, molecular formulas,structural formulas, and boiling points for four straight-chain alka-nes. Recall that a molecular formula shows the type and number ofatoms in a molecule of the compound. A structural formula showshow those atoms are arranged. The number of carbon atoms in astraight-chain alkane affects the state of the alkane at room tempera-ture. Methane and propane are gases. Pentane and octane are liquids.The more carbon atoms, the higher the boiling point is.

What is another name for a saturated hydrocarbon?

Figure 3 Microorganisms in thestomachs of a cow produce morethan 500 liters of methane (CH4)per day.

Name Methane PentanePropane Octane

MolecularFormula

C5H12CH4

H

H

H

C H

H

C CH

H

H

C

H

H H

C

H

H

C H

H

H

–42.1°C–161.5°C 36.0°C

H

H

C CH

H

H

C

H

H H

C

H

H

C

H

H

H

C

H

C

H

H

C

H

H

125.6°C

C CH

H

H

C

H

H

H

H

H

C8H18C3H8

BoilingPoint

StructuralFormula

Some Straight-Chain Alkanes

Figure 4 Molecules of ethane,propane, pentane, and octanehave two, three, five, and eightcarbon atoms, respectively.Making GeneralizationsHow does increasing thenumber of carbon atoms affectthe boiling point of a straight-chain alkane?

264 Chapter 9

SaturatedHydrocarbonsIntegrate Language ArtsTell students that one definition ofsaturated is “filled to capacity.” Sosaturated can mean “the inability tocontain, absorb, receive, or hold.” For example, the ground may besaturated with water after a heavyrainstorm, meaning it can absorb nomore water. Have students use thesemeanings to paraphrase the definition of the vocabulary term saturatedhydrocarbon. (Possible answer: In asaturated hydrocarbon, carbon atoms do not have the capacity to bond toadditional hydrogen atoms.)Verbal

Comparing Models of MoleculesPurpose Students compare ball-and-stick models and structural formulas for methane and propane.

Materials molecular model kit

Procedure Write the structuralformulas and chemical formulas formethane and propane on the board.Remind students that a structuralformula provides more information than a molecular formula because itshows how the atoms are arranged in a molecule. Then, show students ball-and-stick models for methane andpropane. Explain that a ball-and-stickmodel shows the angles between atomsin a molecule and the overall shape of the molecule. (Students may recallmethane’s tetrahedral shape from theQuick Lab in Section 6.3.) The bondangle between carbon and hydrogen is 109.5� in methane and propane.

Expected Outcome Students observethe similarities and differences betweenthe structures of methane and propane molecules.Visual, Logical

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Section 9.1 (continued)

Naming Hydrocarbons Names of straight-and branched-chain hydrocarbons use prefixesto indicate the number of carbon atoms in thelongest continuous chain. Except for meth- (1),eth- (2), and prop- (3), the prefixes used matchthose shown in Figure 20 on p. 175. Forbranched-chain hydrocarbons, the carbon

atoms in the longest continuous chain arenumbered beginning at one end of the chain.Prefixes that combine a numeral and a groupdesignation are used to show the type andlocation of branches. Using this system, theofficial name for isobutane (shown in Figure 5)is 2-methylpropane.

Facts and Figures

Comparing Isomers

Materials30 marshmallows, 70 raisins, 50 toothpicks

Procedure 1. Use marshmallows to represent carbon atoms,

and raisins to represent hydrogen atoms, as inthe model of propane shown. CAUTION Donot eat anything in the laboratory. Break thetoothpicks in half to represent single bonds.Build models of five different isomers ofhexane (C6H14).

2. For each model, attach all six carbon atomsfirst. Then attach hydrogen atoms until eachcarbon atom has four bonds.

Analyze and Conclude1. Using Models Draw a structural formula for

each isomer.

2. Predicting Would pentane (C5H12) orheptane (C7H16) have more isomers thanhexane? Explain your answer.

Figure 5 Butane, isobutane, andcyclobutane represent three waysthat carbon atoms are arranged inan alkane—in a straight chain, ina branched chain, and in a ring. Classifying Explain why butaneand cyclobutane are not isomers.

Branched Chains Look at the butane and isobutane formulas inFigure 5. Both compounds have a molecular formula of C4H10, buttheir structural formulas are different. In isobutane, there is a branchat the point where a carbon atom bonds to three other carbon atoms.

Compounds with the same molecular formula but different struc-tural formulas are isomers. Differences in structure affect someproperties of isomers. Butane boils at –0.5°C, but isobutane boils at–11.7°C. The number of possible isomers increases rapidly each timean additional carbon atom is added to the chain. For example, octane(C8H18) has 18 isomers, while decane (C10H22) has 75.

Rings Figure 5 also shows the structural formula for cyclobutane.The carbon atoms in cyclobutane are linked in a four-carbon ring.Because each carbon atom forms bonds with two other carbon atoms,it can bond with only two hydrogen atoms. So cyclobutane (C4H8)molecules have two fewer hydrogen atoms than butane (C4H10) mol-ecules. Most ring alkanes, or cyclic hydrocarbons, have rings with fiveor six carbons.


H

C4H10

Butane

C CH

H

H

C

H

H H

C

H

H

H

C4H10

Isobutane

C CH

H

H

C

H H

H

H

H C

H

H

C4H8

Cyclobutane

CH

H

C

H

H

HH C

H H

C

Comparing Isomers

ObjectiveAfter completing this activity, studentswill be able to• use structural formulas and models to

describe the isomers of hexane.

Skills Focus Observing, Predicting,Using Models

Prep Time 10 minutes.

Materials 30 marshmallows, 70 raisins, 50 toothpicks

Advance Prep Set out raisins,marshmallows, and toothpicks in acentral location.

Class Time 15–20 minutes

Safety Remind students never to eatanything in the laboratory.

Teaching Tips• Display ball-and-stick models that are

initially oriented with the branches atopposite ends. Rotate one model 180�to show that the structural formulasrepresent the same isomer.

Expected Outcome Students shouldbe able to draw the structural formulasfor the isomers of hexane.

Analyze and Conclude1. There are five straight- and branched-chain isomers of hexane:(1) C C C C C C (hexane)

(2) C C C C C (3) C C C C C

C C(2-methylpentane) (3-methylpentane)

(4) C C C C (5) C

C C C C C C(2, 3-dimethylbutane)

C(2, 2-dimethylbutane)

2. Heptane. The greater the number ofcarbon atoms, the greater the possibilityfor different lengths and locations ofbranches along a central chain. Logical

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Hydrocarbons An isomer with branchesoften has a lower boiling point than itscorresponding straight-chain isomer becauseless efficient packing results in weaker inter-molecular forces. There is a strain on rings withonly three or four carbon atoms because of the bond angles between the carbon atoms.

In general, unsaturated hydrocarbons are morereactive than saturated hydrocarbons becauseatoms or groups of atoms can be added to themolecule at the locations of double and triplebonds. Combustion reactions are the exceptionto this trend.

Facts and Figures

Answer to . . .

Figure 4 The boiling point increases.

Figure 5 Cyclobutane and butane donot have the same formula.

Alkane

0260_hsps09te_Ch09.qxp 4/18/07 1:56 PM Page 265

266 Chapter 9

Unsaturated HydrocarbonsA hydrocarbon that contains one or more double or triple bonds isan unsaturated hydrocarbon. These hydrocarbons are classified bybond type and the arrangement of their carbon atoms. Thereare three types of unsaturated hydrocarbons—alkenes, alkynes, andaromatic hydrocarbons.

Alkenes Many fruit-bearing plants produce ethene (C2H4), whichcontrols the rate at which fruits, such as the tomato in Figure 6A, ripen.There is a double bond between the two carbon atoms in ethene.Hydrocarbons that have one or more carbon-carbon double bonds arealkenes. The names of alkenes end in –ene. Plastics used in trash bagsand milk jugs are produced by reactions involving ethene.

Alkynes In 1895, Henry-Louis Le Châtelier reported thata flame produced when ethyne burned had a temperatureabout 1000°C higher than a flame produced when hydrogenburns. Ethyne (C2H2), also known as acetylene, is an alkyne.Alkynes are straight- or branched-chain hydrocarbons thathave one or more triple bonds. Alkyne names end in –yne.

Alkynes are the most reactive hydrocarbon compounds.The welder in Figure 6B is burning a mixture of oxygen andacetylene in an oxyacetylene torch. The temperature of theflame produced approaches 3500°C. At that temperature,most metals can be melted and welded together. The acety-lene and oxygen are stored under pressure in tanks.

Aromatic Hydrocarbons The Belgian stamp in Figure 6Chonors Friedrich Kekulé (1829–1896), who figured out that benzene(C6H6) is an unsaturated hydrocarbon with a ring structure. Althoughthe formula shows alternating single and double bonds, the six bonds inthe ring are identical. Six of the valence electrons are shared by all sixcarbon atoms. Hydrocarbons that contain similar ring structures areknown as aromatic hydrocarbons. The name was chosen because manyof these compounds have strong aromas or odors.

What is an unsaturated hydrocarbon?

EthyneC CH H

Ethene

C CH

H

H

H

Benzene

C

HC

CC

H

C CH H

H H

A

B

C

Figure 6 There are three types ofunsaturated hydrocarbons. A Ethene is an alkene that controlsthe ripening of a tomato. B Ethyne is an alkyne used intorches that cut metals or weldthem together. C Kekulé figuredout the ring structure of thearomatic hydrocarbon benzene.

