States of Matter - Classroom Websites Documents... · Moving Particles Make Up All Matter Matter consists of tiny particles called atoms ... These atoms and molecules are always in

58 Chapter 3

Four States of Matter . . 60Internet Connect . . . . . 64MathBreak . . . . . . . . . . 66Apply . . . . . . . . . . . . . . 67Internet Connect. . . . . . 67

Changes of State . . . . . 68QuickLab . . . . . . . . . . . 71Meteorology

Connection . . . . . . . . 71Internet Connect . . . . . 73

Chapter Review . . . . . . . . . . 76

Feature Articles. . . . . . . . 78, 79

LabBook . . . . . . . . . . . 636–639

States ofMatterStates ofMatter

It Takes Mettle to Melt MetalIf you wanted to make a flavored ice pop, you would pourjuice into a mold and freeze it. You are able to make the ice pop into the desired shape because, unlike solids, liquids will take the shape of their container. Metal workersapply this important property of liquids when they createmetal parts that have complicated shapes. They melt themetal at extremely high temperatures and then pour it into a mold. In this chapter, you will find out more aboutthe properties of different states of matter.

Pre-ReadingQuestions

1. What are the four mostfamiliar states of matter?

2. Compare the motion ofparticles in a solid, a liquid, and a gas.

3. Name three ways matterchanges from one stateto another.

Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 360

Four States of MatterFigure 1 shows a model of theearliest known steam engine,invented about A.D. 60 byHero, a scientist who lived inAlexandria, Egypt. This modelalso demonstrates the fourmost familiar states of matter:solid, liquid, gas, and plasma.The states of matter are thephysical forms in which a sub-stance can exist. For example,water commonly exists inthree different states of mat-ter: solid (ice), liquid (water),and gas (steam).

Moving Particles Make Up All MatterMatter consists of tiny particles called atoms and molecules(MAHL i KYOOLZ) that are too small to see without an amazinglypowerful microscope. These atoms and molecules are always inmotion and are constantly bumping into one another. The stateof matter of a substance is determined by how fast the particlesmove and how strongly the particles are attracted to one another.Figure 2 illustrates three of the states of matter—solid, liquid,and gas—in terms of the speed and attraction of the particles.

Figure 1 This model of Hero’ssteam engine spins as steamescapes through the nozzles.

Particles of a solid do not movefast enough to overcome thestrong attraction between them,so they are held tightly in place.The particles vibrate in place.

Particles of a liquid move fastenough to overcome some ofthe attraction between them.The particles are able to slidepast one another.

Particles of a gas move fastenough to overcome nearlyall of the attraction betweenthem. The particles moveindependently of one another.

Figure 2 Models of a Solid, a Liquid, and a Gas

Gas

Solid

Liquid

Plasma

Section

1

states of matter pressuresolid Boyle’s lawliquid Charles’s lawgas plasma

◆ Describe the properties sharedby particles of all matter.

◆ Describe the four states of mat-ter discussed here.

◆ Describe the differencesbetween the states of matter.

◆ Predict how a change in pres-sure or temperature will affectthe volume of a gas.



Figure 4 Differing arrangements of particles in crys-talline solids and amorphous solids lead to differentproperties. Imagine trying to hit a home run with arubber bat!

Solids Have Definite Shape and VolumeLook at the ship in Figure 3. Even in a bottle, it keepsits original shape and volume. If you moved theship to a larger bottle, the ship’s shape and vol-ume would not change. Scientifically, the statein which matter has a definite shape and vol-ume is solid. The particles of a substance in asolid are very close together. The attractionbetween them is stronger than the attractionbetween the particles of the same substance inthe liquid or gaseous state. The atoms or mol-ecules in a solid move, but not fast enough toovercome the attraction between them. Each parti-cle vibrates in place because it is locked in positionby the particles around it.

