Planning Guide

PACING • 45 min pp. 3 –5 EXT Graphing Calculator Graphing Experimental Data, p. 23

TR 1A Top Eight Chemicals Made in the United States

TE Reading Skill Builder K/W/L, p. 2 b TE Lesson Starter, p. 3 g TE Visual Strategy, p. 3 g TE Class Discussion, p. 5 g

Section 1 Chemistry is a Physical Science

PACING • 90 min pp. 6 – 15Section 2 Matter and Its Properties

EXT Historical Chemistry A Broken Rule: Chemical Reactions of the Noble Gases, p. 9 g

TR 1 Water in Three States TR 2 Comparison of Physical and Chemical

Properties TR 3 Classifying Matter TR 4 Electrolysis of Water TR 5 Evidence of a Chemical Change TR 6 Pure Substances TR 7 Types of Mixtures TR 2A Properties of Matter TR 3A Examples of Mixtures

TE Lesson Starter, p. 6 g TE Reading Skill Builder Discussion, p. 7 b TE Demonstration, p. 7 ◆ TE Demonstration, p. 8 ◆ TE Class Discussion, p. 9 g TE Reading Skill Builder Vocabulary Building, p. 12 b SE Cross-Disciplinary Connection Secrets of the Cremona

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INQUIRY gANC Datasheets for In-Text Labs

2A Chapter 1 Matter and Change

SECTIONS LABS, DEMONSTRATIONS, AND ACTIVITIES TECHNOLOGY RESOURCES

PACING • 45 min pp. 16 – 20Section 3 Elements

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Symbols’ Origins

TE Lesson Starter, p. 16 g TE Table Strategy, p. 16 g TE Reading Skill-Builder Brainstorming, p. 16 b TE Visual Strategy, p. 17 g SE Chemistry in Action Superconductors, p. 18

Matter and Change To shorten your instruction because of time limitations, omit the Chapter Lab.

Compression Guide

CHAPTER 1

CHAPTER REVIEW, ASSESSMENT, AND STANDARDIZED TEST PREPARATION

SE Chapter Highlights, p. 21 SE Chapter Review, pp. 22 – 23 SE Math Tutor, p. 24 SE Standardized Test Prep, p. 25ANC Chapter Test A gANC Chapter Test B a OSP Test GeneratorOSP Scoring Rubrics and Classroom Management

Checklists

PACING • 90 min

Online and Technology Resources

Visit go.hrw.com to find a variety of online resources. To access this chapter’s extensions, enter the keyword HC6MTXXT and click the “go” button. Click Holt Online Learning for an online edition of this textbook, and other interactive resources.

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Chapter 1 Planning Guide 2B

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www.scilinks.orgMaintained by the National Science Teachers Association.

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ClassroomTechnology

Matter and Change

Chapter OverviewSection 1 defines the field of chemistry and distinguishesbetween different branches of chemistry.

Section 2 defines matter and contrasts major physical andchemical changes that mattercan undergo. This section alsooutlines the basic form of achemical equation and describeshow matter is classified.

Section 3 introduces the peri-odic table as a classificationscheme for the elements withdescriptions of metals, non-metals, and metalloids.

Concept BaseThis text assumes that studentshave some prior background inthe physical sciences. Therefore,terms such as energy, atom,element, compound, proton,neutron, and electron should befamiliar to them.

CHAPTER 1

2

Matter and ChangeChemistry is central to all of the sciences.

C H A P T E R 1

Reading Skill Builder

K/W/L Students probably havepreconceptions about chemistry.Have them list what they knowabout chemistry. Then have themlist what they want to know aboutit. After they have completedSection 1, have them look at theirlists and write down what theyhave learned about chemistry. Also,have them write down any newquestions that they may have afterreading the section.

Tartaric Acid Crystals

M A T T E R A N D C H A N G E 3

Lesson StarterHave students consider all of theobjects in their classroom that arerelated to the study of chemistry.Bring different materials, such asplastics, fabrics, fertilizer, clothes,cooking oil, motor oil, nail polish,nail polish remover, aspirin, and vitamins, to class to help initiate discussion. Have students considertheir daily activities. How many ofthese activities have something to do with chemistry?

Visual StrategyUse this figure to remind

students that there are limits to theability of our senses to make mea-surements. Instruments extend oursenses and allow us to make quanti-tative measurements. Try to get stu-dents to recognize the benefits ofmaking observations that includemeasurements.

FIGURE 1

GENERAL

GENERAL

SECTION 1

3

SECTION 1

OBJECTIVES

Define chemistry.

List examples of the branchesof chemistry.

Compare and contrast basic research, appliedresearch, and technologicaldevelopment.

Chemistry Is aPhysical Science

T he natural sciences were once divided into two broad categories:the biological sciences and the physical sciences. Living things are themain focus of the biological sciences. The physical sciences focus mainly on nonliving things. However, because we now know that bothliving and nonliving matter consist of chemical structures, chemistry iscentral to all the sciences, and there are no longer distinct divisionsbetween the biological and physical sciences.

Chemistry is the study of the composition, structure, and properties ofmatter, the processes that matter undergoes, and the energy changes thataccompany these processes. Chemistry deals with questions such as,What is a material’s makeup? How does a material change when heat-ed, cooled, or mixed with other materials and why does this behavioroccur? Chemists answer these kinds of questions during their work.

Instruments are routinely used in chemistry to extend our ability toobserve and make measurements. Instruments make it possible, for exam-ple, to look at microstructures—things too tiny to be seen with the unaid-ed eye. The scanning electron microscope reveals tiny structures bybeaming particles called electrons at materials. When the electrons hit amaterial, they scatter and produce a pattern that shows the material’smicrostructure. Invisible rays called X rays can also be used to

(a) (b)

FIGURE 1 A balance (a) is aninstrument used to measure themass of materials. A sample of DNAplaced in a scanning tunneling micro-scope produces an image (b) showingthe contours of the DNA’s surface.

determine microstructures. The patterns that appear, called X-ray diffrac-tion patterns, can be analyzed to reveal the arrangement of atoms, mole-cules, or other particles that make up the material. By learning aboutmicrostructures, chemists can explain the behavior of macrostructures—the visible things all around you.

Branches of Chemistry

Chemistry includes many different branches of study and research. Thefollowing are six main areas, or branches, of study. But like the biologi-cal and physical sciences, these branches often overlap.1. Organic chemistry—the study of most carbon-containing compounds2. Inorganic chemistry—the study of non-organic substances, many of

which have organic fragments bonded to metals (organometallics)3. Physical chemistry—the study of the properties and changes of

matter and their relation to energy4. Analytical chemistry—the identification of the components and com-

position of materials5. Biochemistry—the study of substances and processes occurring in

living things6. Theoretical chemistry—the use of mathematics and computers to

understand the principles behind observed chemical behavior and todesign and predict the properties of new compounds

In all areas of chemistry, scientists work with chemicals. A chemicalis any substance that has a definite composition. For example, considerthe material called sucrose, or cane sugar. It has a definite compositionin terms of the atoms that compose it. It is produced by certain plants inthe chemical process of photosynthesis. Sucrose is a chemical. Carbondioxide, water, and countless other substances are chemicals as well.

Knowing the properties of chemicals allows chemists to find suitableuses for them. For example, researchers have synthesized new sub-stances, such as artificial sweeteners and synthetic fibers. The reactionsused to make these chemicals can often be carried out on a large scaleto make new consumer products such as flavor enhancers and fabrics.

Basic ResearchBasic research is carried out for the sake of increasing knowledge, suchas how and why a specific reaction occurs and what the properties of asubstance are. Chance discoveries can be the result of basic research.Theproperties of Teflon™, for example, were first discovered by accident. Aresearcher named Roy Plunkett was puzzled by the fact that a gas cylin-der used for an experiment appeared to be empty even though the mea-sured mass of the cylinder clearly indicated there was something inside.Plunkett cut the cylinder open and found a white solid. Through basicresearch, Plunkett’s research team determined the nonstick properties,molecular structure, and chemical composition of the new material.

C H A P T E R 14

SECTION 1

4

SECTION 1

• Students should know that thereare no clear-cut divisions that separate one kind of chemist fromanother. Just as doctors specializein a certain type of medicine,chemists too have more specializedfields of study, but these fieldsoften overlap.

• Have students bring in articlesfrom news magazines and otherperiodicals showing chemistry inaction. Photography magazines are one good source. Students are often surprised at the numberof industries that rely in some wayon basic chemical knowledge.

CommonMisconceptionStudents often think of chemicals asartificial, or unnatural. You want themto understand that all matter—livingand nonliving, natural or artificial—has a chemical basis. Ask students totry naming anything that they think isnot made of at least one chemical.

Teaching Tip✔

Applied ResearchApplied research is generally carriedout to solve a problem. For example,when certain refrigerants escape intothe upper atmosphere, they damage theozone layer, which helps block harmfulultraviolet rays from reaching the sur-face of Earth. In response to concernsthat this atmospheric damage couldpose health problems, chemists havedeveloped new refrigerants. In appliedresearch, researchers are driven not bycuriosity or a desire to know but by adesire to solve a specific problem.

TechnologicalDevelopmentTechnological development typicallyinvolves the production and use ofproducts that improve our quality oflife. Examples include computers,catalytic converters for cars, andbiodegradable materials.

Technological applications often lag far behind the discoveries thatare eventually used in technologies. For example, nonstick cookware, atechnological application, was developed well after the accidental dis-covery of Teflon. When it was later discovered that the Teflon coatingon cookware often peeled off, a new challenge arose. Using appliedresearch, scientists were then able to improve the bond between theTeflon and the metal surface of the cookware so that it did not peel.

Basic research, applied research, and technological development oftenoverlap. Discoveries made in basic research may lead to applications thatcan result in new technologies. For example, knowledge of crystals andlight that was gained from basic research was used to develop lasers. Itwas then discovered that pulses of light from lasers can be sent throughoptical fibers. Today, telephone messages and cable television signals arecarried quickly over long distances using fiber optics.