266 Chapter 9

UnsaturatedHydrocarbonsIntegrate Social StudiesFriedrich August Kekulé claimed to have developed the model for the ringstructure of benzene after he had adream about a snake chasing its owntail. Have students find out more aboutthis German chemist’s work. Ask, Whatother major contribution did Kekulémake to organic chemistry? (In 1854,he was one of the first to theorize thatcarbon forms four bonds.)Verbal

Integrate HealthThe terms saturated and unsaturated arealso used to describe fats. The term fat iscommonly used to refer to the fats andoils that are obtained from animals andplants. (These fats are esters that formwhen fatty acids react with glycerol, analcohol with three �OH groups.) Thereare three long hydrocarbon chains ineach fat molecule. The chains contain aneven number of carbon atoms (typicallybetween 12 and 24). If the hydrocarbonchains contain only single bonds, thenthe fat is classified as a saturated fat. Ifthere are one or more double or triplebonds in the hydrocarbon chains, thenthe fat is classified as an unsaturated fat.Unsaturated fats, such as corn oil andolive oil, are generally liquids at roomtemperature. Saturated fats, such asbutter and bacon grease, tend to besolids at room temperature. A diet highin saturated fats has been linked to heartdisease. Have students examine foodlabels to determine which types of foodscontain saturated and unsaturated fats.You may also ask students to researchwhether cooking with unsaturated fats,such as olive oil, provides any healthbenefits other than preventing heart disease.Visual

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Figure 7 Fossil fuels form fromthe remains of plants andanimals. A The ferns shown aresimilar to ferns that lived millionsof years ago. B The imprints offerns left on the lump of coal areevidence that the coal formedwhen plant remains werecompressed under layers of rockand soil.

Fossil FuelsSome hydrocarbons were formed from plants and animals that lived inEarth’s oceans and swamps millions of years ago. After those plantsand animals died, they were buried under layers of rock and soil. Hightemperature and pressure deep in Earth’s crust changed those remainsinto deposits of hydrocarbons called fossil fuels. Fossil fuels are mix-tures of hydrocarbons that formed from the remains of plants oranimals. Three types of fossil fuels are coal, natural gas, andpetroleum. The type of fossil fuel produced depends on the origin ofthe organic material and the conditions under which it decays.

Coal The ferns in Figure 7A are similar to those that produced thecoal in Figure 7B. Coal is a solid fossil fuel that began to form about300 million years ago in ancient swamps. Giant tree ferns and otherplants were buried in those swamps. After millions of years of pres-sure, the plant remains produced a mixture of hydrocarbons. Most ofthe hydrocarbons in coal are aromatic hydrocarbons with high molarmasses. These compounds have a high ratio of carbon to hydrogen. Soburning coal produces more soot than burning other fossil fuels does.

Natural Gas The second main fossil fuel, natural gas, formed fromthe remains of marine organisms. The main component of natural gasis methane—the same compound produced by cows as they digest grass.Natural gas also contains ethane, propane, and isomers of butane.Natural gas is distributed through a network of underground pipes. It isused for heating and cooking, and to generate some electricity. Depositsof natural gas are found along with deposits of coal and petroleum.

Petroleum The third main fossil fuel, petroleum, also formed fromthe remains of marine organisms. Petroleum, often known as crude oil,is pumped from deep beneath Earth’s surface. It is a complex liquid mix-ture of hydrocarbons, mainly long-branched alkanes and alkenes. Forpetroleum to be useful, it must be separated into simpler mixtures, orfractions, such as gasoline and heating oil.

A

B

Fossil Fuels

Fractional Distillation

Purpose Students will observefractional distillation of a mixture of organic compounds.

Materials distillation apparatus withstand, 50 mL water, 50 mL ethanol, 60 mL mineral oil, hot plate, 60-mLbeakers (6), concave glass beaker covers (3), shield, dropper pipets (5)

Procedure Explain that fractionaldistillation is a method of separatingmixtures using differences in boilingpoints. Measure 50 mL of water and 50 mL of ethanol in two different beakersand mix them together in the distillationchamber. Heat the mixture, keeping thetemperature at about 85�C, just above theboiling point of ethanol and below theboiling point of water. Three times duringthe process, collect the distilled liquid(distillate) in a separate beaker, and coverthe beaker. After you complete thedistillation, place a drop of pure ethanoland a drop of pure water in a beaker ofmineral oil. Next, place a drop from eachbeaker of distilled liquid into the mineraloil. Have students notice whether thedrops float or how quickly they sink.

Safety Place a blast shield between theequipment and students. Use mitts ortongs to handle hot glass.

Expected Outcome The ethanol willcollect more rapidly in the catch beaker.Pure ethanol floats in mineral oil, andpure water sinks. Students can infer therelative concentrations of ethanol andwater in each distillate sample by thebehavior of the drops in the mineral oil.Visual

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Download a worksheet on fossilfuels for students to complete, andfind additional teacher supportfrom NSTA SciLinks.

Answer to . . .

A hydrocarbon thatcontains one or more

double or triple bonds


268 Chapter 9

Figure 8 The petroleum pumpedfrom underground deposits is acomplex mixture of hydrocarbons.A At a refinery, petroleum isseparated into mixtures calledfractions. B The diagram showssome of the fractions that can becollected from a distillation tower.The labels provide data on thecompounds within a fraction. Forexample, compounds in kerosenehave from 12 to 16 carbon atomsand condense at temperaturesbetween 200°C and 250°C.Interpreting Diagrams Howmany carbon atoms are there inthe compounds in the petroleumgas fraction?

Petroleum gas < 40°C C1 to C4

Crude oil

Crude oil vapors

Heating burner

Distillation Tower

Gasoline 40°–200°C C5 to C12

Kerosene, jet fuel 200°–250°C C12 to C16

Heating oil 250°–300°C C15 to C18

Lubricating oil 300°–370°C ≥ C19

Residue, asphalt ≥ C25

BA

The diagram in Figure 8B shows how petroleum is separated intofractions through a type of distillation called fractional distillation.When petroleum is heated in a distillation tower, most of the hydro-carbons vaporize. The vapors rise through the tower and condense asthe temperature decreases. Compounds with higher boiling points con-dense first. They are collected near the bottom of the tower.

Combustion of Fossil FuelsThe energy released from fossil fuels through combustion is used toheat buildings, cook food, or for transportation. Recall that energyfrom the combustion of propane heats the air in a hot-air balloon.

C3H8 � 5O2h 3CO2 + 4H2O (complete combustion)

The primary products of the complete combustion of fossil fuelsare carbon dioxide and water. Burning fossil fuels increases the amountof carbon dioxide in the atmosphere. This increase may affect tempera-tures, amounts of rain, and sea levels worldwide. Some sulfur andnitrogen are in fossil fuels, and air contains nitrogen. So nitrogen oxidesand sulfur dioxide are produced during the combustion of fossil fuels.

Incomplete Combustion In stoves and furnaces, there maynot be enough oxygen available for complete combustion of all the fuel.So a deadly gas, carbon monoxide, is produced. This colorless, odor-less gas can be inhaled and absorbed by blood. It keeps hemoglobinfrom carrying oxygen to cells. Safety experts recommend that homesheated with natural gas or heating oil have carbon monoxide detectors.

2C3H8 � 7O2h 6CO + 8H2O (incomplete combustion)

When fossil fuels undergo incomplete combustion in factories or powerplants, they also produce tiny particles of carbon. Inhaling these parti-cles can cause heart and lung problems.

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268 Chapter 9

Build Science SkillsProblem Solving Tell students thatthey are given an unknown alkane. Have them use Figure 8 to answer thefollowing question. Ask, How could you determine if the alkane is one ofthe components of gasoline? (If itsboiling point is between 40�C and 100�C,then the alkane may be a component of gasoline.)Visual, Logical

FYIIn industry documents that describefractional distillation, there is variation in the names of the fractions collected,the length of the carbon chains in a fraction, and the temperature range at which a fraction is collected. There is agreement on how the processseparates the numerous substances in petroleum into fractions.

Combustion of Fossil FuelsBuild Math SkillsBalancing Equations Remindstudents that only the coefficients infront of the formulas, and not thesubscripts in the formulas, may bechanged when they balance anequation. Have students practicebalancing the equation for the complete combustion of ethane:

C2H6 + O2 h CO2 + H2O

(2C2H6 + 7O2 h 4CO2 + 6H2O)

Then, have students determine thebalanced equation for incompletecombustion of ethane.

(2C2H6 + 5O2 h 4CO + 6H2O)Logical

Direct students to the Math Skills in the Skills and Reference Handbookat the end of the student text foradditional help.

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Octane Number Octane ratings are used to compare blends of gasoline. Twosubstances found in gasoline are used asreference fuels: n-heptane and isooctane(2,2,4-trimethylpentane). Because n-heptaneself-ignites when compressed, it burns toorapidly, causing a knocking sound in a poorlyperforming engine. Isooctane will not self-

ignite if it is compressed before sparking. The octane rating describes a blend as thoughit contained only n-heptane and isooctane.With an octane rating of 89, gasoline performsas if it contained 89% isooctane and 11% n-heptane. With a higher octane rating, thepossibility of knocking is lower.

Facts and Figures

Find links to additional activitiesand have students monitorphenomena that affect Earth and its residents.

Section 9.1 Assessment

Reviewing Concepts1. Name three forms of carbon.