Two Types of Solids Solids are often divided into two cat-egories—crystalline and amorphous (uh MOHR fuhs). Crystallinesolids have a very orderly, three-dimensional arrangement ofatoms or molecules. That is, the particles are arranged in arepeating pattern of rows. Examples of crystalline solids includeiron, diamond, and ice. Amorphous solids are composed ofatoms or molecules that are in no particular order. That is, eachparticle is in a particular spot, but the particles are in no organ-ized pattern. Examples of amorphous solids include rubber andwax. Figure 4 illustrates the differences in the arrangement ofparticles in these two solids.

States of Matter 61

The particles in anamorphous soliddo not have anorderly arrangement.

The particles in acrystalline solidhave a very orderlyarrangement.

Figure 3 Because this ship is asolid, it does not take the shapeof the bottle.

Imagine that you are a parti-cle in a solid. Your position inthe solid is your chair. In yourScienceLog, describe the dif-ferent types of motion thatare possible even though youcannot leave your chair.


Liquids Change Shape but Not VolumeA liquid will take the shape of whatever container it is put in.You are reminded of this every time you pour yourself a glassof juice. The state in which matter takes the shape of its con-

tainer and has a definite volume is liquid. The atoms ormolecules in liquids move fast enough to overcome

some of the attractions between them. The parti-cles slide past each other until the liquid takesthe shape of its container. Figure 5 shows howthe particles in juice might look if they werelarge enough to see.

Even though liquids change shape, they donot readily change volume. You know that acan of soda contains a certain volume of liquidregardless of whether you pour it into a largecontainer or a small one. Figure 6 illustrates thispoint using a beaker and a graduated cylinder.

Chapter 362

The Boeing 767 Freighter, atype of commercial airliner,has 187 km (116 mi) ofhydraulic tubing.

Figure 6 Even when liquidschange shape, they don’t changevolume.

The Squeeze Is On Because the particles in liquids are closeto one another, it is difficult to push them closer together. Thismakes liquids ideal for use in hydraulic (hie DRAW lik) sys-tems. For example, brake fluid is the liquid used in the brakesystems of cars. Stepping on the brake pedal applies a force tothe liquid. The particles in the liquid move away rather thansqueezing closer together. As a result, the fluid pushes the brakepads outward against the wheels, which slows the car.

Figure 5 Particles in a liquidslide past one another untilthe liquid conforms to theshape of its container.


A Drop in the Bucket Two other important properties ofliquids are surface tension and viscosity (vis KAHS uh tee). Surfacetension is the force acting on the particles at the surface of a liquid that causes the liquid to form spherical drops, as shown in Figure 7. Different liquids have different surfacetensions. For example, rubbing alcohol has a lower surface tension than water, but mercury has a higher surface tensionthan water.

Viscosity is a liquid’s resistance to flow. In general, thestronger the attractions between a liquid’s particles are, themore viscous the liquid is. Think of the difference betweenpouring honey and pouring water. Honey flows more slowlythan water because it has a higher viscosity than water.

Gases Change Both Shape and VolumeHow many balloons can be filled from a single metal cylin-der of helium? The number may surprise you. One cylindercan fill approximately 700 balloons. How is this possible?After all, the volume of the metal cylinder is equal to thevolume of only about five inflated balloons.

It’s a Gas! Helium is a gas. Gas is thestate in which matter changes in bothshape and volume. The atoms or mol-ecules in a gas move fast enough tobreak away completely from oneanother. Therefore, the particles of asubstance in the gaseous state have lessattraction between them than particlesof the same substance in the solid orliquid state. In a gas, there is emptyspace between particles.

The amount of empty space in a gascan change. For example, the heliumin the metal cylinder consists of atomsthat have been forced very closetogether, as shown in Figure 8. As thehelium fills the balloon, the atomsspread out, and the amount of emptyspace in the gas increases. As you con-tinue reading, you will learn how thisempty space is related to pressure.

63

Figure 7 Liquids formspherical drops as a resultof surface tension.