M A T T E R A N D C H A N G E 5 5

SECTION 1

Class DiscussionSurvey students to find out if anyonehas a friend or relative who works inthe field of chemistry. Invite these peo-ple to speak to the class and describetheir work. Encourage students tobring questions to class regarding thelevel of chemistry education the speak-er needed to work in his or her field.Assign students the task of collectingitems for a “Chemistry Careers” bul-letin board. Award extra credit to students who find information onchemistry careers that are not withinthe traditional “scientist” role.

CommonMisconceptionStudents often think that scienceand technology are the same.Science includes knowledge in itsmajor disciplines, such as biology,chemistry, and physics. Technology is the application of that knowledgefor practical purposes.

1. Chemistry is the study of the com-position, structure, and properties of matter and the changes matterundergoes.

2. organic, inorganic, physical, analyti-cal, biochemistry, theoretical chemistry

3. Basic research is conducted for thesake of knowledge only and not tomeet practical goals. Applied researchis conducted to meet goals defined byspecific needs. Technology employsexisting knowledge to make life easi-er or more convenient.

4. Answers will vary. Students maymention improvements in devicessuch as cell phones that take pictures,portable CD players, and digital cam-eras. Scientific advancements mayinclude improvements in health care,food science, and pollution control.

SECTION REVIEW

GENERAL

FIGURE 2 The chemical structure of the material in an optical fibergives it the property of total internal reflection. This property, whichallows these fibers to carry light, was discovered through basic andapplied research. The use of this property to build networks by sendingdata on light pulses is the technological development of fiber optics.

1. Define chemistry.

2. Name six branches of study in chemistry.

3. Compare and contrast basic research, appliedresearch, and technological development.

Critical Thinking

4. INFERRING RELATIONSHIPS Scientific and techno-logical advances are constantly changing howpeople live and work. Discuss a change that youhave observed in your lifetime and that has madelife easier or more enjoyable for you.

SECTION REVIEW

(a)

(b)

Carbon atom

Hydrogen atom

Carbon atomOxygen atom

C H A P T E R 16

SECTION 1

6

SECTION 2

Lesson StarterDetermine the mass of a deflatedballoon. Then blow up the balloon,tie it, and find its new mass. Becausethe balloon increases in mass, thematter in the balloon must have mass.Point out to students that matterdoes not need to be visible to us andthat it may be made of particles thatwe cannot see.

Ask students to consider the followingquestions: Which is heavier, a poundof lead or a pound of feathers? Whatdoes a pound represent? What hap-pens to the matter of an astronautwho is weightless?

Divide the class into small groupsto design a tool that could be used to weigh something aboard thespace shuttle. Use the Internet to find out how NASA really does it.

Visual StrategyBe sure students under-

stand that the models used through-out this book are representations ofatoms, elements, and compounds.

Have students compare the mod-els shown. Point out that chemistshave different ways of representingthe structures of substances. The diamond model is a ball-and-stickrepresentation. Sucrose is shown as a space-fill model. Students willsee both types throughout this book.

Explain that sucrose has fixed proportions of the elements thatmake it up. Carbon consists of all ofthe same kind of atoms. In this case,the element shown is a solid, so themodel reflects the extended array ofa crystal. Be sure students under-stand that elements such as sulfur,phosphorus, and oxygen consist ofmolecules that have a fixed numberof atoms per molecule.

FIGURE 3

GENERAL

Teaching Tip

GENERALSECTION 2 Matter and Its

Properties

L ook around you. You can see a variety of objects—books, desks,chairs, and perhaps trees or buildings outside. All those things are madeup of matter, but exactly what is matter? What characteristics, or prop-erties, make matter what it is? In this section, you will learn the answersto these questions.

Explaining what matter is involves finding properties that all matterhas in common. That may seem difficult, given that matter takes somany different forms. For the moment, just consider one example ofmatter—a rock. The first thing you might notice is that the rock takesup space. In other words, it has volume. Volume is the amount of three-dimensional space an object occupies. All matter has volume. All mat-ter also has a property called mass. Mass is a measure of the amount ofmatter. Mass is the measurement you make using a balance. Matter canthus be defined as anything that has mass and takes up space. These twoproperties are the general properties of all matter.

Basic Building Blocks of Matter

Matter comes in many forms. The fundamental building blocks of mat-ter are atoms and molecules. These particles make up elements andcompounds. An atom is the smallest unit of an element that maintains thechemical identity of that element. An element is a pure substance thatcannot be broken down into simpler, stable substances and is made ofone type of atom. Carbon is an element and contains one kind of atom.

OBJECTIVES

Distinguish between the physical properties and chemical properties of matter.

Classify changes of matter asphysical or chemical.

Explain the gas, liquid,and solid states in terms of particles.

Explain how the law of con-servation of energy applies tochanges of matter.

Distinguish between a mix-ture and a pure substance.

FIGURE 3 Both elements and compounds are made of atoms, as shown inthese models of (a) diamond and (b) sucrose (table sugar).

✔

A compound is a substance that can be broken down into simple sta-ble substances. Each compound is made from the atoms of two or moreelements that are chemically bonded. Water is an example of a com-pound. It is made of two elements, hydrogen and oxygen. The atoms ofhydrogen and oxygen are chemically bonded to form a water molecule.You will learn more about the particles that make up compounds whenyou study chemical bonding in Chapter 6. For now, you can think of amolecule as the smallest unit of an element or compound that retains allof the properties of that element or compound.

Properties and Changes in Matter

Every substance, whether it is an element or a compound, has charac-teristic properties. Chemists use properties to distinguish between sub-stances and to separate them. Most chemical investigations are relatedto or depend on the properties of substances.

A property may be a characteristic that defines an entire set of sub-stances. That property can be used to classify an unknown substance asa member of that group. For example, many elements are classified asmetals. The distinguishing property of metals is that they conduct elec-tricity well. Therefore, if an unknown element is tested and found toconduct electricity well, it is a metal.

Properties can help reveal the identity of an unknown substance.However, conclusive identification usually cannot be made based ononly one property. Comparisons of several properties can be usedtogether to establish the identity of an unknown. Properties are eitherintensive or extensive. Extensive properties depend on the amount ofmatter that is present. Such properties include volume, mass, and theamount of energy in a substance. In contrast, intensive properties do notdepend on the amount of matter present. Such properties include themelting point, boiling point, density, and ability to conduct electricity andto transfer energy as heat. Intensive properties are the same for a givensubstance regardless of how much of the substance is present. Propertiescan also be grouped into two general types: physical properties andchemical properties.

Physical Properties and Physical ChangesA physical property is a characteristic that can be observed or measuredwithout changing the identity of the substance. Physical properties describethe substance itself, rather than describing how it can change into othersubstances. Examples of physical properties are melting point and boilingpoint.Those points are, respectively, the temperature at which a substancemelts from solid to liquid and the temperature at which it boils from liq-uid to gas. For example, water melts from ice to liquid at 0°C (273 K or32°F). Liquid water boils to vapor at 100°C (373 K or 212°F).

A change in a substance that does not involve a change in the identityof the substance is called a physical change. Examples of physical

M A T T E R A N D C H A N G E 7 7

SECTION 2

The particles that make up compoundswill be further discussed in Chapter 6.Students may be confused regardingthe use of the term molecule becauseall compounds are not made of mol-ecules. It is not necessary to get intothe details now.

DEMONSTRATIONS• Have students look at water and

glycerin. They look the same, butthey feel different. Tell studentsthat a difference in properties may not be immediately obvious,so we use instruments to measuredifferences that we may not beable to see. Have students specu-late about whether the two liquidsare different substances. Corn syrupcan be used in place of glycerin.

• Show students the difference in electrical conductivity between distilled water and salt water. Thisdemonstration shows students thatdifferences in properties are notalways obvious without using aninstrument to measure properties.

Teaching Tip✔

Reading Skill Builder

DISCUSSION Have studentsread about physical and chemicalproperties and changes. Then havethem choose items in the class-room and classify the properties ofeach item, giving justification foreach classification.

FIGURE 4 Water boils at 100°Cno matter how much water is in thecontainer. Boiling point is an inten-sive property.

changes include grinding, cutting, melting, and boiling a material. Thesetypes of changes do not change the identity of the substance present.

Melting and boiling are part of an important class of physicalchanges called changes of state. As the name suggests, a change of stateis a physical change of a substance from one state to another. The threecommon states of matter are solid, liquid, and gas.

Matter in the solid state has definite volume and definite shape. Forexample, a piece of quartz or coal keeps its size and its shape, regardlessof the container it is in. Solids have this characteristic because the par-ticles in them are packed together in relatively fixed positions. The par-ticles are held close together by the strong attractive forces betweenthem, and only vibrate about fixed points.

Matter in the liquid state has a definite volume but an indefinite shape;a liquid assumes the shape of its container. For example, a given quan-tity of liquid water takes up a definite amount of space, but the watertakes the shape of its container. Liquids have this characteristic becausethe particles in them are close together but can move past one another.The particles in a liquid move more rapidly than those in a solid. Thiscauses them to overcome temporarily the strong attractive forcesbetween them, allowing the liquid to flow.

Matter in the gas state has neither definite volume nor definite shape.For example, a given quantity of helium expands to fill any size contain-er and takes the shape of the container.All gases have this characteristicbecause they are composed of particles that move very rapidly and areat great distances from one another compared with the particles of liq-uids and solids.At these great distances, the attractive forces between gasparticles have less of an effect than they do at the small distances

between particles of liquids and solids.An important fourth state of matter is plasma. Plasma is a

high-temperature physical state of matter in which atoms losemost of their electrons, particles that make up atoms. Plasma isfound in fluorescent bulbs.

Melting, the change from solid to liquid, is an example ofa change of state. Boiling is a change of state from liquid togas. Freezing, the opposite of melting, is the change from aliquid to a solid. A change of state does not affect the identi-ty of the substance. For example, when ice melts to liquidwater or when liquid water boils to form water vapor, thesame substance, water, is still present, as shown in Figure 6.The water has simply changed state, but it has not turned intoa different compound. Only the distances and interactionsbetween the particles that make up water have changed.