2. What two factors can affect the propertiesof a hydrocarbon?

3. Name the three categories of unsaturatedhydrocarbons.

4. Name the three main fossil fuels.

5. What are the two primary products of thecomplete combustion of fossil fuels?

6. What are three ways that carbon atoms can bearranged in hydrocarbon molecules?

Critical Thinking7. Classifying Why isn’t carbon dioxide

considered an organic compound?

8. Applying Concepts Draw structuralformulas for the two branched-chain isomersof pentane, C5H12.

Saturation Compare the way saturatedand unsaturated are used in describinghydrocarbons to how they were used indescribing solutions in Section 8.2.


Figure 9 This statue of GeorgeWashington was sculpted frommarble in 1918. The photographwas taken in the 1990s. Thedamage was done by calciumcarbonate in the marble reactingwith sulfuric acid in acid rain.

Acid Rain The combustion of fossil fuels causes the acidity of rainto increase. Rain is always slightly acidic, with a pH of about 5.6,because carbon dioxide dissolves in water droplets and forms carbonicacid, H2CO3. Sulfur dioxide and nitrogen oxides released into theatmosphere also dissolve in water, forming sulfuric acid, H2SO4, andnitric acid, HNO3. The pH of rain containing sulfuric acid and nitricacid can be as low as 2.7. These acids damage stone structures like thestatue in Figure 9. They also damage metal and concrete.

For: Activity on acid rain

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Build Math SkillsInterpreting Equations Write theequations for the complete andincomplete combustion of propane onthe board. Ask, Why are there 5 molesof oxygen in the equation for thecomplete combustion, but 7 moles of oxygen in the equation for theincomplete combustion? Let studentsfigure out that the number of moles ofmethane is not the same in the twoequations. Then, multiply the coefficientsin the first equation by 2 to show that theamount of oxygen used is greater. Logical

Direct students to the Math Skills in the Skills and Reference Handbookat the end of the student text foradditional help.

ASSESS Evaluate UnderstandingHave students make flashcards for thekey concepts and vocabulary in thissection. For example, for each type of unsaturated hydrocarbon, they canmake a card that has an example and a definition. Students can use theflashcards to quiz one another.

ReteachUse the structural formulas in the texton pp. 265 and 266 to review each typeof hydrocarbon.

In a saturated solution, the solventcontains the maximum amount of soluteat a given temperature. A saturatedhydrocarbon contains the maximumnumber of hydrogen atoms for eachcarbon atom. More solute can be addedto an unsaturated solution. Morehydrogen atoms can be added to anunsaturated hydrocarbon.

If your class subscribesto the Interactive Textbook, use it toreview key concepts in Section 9.1.

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5. Carbon dioxide and water6. As a straight chain, a branched chain, or a ring7. Carbon dioxide does not contain anyhydrogen atoms.8. C C C C C

C C C C(2-methylbutane)

C(2, 2-dimethylpropane)


1. Diamond, graphite, and fullerenes are formsof carbon.2. Factors that determine the properties of a hydrocarbon are the number of carbonatoms and how the atoms are arranged.3. The three types of unsaturated hydro-carbons are alkenes, alkynes, and aromatichydrocarbons.4. Three types of fossil fuels are coal, naturalgas, and petroleum.

Answer to . . .

Figure 8 Molecules of compounds in petroleum gas contain one to fourcarbon atoms.

PPLS


Breathing EasyCoal-burning power stations produce more than halfthe electricity used in the United States. An averagecoal-burning power station emits about 10,000 tonsof sulfur dioxide and the same amount of nitrogenoxides each year.

Air in

FURNACE 2

Morelimestoneadded

Hot airjets

Unburnedfuel fromfurnace 1

FURNACE 1Cyclone separator

Hot gases out

Air in

Coal

Cycloneseparator

■1 Washing coalThe coal is crushedand washed toremove sulfur fromits surface. When thecoal is placed in awater-filled tank, thecoal floats to thesurface while thesulfur impurities sinkto the bottom.

■2 Furnace 1 A mixture of coal andlimestone floats on a stream of hot airin the furnace. Calcium carbonate in thelimestone reacts with sulfur dioxide toform calcium sulfate. The amount of airis limited and the temperature is heldlow to keep nitrogen from reactingwith oxygen.

■4 Furnace 2 Unburned coal fromthe first furnace is transferred intofurnace 2 for further burning. Morelimestone is added to react with anysulfur dioxide produced.

■3 Cycloneseparator Thecyclone separatesthe unburned fuelfrom the hot gases.

Coal andlimestone

270 Chapter 9

Oxides of sulfer and nitrogen cause smog and acid rain. Theyalso can irritate your lungs. The United States has a Clean CoalTechnology Program that encourages the development oftechnologies for reducing emissions of these harmful gases. Thediagram shows steps in the process for reducing these emissions.The process begins when sulfur is washed from the surface ofcoal and ends when cleaner air is released into the atmosphere.

270 Chapter 9

Breathing EasyBackgroundThe Department of Energy began The Clean Coal Technology Program inresponse to concerns about acid rain. Thediagram illustrates some of the methodsused to reduce emissions of nitrogenoxides and sulfur dioxide. (1) Sulfur that is not bonded to carbon is removed whencoal is crushed and washed. (2) Jets of air keep limestone and crushed coalsuspended so that the limestone can react with the sulfur dioxide. Because the temperature in the furnace is low andthe amount of air is limited, most of theoxygen reacts with fuel, not nitrogen. (7) Smokestacks may contain electrostaticprecipitators and scrubbers. As particles of ash pass through the precipitator, theygain a charge. They can be collected on a plate with an opposite charge. In onetype of scrubber, limewater is sprayed intothe stream of waste gases. The calciumhydroxide reacts with sulfur dioxide andforms solid calcium sulfate.

Build Science SkillsObserving

Purpose In this activity, students will use physical properties to separate a mixture of coal and sulfur.

Materials 100-mL beaker containing a 1:1 mixture of sulfur powder and coal dust, 100-mL graduated cylinder,stirring rod, distilled water, plastic pipet,100-mL beaker


Procedure Provide each group with a beaker containing 10 g of the sulfur-coal mixture. Have them add 30 mL ofwater to the beaker and mix using astirring rod. Allow layers to form in themixture. Next have students use a pipetto transfer the layer of water containingcoal dust to a second beaker. Stir themixture and allow layers to form again.Have students compare their activity to the process described in Step 1 of the diagram.

Safety Students should wear safetygoggles and aprons.

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Catalytic Converters The combustion ofpetroleum products in internal combustionengines produces emissions that contribute to air pollution. In a vehicle’s exhaust system,there is a catalytic converter. This devicecontains a mixture of catalysts for the oxi-dation of carbon monoxide and unburned

hydrocarbons to carbon dioxide and waterand the reduction of nitrogen oxides tonitrogen. The catalysts may be transitionmetals, such as platinum palladium, andrhodium; or oxides of transition metals, such as CuO and Cr2O3.

Facts and Figures

� Research the process of coal gasification. Writea paragraph describing one of the methodsused to convert coal into flammable gases.What gases are produced?What are the benefits ofcoal gasification? Are thereany problems withthe technology?

� Take a Discovery Channel VideoField Trip by watching“Clean Energy.”

Going Further

Gas turbine

Electricgenerator

Steamturbine

Condenser

Particlefilters

Heatexchanger

Chimney

Steamout

Boiler

Water in

■6 Particle filterHot gases from the furnacesare fed through filtersmade of tightly wovenfabric. The filters trap tinyparticles of coal and ashand prevent them fromentering the gas turbine.

■7 Heat exchanger Wastegases are cooled in theheat exchanger by a coilcontaining cold water. Thecooled and cleaned gases,containing dramaticallyreduced amounts of sulfurdioxide and nitrogenoxides, are emitted fromthe chimney.

■5 Boiler Water from thecondenser flows through pipesin the boiler. Hot gases fromfurnace 2 are fed into theboiler to heat the water. Thesteam created is used to spin asteam turbine. The exhaustgases are recycled back tofurnace 2. Video Field Trip


Expected Outcome Most of the sulfurwill settle to the bottom of the first beakerwhile the coal dust floats. Any remainingsulfur will settle to the bottom of thesecond beaker. This activity demonstrateswhat happens when coal is crushed andwashed prior to burning.Visual, Kinesthetic

Going FurtherThe United States Department of Energy has funded research into coalgasification. They are encouraging thedevelopment of methods for convertingsolid coal into gases that can be used to generate power. During gasification,coal reacts with steam and oxygen at a high temperature and pressure. Themethods produce a mixture of gases.Hydrogen and carbon monoxide aretypical products. The hydrogen can be separated from the raw mixture and used directly as fuel or it can becombined with carbon monoxide toproduce methane. Any carbon dioxideproduced is captured for commercialapplications or sequestered to prevent its release into the atmosphere.