Figure 8 The particles of the gas in thecylinder are much closer together thanthe particles of the gas in the balloons.


Gas Under PressurePressure is the amount of force exerted on a given area. Youcan think of this as the number of collisions of particles againstthe inside of the container. Compare the basketball with thebeach ball in Figure 9. The balls have the same volume andcontain particles of gas (air) that constantly collide with oneanother and with the inside surface of the balls. Notice, how-ever, that there are more particles in the basketball than inthe beach ball. As a result, more particles collide with theinside surface of the basketball than with the inside surface ofthe beach ball. When the number of collisions increases, theforce on the inside surface of the ball increases. This increasedforce leads to increased pressure.

Chapter 364

Figure 9 Both balls shown here are full of air, but the pressure inthe basketball is higher than the pressure in the beach ball.

1. List two properties that all particles of matter have incommon.

2. Describe solids, liquids, and gases in terms of shape andvolume.

3. Why can the volume of a gas change?

4. Applying Concepts Explain what happens inside the ballwhen you pump up a flat basketball.

The beach ball has a lower pressurethan the basketball because the lessernumber of particles of gas are fartherapart. Therefore, they collide with theinside of the ball at a slower rate.

The basketball has a higher pressurethan the beach ball because the greaternumber of particles of gas are closertogether. Therefore, they collide withthe inside of the ball at a faster rate.

REVIEW

Self-CheckHow would an increasein the speed of theparticles affect thepressure of gas in ametal cylinder? (Seepage 724 to check youranswer.)

NSTA

TOPIC: Solids, Liquids, and GasesGO TO: www.scilinks.orgsciLINKS NUMBER: HSTP060


Laws Describe Gas BehaviorEarlier in this chapter, you learned about the atoms and mol-ecules in both solids and liquids. You learned that comparedwith gas particles, the particles of solids and liquids are closelypacked together. As a result, solids and liquids do not changevolume very much. Gases, on the other hand, behave differ-ently; their volume can change by a large amount.

It is easy to measure the volume of a solid or liquid, buthow do you measure the volume of a gas? Isn’t the volume ofa gas the same as the volume of its container? The answer isyes, but there are other factors, such as pressure, to consider.

Boyle’s Law Imagine a diver at a depth of 10 m blowing abubble of air. As the bubble rises, its volume increases. By thetime the bubble reaches the surface, its original volume willhave doubled due to the decrease in pressure. The relation-ship between the volume and pressure of a gas is known asBoyle’s law because it was first described by Robert Boyle, aseventeenth-century Irish chemist. Boyle’s law states that fora fixed amount of gas at a constant temperature, the volumeof a gas increases as its pressure decreases. Likewise, the vol-ume of a gas decreases as its pressure increases. Boyle’s law isillustrated by the model in Figure 10.

States of Matter 65

Releasing the plunger allowsthe gas to change to an inter-mediate volume and pressure.

Pushing the plunger increasesthe pressure of the gas. Theparticles of gas are forcedcloser together. The volume of the gas decreases as thepressure increases.

Lifting the plunger decreasesthe pressure of the gas. Theparticles of gas spread fartherapart. The volume of the gasincreases as the pressuredecreases.

Figure 10 Boyle’s LawEach illustration shows the same piston and thesame amount of gas at the same temperature.


Weather balloons demonstrate a practical use of Boyle’slaw. A weather balloon carries equipment into the atmosphereto collect information used to predict the weather. This balloonis filled with only a small amount of gas because the pressureof the gas decreases and the volume increases as the balloonrises. If the balloon were filled with too much gas, it wouldpop as the volume of the gas increased.

Charles’s Law An inflated balloon will also pop when it getstoo hot, demonstrating another gas law—Charles’s law.Charles’s law states that for a fixed amount of gas at a con-stant pressure, the volume of the gas increases as its tempera-ture increases. Likewise, the volume of the gas decreases as itstemperature decreases. Charles’s law is illustrated by the modelin Figure 11. You can see Charles’s law in action by puttingan inflated balloon in the freezer. Wait about 10 minutes, andsee what happens!