Chemical Properties and Chemical ChangesPhysical properties can be observed without changing theidentity of the substance, but properties of the second type—chemical properties—cannot. A chemical property relates to asubstance’s ability to undergo changes that transform it into dif-ferent substances. Chemical properties are easiest to see when

C H A P T E R 18

SECTION 1

8

SECTION 2

Present different properties to stu-dents and have them determinewhether they are intensive or exten-sive properties. Density, conductivity,and melting and boiling points areexamples of intensive properties.Energy absorbed, volume, and massare extensive properties. Comparethe two types of properties by heating100 mL and 400 mL of water. Bothwill boil at the same temperature(intensive) but the 400 mL samplewill absorb more energy (extensive)and will therefore take longer toreach the boiling point. Ask studentsto predict which beaker will return toroom temperature first.

Along with the three common statesof matter, there are several more. Theultradense matter in a neutron star is unlike a solid, a liquid, or a gas.Other forms of matter, such as theBose-Einstein condensate, can be created at low temperatures whenseveral atoms occupy the same quan-tum state.

DEMONSTRATIONYou can easily model the amount of energy a substance can have byputting marbles in a plastic cup orplastic beaker. The intensity withwhich you shake the beaker repre-sents the energy of the particles andis demonstrated by how much themarbles move. With very little shak-ing, the marbles merely vibrate intheir positions, like the particles of a solid. With moderate shaking, themarbles move relative to one anotherbut stay inside the container (as in aliquid). With vigorous shaking, themarbles have enough energy toescape the container (as with a gas).

Teaching Tip

Teaching Tip✔

✔

FIGURE 5 Because it possesses certain chemicalproperties, a test strip containing Benedict’s solu-tion is used to test for the presence of sugar inurine. The test strip is dipped into the sample. Thetest strip is then matched to a color scale to deter-mine the sugar level in the urine.

www.scilinks.orgTopic: Physical/Chemical

ChangesCode: HC61145

substances react to form new substances. For example, the ability ofcharcoal (carbon) to burn in air is a chemical property. When charcoalburns, it combines with oxygen in air to become a new substance, carbondioxide gas. After the chemical change, the amounts of the original sub-stances, carbon and oxygen, are less than before. A different substancewith different properties has been formed. Other examples of chemicalproperties include the ability of iron to rust by combining with oxygen inair and the ability of silver to tarnish by combining with sulfur.

A change in which one or more substances are converted into differentsubstances is called a chemical change or chemical reaction. The sub-stances that react in a chemical change are called the reactants. The sub-stances that are formed by the chemical change are called the products. Inthe case of burning charcoal, carbon and oxygen are the reactants in acombustion, or burning, reaction. Carbon dioxide is the product. Thechemical change can be described as follows:

Carbon plus oxygen yields (or forms) carbon dioxide.

Arrows and plus signs can be substituted for the words yields and plus,respectively:

carbon + oxygen ⎯→ carbon dioxide

M A T T E R A N D C H A N G E 9 9

SECTION 2

Solid

Gas

Liquid

FIGURE 6 Models for water in three states. The molecules areclose together in the solid and liquidstates but far apart in the gas state.The molecules in the solid state arerelatively fixed in position, but thosein the liquid and gas states can flowaround each other.

Write symbols on the board to show aphysical change, such as the boiling ofwater. Then write symbols on theboard to show a chemical change,such as the production of hydrogenand oxygen gases from water. In thechemical change, the symbols for theelements have been rearranged, whichemphasizes the difference betweenphysical and chemical changes. Also,students begin to appreciate how use-ful symbols can be in representingphysical and chemical changes.

Visual StrategyHelp students recognize

the differences between the states ofmatter at the macroscopic and micro-scopic levels. They will see illustra-tions throughout this book showingmicromodels for systems that explainthe macrophenomena they observe.Point out that ice floats on waterbecause it is less dense. The modelfor ice shows that its structure is lessdense than that of the liquid.

Class DiscussionHave students brainstorm aboutchemical changes with which they are familiar. Food digestion and rusting are two common examples.

GENERAL

FIGURE 6

GENERAL

Teaching Tip✔

Historical ChemistryGo to go.hrw.com for a full-lengtharticle on the chemical reactions ofnoble gases.

Keyword: HC6MTXX

The decomposition of the mercury compound shown in Figure 7 canbe expressed as follows:

mercury(II) oxide ⎯→ mercury + oxygen

Chemical changes and reactions, such as combustion and decomposi-tion, form products whose properties differ greatly from those of thereactants. However, chemical changes do not affect the total amount ofmatter present before and after a reaction. The amount of matter, andtherefore the total mass, remains the same.

Energy and Changes in MatterWhen physical or chemical changes occur, energy is always involved.The energy can take several different forms, such as heat or light.Sometimes heat provides enough energy to cause a physical change, asin the melting of ice, and sometimes heat provides enough energy tocause a chemical change, as in the decomposition of water vapor toform oxygen gas and hydrogen gas. But the boundary between physicaland chemical changes isn’t always so clear. For example, while mostchemists would consider the dissolving of sucrose in water to be a phys-ical change, many chemists would consider the dissolving of table salt inwater to be a chemical change. As you learn more about the structureof matter, you will better understand why the boundaries betweenchemical and physical changes can be confusing.

C H A P T E R 110

SECTION 1

10

SECTION 2

Make students aware that most phys-ical and chemical changes involvesome transfer of energy. The bodyuses energy from the chemical reac-tions that break down food. Weatherinvolves a transfer of energy to evaporate or condense water in the atmosphere. Therefore, the studyof matter also involves the study ofenergy.

Visual StrategyThis figure gives students

the opportunity to see descriptions ofthe physical and chemical propertiesof substances found in the chemicalliterature.

Have students identify aspects inthis figure that signify a chemicalchange. Ask students to verify thatthe substances produced have prop-erties different from those of thereactant. Tell students that mercury isboth volatile and poisonous. Thedecomposition of mercury oxideshould never be attempted outsidethe classroom or without teachersupervision.

FIGURE 7

GENERAL

Teaching TipMercuryPhysical properties: silver-white,liquid metal; in the solid state, mercury is ductile and malleable and can be cut with a knifeChemical properties: forms alloys with most metals except iron; com-bines readily with sulfur at normal temperatures; reacts with nitric acidand hot sulfuric acid; oxidizes to form mercury(II) oxide upon heating

OxygenPhysical properties: colorless,odorless gas, soluble in waterChemical properties: supportscombustion; reacts with manymetals

Mercury(II) oxidePhysical properties: bright red ororange-red, odorless crystalline solid,almost insoluble in waterChemical properties: decomposeswhen exposed to light or at 500ºC to form mercury and oxygen gas

✔

FIGURE 7 When mercury(II)oxide is heated, it decomposes toform oxygen gas and mercury(which can be seen on the side ofthe test tube). Decomposition is achemical change that can beobserved by comparing the proper-ties of mercury(II) oxide, mercury,and oxygen.

• Gifted and Talented

Have students create a chart thatlists examples of chemical changesand physical changes. Students candraw pictures that represent eachexample. Ask the students to labeleach picture with the type of changeand the identity of the substancesbefore and after the change hastaken place. Students may use thetextbook, reference books, and theInternet to complete the charts.

StrategiesStrategiesINCLUSIONINCLUSION

Accounting for all the energy present before and after a change isnot a simple process. But scientists who have done such experimenta-tion are confident that the total amount of energy remains the same.Although energy can be absorbed or released in a change, it is notdestroyed or created. It simply assumes a different form. This is the lawof conservation of energy.

Classification of Matter

Matter exists in an enormous variety of forms. Any sample of matter,however, can be classified either as a pure substance or as a mixture.The composition of a pure substance is the same throughout and doesnot vary from sample to sample. A pure substance can be an element ora compound. Mixtures, in contrast, contain more than one substance.They can vary in composition and properties from sample to sampleand sometimes from one part of a sample to another part of the samesample. All matter, whether it is a pure substance or a mixture, can beclassified in terms of uniformity of composition and properties of agiven sample. Figure 8 illustrates the overall classification of matter intoelements, compounds, and mixtures.

MixturesYou deal with mixtures every day. Nearly every object around you,including most things you eat and drink and even the air you breathe,is a mixture. A mixture is a blend of two or more kinds of matter, each

M A T T E R A N D C H A N G E 11 11

SECTION 2

DEMONSTRATIONHave students bring in matter thatrepresents heterogeneous and homo-geneous mixtures. Granite and milkare two common heterogeneous mixtures; different components ofthese mixtures have different physi-cal properties. A solution—such as a soft drink—or a metallic alloy areboth examples of a homogeneousmixture. The physical properties in ahomogeneous mixture are the sameregardless of how the mixture isdivided. Students might enjoy a study of frosted cupcakes (a hetero-geneous mixture) and soft drinks (a homogeneous mixture).

Visual StrategyHave students carefully

examine this chart. Have them usethe chart by asking them to classifyexamples of matter they havebrought to class. Ask students whereatoms and molecules would fit intothis scheme. You may also want pairsof students to brainstorm about other examples for each type of matter listed on the chart.

FIGURE 8

GENERAL

Matter

Can it be separated?

Pure substancesMixtures

Is thecomposition

uniform?

Can it be decom-posed by ordinarychemical means?

Homogeneous mixtures

(air, sugar in water,stainless steel)

Heterogeneousmixtures

(granite, wood,blood)

Compounds(water, sodium

chloride, sucrose)

Elements(gold, aluminum,oxygen, chlorine)

Yes No Yes No

Yes No

FIGURE 8 This classificationscheme for matter shows the relationships among mixtures,compounds, and elements.

of which retains its own identity and properties. The parts, or compo-nents, of a mixture are simply mixed together physically and can usuallybe separated. As a result, the properties of a mixture are a combinationof the properties of its components. Because mixtures can contain vari-ous amounts of different substances, a mixture’s composition must bespecified. This is often done in terms of percentage by mass or by vol-ume. For example, a mixture might be 5% sodium chloride and 95%water by mass.

Some mixtures are uniform in composition; that is, they are said to behomogeneous. They have the same proportion of components through-out. Homogeneous mixtures are also called solutions. A salt-water solu-tion is an example of such a mixture. Other mixtures are not uniformthroughout; that is, they are heterogeneous. For example, in a mixtureof clay and water, heavier clay particles concentrate near the bottom ofthe container.