If students search the Internet, theywill find descriptions of multiple methodsfor coal gasification, and information on the advantages and drawbacks of the methods. The main advantages ofcoal gasification are a reduction in airpollution and an increase in efficiency(more energy produced from the sameamount of coal). For now, drawbacksinclude the cost of equipment and ahigher cost per kilowatt for powergeneration. Other drawbacks are theamount of water required and theamount of wastewater produced. Verbal, Portfolio

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After students have viewed the Video Field Trip, askthem the following questions: What substancesdoes a fuel cell use to produce energy? Whatform of energy is produced? (The fuel cell usesoxygen [from air] and hydrogen. The fuel cellproduces electrical energy.) What technologicaladvance made fuel cells more efficient? (Thedevelopment of a new kind of membrane to separatethe oxygen and hydrogen) Give one advantage

that a fuel cell has over an internal combustionengine. (Student answers may include having nomoving parts, producing only water as a product, and being quieter.) What advantage does a vehi-cle that uses a fuel cell have over a vehicle thatuses batteries? (As long as fuel is provided, the fuelcell will continue to work.) If fuel cells are moreefficient (that is, if they have a higher ratio ofoutput energy to input energy) than internalcombustion engines, why do most cars still have internal combustion engines? (Because ofthe large investment already made in internal engine technology)

Video Field Trip

Clean Energy


9.2 Substituted Hydrocarbons

Key ConceptsWhat functional groups arefound in alcohols, organicacids, and organic bases?

How are esters formed?

Vocabulary◆ substituted hydrocarbon◆ functional group

Reading StrategyMonitoring YourUnderstanding Copy thetable. As you read, completethe table by connecting eachfunctional group with thetype of compound that con-tains the functional group.

b. ?

a. ?

c. ?

Functional Group Type of Compound

OH

COOH

NH2

–

–

–

Figure 10 Hydrocarbons inwhich some hydrogen atomshave been replaced can becompared to an electric drillwith attachments. Inferring What determines thefunction of the drill, the drillitself or the attachments?

The electric drill in Figure 10 can be used to drill holes, tighten a screw,or sand a rough surface. To change the function of the drill, you replace,or substitute, an attachment. A carbon atom in an organic compoundcan have four attachments. In a methane molecule (CH4), the carbonatom has four identical attachments—its hydrogen atoms. Whenmethane reacts with chlorine, chlorine atoms replace hydrogen atoms.

CH4 � Cl2h CH3Cl � HCl

Chloromethane and hydrogen chloride are products of the reactionbetween methane and chlorine. So are compounds with two, three, orfour chlorine atoms. Organic compounds containing chlorine or otherhalogens are halocarbons. Almost all the halocarbons found on Earthwere released from refrigerators, air conditioners, or aerosol sprays.Researchers have established that halocarbons containing chlorine andfluorine deplete Earth’s protective ozone layer. The manufacture ofchlorofluorocarbons has been restricted since 1990.

A hydrocarbon in which one or more hydrogen atoms have beenreplaced by an atom or group of atoms is a substituted hydrocarbon.The substituted atom or group of atoms is called a functional groupbecause it determines the properties of the compound. Alcohols, organicacids, organic bases, and esters are substituted hydrocarbons.

hole saw bit

twist drill bit

Forstner drill bit

Phillips screwdriver bit

drum sander

272 Chapter 9

272 Chapter 9

FOCUS

Objectives9.2.1 Classify substituted

hydrocarbons based on their functional groups.

9.2.2 Describe some properties and reactions of five types ofsubstituted hydrocarbons.

Build VocabularyWord Forms Before students read this section, have them look up thewords substitute and functional. Then,have students write a prediction for the meanings of the terms substitutedhydrocarbon and functional group. Afterstudents study the section, have themlook at their predictions and discuss anydifferences between their predictionsand the definitions in the text.

Reading Strategya. alcohol b. organic acidc. organic base

INSTRUCT

Modeling Functional Groups

Purpose Students make an analogybetween an appliance’s attachmentsand functional groups.

Materials any appliance that hasattachments with different functions

Procedure Demonstrate how theappliance works. Show students howeach attachment performs a differentfunction. Use these differences to explainhow functional groups determine theproperties of substituted hydrocarbons.

Safety Handle the appliance and its attachments according to themanufacturer’s safety recommendations.

Expected Outcome Students will be able to compare the attachments of an appliance to functional groups in substituted hydrocarbons.Visual, Logical

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Reading Focus

1

Section 9.2

Print• Reading and Study Workbook With

Math Support, Section 9.2• Math Skills and Problem Solving

Workbook, Section 9.2•Transparencies, Section 9.2

Technology • Interactive Textbook, Section 9.2• Presentation Pro CD-ROM, Section 9.2

Section Resources


Exploring Boiling Pointsof Chlorocarbons

Use the data given to construct a graph withNumber of Chlorine Atoms, from 0 to 4, on thehorizontal axis and Boiling Point on the verticalaxis. Draw a smooth curve connecting the points.

1. Using Graphs Predict the boiling point ofdichloromethane.

2. Relating Cause and Effect What effectdoes increasing the number of chlorine atomshave on the boiling point?

Name Formula Boiling Point (°C)

Methane

Chloromethane

Dichloromethane

Trichloromethane

Tetrachloromethane

CH4

CH3Cl

CH2Cl2

CHCl3

CCl4

61

77

Boiling Points of Methaneand Its Substituted Chlorocarbons

?

�161

�24

AlcoholsMethanol, CH3OH, is used as a fuel in some motorcycles. Ethanol,CH3CH2OH, is often mixed with gasoline to help the gasoline burnmore completely. Methanol and ethanol are alcohols. The name of analcohol ends in –ol. The functional group in an alcohol is ahydroxyl group, –OH. When a halocarbon reacts with a base, theproducts are an alcohol and salt.

CH3Cl � NaOH h CH3OH � NaCl

An alcohol can also be made by reacting an alkene with water.

Organic Acids and BasesThe sharp, sour taste of a lemon comes from citric acid, an organic acid.

The functional group in organic acids is a carboxyl group,–COOH. Names of organic acids end in -oic. Organic acids tend tohave sharp tastes and strong odors. The simplest organic acid ismethanoic acid, which is also known as formic acid. Vinegar is a solu-tion of water and the organic acid ethanoic acid, which is usuallyreferred to as acetic acid. If the ants in Figure 11 sprayed the formicacid they produce on your skin, your skin would itch or burn.

Figure 11 Birds sometimes willsit on an ants’ nest and allow theants to crawl over them. Themethanoic acid sprayed by theants is a natural pesticide thatkills mites in the birds’ feathers.

3. Formulating Hypotheses Why is the boilingpoint of CH3Br higher than the boiling point ofCH3Cl? (Hint: Compare the atomic masses forbromine and chlorine.)

Ethene

C CH

H

H

H

Water

H H+OH

Ethanol

H C

H

H H

OH

C Hh

H C O

O

H

Methanoic acid Ethanoic acid

H C

H

H

O

C OH

Exploring Boiling Points of Chlorocarbons1. Acceptable answers include tempera-tures between �24�C and 61�C. (Theboiling point of dichloromethane is 40�C.)2. As the number of chlorine atomsincreases, the boiling point increases.3. Bromine is more massive than chlorine.

For Extra HelpDemonstrate how to use a curve on a graph to estimate the value of anunknown data point. Find the appropriatevalue on the horizontal axis. Use a ruler to intersect the curve above that value.Turn the ruler 90° and read the verticalvalue for the intersection point. Visual

Alcohols Build Science SkillsApplying Concepts Ask students topredict the products for the completecombustion of methanol and ethanol.Then, have them write balancedequations for these reactions.

2CH3OH + 3O2 h 2CO2 + 4H2OC2H5OH + 3O2 h 2CO2 + 3H2O

Logical

FYIThere are multiple methods for theformation of alcohols, includingfermentation and reduction ofaldehydes and ketones.

Organic Acids and Bases Build Reading LiteracyCompare and Contrast Refer to page 226D in Chapter 8, which providesguidelines for comparing and contrasting.

Have students read the text on pp. 273–274 related to organic acidsand bases. Ask, How do organic acidsand bases differ? (Organic acids have acarboxyl group, while organic bases havean amino group.) How are organic acidsand bases similar? (They are substitutedhydrocarbons with strong odors.) Verbal

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Customize for Inclusion Students

Learning DisabledMake concept maps for each section and coverthem with clear contact paper. Then, cut themaps into puzzle pieces. Provide students with the pieces and have them put the puzzletogether. After students complete the puzzle,have them make flashcards with conceptconnections and added notes. For example,

students may have cards with the names of compounds on one side and structuralformulas on the other. They may also have keyconcept cards with an important word missing:

form when organic acidsreact with alcohols. The answer on the back of the card would be Esters.

Answer to . . .

Figure 10 The attachments deter-mine the specific function of the drill.



Do you know the smell of rotten fish? Then you’ve encountered atype of substituted hydrocarbon called an amine. Amines are organicbases. The functional group in an amine is an amino group, –NH2.Amines are found in paints, dyes, and disinfectants. In Section 9.3 youwill study the role organic bases play in the formation of organic com-pounds that are essential for life.

EstersOne group of substituted hydrocarbons accounts for the flavors ofmany foods and the pleasant odor of many flowers. These compoundsare known as esters. Esters form when organic acids react withalcohols. The second product of the reaction is water. For example,ethanoic acid can react with methanol to produce methyl ethanoate(methyl acetate). The reaction is reversible.

Esters are used in many processed foods to produce flavors such asstrawberry, banana, and grape. Flowers like the roses in Figure 12 pro-duce esters and other compounds with distinctive odors that attractinsects for pollination. Sometimes, the compounds produced by the plantmimic compounds produced by the insect.

H C

H

H

H

H

O

C O C H

Methyl ethanoate Water

H C

H

H

O

C OH

Ethanoic acid Methanol

C

H

H

HHO HOHH++ +

Reviewing Concepts1. What functional groups are found in

alcohols, organic acids, and organic bases?