Chapter 366

Gas Law GraphsEach graph below illustratesa gas law. However, the vari-able on one axis of eachgraph is not labeled. Answerthe following questions foreach graph:

1. As the volume increases,what happens to the miss-ing variable?

2. Which gas law is shown?

3. What label belongs on theaxis?

4. Is the graph linear or non-linear? What does this tellyou?

MATH BREAK

Graph A

Graph B

?

Volu

me

?

Volu

me

See Charles’s law in action foryourself using a balloon

on page 636 of theLabBook.

Lowering the temperature of the gas causes the particles to movemore slowly. They hit the sides of the piston less often and with lessforce. As a result, the volume of the gas decreases.

Raising the temperature of the gas causes the particles to movemore quickly. They hit the sides of the piston more often and withgreater force. As a result, the volumeof the gas increases.

Figure 11 Charles’s LawEach illustration shows the same piston and thesame amount of gas at the same pressure.


PlasmasScientists estimate that more than 99 percent of the knownmatter in the universe, including the sun and other stars, ismade of a state of matter called plasma. Plasma is the state ofmatter that does not have a definite shape or volume andwhose particles have broken apart.

Plasmas have some properties that are quite different fromthe properties of gases. Plasmas conduct electric current, whilegases do not. Electric and magnetic fields affect plasmas butdo not affect gases. In fact, strongmagnetic fields are used to con-tain very hot plasmas that woulddestroy any other container.

Natural plasmas are found inlightning, fire, and the incrediblelight show in Figure 12, called theaurora borealis (ah ROHR uh BOHR

ee AL is). Artificial plasmas, foundin fluorescent lights and plasmaballs, are created by passing elec-tric charges through gases.

States of Matter 67

1. When scientists record the volume of a gas, why do theyalso record the temperature and the pressure?

2. List two differences between gases and plasmas.

3. Applying Concepts What happens to the volume of aballoon left on a sunny windowsill? Explain.

Figure 12 Auroras, like theaurora borealis seen here, formwhen high-energy plasma col-lides with gas particles in theupper atmosphere.

Charles’s Law and Bicycle Tires

One of your friends overinflated thetires on her bicycle. Use Charles’s law to explain why she should let out some of the air before going for a ride on a hot day.

REVIEW

NSTA

TOPIC: Natural and Artificial PlasmaGO TO: www.scilinks.orgsciLINKS NUMBER: HSTP065

Chapter 3

Changes of StateA change of state is the conversion of a substance from onephysical form to another. All changes of state are physicalchanges. In a physical change, the identity of a substance doesnot change. In Figure 13, the ice, liquid water, and steam areall the same substance—water. In this section, you will learnabout the four changes of state illustrated in Figure 13 as wellas a fifth change of state called sublimation (SUHB li MAY shuhn).

Energy and Changes of StateDuring a change of state, the energy of a substance changes.The energy of a substance is related to the motion of its par-ticles. The molecules in the liquid water in Figure 13 movefaster than the molecules in the ice. Therefore, the liquid waterhas more energy than the ice.

If energy is added to a substance, its particles move faster.If energy is removed, its particles move slower. The tempera-ture of a substance is a measure of the speed of its particlesand therefore is a measure of its energy. For example, steamhas a higher temperature than liquid water, so particles insteam have more energy than particles in liquid water. A trans-fer of energy, known as heat, causes the temperature of a sub-stance to change, which can lead to a change of state.

Freezing

Vapo

riza

tion

Melting

Cond

ensa

tio

n

Figure 13 The terms in the arrows arechanges of state. Water commonly goesthrough the changes of state shown here.

Want to learn how to get

power fromchanges ofstate? Steam

ahead topage 79.