Some mixtures can be separated by filtration or vaporized to sepa-rate the different components. Filtration can be used to separate a mix-ture of solid barium chromate from the other substances, as shown inthe beaker in Figure 9a. The yellow barium compound is trapped by thefilter paper, but the solution passes through. If the solid in a liquid-solidmixture settles to the bottom of the container, the liquid can be care-fully poured off (decanted).A centrifuge (Figure 9b) can be used to sep-arate some solid-liquid mixtures, such as those in blood. Anothertechnique, called paper chromatography, can be used to separate mix-tures of dyes or pigments because the different substances move at dif-ferent rates on the paper (Figure 9c).

C H A P T E R 112

SECTION 1

12

SECTION 2

Visual StrategyEither physical or chemi-

cal properties can be used to separatecomponents in a mixture. Ask studentswhether the examples in this figureare being separated based on theirphysical properties or their chemicalproperties. (All of the methods in thisfigure are using physical means toseparate mixtures.)

FIGURE 9

GENERAL

This may be a good time to reviewwith students the use of materialsafety data sheets (MSDS), the Merck Index, the CRC Handbook of Chemistry and Physics, Lange’sHandbook of Chemistry, or other reference materials you may haveavailable in the laboratory. It isimportant that students take respon-sibility for knowing the hazards ofchemicals in the classroom.

Teaching Tip

(c)(b)(a)

FIGURE 9 (a) Barium chromate can be separated from the solution in thebeaker using filtration. (b) A centrifuge can be used to separate certain solidcomponents. The centrifuge spins rapidly, which causes the solids to settle to thebottom of the test tube. (c) The components of an ink can be separated usingpaper chromatography.

Reading Skill Builder

VOCABULARY BUILDINGPoint out that the words homoge-neous and heterogeneous have thefollowing Greek prefixes: homo-meaning “same” and hetero-meaning “different.” Help themuse this information to developdefinitions, such as a homoge-neous mixture is one that appearsthe same throughout; a heteroge-neous mixture is one in which dif-ferences can be seen. Invitestudents to list word pairs, such ashomonym and heteronym, thathave these prefixes and look uptheir meanings.

✔

Pure SubstancesAny sample of a pure substance is homogeneous. A pure substance hasa fixed composition and differs from a mixture in the following ways:1. Every sample of a given pure substance has exactly the same charac-

teristic properties. All samples of a pure substance have the samecharacteristic physical and chemical properties. These properties areso specific that they can be used to identify the substance. In contrast,the properties of a mixture depend on the relative amounts of themixture’s components.

2. Every sample of a given pure substance has exactly the same compo-sition. Unlike mixtures, all samples of a pure substance have thesame makeup. For example, pure water is always 11.2% hydrogenand 88.8% oxygen by mass.

Pure substances are either compounds or elements.A compound canbe decomposed, or broken down, into two or more simpler compoundsor elements by a chemical change. Water is a compound made of hydro-gen and oxygen chemically bonded to form a single substance. Watercan be broken down into hydrogen and oxygen through a chemicalreaction called electrolysis, as shown in Figure 10a.

Sucrose is made of carbon, hydrogen, and oxygen. Sucrose breaksdown to form the other substances shown in Figure 10b. Under intenseheating, sucrose breaks down to produce carbon and water.

M A T T E R A N D C H A N G E 13 13

SECTION 2

Visual StrategyTwo very different reac-

tions are shown, but they are bothdecomposition reactions. Ask stu-dents how they know that a chemicalreaction has taken place in each photograph. Students should recog-nize that gases are produced duringthe electrolysis of water, while there is a color change in the oxidation of sugar.

Point out to students that hydrogen gas differs chemically from oxygen gas even though they lookthe same. Use this illustration to reinforce the definitions of atoms,molecules, and compounds. Studentsshould also note that two states ofmatter are represented in the elec-trolysis experiment.

FIGURE 10

GENERAL

(a) (b)

Hydrogenmolecule, H2

Watermolecule, H2O

Oxygen molecule, O2

FIGURE 10 (a) Passing an electric current through water causes the compound to breakdown into the elements hydrogenand oxygen, which differ in compo-sition from water. (b) When sucroseis heated, it caramelizes. When it is heated to a high enough tempera-ture, it breaks down completely into carbon and water.

Laboratory Chemicals and PurityThe chemicals in laboratories are generally treated as if they are pure.However, all chemicals have some impurities. Chemical grades of puri-ty are listed in Table 1. The purity ranking of the grades can vary whenagencies differ in their standards. For some chemicals, the USP grademay specify higher purity than the CP grade. For other chemicals, theopposite may be true. However, the primary standard reagent grade isalways purer than the technical grade for the same chemical. Chemistsneed to be aware of the kinds of impurities in a reagent because theseimpurities could affect the results of a reaction. For example, the chem-ical label shown in Figure 11 shows the impurities for that grade. Thechemical manufacturer must ensure that the standards set for thatreagent by the American Chemical Society are met.

C H A P T E R 114

SECTION 1

14

SECTION 2

Table 1 Establishing standards forchemical purity is the mission of theAmerican Chemical Society Committeeon Analytical Reagents. This groupcompiles the data and publishes thetests to determine if a manufacturedchemical meets specifications for purity.

Show students labels from stock-room reagents of different grades.Allow students to look through yourchemical supply catalog for the listingof reagent grades provided by that dis-tributor. Have them compare prices fordifferent grades of the same chemical.

Note that the names of grades in this table can vary by chemicalmanufacturer.

1. a. Physical properties can beobserved without changing the iden-tity of the substance; chemical prop-erties are observed by changing thesubstance into different substances.b. physical: color, size, boiling point,etc.; chemical: burning of coal, rust-ing of iron, etc.

2. a. physicalb. physicalc. chemical

3. You can compare the sample withthe characteristic properties of solids,liquids, and gases. If the sample hasa fixed shape, it is a solid. If its vol-ume changes to fill the volume of different containers, then it is a gas.If neither condition applies, the sample is a liquid.

4. Mixtures contain two or moresubstances blended together andgenerally can be separated. Pure substances have a fixed composition.

5. The compositions are identical.Sucrose is a compound, so it musthave a definite composition no mat-ter what its source is.

SECTION REVIEW

TABLE STRATEGY

FIGURE 11 The labeling on a reagent bottle lists the grade of the reagentand the percentages of impurities for that grade. What grade is this chemical?

1. a. What is the main difference between physicalproperties and chemical properties?

b. Give an example of each.

2. Classify each of the following as either a physicalchange or a chemical change.a. tearing a sheet of paperb. melting a piece of waxc. burning a log

3. How do you decide whether a sample of matter isa solid, liquid, or gas?

4. Contrast mixtures with pure substances.

Critical Thinking

5. ANALYZING INFORMATION Compare the composi-tion of sucrose purified from sugar cane with thecomposition of sucrose purified from sugar beets.Explain your answer.

SECTION REVIEW

Primary standard reagents

ACS (American ChemicalSociety–specifiedreagents)

USP (United StatesPharmacopoeiastandards)

CP (chemically pure;purer than technicalgrade)

NF (National Formularyspecifications)

FCC (Food ChemicalCode specifications)

Technical (industrialchemicals)

TABLE 1 Some Grades of Chemical Purity↑⏐⏐⏐⏐⏐⏐⏐⏐⏐⏐⏐⏐⏐⏐⏐⏐⏐⏐

Incr

easi

ng p

urity

M A T T E R A N D C H A N G E 15 15

SECTION 2

Secrets of the Cremona Violins

What are the most beautiful sound-ing of all violins? Most professionalswill pick the instruments created in Cremona, Italy, following theRenaissance. At that time, AntonioStradivari, the Guarneri family, andother designers created instrumentsof extraordinary sound that have yetto be matched. The craftsmen werenotoriously secretive about theirtechniques, but, based on 20 years ofresearch, Dr. Joseph Nagyvary, a pro-fessor of biochemistry at Texas A&MUniversity, thinks he has discoveredthe key to the violins’ sound hiddenin the chemistry of their materials.

According to Dr. Nagyvary,Stradivarius instruments are nearlyfree of the shrill, high-pitched noises produced by modern violins.Generally, violin makers attribute thisto the design of the instrument, butDr. Nagyvary traces it to a differentsource. In Stradivari’s day, wood forthe violins was transported by float-ing it down a river from the moun-tains to Venice, where it was storedin sea water. Dr. Nagyvary first theo-rized that the soaking process couldhave removed ingredients from thewood that made it inherently noisy.His experiments revealed thatmicrobes and minerals also permeat-ed the wood, making their own con-tribution to the mellow musicalsound. Attempting to reproduce theeffects of sea water, Dr. Nagyvarysoaks all his wood in a “secret”solution. One of his favorite ingredi-ents is a cherry-and-plum puree,

which contains an enzyme calledpectinase. The pectinase softens thewood, making it resonate morefreely.

“The other key factor in a violin’ssound,” says Dr. Nagyvary, “is thefinish, which is the filler and the var-nish covering the instrument. Mostmodern finishes are made from rub-bery materials, which limit the vibra-tions of the wood.” Modern analysishas revealed that the Cremona finishwas different: it was a brittle mineralmicrocomposite of a very sophisti-cated nature. According to historicalaccounts, all violin makers, includingStradivari, procured their varnishesfrom the local drugstore chemist,and they didn’t even know whatthey were using! Dr. Nagyvary andhis co-workers have identified mostof the key ingredients of theCremona finish.

Many new violins made from thetreated wood and replicated finishhave been made, and their soundhas been analyzed by modern signalanalyzers. These violins have beenfavorably compared with authenticStradivari violins.

A number of expert violinists havepraised the sound of Dr. Nagyvary’sinstruments, but some violin makersremain skeptical of the chemist’sclaims. They insist that it takes manyyears to reveal just how good a vio-lin is. In the meantime, almost every-one agrees that the art and scienceof violin making are still epitomizedby the instruments of Cremona.

1. According to Dr. Nagyvary, whatare two factors that are believedto have created the uniquesound of the Stradivari violins?

2. Use the library or Internetresources to find additionalinformation about the Cremonaviolin makers. Who were some ofthe other instrument makers dur-ing the time period in whichStradivari was alive? Were otherstringed instruments made bythese artisans? What are theestimated present-day values ofinstruments made during thisperiod in Cremona?