2. Which types of compounds can react toproduce esters?

3. What is a substituted hydrocarbon?

4. When a halocarbon reacts with a base, whatproducts are produced?

5. What are two properties of organic acids?

Critical Thinking6. Classifying An unknown compound has no

noticeable odor. Explain why the compound isunlikely to be an organic acid, an organicbase, or an ester.

7. Inferring What kind of organic compoundgives a vitamin-C tablet its sour taste?

8. Applying Concepts Name one kind ofsubstituted hydrocarbon you would expect to find in artificially flavored grape jelly.

Figure 12 Many compounds inrose petals contribute to thefragrance of a rose. Some ofthese compounds are esters,which tend to have pleasant,sweet odors.

Types of Reactions Alcohols can be madeby reacting halocarbons with bases, oralkenes with water. Review the general typesof reactions presented in Section 7.2. Whichtypes best describe the two methods forproducing an alcohol? Explain your choices.

274 Chapter 9

274 Chapter 9

Esters

Students may not know that an objecthas an odor because molecules fromsubstances in the object interact withchemoreceptors in the nose. Studyingesters is a good way to challenge thismisconception. Have students smellsome fragrant objects, such as apples,bananas, or flowers. Explain that someof the compounds responsible for theodors are esters. Logical, Kinesthetic

Use Community ResourcesHave a pharmacist speak to the classabout how functional groups determinethe effect of a medicine. Have studentsask how to find information on thechemical composition of active ingredients in prescription and over-the-counter drugs. Interpersonal

ASSESSEvaluate UnderstandingHave students design and play amatching game that uses cards thatidentify the formulas and characteristicsof each functional group described inthe section.

ReteachUse short phrases to summarize thecharacteristics of functional groups. For example, say that amines smell likerotten fish and esters have pleasantsmells, like some flowers. Review othercharacteristics, such as chemicalstructure, for each functional group.

Replacing a halogen with a hydroxylgroup is a double-replacement reactionbecause the hydroxyl group and thehalogen exchange places. The reactionof alkenes with water to produce analcohol is a synthesis reaction becausetwo reactants join to form one product.

If your class subscribes to the Interactive Textbook, use it toreview key concepts in Section 9.2.

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4. An alcohol and a salt5. Organic acids contain carboxyl groups andhave a sharp, sour taste and a strong smell.6. Organic acids, organic bases, and esterstend to have noticeable smells.7. An organic acid8. An ester


1. Alcohols have hydroxyl groups, organicacids have carboxyl groups, and organic bases have amino groups.2. Esters form when organic acids react with alcohols.3. A hydrocarbon in which a functional grouphas been substituted for a hydrogen atom


9.3 Polymers

Reading StrategyIdentifying Main Ideas Before you read,copy the concept map. As you read, com-plete the map to summarize two main ideasabout polymers.

Key ConceptsWhat is one way thatpolymers can be classified?

What are three examplesof synthetic polymers?

What are four types ofpolymers that organismscan produce?

Vocabulary◆ polymer◆ monomers◆ carbohydrates◆ nucleic acids◆ amino acid◆ protein

Freight trains, like those in Figure 13, use different types of cars totransport goods. A flatcar with no sides or roof is used to haul steelbeams. Grain is carried in covered hoppers, which have a hatch at thetop and a chute at the bottom. Liquids travel in tank cars. The carson a train may be all the same type or a mixture of different types. Onaverage, about 100 cars are linked together behind the locomotive ona freight train.

Like freight trains, some molecules are built up from smaller unitslinked together. A polymer is a large molecule that forms when manysmaller molecules are linked together by covalent bonds. The smallermolecules that join together to form a poly-mer are monomers. Poly- means “many.”Mono- means “one.” In some polymers, thereis only one type of monomer. Other polymershave two or more kinds of monomers.

Polymers can be classified as naturalpolymers or synthetic polymers. Manyimportant types of biological molecules arenatural polymers. Organisms produce thesepolymers in their cells. Synthetic polymers aredeveloped by chemists in research laboratoriesand manufactured in factories. Both types ofpolymers have industrial uses. For example,silk and cotton fabrics are woven from naturalpolymer fibers, while polar fleece is made froma synthetic polymer.

a. ? polymers

b. ?

c. ?form

which can be


Figure 13 Couplers that interlocklike the fingers of your handsconnect one railroad car toanother. Many cars can be joinedtogether to form a train, becausethere is a coupler on both ends of a car. Using Analogies How isa polymer like a train?

FOCUS

Objectives9.3.1 Distinguish a monomer

from a polymer.9.3.2 Compare three examples

of synthetic polymers.9.3.3 Describe the structures and

functions of four types ofnatural polymers.

Build VocabularyWord-Part Analysis Have studentsbreak the vocabulary terms polymer,monomer, and carbohydrate into roots,prefixes, or suffixes. Students may needto use a dictionary to find the meaningsof some parts. (Monomer has the prefixmono- meaning “one.” Monomers arethe single units that make up polymers.Polymer has the prefix poly- meaning“many.” Polymers contain manymonomers. Carbohydrate has the prefixcarbo- which means it contains carbon,and the suffix -hydrate which means italso contains the components of water—hydrogen and oxygen.)

Reading Strategya. monomersb. and c. natural/synthetic

INSTRUCTBuild Reading LiteracyUse Prior Knowledge Refer to page 2D in Chapter 1, which providesguidelines for using prior knowledge.

Before students read, ask them to listdifferent fibers used to make fabrics,such as wool and polyester. Have themdiscuss which fibers they think arenatural and identify their sources.Verbal, Intrapersonal

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Reading Focus

1


Print• Laboratory Manual, Investigations 9A

and 9B• Reading and Study Workbook With

Math Support, Section 9.3• Transparencies, Section 9.3

Technology • Interactive Textbook, Section 9.3• Presentation Pro CD-ROM, Section 9.3• Go Online, NSTA SciLinks, Polymers

Section Resources

Section 9.3

Answer to . . .

Figure 13 Like a train, a polymer ismade up of single units that are joinedtogether.

PPLS

9.3 Polymers









a. ? polymers

b. ?

c. ?form

which can be



9.3 Polymers









a. ? polymers

b. ?

c. ?form

which can be




276 Chapter 9

Synthetic PolymersThe properties of a polymer depend on the type and number of mono-mers in the polymer. Rubber, nylon, and polyethylene are threeexamples of compounds that can be synthesized.

Rubber The sap collected from rubber trees in tropical regions con-tains rubber. So why would a chemist make synthetic rubber? Thesupply of natural rubber is limited. During World War II, the alliescould not obtain natural rubber. Chemists worked hard to produce asynthetic rubber, using hydrocarbons from petroleum. Natural rubberand synthetic rubbers contain different monomers and have differentproperties. The tires in Figure 14A will resist wear and be less likely toleak if they are made of synthetic rubber. Rubber is used as an adhe-sive. The How It Works box on page 277 explains how adhesives work.

Nylon In the 1930s, Wallace Carothers was trying to produce a syn-thetic polymer to replace silk. The polymer he produced was nylon,which has properties not found in natural polymers. Nylon fibers arevery strong, durable, and shiny. Nylon is used in parachutes, wind-breakers, fishing line, carpets, and ropes like the one in Figure 14B.

Polyethylene Plastic milk bottles, plastic wrap, and the plasticshapes in Figure 14C are made of polyethylene. This polymer formswhen ethene (or ethylene) molecules link head to tail. The number ofcarbon atoms in a polyethylene chain affects the properties of the poly-mer. The more carbon atoms in the chain, the harder the polymer is.

What determines the hardness of polyethylene?

For: Links on polymers

Visit: www.SciLinks.org

Web Code: ccn-1093

C C

H

H

H

H

C C

H

H

H

H

C C

H

H

H

H

+ + hn

n

C C

H

H

C

H

H

H

H

C C

H

H

C

H

H

H

H

Figure 14 Synthetic polymers areused to make tires, ropes, andplastic objects. A About half therubber produced in the worldis used to manufacture tires. B Nylon is a good choice for arope because its fibers are strongand do not wear out easily. C The hard plastic shapes aremade from a high-densitypolyethylene polymer.Inferring At room temperature,polymers are most likely to existas which state of matter?

A B C

276 Chapter 9

Synthetic PolymersUse VisualsFigure 14 Have students look at theobjects in Figure 14. Ask, What are somephysical properties of rubber, nylon,and polyethylene? (Possible answer:Rubber resists wear. Nylon is durable andstrong. High-density polyethylene is hard.)What are some ways that each of thepolymers is used? (Possible answer:Rubber is used for tires and as an adhesive.Nylon is used for parachutes, windbreakers,fishing line, carpets, and rope. Polyethyleneis used for milk bottles and plastic wrap.)Visual, Logical

Integrate Social StudiesNatural rubber collected from trees is softand sticky. In 1839, Charles Goodyearfound that when sulfur is added to rubberand the mixture is heated, the rubber isno longer sticky. Have students researchother topics related to polymers. Possibletopics include the discovery of nylon, the discovery of artificial silk (later calledrayon) by Hilaire de Chardonnet, or theuse of polymers in the film industry.Students may also want to researchcurrent efforts to recycle plastics,including the codes used on plasticproducts. Have students use posters orcomputer graphics to prepare a report on their research. Verbal, Portfolio

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Download a worksheet onpolymers for students to complete,and find additional teacher supportfrom NSTA SciLinks.