68

Section

2

change of state boilingmelting evaporationfreezing condensationvaporization sublimation

◆ Describe how substances changefrom state to state.

◆ Explain the difference betweenan exothermic change and anendothermic change.

◆ Compare the changes of state.



Melting: Solids to LiquidsMelting is the change of state from a solid to a liquid. This iswhat happens when an ice cube melts. Figure 14 shows a metalcalled gallium melting. What is unusual about this metal isthat it melts at around 30°C. Because your normal body tem-perature is about 37°C, gallium will melt right in your hand!

The melting point of a substance is the temperature at whichthe substance changes from a solid to a liquid. Melting pointsof substances vary widely. The melting point of gallium is 30°C. Common table salt, however, has a melting point of 801°C.

Most substances have a unique melting point that can beused with other data to identify them. Because the meltingpoint does not change with different amounts of the sub-stance, melting point is a characteristic property of a substance.

Absorbing Energy For a solid to melt, particles must over-come some of their attractions to each other. When a solid isat its melting point, any energy it absorbs increases the motionof its atoms or molecules until they overcome the attractionsthat hold them in place. Melting is an endothermic changebecause energy is absorbed by the substance as it changes state.

Freezing: Liquids to SolidsFreezing is the change of state from a liquid to a solid. Thetemperature at which a liquid changes into a solid is its freez-ing point. Freezing is the reverse process of melting, so freez-ing and melting occur at the sametemperature, as shown in Figure 15.

Removing Energy For a liquid tofreeze, the motion of its atoms ormolecules must slow to the pointwhere attractions between them over-come their motion. If a liquid is atits freezing point, removing moreenergy causes the particles to beginlocking into place. Freezing is anexothermic change because energy isremoved from, or taken out of, thesubstance as it changes state.

States of Matter 69

Figure 14 Even though galliumis a metal, it would not be veryuseful as jewelry!

Figure 15 Liquid waterfreezes at the sametemperature that icemelts—0°C.

If energy is added at0°C, the ice will melt.

If energy is removedat 0°C, the liquidwater will freeze.


Vaporization: Liquids to GasesOne way to experience vaporization (VAY puhr i ZAY shuhn) isto iron a shirt—carefully!—using a steam iron. You will noticesteam coming up from the iron as the wrinkles are eliminated.

This steam results from the vaporization of liquid water bythe iron. Vaporization is simply the change of state froma liquid to a gas.

Boiling is vaporization that occurs throughout a liquid.The temperature at which a liquid boils is called its boilingpoint. Like the melting point, the boiling point is a char-acteristic property of a substance. The boiling point of wateris 100°C, whereas the boiling point of liquid mercury is357°C. Figure 16 illustrates the process of boiling and a sec-

ond form of vaporization—evaporation (ee VAP uh RAY shuhn).Evaporation is vaporization that occurs at the surface of a

liquid below its boiling point, as shown in Figure 16. Whenyou perspire, your body is cooled through the process of evapo-ration. Perspiration is mostly water. Water absorbs energy fromyour skin as it evaporates. You feel cooler because your bodytransfers energy to the water. Evaporation also explains whywater in a glass on a table disappears after several days.

Chapter 370

Figure 16 Both boilingand evaporation changea liquid to a gas.

Self-CheckIs vaporization anendothermic orexothermic change?(See page 724 to checkyour answer.)

Boilingpoint

Boilingpoint

Boiling occurs in a liquid at its boiling point.As energy is added to the liquid, particlesthroughout the liquid move fast enough tobreak away from the particles around themand become a gas.

Evaporation occurs in a liquid belowits boiling point. Some particles at thesurface of the liquid move fast enoughto break away from the particlesaround them and become a gas.


Boiling Water Is Cool

1. Remove the capfrom a syringe.

2. Place the tip of thesyringe in the warmwater provided byyour teacher. Pull theplunger out until you have10 mL of water in thesyringe.