Questions

Dr. Nagyvary and his violin

Cross-DisciplinaryConnection

Class DiscussionThis story is a good example of howchemistry plays a fundamental role in other areas of study. Dr. Nagyvary’sstudy of biochemistry and interest in music led him to investigate theorigin and nature of the famousStradivarius sound.

Students may be surprised tolearn that modern technology hasnot been able to duplicate the effectcreated by the violin makers ofCremona.

This story is also a good exampleof the concept of reverse engineer-ing. Reverse engineering is anattempt to duplicate a productalready in existence.

Answers1. One factor was the soaking in seawater of the wood used to make theviolins and the introduction ofmicrobes and minerals into the wood.Another factor was the varnish usedto create the finish on the violins.

2. Student answers will vary. Otherimportant Cremona violin makerswere the members of the Amati andthe Guarneri families. Other instru-ments made by these instrument-makers include the viola, and thevioloncello. Present-day values ofthese instruments can reach up toseveral million dollars.

C H A P T E R 116

SECTION 1

16

SECTION 3

Lesson StarterThis might be a good time to makecopies of the blackline-master period-ic table for each student for use dur-ing class and tests. Use these periodictables or the large table in the roomto get students to practice locatingparticular elements on the table.

Table 2 Have students use the CRC Handbook of Chemistry andPhysics to find the language of origin(or meaning) for each of the oldernames listed in the table.

stibium—Latincuprum—Latinaurum—Latinferrum—Latinplumbum—Latinhydrargyrum—Latinkalium—Latinargentum—Latinnatrium—Latinstannum—Latinwolfram—German

Have students memorize the namesand symbols of the first 36 elements.Quiz them on sets of 12 each weekfor three weeks. This exercise willhelp students prepare for writing for-mulas and balancing equations laterin the text. They will also learn namesof other common elements with fre-quent use throughout the course.

Teaching Tip

TABLE STRATEGY

GENERALSECTION 3 Elements

A s you have read, elements are pure substances that cannot bedecomposed by chemical changes. The elements serve as the buildingblocks of matter. Each element has characteristic properties. The ele-ments are organized into groups based on similar chemical properties.This organization of elements is the periodic table, which is shown inFigure 12 on the next page.

Introduction to the Periodic Table

Each small square of the periodic table shows the symbol for the ele-ment and the atomic number. For example, the first square, at the upperleft, represents element 1, hydrogen, which has the symbol H. As youlook through the table, you will see many familiar elements, includingiron, sodium, neon, silver, copper, aluminum, sulfur, and lead. You canoften relate the symbols to the English names of the elements. Somesymbols are derived from the element’s older name, which was often inLatin. Still others come from German. For example, wolfram comesfrom the German name for tungsten. Table 2 lists some elements andtheir older names.

OBJECTIVES

Use a periodic table to nameelements, given their symbols.

Use a periodic table to writethe symbols of elements,given their names.

Describe the arrangement of the periodic table.

List the characteristics thatdistinguish metals, nonmetals,and metalloids.

Modern name Symbol Older name

Antimony Sb stibium

Copper Cu cuprum

Gold Au aurum

Iron Fe ferrum

Lead Pb plumbum

Mercury Hg hydrargyrum

Potassium K kalium

Silver Ag argentum

Sodium Na natrium

Tin Sn stannum

Tungsten W wolfram

TABLE 2 Elements with Symbols Based on OlderNames

✔

Reading Skill Builder

BRAINSTORMING Reviewwith students the definition of ele-ment. Have them brainstorm a list of substances that they think are ele-ments. Have them use Section 3 to confirm whether each of the sub-stances on their list is an elementand to devise a classification systemfor elements.

www.scilinks.orgTopic: Periodic TableCode: HC61125

The vertical columns of the periodic table are called groups, orfamilies. Notice that they are numbered from 1 to 18 from left to right.Each group contains elements with similar chemical properties. Forexample, the elements in Group 2 are beryllium, magnesium, calcium,strontium, barium, and radium. All of these elements are reactive met-als with similar abilities to bond to other kinds of atoms. The two majorcategories of elements are metals and nonmetals. Metalloids have prop-erties intermediate between those of metals and nonmetals.

The horizontal rows of elements in the periodic table are calledperiods. Physical and chemical properties change somewhat regularlyacross a period. Elements that are close to each other in the same period tend to be more similar than elements that are farther apart.For example, in Period 2, the elements lithium and beryllium, in Groups 1 and 2, respectively, are somewhat similar in properties. However,their properties are very different from the properties of fluorine, thePeriod-2 element in Group 17.

The two sets of elements placed below the periodic table make upwhat are called the lanthanide series and the actinide series. Thesemetallic elements fit into the table just after elements 57 and 89. Theyare placed below the table to keep the table from being too wide.

There is a section in the back of this book called the ElementsHandbook which covers some elements in greater detail. You will useinformation from the handbook to complete the questions in the Usingthe Handbook sections in the chapter reviews.

M A T T E R A N D C H A N G E 17 17

SECTION 3

Assign each student a different element to research, or have an “element of the day,” where a particular element, its properties,and its position on the periodic table are highlighted.

Visual StrategyThe periodic table will

be formally introduced in Chapter 5.This table is included here to givestudents a context for the discussionof elements.

Be sure students recognize the difference between the verticalcolumns (groups, or families) and thehorizontal rows (periods) on the peri-odic table. Point out that the mem-bers of the same group have verysimilar chemical properties. Tell stu-dents that the elements at the baseof the table are placed there for con-venience. Placing them in the correctsequence makes the table very wide.

Use the periodic table to point out that there are many more metalsthan there are nonmetals. Summarizethe differences between the propertiesof metals and those of nonmetals.

FIGURE 12

GENERAL

Teaching Tip

Periodic Table

1

H

3

Li11

Na19

K37

Rb55

Cs87

Fr

4

Be12

Mg20

Ca38

Sr56

Ba88

Ra

5

B13

Al31

Ga49

In81

Tl

6

C14

Si32

Ge50

Sn82

Pb

7

N15

P33

As51

Sb83

Bi

8

O16

S34

Se52

Te84

Po

9

F17

Cl35

Br53

I85

At

21

Sc39

Y57

La89

Ac

22

Ti40

Zr72

Hf104

Rf

23

V41

Nb73

Ta105

Db

24

Cr42

Mo74

W106

Sg

25

Mn43

Tc75

Re107

Bh

26

Fe44

Ru76

Os108

Hs

27

Co45

Rh77

Ir109

Mt

28

Ni46

Pd78

Pt110

Ds

29

Cu47

Ag79

Au111

Rg

30

Zn48

Cd80

Hg

Group 1

2

He10

Ne18

Ar36

Kr54

Xe86

Rn

66

Dy98

Cf

67

Ho99

Es

68

Er100

Fm

69

Tm101

Md

70

Yb102

No

58

Ce90

Th

59

Pr91

Pa

60

Nd92

U

61

Pm93

Np

62

Sm94

Pu

63

Eu95

Am

64

Gd96

Cm

65

Tb97

Bk103

Lr

Group 18

Group 2

Group 3 Group 4 Group 5 Group 6 Group 7 Group 8 Group 9 Group 10 Group 11 Group 12

Group 13 Group 14 Group 15 Group 16 Group 17Metals

Metalloids

Nonmetals

71

Lu

FIGURE 12 The periodic table ofelements. The names of the elementscan be found on Table A-6 in the appendix.

✔

www.scilinks.orgTopic: Element NamesCode: HC60495

go.hrw.com

Topic: Periodic TableCode: Holt PeriodicVisit this site for updatesto the periodic table.

Types of Elements

The periodic table is broadly divided into two main sections: metalsand nonmetals. As you can see in Figure 12, the metals are at the leftand in the center of the table. The nonmetals are toward the right.Some elements, such as boron and silicon, show characteristics of bothmetals and nonmetals.

MetalsSome of the properties of metals may be familiar to you. For example,you can recognize metals by their shininess, or metallic luster. Perhapsthe most important characteristic property of metals is the ease withwhich they conduct electricity and transfer energy. Thus, a metal is anelement that is a good electrical conductor and a good heat conductor.

At room temperature, most metals are solids. Most metals also havethe property of malleability, that is, they can be hammered or rolled intothin sheets. Metals also tend to be ductile, which means that they can bedrawn into a fine wire. Metals behave this way because they have hightensile strength, the ability to resist breaking when pulled.

Although all metals conduct electricity well, metals also have verydiverse properties. Mercury is a liquid at room temperature, whereastungsten has the highest melting point of any element. The metals inGroup 1 are so soft that they can be cut with a knife, yet others, such aschromium, are very hard. Some metals, such as manganese and bismuth,are very brittle, yet others, such as iron and copper, are very malleableand ductile. Most metals have a silvery or grayish white luster. Twoexceptions are gold and copper, which are yellow and reddish brown,respectively. Figure 13 shows examples of metals.

C H A P T E R 118

SECTION 1

18

SECTION 3

Visual StrategyUse this figure to show

how the properties of metals oftendetermine how they are used, andexplain that this is an example of thelink between science and technology.Have students brainstorm aboutother uses of metals that depend ontheir physical or chemical properties.

CommonMisconceptionStudents often think that all “metals”are the same. Because they are familiar with rusting as a corrosiveproperty of iron, they may think thatall metals rust. Make sure theyunderstand that the definition andcharacteristics of metals are based on their functional properties and not just their appearance.

FIGURE 13

GENERAL

(a) (b) (c)

FIGURE 13 (a) Gold has a lowreactivity, which is why it may befound in nature in relatively pureform. (b) Copper is used in wiringbecause it is ductile and conductselectrical energy (c) Aluminum ismalleable. It can be rolled into foilthat is used for wrapping food.

SuperconductorsAny metal becomes a better conductorof electrical energy as its temperaturedecreases. In 1911, scientists discoveredthat when mercury is cooled to about −269°C, it loses all resistance andbecomes a superconductor. Scientistshave long tried to find a material thatwould superconduct at temperaturesabove −196°C, the boiling point of liquid nitrogen. In 1987, scientists dis-covered ceramic materials that becamesuperconductors when cooled only to −183°C. These “high-temperature”superconductors are used to build verypowerful electromagnets. Ceramic elec-tromagnets are used in medical mag-netic resonance imaging (MRI) machinesand in high-efficiency electric motorsand generators.