Customize for English Language Learners

Think-Pair-ShareHave students work in pairs to think of moreanalogies for polymers. Examples include

beads in a necklace and links in a chain.Strengthen discussion skills by having studentsshare their examples with the class.

Answer to . . .

Figure 14 Polymers are most likely to be solids at room temperature.

The hardness of poly-ethylene is determined

by the number of carbon atoms in thechain. The more carbon atoms thereare, the harder the polymer is.

Synthetic AdhesivesAdhesion is the force of attraction between molecules ofdifferent substances whose surfaces are in contact. Theseforces are rarely strong enough to bind two surfacestogether. An adhesive placed between the surfaces bindsthem together. Most adhesives are synthetic polymers.The diagram illustrates how some adhesives work. Theadhesive remains liquid until the surfaces are in position.Then the adhesive sets. Interpreting Diagrams Explainthe purpose of a stabilizer in an adhesive.

Liquid adhesiveIn a typical adhesive,

monomer molecules anda stabilizer are in asolvent. The stabilizerstops the monomersfrom forming asolid polymer.

Types of adhesion Adhesion can work in three ways.Molecules of the polymer may fill crevices in the surfaces being connected.The molecules may also be attracted toone another by intermolecular forces, orthey may react by forming covalent bonds.

Monomersjoin together.

The adhesive setsContact with water in the

air and on the surfaces beingjoined makes the stabilizerinactive. The monomers thenbegin to join together to forma polymer. As the chain lengthens,the adhesive changes from aliquid to a solid.

Stabilizer

Solvent

Permanent adhesionAn epoxy resin was used toattach the automobile to thebillboard. Epoxy resins areoften stored in two parts thatare mixed just before theepoxy is used. Strong bindingforces in these adhesives makethem heat- and water-resistant.

Applying the adhesive Some of

the liquid is squeezed onto one of the surfaces to be joined.

Tube

Monomermolecule


Temporary adhesionThe sticky strip on a reusablenote is an adhesive containingtiny spheres. The spheres limitthe amount of surface areathat makes contact, so the notesticks lightly and repositionseasily.

Synthetic AdhesivesThe invention of reusable notes began in 1968 when Dr. Spencer Silver wasattempting to make a strong adhesive.One of the adhesives he produced was just strong enough to hold paperstogether, but it was weak enough thatthe papers could be separated withoutdamage. Silver tried to develop a use for the weak adhesive, but it was hiscolleague, Art Fry, who realized theadhesive’s potential. While singing in a choir, Fry was bothered by bookmarksslipping out of pages. By applying some of the weak adhesive to paper, Fry developed a reusable bookmark that could stick to pages withoutharming them. The adhesive is nowused to produce the familiar, multi-colored reusable notes.

Interpreting Diagrams Stabilizers areused to prevent the adhesive monomersfrom forming a solid polymer.Logical

For EnrichmentHave students work in pairs and devisean experiment to compare two types of commercially-available adhesives.Remind them to start by forming ahypothesis and writing a plan for theirexperiment. Suggest that they develop a number scale for reporting how well each adhesive binds two surfacestogether. Materials may include paper,metal foil, or wooden craft sticks. Kinesthetic, Logical

FYIAlthough the terms are used inter-changeably, glue refers to naturalproducts and adhesives refers to synthetics.

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Natural PolymersAlmost all of the large molecules produced by organisms are polymers.

Four types of polymers produced in plant and animal cells arestarches, cellulose, nucleic acids, and proteins.

Starches Many animals are attracted to sweet-tasting foods. Thecompounds responsible for this sweetness are often sugars. Simplesugars have the formula C6H12O6. They can exist as straight chains orrings. The simple sugars glucose and fructose can react to form sucrose(table sugar). Glucose monomers join to form starches as shown below.

Typically, a starch contains hundreds of glucose monomers. Plantsstore starches for food and to build stems, seeds, and roots. Flour forthe bread, pasta, and tortillas shown in Figure 15 is made by grindingthe seeds of grains, such as wheat and corn. Simple sugars, slightlymore complex sugars such as sucrose, and polymers built from sugarmonomers are all classified as carbohydrates.

Cellulose The carbohydrate cellulose is the main component ofcotton and wood. It is the most abundant of all organic compoundsfound in nature. Cellulose molecules contain 3000 or more glucosemonomers. Cellulose gives strength to plant stems and tree trunks.Most animals cannot digest cellulose.

Distinguishing Sugars From Starches

Materials1 slice each of potato, ripe apple, and bread; 15 mL cornstarch; 15 mL table sugar; iodine in dropper bottle; 6 small paper plates

Procedure 1. Place one sample of each food on a paper

plate. CAUTION Never eat anything in a lab.

2. Place 2 to 3 drops of iodine solution on thecornstarch. Record your observations.

3. Repeat Step 2 using sugar instead of cornstarch.

4. Place 2 to 3 drops of iodine on each of theother food samples. Record your observations.

Analyze and Conclude1. Classifying How can an iodine solution be

used to distinguish a sugar from a starch?

2. Drawing Conclusions Which of the foodsamples contained starch?

3. Predicting What other foods would turndark when tested with iodine solution?

278 Chapter 9

Figure 15 All the foods showncontain starch, which is a polymerof the simple sugar glucose.Observing Identify foods that you recognize in the photograph.

Glucose A type of starch found in plants

CH2OH

OH

OH

O

O O

CH2OH

OH

OH

O

O

CH2OH

OH

OH

O

O

CH2OH

OH

OH

O

HO OH

278 Chapter 9

Natural Polymers

Distinguishing Sugars From Starches

ObjectiveAfter completing this activity, studentswill be able to• use iodine to test for the presence

of starch in foods.

Skills Focus Observing, FormulatingHypotheses, Inferring

Prep Time 15 minutes

Materials 1 slice each of potato, ripe apple, bread; 15 mL cornstarch; 15 mL table sugar; iodine in a dropperbottle; 6 small paper plates

Advance Prep Cut apples, potatoes,and bread into small cubes (about 1 cm3). Place iodine solution in labeleddropper bottles.


Safety Students should wear safetygoggles and aprons. Remind studentsnot to eat anything in the lab. Ifstudents slice their own apples andpotatoes, remind them to be carefulwhen handling sharp objects.

Teaching Tips • Do not slice the apples and potatoes

until right before class. Oxidation willcause them to turn brown, making it difficult to observe the results.

• Make sure that the apples are very ripe,but not rotten. In an unripe apple, all of the starch may not be converted tosugar, and students may get a positiveresult. Test one apple in advance.

Expected Outcome Iodine solutionchanges color in the presence of starch.Iodine will change from orange-rust tobrown or blue-black with the cornstarch,potato, and bread. Iodine will not changecolor with the sugar or the apple.

Analyze and Conclude1. Iodine will change color with starch,but not with a sugar.2. The cornstarch, potato, and breadcontain starch. 3. Possible answers include corn, flour,cereals, or any of the foods shown inFigure 15. Visual, Logical

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Starchy Root Cassava is a starchy tuber that isa food staple for many people in South America,West Africa, and the Caribbean. Cassava issimilar to the sweet potato, except that some

varieties contain prussic acid. If not prepared by grating, pressing, and heating, cassava istoxic. Tapioca is a product of cassava roots.

Facts and Figures


Nucleic Acids There are molecules in each cell of a plant or animalthat store information about its structures and functions. These mol-ecules are nucleic acids. Nucleic acids are large nitrogen-containingpolymers found mainly in the nuclei of cells. There are two types ofnucleic acid, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).

The monomers in a nucleic acid are nucleotides. Figure 16A showsthe three parts of a DNA nucleotide. The yellow circle represents aphosphate group. The green pentagon represents deoxyribose sugar,which has a five-atom ring. The purple rectangle represents an organicbase. The bases in DNA are adenine, thymine, cytosine, and guanine.

When two strands of DNA line up as shown in Figure 16B, an ade-nine base always pairs up with a thymine base, and a cytosine basealways pairs up with a guanine base. These pairs of bases are arrangedlike the rungs of a ladder. The strands are held together by strong inter-molecular attractions between hydrogen atoms on one strand andnitrogen or oxygen atoms on the other strand. Figure 16C shows howthe strands twist around each other in a structure called a double helix.The order of the base pairs in a strand is a code that stores informationthat is used to produce proteins.

What are the two types of nucleic acids?

A

B

C

Phosphate

Adenine

Thymine

Cytosine

Guanine

Deoxyribosesugar

Figure 16 Nucleic acids are polymers that store thegenetic information that gives the girls in thephotograph their distinct physical characteristics. A The monomers in DNA have three components—aphosphate group, a sugar, and one of four organicbases. B Two strands of DNA are held together byintermolecular attractions between the organic bases. C The shape of DNA is like a twisted ladder. Phosphate-sugar chains form the sides of the ladder. The rungs of the ladder are pairs of bases.

A

CG

T

T A

A T

CG

GC

CG

T A

CG

CG

GC

A T

Use VisualsFigure 16 Have students examine thethree-part diagram of DNA. Ask, Whichpart of the diagram (A, B, or C) showsa single monomer of a nucleic acid?(Part A shows one nucleotide unit.) Howare Parts B and C of the diagramrelated? (Part B shows two strands of thepolymer, each containing many monomerunits. Part C shows how the strands in Part B twist to form a double helix.) Explainthat the strands of DNA need to separatewhen DNA replicates (makes copies ofitself). Ask, If the strands were heldtogether by covalent bonds instead ofintermolecular attractions, how mightthis affect DNA replication? (Becausecovalent bonds are stronger than inter-molecular attractions, more energy wouldbe required to separate the strands.)Visual, Logical

FYIRNA is different from DNA in severalways. The sugar in RNA is ribose insteadof deoxyribose. RNA contains the baseuracil instead of thymine. RNA has onlyone strand.