Copper: A Typical MetalCopper has a characteristic reddish color and a metallic luster. It isfound naturally in minerals such as chalcopyrite and malachite. Purecopper melts at 1083°C and boils at 2567°C. It can be readily drawn intofine wire, pressed into thin sheets, and formed into tubing. Copper con-ducts electricity with little loss of energy.

Copper remains unchanged in pure, dry air at room temperature.When heated, it reacts with oxygen in air. It also reacts with sulfur andthe elements in Group 17 of the periodic table. The green coating on apiece of weathered copper comes from the reaction of copper with oxy-gen, carbon dioxide, and sulfur compounds. Copper is an essential min-eral in the human diet.

NonmetalsMany nonmetals are gases at room temperature. These include nitro-gen, oxygen, fluorine, and chlorine. One nonmetal, bromine, is a liquid.The solid nonmetals include carbon, phosphorus, selenium, sulfur, andiodine. These solids tend to be brittle rather than malleable and ductile.Some nonmetals are illustrated in Figure 14.

Low conductivity can be used to define nonmetals. A nonmetal is anelement that is a poor conductor of heat and electricity. If you look atFigure 12, you will see that there are fewer nonmetals than metals.

Phosphorus: A Typical NonmetalPhosphorus is one of five solid nonmetals. Pure phosphorus is known intwo common forms. Red phosphorus is a dark red powder that melts at597°C. White phosphorus is a waxy solid that melts at 44°C. Because itignites in air at room temperature, white phosphorus is stored under water.

Phosphorus is too reactive to exist in pure form in nature. It is pre-sent in huge quantities in phosphate rock, where it is combined withoxygen and calcium. All living things contain phosphorus.

MetalloidsAs you look from left to right on the periodic table, you can see that themetalloids are found between the metals and the nonmetals. A metalloid

M A T T E R A N D C H A N G E 19 19

SECTION 3

The properties of the elements arediscussed in greater detail in theElements Handbook in the back ofthis book. Students can look over thetransition-metal section to find outmore about copper. Group 15 coversphosphorus, and Group 14 includes a section on the properties of semiconductors.

USING THE HANDBOOK

(a) (b) (c) (d)

FIGURE 14 Various nonmetallicelements: (a) carbon, (b) sulfur,(c) phosphorus, and (d) iodine

FIGURE 15 Selenium is a non-metal, though it looks metallic.

is an element that has some characteristics of metals and some character-istics of nonmetals. All metalloids are solids at room temperature. Theytend to be less malleable than metals but not as brittle as nonmetals.Some metalloids, such as antimony, have a somewhat metallic luster.

Metalloids tend to be semiconductors of electricity. That is, their abil-ity to conduct electricity is intermediate between that of metals and thatof nonmetals. Metalloids are used in the solid state circuitry found indesktop computers, digital watches, televisions, and radios.

Noble GasesThe elements in Group 18 of the periodic table are the noble gases.These elements are generally unreactive. In fact, it was not until 1962 that the first noble gas compound, xenon hexafluoroplatinate, was pre-pared. Low reactivity makes the noble gases very different from the otherfamilies of elements. Group 18 elements are gases at room temperature.Neon, argon, krypton, and xenon are all used in lighting. Helium is usedin party balloons and weather balloons because it is less dense than air.

C H A P T E R 120

SECTION 1

20

SECTION 3

1. oxygen, sulfur, copper, silver

2. Fe, N, Ca, Hg

3. Elements in a group have similarchemical properties and will there-fore undergo the same types of reactions.

4. Metals tend to be shiny, malleable,ductile, and good conductors of heatand electricity. Nonmetals tend to bebrittle and poor conductors of heatand electricity. Metalloids tend to beintermediate in properties betweenmetals and nonmetals and are there-fore semiconductors of electricity.

5. The element is relatively unreac-tive. If it were reactive, it would havecombined with other elements, suchas oxygen in the air, to form com-pounds. If it is shiny, malleable, andductile, a good conductor of electricalenergy, and can transfer energy asheat well, it is probably a metal. If itis a nonconductor, it is probably anonmetal.

SECTION REVIEW

1. Use the periodic table to write the names for thefollowing elements: O, S, Cu, Ag.

2. Use the periodic table to write the symbols for thefollowing elements: iron, nitrogen, calcium, mercury.

3. Which elements are most likely to undergo thesame kinds of reactions, those in a group or thosein a period?

4. Describe the main differences between metals,nonmetals, and metalloids.

Critical Thinking

5. INFERRING CONCLUSIONS If you find an elementin nature in its pure elemental state, what can youinfer about the element’s chemical reactivity? Howcan you tell whether that element is a metal or anonmetal?

SECTION REVIEW

FIGURE 16 Some noble gases areused to make lighted signs of variouscolors.

M A T T E R A N D C H A N G E 21 21

1. the study of the composition,structure, and properties of matter and the changes thatmatter undergoes

2. organic chemistry

3. a substance that has a definitecomposition

4. a. physicalb. organicc. biochemical

5. a. applied researchb. basic researchc. technological development

6. a. a measure of an amount ofmatterb. a measure of an amount ofspace

7. The proportions of elements in apure compound are fixed.

8. a. A property is any characteris-tic of a substance or material.b. Properties are useful for clas-sifying unknown materials asmembers of known groups orsubgroups of substances or foridentifying substances directly.

9. Extensive properties depend onthe amount of matter that is pre-sent. Intensive properties do not.

10. a. a property that describes asubstance’s ability to undergochanges that alter its identityb. Examples include the ability ofcoal to burn and the ability ofiron to rust.

REVIEW ANSWERS

CHAPTER REVIEW

C H A P T E R H I G H L I G H T S

• All matter has mass and takes up space. Mass is one measureof the amount of matter.

• Chemical properties refer to a substance’s ability to undergochanges that alter its composition and identity.

• An element is composed of one kind of atom. Compounds aremade from two or more elements in fixed proportions.

• All substances have characteristic properties that enable chemiststo tell the substances apart and to separate the substances.

• Physical changes do not involve changes in identity of a substance.

• The three major states of matter are solid, liquid, and gas.Changes of state, such as melting and boiling, are physicalchanges.

• In a chemical change—or a chemical reaction—the identity ofthe substance changes.

• Energy changes accompany physical and chemical changes.Energy may be released or absorbed, but it is neither creatednor destroyed.

• Matter can be classified into mixtures and pure substances.

• Chemistry is the study of the composition, structure, and proper-ties of matter and the changes that matter undergoes.

• A chemical is any substance that has a definite composition or isused or produced in a chemical process.

• Basic research is carried out for the sake of increasing knowl-edge. Applied research is carried out to solve practical problems.Technological development involves the use of existing knowl-edge to make life easier or more convenient.

chemistrychemical

massmatteratomelementcompoundextensive propertyintensive propertyphysical propertyphysical change

change of statesolidliquidgasplasmachemical propertychemical changechemical reactionreactant

Vocabulary

Vocabulary

Chemistry Is a Physical Science

Matter and Its Properties

• Each element has a unique symbol. The periodic table shows theelements organized by their chemical properties. Columns on thetable represent groups or families of elements that have similarchemical properties. Properties vary across the rows, or periods.

• The elements can be classified as metals, nonmetals, metalloids,and noble gases. These classes occupy different areas of theperiodic table. Metals tend to be shiny, malleable, and ductileand tend to be good conductors. Nonmetals tend to be brittleand tend to be poor conductors.

• Metalloids are intermediate in properties between metals andnonmetals, and they tend to be semiconductors of electricity.The noble gases are generally unreactive elements.

groupfamilyperiodmetalnonmetalmetalloid

Vocabulary

Elements

22

C H A P T E R R E V I E W11. A physical change does not

involve a change in a substance’sidentity; a chemical change con-verts one substance into othersubstances.

12. a. A solid has a definite volumeand a definite shape, whereas aliquid has a definite volume buttakes the shape of its container.b. A gas has neither a definite volume nor a definite shape, buta liquid has a definite volume.c. Liquids and gases take theshape of the container.d. A plasma is a high-temperature physical state ofmatter in which atoms lose theirelectrons.

13. a change of a substance fromone state of matter to another

14. Reactants are potassium andwater; products are potassiumhydroxide and hydrogen.

15. It must be a mixture.

16. Elements with similar propertiesare placed in the same verticalcolumns. Properties vary from leftto right along the rows.

17. Metals (at left and center oftable) are good heat conductorsand electrical conductors.Nonmetals (at right of table)tend to be poor conductors.Metalloids (between metals andnonmetals) are intermediate inproperties and are semiconduc-tors. Noble gases (at extremeright) are generally unreactive.

18. X is probably a nonmetal on theright side of the table. Z is a metalon the left side or in the middle ofthe table.

19. a. potassium, metalb. silver, metalc. silicon, metalloidd. sodium, metale. mercury, metalf. helium, noble gas

C H A P T E R 122

Chemistry Is a Physical ScienceSECTION 1 REVIEW

1. What is chemistry? 2. What branch of chemistry is most concerned

with the study of carbon compounds?3. What is meant by the word chemical, as used by

scientists?4. In which of the six branches of chemistry would

a scientist be working if he or she were doingthe following:a. investigating energy relationships for various

reactionsb. comparing properties of alcohols with those

of sugarsc. studying reactions that occur during the

digestion of food5. Identify each of the following as an example of

either basic research, applied research, or tech-nological development:a. A new type of refrigerant that is less damag-

ing to the environment is developed.b. A new element is synthesized in a particle

accelerator.c. A computer chip is redesigned to increase

the speed of the computer.

Matter and Its PropertiesSECTION 2 REVIEW

6. a. What is mass?b. What is volume?

7. How does the composition of a pure compounddiffer from that of a mixture?

8. a. Define property.b. How are properties useful in classifying

materials?9. What is the difference between extensive prop-

erties and intensive properties? 10. a. Define chemical property.

b. List two examples of chemical properties.11. Distinguish between a physical change and a

chemical change.

12. a. How does a solid differ from a liquid?b. How does a liquid differ from a gas?c. How is a liquid similar to a gas?d. What is a plasma?

13. What is meant by a change in state?14. Identify the reactants and products in the fol-

lowing reaction:potassium + water ⎯→

potassium hydroxide + hydrogen15. Suppose different parts of a sample material

have different compositions. What can you con-clude about the material?

ElementsSECTION 3 REVIEW

16. What is the significance of the vertical columnsof the periodic table? What is the significance ofthe horizontal rows?

17. Compare the physical properties of metals, non-metals, metalloids, and noble gases, and describewhere in the periodic table each of these kindsof elements is located.

18. Suppose element X is a poor conductor of elec-tricity and breaks when hit with a hammer.Element Z is a good conductor of electricityand heat. In what area of the periodic tabledoes each element most likely belong?

19. Use the periodic table to write the names of theelements that have the following symbols, andidentify each as a metal, nonmetal, metalloid, ornoble gas.a. K c. Si e. Hgb. Ag d. Na f. He

20. An unknown element is shiny and is found tobe a good conductor of electricity. What otherproperties would you predict for it?

21. Use the periodic table to identify the groupnumbers and period numbers of the followingelements:a. carbon, C c. chromium, Crb. argon, Ar d. barium, Ba

CHAPTER REVIEW

CHAPTER REVIEW

M A T T E R A N D C H A N G E 23 23

20. may be malleable and ductileand a good conductor of energyas heat

21. a. 14, 2 c. 6, 4b. 18, 3 d. 2, 6

22. a. a property that can be observedor measured without changing theidentity of the substanceb. Examples include color, odor,length, size, and melting point.

23. Compounds can be separatedinto elements by chemical means.Elements cannot be separatedinto simpler substances by chemi-cal means.

24. a. physical, because the woodremains woodb. chemical, because the milkchanges composition, as signifiedby the change in flavorc. physical, because the butterremains butter

25. A molecule is the smallest unit of asubstance that keeps all of thephysical and chemical properties ofthat substance. An element is com-posed of molecules that can besingle atoms or can be more thanone of the same kind of atom. Acompound is composed of two ormore elements, so a molecule of acompound is made up of two ormore different kinds of atoms.

26. Answers will vary. Physical prop-erties include shape, texture,state of matter, and taste.Chemical properties could not beobserved unless a chemicalchange was attempted.

Answers are continued on page 27A.

CHAPTER REVIEW

22. a. Define physical property.b. List two examples of physical properties.

23. How can you tell the difference between an ele-ment and a compound?

24. Identify each of the following as either a physi-cal change or a chemical change. Explain youranswers.a. A piece of wood is sawed in half.b. Milk turns sour.c. Melted butter solidifies in the refrigerator.

25. Write a brief paragraph that shows that youunderstand the following terms and the rela-tionships between them: atom, molecule, com-pound, and element.

26. Pick an object you can see right now. List threeof the object’s physical properties that you canobserve. Can you also observe a chemical prop-erty of the object? Explain your answer.

27. Interpreting Concepts One way to makelemonade is to start by combining lemon juiceand water. To make the lemonade taste betteryou could add some sugar. Is your lemonade-sugar combination classified as a compound ora mixture? Explain your answer.

28. Analyzing Results A pure white, solid materi-al that looks like table salt releases gas whenheated under certain conditions. There is nochange in the appearance of the solid, but thereactivity of the material changes.a. Did a chemical or physical change occur?

How do you know?b. Was the original material an element or a

compound?

29. Interpreting Conceptsa. Is breaking an egg an example of a physical

or chemical change? Explain your answer.b. Is cooking an egg an example of a physical or

chemical change? Explain your answer.

CRITICAL THINKING

MIXED REVIEW

30. Review the information on trace elements inthe Elements Handbook in the back of this text.a. What are the functions of trace elements in

the body?b. What transition metal plays an important role

in oxygen transport throughout the body?c. What two Group 1 elements are part of the

electrolyte balance in the body?

31. Research any current technological product ofyour choosing. Find out about its manufactureand uses. Also find out about the basic researchand applied research that made its developmentpossible.

32. Investigate current and proposed technologicalapplications of superconductors. Find out whichof these applications have been successfullytested or are already in use.

33. During a 1 h period, make a list of all thechanges that you see around you and thatinvolve matter. Note whether each changeseems to be a physical change or a chemicalchange. Give reasons for your answers.

34. Make a concept map using at least 15 terms fromthe vocabulary lists. An introduction to conceptmapping is found in Appendix B of this book.

ALTERNATIVE ASSESSMENT

RESEARCH & WRITING

USING THE HANDBOOK

Graphing CalculatorGraphing Tabular Data

Go to go.hrw.com for a graphing calculatorexercise that asks you to graph temperaturevs. time for a chemical reaction.

Keyword : HC6MTXX

24

1. a. 5 significant figuresb. 4 significant figures

2. a. 4.21 g/cm3

b. 16.5 g

A calculator gives results with asmany digits as are available in the cal-culator display. However, a calculationcannot increase the certainty of themeasurements used in the calculation.So, tell your students to follow therules listed when they use a calculator.

Remind students that in order toavoid accumulation of large roundingerrors, they should not round afterindividual steps. Tell students that theyshould wait until they have finishedthe entire calculation.

Teaching Tip

ANSWERS

CHAPTER REVIEW

Problem Solving S-

SAMPLE 1 SAMPLE 2

How many significant figures does 0.007 09 kghave?

All nonzero digits are significant. The zerobetween the 7 and 9 is significant.The zeros to theleft of the decimal point are not significant. Thequantity 0.007 09 kg has 3 significant figures.

Divide 79.7 g by 0.89 cm3.The quantity 79.7 g has 3 significant figures, but

0.89 cm3 has only 2 significant figures. So, theproduct 8.955 056 18 g/cm3 must be rounded to 2significant figures. The rounded quantity is9.0 g/cm3.

C H A P T E R 124

The certainty of a measurement is expressed by significant figures. Significant figures ina measurement consist of all the digits known with certainty plus one final digit. Lookat the reading below, which was obtained when measuring the mass of a paper clip.

mass of paperclip

Balance reading = 2.37 g

You know with certainty that the paper clip has a mass of 2.3 g. You can also estimatean additional mass of 0.07 g for a total of 2.37 g. Each of the three digits in 2.37 g issignificant because it is either certain or estimated.

2 3

• Every nonzero digit is significant. Zeros between nonzero digits are significant.

• Zeros appearing in front of the first nonzero digit are not significant.

• If there is no decimal point, zeros that follow the last nonzero digit are not significant.

• If there is a decimal point, zeros that follow the last nonzero digit are significant.

• When measurements are added or subtracted, the result must be rounded to thesame number of decimal places that the quantity with the fewest decimal places has.

• When measurements are multiplied or divided, the result must be rounded to thesame number of significant figures that the quantity with the smallest number ofsignificant figures has.

✔

1. Determine the number of significant figures.

a. 42.200 Lb. 0.055 00 mol

2. Perform the following calculations and apply therules for significant figures.

a. 56.05 g ÷ 13.3 cm3 b. 1.057 g + 3.02 g + 12.4 g

PRACTICE PROBLEMS

Math Tutor SIGNIFICANT FIGURES

M A T T E R A N D C H A N G E 25 25

To give students practice under morerealistic testing conditions, give them60 minutes to answer all of the ques-tions in this Standardized TestPreparation.

1. C

2. C

3. D

4. B

5. C

6. C

7. C

8. A

9. B

10. Answers may vary.

11. Observations C and G are chemi-cal properties; the others arephysical properties.

12. In a chemical change, one ormore substances are convertedinto different substances. A phys-ical change does not involve achange in the identity of the sub-stance or substances present.Student examples of each kind ofchange will vary.

13. metals: shiny; good conductors ofheat; good conductors of electric-ity; malleable or ductile; most aresolids at room temperature

nonmetals: poor conductors ofheat; poor conductors of electric-ity; many are gases at room tem-perature; those that are solidsare brittle rather than malleableor ductile

metalloids: properties intermedi-ate between those of metals andnonmetals; less malleable thanmetals but not as brittle as solidnonmetals; most are semiconduc-tors of electricity

TEST ANSWERS

CHAPTER REVIEW

Answer the following items on a separate piece of paper.

MULTIPLE CHOICE

1.Magnesium reacts with hydrochloric acid toproduce magnesium chloride and hydrogen gas.The reactants in this reaction areA. magnesium and magnesium chloride.B. hydrochloric acid and hydrogen gas.C. magnesium and hydrochloric acid.D. magnesium chloride and hydrogen gas.

2.Matter that has a definite shape and a definitevolume isA. a liquid. C. a solid.B. an element. D. a gas.

3.We know that air is a mixture and not a compound becauseA. it can be heated to a higher temperature.B. it can be compressed to a smaller volume.C. it is colorless.D. its composition can vary.

4.Matter can be defined as anything thatA. has weight.B. has mass and volume.C. is uniform throughout.D. exhibits both chemical and physical properties.

5.Which of the following is best classified as ahomogeneous mixture?A. pizza C. hot teaB. blood D. copper wire

6.A compound differs from a mixture in that acompoundA. contains only one element.B. varies in chemical composition depending

on the sample size.C. has a definite composition by mass of the

elements that the compound contains.D. can be classified as either heterogeneous or

homogeneous.7.Which of the following is not a physical state

of matter?A. solid C. elementB. gas D. liquid

8.Three of the following must contain two ormore kinds of atoms. Which one does notcontain two or more kinds of atoms?A. elementB. compoundC. homogeneous mixtureD. heterogeneous mixture

9.Which of the following symbols does not matchthe element name given?A. Al, aluminumB. Co, copperC. K, potassiumD. P, phosphorus

SHORT ANSWER

10.Give three examples of mixtures, and tellwhether each one is homogeneous or hetero-geneous. Give three examples of compounds.

11.In trying to identify a sample of a pure sub-stance, we observe the following properties.Tell whether each one is a chemical property or a physical property.A. Its mass is 124.3 g.B. It is a shiny solid at room temperature.C. It is easily etched by nitric acid.D. It melts when heated to 670°C.E. It is 31.7 centimeters long.F. It is a good heat conductor.G. It burns in air.H. It is a good conductor of electrical energy.