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Answer to . . .

Figure 15 Answers may includewaffles, bread, pasta, oats, tortillas,rice, and cereal.

RNA and DNA


280 Chapter 9


Reviewing Concepts1. Describe a way that polymers can

be classified.

2. Name three synthetic polymers.

3. What are four types of polymers that canbe found in the cells of organisms?

4. What are the three parts of a nucleotide?

5. What holds the bases together in DNA?

6. What two functional groups are found inamino acids?

Critical Thinking7. Using Analogies Which natural polymers

are like a train with identical freight cars andwhich are like a train with a mixture ofdifferent cars?

8. Inferring There is another system forclassifying carbohydrates that uses thecategories monosaccharides, disaccharides,and polysaccharides. Where would youplace glucose, sucrose, and cellulose inthis classification system? Give a reason foryour answer.

Compare-Contrast Paragraph Write aparagraph comparing natural and syntheticpolymers in general. How are they similar?How are they different?

Proteins Recall that organic acids contain a –COOH group andorganic bases, or amines, contain an –NH2 group. There is one sub-stituted hydrocarbon that contains both groups. An amino acid is acompound that contains both carboxyl and amino functional groupsin the same molecule. There are about 20 amino acids that your bodyneeds to function.

Your cells can manufacture some, but not all, of the amino acids.For example, your body can make glycine, but not phenylalanine. Theessential amino acids that your body cannot make must come fromfoods like those in Figure 17.

Your cells use amino acids as the monomers for constructing pro-tein polymers. A protein is a polymer in which at least 100 amino acidmonomers are linked through bonds between an amino group and acarboxyl group. The instructions for making proteins are stored inDNA. Proteins make up the fibers of your muscles, your hair andfingernails, and the hemoglobin in your blood. Your body may con-tain as many as 300,000 different proteins.

H

H H

C

H

N

O

C OH

Glycine Phenylalanine

H H

C

H

N

O

C OHC

H

H

Figure 17 The foods shown areall good protein sources.Classifying Group the foods intothree or four categories.

280 Chapter 9

Build Science SkillsComparing and Contrasting Havestudents compare and contrast proteinsand nucleic acids. Ask, What do thesetwo types of polymers have in com-mon? (Both have important biologicalfunctions, and the monomers of both are acids.) How do these two types of polymers differ? (The monomers in nucleic acids are nucleotides. Themonomers in proteins are amino acids.)Logical

Integrate HealthEggs, milk, meat, and fish usually containall the essential amino acids. Individualplant foods do not. A strict vegetarianmust eat a combination of foods toobtain all the essential amino acids. Havestudents research and prepare postersshowing foods (such as beans and rice)that provide the complete set of essentialamino acids.Visual

ASSESSEvaluate UnderstandingHave students write down the followinglist of polymers: polyethylene, starch,cellulose, nucleic acids, and proteins.Then, have students identify themonomers for each polymer.

ReteachUse the equation in the text on pp. 276 and 278 to compare a synthetic and a natural polymer.

Paragraphs should include the following.Similarities: made up of smaller moleculescalled monomers that are linked togetherby covalent bonds. Differences: syntheticpolymers are developed by chemists;organisms produce natural polymers.


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7. Starches and cellulose are like trains withidentical cars, and proteins and nucleic acidsare like trains with a mixture of different cars. 8. Glucose is a monosaccharide because itsmolecules are single sugar units. Sucrose is adisaccharide because its molecules contain aglucose unit and a fructose unit linkedtogether. Cellulose is a polysaccharide becauseit contains many glucose units linked together.


1. The two main types of polymers are naturaland synthetic.2. Rubber, nylon, and polyethylene3. Starches, cellulose, nucleic acids, and proteins4. Organic base, phosphate group, and a sugar5. Strong intermolecular attractions6. Amino acids contain a carboxyl group andan amino group.

Answer to . . .

Figure 17 Possible answers include:seafood, meat, beans, and nuts.


Should People ConserveFossil Fuels?

Fossil fuels are still abundant. People can continue to use the known supply of fossilfuels at current rates for many years. New technologymakes finding and extracting oil, coal, and naturalgas easier. For example, in 1978 scientists thoughtthere was about 648 billion barrels of oil remainingworldwide. However, with new discoveries andimproved technology, optimists now think there maybe as much as 3 trillion barrels remaining. Even ifthe use of oil increased, scientists would still haveseveral hundred years to develop alternative fuels andnew refining processes. In addition, technologies arereducing the amount of sulfur dioxide and nitrogenoxides released when fossil fuels are burned.

Fossil fuels must be conserved. Advances in technology will serve only to speed up therate at which oil is extracted from oil reserves. Theamount of oil available for consumers will rise, andpeople will feel no need to conserve. At some point,production will decrease as supplies dwindle. Theemissions produced when fossil fuels burn put societyas a whole at risk. Despite more efficient methods ofcombustion, more than 6 billion tons of carbondioxide was released into the atmosphere in 1997.Developing alternative sources of energy now willreduce pollution in the future. These alternatives alsofree fossil fuels for use in the production of plastics,paints, medicines, and other essential materials.

1. Defining the Issue In your own words,describe the issue that needs to be resolvedabout the use of fossil fuels.

2. Analyzing the Viewpoints List threearguments made by those who think that fossilfuels do not need to be conserved. List threearguments made by people who think that fossilfuels must be conserved.

3. Forming Your Opinion Should peopleconserve fossil fuels? Did you find any convincingargument for or against conservation?

The Viewpoints

Research and Decide

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Many people depend on fossil fuels such as petroleum, or crude oil. Nearly28 billion barrels of oil was consumed in 2002. More than 14 billion barrelswas used to supply energy for automobiles, airplanes, and other means oftransportation. Fractions of crude oil are also used to produce plastics, dyes,fertilizers, solvents, aerosols, explosives, paints, soaps, and medicines.

Scientists estimate that annual consumption of oil will increase to38.6 billion barrels by 2020. Scientists disagree about how much of theremaining supply should be used. Some scientists say that there is morefossil fuels remaining than predicted and that there is no crisis. Otherssuggest that scientists must quickly develop alternative sources of energy fortransportation, such as solar power, hydrogen fuel cells, or fuels made fromplants. Alternative energy sources would reduce the use of fossil fuels andlimit the amount of pollution during their combustion.

4. Role-Playing You manufacture a product thathas parts made from synthetic polymers. Thepolymers are made from compounds found in oil.Your costs would increase without the polymers.Write a letter to your senator stating your point ofview on funding alternative energy research.


Should People ConserveFossil Fuels?BackgroundIndustrialized societies are highlydependent on fossil fuels. These fuelsprovide the energy for heating, cooling,and lighting commercial and residentialbuildings; operating industrial machineryand home appliances; and transportinggoods and people. A reduction in thesupply of fossil fuels or an increase intheir cost would have a major impact onthe economy of an industrialized society.In these countries the availability and useof fossil fuels is an important domesticand foreign policy issue. The effect onthe environment of the combustion offossils fuels is also an important issue. So is the extraction, refining, andtransporting of fossil fuels.

Answers1. Should fossil fuels be conserved? 2. Acceptable answers againstconservation include: Reserves aregreater than previously thought; tech-nology makes finding and extractingfuels easier; scientists have time todevelop alternative technologies;technologies have reduced the emissionof sulfur and nitrogen oxides when fossilfuels are burned. Acceptable answers infavor of conservation include: Advancesin technology will increase the rate ofconsumption; eventually production willdecrease; despite more efficient methodsof combustion, tons of carbon dioxideare still released into the atmosphere.3. Students should present arguments to support their decisions.4. Acceptable answers will includepersuasive reasoning to explain thechosen point of view.

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Have students further research the issues related to this topic.


9.4 Reactions in Cells

Reading StrategySummarizing Copy the table. As you read,complete the table by recording a main ideafor each heading.

Key ConceptsWhat energy conversiontakes place duringphotosynthesis?

How are photosynthesisand cellular respirationrelated?

What molecules help cellsfunction efficiently?

Vocabulary◆ photosynthesis◆ enzymes◆ vitamins

For thousands of years, people used whale oil and other animal fatsas fuels for their lamps. As fats burn, they combine with oxygen andproduce carbon dioxide and water. They also release energy in the formof heat and light. In a lamp, combustion takes place rapidly. In the cellsof organisms, a more controlled version of the process releases energystored in molecules. Some of the energy released helps maintain yourinternal body temperature at or close to 37°C.

Reactions that take place in cells follow the same rules as reactionsthat take place in a research laboratory or classroom. Some reactionsgo to completion and some reach an equilibrium point. Many reac-tions occur in solution and catalysts are often needed. Energy istransferred and energy is converted from one form to another.Photosynthesis and cellular respiration are two processes that alloworganisms to meet their energy needs.

PhotosynthesisThe sun is the primary source of energy for most plants and animals.During photosynthesis, plants chemically combine carbon dioxide andwater into carbohydrates. The process requires light and chlorophyll, agreen pigment in plants. This equation summarizes the process.