EXTENDED RESPONSE

12.Describe the difference between a chemicalchange and a physical change. Give one example of each kind of change.

13.Describe general properties of metals,nonmetals, and metalloids.

Remember that if you can elimi-nate two of the four answer choices, your chances ofchoosing the correct answer choice will double.

Standardized Test Prep

C H A P T E R 12626

RECOMMENDED TIME1 hour

RATINGSTEACHER PREPARATION 2STUDENT SETUP 3CONCEPT LEVEL 3CLEANUP 2

MATERIALS(for each lab group)• 20 g samples of salt, sand, iron

filings, poppy seeds, and the mixture of these four materials

• Petri dish• tape dispenser with transparent

tape

ADDITIONAL EQUIPMENT(shared by the class)• 500 mL distilled water• cotton balls, 15• filter funnels, 15• filter papers, 50• forceps, 10• magnets, 15• paper clips, 10• pipets, 30• plastic forks, 10• plastic spoons, 10• plastic straws, 10• roll of aluminum foil• roll of paper towels• roll of tissue paper • rubber stoppers, 15• test tubes, 50 (13 × 100)• test-tube rack• wooden splints, 10

CHAPTER LAB

Mixture Separation

CHAPTER LABSEE PRE-LAB

EXTRACTION AND FILTRATION

BACKGROUNDThe ability to separate and recover pure substancesfrom mixtures is extremely important in scientificresearch and industry. Chemists need to work withpure substances, but naturally occurring materials areseldom pure. Often, differences in the physical prop-erties of the components in a mixture provide themeans for separating them. In this experiment, youwill have an opportunity to design, develop, andimplement your own procedure for separating a mix-ture. The mixture you will work with contains salt,sand, iron filings, and poppy seeds. All four sub-stances are in dry, granular form.

SAFETY

For review of safety, please see Safety in theChemistry Laboratory in the front of your book.

PREPARATION1. Your task will be to plan and carry out the sepa-

ration of a mixture. Before you can plan yourexperiment, you will need to investigate theproperties of each component in the mixture.The properties will be used to design your mix-ture separation. Copy the data table on the following page in your lab notebook, and use it to record your observations.

PROCEDURE1. Obtain separate samples of each of the four

mixture components from your teacher. Use theequipment you have available to make observa-tions of the components and determine theirproperties. You will need to run several tests witheach substance, so don’t use all of your sample

OBJECTIVES

• Observe the chemical and physical proper-ties of a mixture.

• Relate knowledge of chemical and physicalproperties to the task of purifying themixture.

• Analyze the success of methods of purifyingthe mixture.

MATERIALS

• aluminum foil

• cotton balls

• distilled water

• filter funnels

• filter paper

• forceps

• magnet

• paper clips

• paper towels

• Petri dish

• pipets

• plastic forks

• plastic spoons

• plastic straws

• rubber stoppers

• sample of mixtureand components(sand, iron filings,salt, poppy seeds)

• test tubes and rack

• tissue paper

• transparent tape

• wooden splints

TEACHER‘S NOTES

C H A P T E R 12626

EASY HARD

1 2 3 4

INQUIRYL A B?

27 27

13-1 TEACHER‘S NOTES

on the first test. Look for things like whether the substance is magnetic, whether it dissolves,or whether it floats. Record your observations in your data table.

2. Make a plan for what you will do to separate amixture that includes the four components fromstep 1. Review your plan with your teacher.

3. Obtain a sample of the mixture from yourteacher. Using the equipment you have avail-able, run the procedure you have developed.

CLEANUP AND DISPOSAL4. Clean your lab station. Clean all equip-

ment, and return it to its proper place.Dispose of chemicals and solutions inthe containers designated by your teacher. Donot pour any chemicals down the drain or throwanything in the trash unless your teacher directsyou to do so. Wash your hands thoroughly afterall work is finished and before you leave the lab.

ANALYSIS AND INTERPRETATION1. Evaluating Methods: On a scale of 1 to 10, how

successful were you in separating and recoveringeach of the four components: sand, salt, iron filings, and poppy seeds? Consider 1 to be thebest and 10 to be the worst. Justify your ratingsbased on your observations.

CONCLUSIONS1. Evaluating Methods: How did you decide on

the order of your procedural steps? Would anyorder have worked?

SOLUTION/MATERIALSPREPARATION1. Mix about 5 g of each of the fourcomponents in a large resealable(zippered) plastic bag for each labgroup. Give 20 g samples of each ofthe four components to each labgroup for step 1 of the procedure.They may be dispensed in stopperedtest tubes to the students.2. You may wish to modify the list of additional equipment, but the listshould remain extensive enough toprovide students with a wide rangeof choices.

REQUIRED PRECAUTIONS• Safety goggles and a lab apron

must be worn at all times.• Read all safety precautions, and

discuss them with your students.• In case of a spill, use a damp cloth

or paper towels to mop up the spill.Then rinse the cloth in runningwater at the sink, wring it out thoroughly, and put it in the trash.

PRE-LAB DISCUSSIONThis experiment is intended to be anopen-ended, self-designed activity inwhich students are presented onlywith the problem and a list of equip-ment available to them. They arerequired to develop and test theirown procedures. To shorten the timenecessary, allow 15–20 min of classor lab time for students to plan theirexperiments, or assign the develop-ment of a written plan as homeworkprior to the lab. Some of the separa-tion procedures (especially thoseinvolving evaporation of water) mayrequire equipment such as Petri dish-es to stand overnight.

It is best to avoid giving directanswers to any student’s questions.Encourage members of each labteam to work cooperatively as theydevelop their procedural plan.

Continued on page 27A

DATA TABLE

Properties Sand Iron filings Salt Poppy seeds

Dissolves

Floats

Magnetic

Other

2. Designing Experiments: If you could do the lab over again, what would you do differently?Be specific.

3. Designing Experiments: Name two materials or tools that weren’t available that might havemade your separation easier.

4. Applying Ideas: For each of the four compo-nents, describe a specific physical property thatenabled you to separate the component fromthe rest of the mixture.

EXTENSIONS1. Evaluating Methods: What methods could be

used to determine the purity of each of yourrecovered components?

2. Designing Experiments: How could you sepa-rate each of the following two-part mixtures?a. aluminum filings and iron filingsb. sand and gravelc. sand and finely ground polystyrene foamd. salt and sugare. alcohol and waterf. nitrogen and oxygen

3. Designing Experiments: One of the componentsof the mixture in this experiment is in a differentphysical state at the completion of this experi-ment that it was at the start. Which one? Howwould you convert that component back to itsoriginal state?

TEACHER‘S NOTES

M A T T E R A N D C H A N G E 27 27

Continued from page 2327. a mixture; The lemon juice, water, and sugar are not

chemically combined.

28. a. chemical; The physical appearance does notchange, but the process of heating the materialproduces a gas and changes its reactivity.b. compound; The original solid material is observedto break down and form a gas and a different solid.A compound could be broken down by heating. Anelement cannot be broken down by heating.

29. a. Breaking an egg is a physical change because thechemical nature of the egg has not been affected.b. Cooking an egg is a chemical change becausethe chemical properties of the egg are changed bythe transfer of energy as heat.

30. a. Trace elements are minerals that are essentialfor normal body function.b. ironc. sodium, potassium

31. Student reports will vary. You can use the scoringrubric on the One-Stop Planner CD-ROM to set cri-teria for evaluating student reports.

32. Student reports will vary. Superconductors are cur-rently used in magnetic resonance imaging (MRI),MAGLEV transportation systems, and electrical powerproduction. Scientists are researching the use ofsuperconductors to make computers process informa-tion at increasingly faster speeds. Superconductingradiation detectors and superconducting light detec-tors are also being developed for space researchapplications.

33. Students should be able to correctly categorize mostof the changes on the basis of whether new sub-stances are being formed (chemical changes) or arenot being formed (physical changes).

34. See the criteria for evaluating concept maps on theOne-Stop Planner CD-ROM.

Continued from page 27If you wish, the experiment can be made more

quantitative by emphasizing concepts such as percentcomposition of a mixture and percent recovery. Studentscan measure the mass of the original sample (after therepresentative sample has been set aside) and the massof each of the recovered components (before the repre-

CHAPTER LAB

REVIEW ANSWERS

27A

CONTINUATION OF ANSWERS AND TEACHER’S NOTES

CONTINUATION OF ANSWERS AND TEACHER’S NOTES

sentative sample has been placed in the appropriatewell). These data will allow the class to compare theeffectiveness of different techniques in providing highyields of recovered substances.

DISPOSALPut out five disposal containers, one each for the iron, poppy seeds, sand, salt, and unseparated mixture.Even if students have not done a good job of separa-tion, the materials may be reused the next time the lab is performed because you will be mixing the samesubstances again.

ANALYSIS AND INTERPRETATION—ANSWERS1. Students’ answers will vary. They may justify theirestimations of success by the presence (or lack) ofimpurities in the separated components and by theamount recovered.

CONCLUSIONS—ANSWERS1. Students’ answers will vary.2. Students’ answers will vary but should be logicaland demonstrate students’ understanding of the physi-cal properties of each substance.3. Students’ answers will vary. Note the suggestionsstudents make and consider making those items avail-able the next time you use this experiment.4. Students’ answers will vary but may include magnet-ism, density, and solubility: iron is attracted by a mag-net, salt dissolves in water, poppy seeds float on water,and sand sinks in water.

EXTENSIONS—ANSWERS1. Students’ answers will vary but may include compar-ing the densities of their samples with the densities ofstandard samples of the pure components and pickingthrough small samples from within their samples tocheck for visible impurities.2. Students’ answers will vary but may include the following:a. using a magnetb. pouring the mixture through a screen or sifterc. adding water and checking for flotationd. dissolving the mixture in a solvent that dissolves one component but not the othere. distillationf. distillation3. The table salt, which was a solid at the start of theexperiment, is in solution in the water at the end of theexperiment. The salt could be restored to its originalsolid state by evaporating the water from the solution.

27B