6H2O � 6CO2 � Energy (light)h C6H12O6 � 6O2

During photosynthesis, energy from sunlight is converted intochemical energy. Photosynthesis involves a complex series of chemicalreactions. When all the reactions are complete, the energy from sunlighthas been stored in the covalent bonds of molecules.

Photosynthesis

Cellular Respiration

Enzymes and Vitamins

Heading Main Idea

a. ?

b. ?

c. ?

282 Chapter 9

Figure 18 Unlike a plant, thisrunner must get the energy heneeds from the food he eats.

282 Chapter 9

FOCUS

Objectives9.4.1 Compare photosynthesis

and cellular respiration. 9.4.2 Explain how enzymes and

vitamins help reactions takeplace in cells.

Build VocabularyWeb Diagram Have students create a web diagram relating the terms photosynthesis, cellular respiration,glucose, energy, carbohydrates, digestion,and polymers.

Reading Strategya. During photosynthesis, energy from sunlight is converted into chemical energy.b. During cellular respiration, the energystored in products of photosynthesis is released.c. Enzymes and vitamins are compoundsthat help cells function efficiently atnormal body temperature.

INSTRUCT

PhotosynthesisBuild Reading LiteracySequence Refer to page 290D inChapter 10, which provides guidelinesfor using a sequence.

Have students create a flowchart that follows a carbon atom throughphotosynthesis and cellular respiration.Have students mark where oxygen,water, and energy enter and exit theoverall process.Verbal

Integrate BiologyIn green plants, chlorophyll a and b arethe dominant light-absorbing pigments.These pigments and others contributeto the color of leaves and allow plants to absorb the energy of sunlight. Have interested students researchchlorophyll’s structure. (Chlorophyll has a flat, star-shaped structure with a Mg2� ion in the center.)Logical

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Reading Focus

1

Section 9.4

Print• Reading and Study Workbook With

Math Support, Section 9.4• Transparencies, Section 9.4

Technology • Interactive Textbook, Section 9.4• Presentation Pro CD-ROM, Section 9.4• Go Online, Science News, Organic chemistry

and biochemistry

Section Resources


Photosynthesis

Carbon Dioxide Water Vapor Carbohydrates Oxygen


Energy Released

Light EnergyA

B

Figure 19 Products of cellularrespiration are reactants duringphotosynthesis. A Cellularrespiration and photosynthesisare two parts of the same cycle. B Plants can survive withoutpeople, but people cannot survivewithout plants.

Cellular Respiration What does your body need energy for, besides maintaining a constantbody temperature? Everything! It takes energy to laugh or cry, to heala bone or a paper cut, to climb a rope or a staircase, or even to sleep.

During cellular respiration, the energy stored in the products ofphotosynthesis is released. Like photosynthesis, cellular respirationis a complex series of reactions. This equation is a summary of theoverall process.

C6H12O6 � 6O2h 6H2O � 6CO2 � Energy (heat)

Figure 19 summarizes the relationship between photosynthesis andcellular respiration. Each process produces the reactants for the otherprocess. Carbon dioxide and water are reactants in photosynthesis andproducts of cellular respiration. Carbohydrates and oxygen are reac-tants in cellular respiration and products of photosynthesis.

In the equation for cellular respiration, glucose is reacting withoxygen. The glucose can come from simple sugars or from starches,because starch is a polymer of glucose. During digestion, starch breaksdown into glucose. This process is an example of depolymerization.Fats are also a good source of energy. One gram of fat produces twicethe energy of one gram of a carbohydrate.

Which produces more energy per gram, a carbo-hydrate or a fat?

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Students may confuse cellular respiration,respiration, and breathing. Explain thatcellular respiration is a chemical processthat releases energy stored in molecules.During respiration, oxygen and carbondioxide are exchanged between cells,blood, and air in the lungs. Breathing isthe movement of air into and out of thelungs by inhalation and exhalation. Verbal

Photosynthesis and Cellular Respiration

Purpose Students learn about theproducts of photosynthesis and cellular respiration.

Materials methylene blue, water, 500-mL beaker, elodea sprig, straw

Procedure Explain that methylene blueturns orange in the presence of carbondioxide. Place five drops of methyleneblue in a beaker of water. Use the straw to blow into the water. After the solutionchanges color, remove the straw. Place an elodea sprig into the solution and placethe beaker in sunlight. Have studentsnotice the color change every fiveminutes for the next thirty minutes.

Safety Do not ingest any of themethylene blue.

Expected Outcome The solution turnsorange when it absorbs carbon dioxidefrom exhaled air. As the elodea removescarbon dioxide from the solution, thecolor changes back to blue. Visual

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Customize for Inclusion Students

GiftedSome organisms release the energy stored incompounds through an anaerobic processcalled fermentation. (Anaerobic means “in the absence of oxygen.”) The products of thefermentation of carbohydrates are ethanol and carbon dioxide.

C6H12O6 h 2CH3CH2OH + 2CO2

Have students research and write a shortreport about fermentation. Suggest that theyinclude information about common examplesof fermentation. Many commercial products,including cheese, antibiotics, and vitamins, are produced by fermentation. Students mightalso want to research what causes lactic acid to build up in muscles and how athletes canreduce this process.

Answer to . . .

A fat

PPLS

Find links to additional activitiesand have students monitorphenomena that affect Earth and its residents.


284 Chapter 9


Reviewing Concepts1. What happens to sunlight during

photosynthesis?

2. Describe the relationship betweenphotosynthesis and cellular respiration.

3. What molecules improve the efficiency of cell functions?

4. What happens to starch during digestion?

5. Why can’t an increase in temperature be usedto speed up reactions in cells?

Critical Thinking6. Formulating Hypotheses Why must com-

bustion in cells take place in multiple steps?

7. Drawing Conclusions Some bacteria do notrequire oxygen. How would the disappearanceof plants affect these bacteria?

8. Inferring What affect could a lack ofessential amino acids have on reactions in aperson’s body?

Figure 20 Lemons, limes, andoranges are sources of vitamin C.Drawing Conclusions Is vitaminC soluble in fat or in water?

Explanatory Paragraph Check the labelon a package of multivitamins and minerals.Compare the masses of the minerals to themasses of the vitamins included in a singlepill. Discuss any trend that you detect.

Enzymes and VitaminsWithout some help, many of the reactions that take place in your cellswould not happen fast enough to keep the cells alive. Your internaltemperature should not vary more than a few degrees from 37°C.So you cannot increase the temperature to speed up a reaction inyour cells. Enzymes and vitamins are compounds that help cellsfunction efficiently at normal body temperature.

Enzymes Without enzymes, cells could not digest food or extractenergy from food. Enzymes are proteins that act as catalysts for reac-tions in cells. Enzymes allow reactions to proceed faster at much lowertemperatures than would normally happen. Your body uses thousandsof enzymes to control reactions within your cells. Pepsin, for example,is an enzyme that breaks apart proteins. It works only in the acidicenvironment of the stomach. Some enzymes require a co-enzyme tofunction, often a metal ion or a water-soluble vitamin.

Vitamins In the 1800s, British sailors ate limes on long sea voyages.The limes were protection against scurvy, which causes severe pain andweakness. Limes contain vitamin C. Vitamins are organic compoundsthat organisms need in small amounts, but cannot produce. A vitaminthat dissolves in water, such as vitamin C, gets eliminated from thebody and must be replaced daily. A vitamin that dissolves in fats, suchas vitamin A, can build up over time in body tissues. Taking excessamounts of fat-soluble vitamins may be harmful.

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284 Chapter 9

Enzymes and Vitamins

Denaturing an Enzyme

Purpose Students will observe how enzyme activity is affected by temperature.

Materials potato, sharp knife, cuttingsurface, 3% hydrogen peroxide solution,water, 500-mL beakers (2), hot plate

Procedure Fill a beaker halfway withwater and use the hot plate to boil thewater. Cut a potato into small cubes(about 1 cm3). Place some of the cubes inthe boiling water and allow them to cookfor several minutes. Fill a second beakerhalfway with hydrogen peroxide solution.Place some of the raw cubes in the hydro-gen peroxide solution. Have studentsobserve the gas bubbles that form on thesurface of the potato cubes. Explain thatan enzyme in the potato is speeding upthe reaction that decomposes hydrogenperoxide into water and oxygen. Explainthat enzymes lose their ability to speed up reactions when they are damaged byan increase in temperature. Place some ofthe cooked potato cubes in the hydrogenperoxide and have students note that gasbubbles do not form (or form at a muchslower rate). Visual

ASSESSEvaluate UnderstandingHave groups of students write four reviewquestions with answers.

ReteachHave students use Figure 19 to reviewthe relationships between photosynthesisand cellular respiration.

The masses of the vitamins in the pillsare small (micrograms) compared to the masses of the minerals (milligrams).


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6. Multiple steps allow the cells to release theenergy stored in chemical bonds in smalleramounts, rather than all at once, which couldcause the temperature in a cell to rise.7. It’s likely that these bacteria would not beaffected because they do not require the oxygenthat plants produce during photosynthesis.8. Without these essential amino acids, thebody would not be able to produce enzymesneeded for cellular reactions.


1. Sunlight is converted into chemical energy.2. The products of one process are thereactants in the other.3. Enzymes and vitamins4. Starch is broken down into glucose, whichcan be used in cellular respiration.5. The internal temperature should not varymore than a few degrees from 37�C.Answer to . . .

Figure 20 Soluble in water

section 9.1 9.1 carbon compoundsmrbakerphysical.weebly.com/uploads/3/0/8/0/... · 262 chapter 9 u...

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