3. Tightly cap the syringe.

4. Hold the syringe, andslowly pull the plunger out.

5. Observe any changes yousee in the water. Recordyour observations in yourScienceLog.

6. Why are you not burned bythe boiling water in thesyringe?

Pressure Affects Boiling Point Earlier you learned that waterboils at 100�C. In fact, water only boils at 100�C at sea levelbecause of atmospheric pressure. Atmospheric pressure is causedby the weight of the gases that make up the atmosphere.Atmospheric pressure varies depending on where you are inrelation to sea level. Atmospheric pressure is lower at higherelevations. The higher you go above sea level, the less air thereis above you, and the lower the atmospheric pressure is. If youwere to boil water at the top of a mountain, the boiling pointwould be lower than 100�C. For example, Denver, Colorado, is1.6 km (1 mi) above sea level and water boils there at about95�C. You can make water boil at an even lower temperatureby doing the QuickLab at right.

Condensation: Gases to LiquidsLook at the cool glass of lemonade in Figure 17. Notice thebeads of water on the outside of the glass. These form asa result of condensation. Condensation is the change ofstate from a gas to a liquid. The condensation point of asubstance is the temperature at which the gas becomes aliquid and is the same temperature as the boiling point ata given pressure. Thus, at sea level, steam condenses to form water at 100�C—the same temperature at which water boils.

For a gas to become a liquid,large numbers of atoms or mol-ecules must clump together.Particles clump together whenthe attraction between themovercomes their motion. For thisto occur, energy must be re-moved from the gas to slow the particles down. Therefore,condensation is an exothermicchange.

71States of Matter

MeteorologyC O N N E C T I O N

The amount of gaseous water thatair can hold decreases as the tem-perature of the air decreases. As theair cools, some of the gaseous watercondenses to form small drops ofliquid water. These drops formclouds in the sky and fog near theground.

Figure 17 Gaseous water inthe air will become liquid whenit contacts a cool surface.


Sublimation: Solids Directly to GasesLook at the solids shown in Figure 18. The solid on the left isice. Notice the drops of liquid collecting as it melts. On theright, you see carbon dioxide in the solid state, also called dryice. It is called dry ice because instead of melting into a liquid,

it goes through a change of state called subli-mation. Sublimation is the change of state froma solid directly into a gas. Dry ice is colder thanice, and it doesn't melt into a puddle of liquid.It is often used to keep food, medicine, andother materials cold without getting them wet.

For a solid to change directly into a gas, theatoms or molecules must move from being verytightly packed to being very spread apart. Theattractions between the particles must be com-pletely overcome. Because this requires the addi-tion of energy, sublimation is an endothermicchange.

Comparing Changes of StateAs you learned in Section 1 of this chapter, thestate of a substance depends on how fast its atomsor molecules move and how strongly they areattracted to each other. A substance may undergoa physical change from one state to another byan endothermic change (if energy is added) oran exothermic change (if energy is removed).The table below shows the differences betweenthe changes of state discussed in this section.

Chapter 372

Summarizing the Changes of State

Ice melts into liquid water at 0�C.

Liquid water freezes into ice at 0�C.

Liquid water vaporizes into steamat 100°C.

Steam condenses into liquid water at 100�C.

Solid dry ice sublimes into a gas at –78�C.

Melting solid liquid endothermic

Freezing liquid solid exothermic

Vaporization liquid gas endothermic

Condensation gas liquid exothermic

Sublimation solid gas endothermic

Change of state Direction Example

�

�

�

�

�

Figure 18 Ice melts, but dry ice, on the right,turns directly into a gas.

Endothermic or exothermic?


Temperature Change Versus Change of StateWhen most substances lose or absorb energy, one of two thingshappens to the substance: its temperature changes or its statechanges. Earlier in the chapter, you learned that the temper-ature of a substance is a measure of the speed of the particles.This means that when the temperature of a substance changes,the speed of the particles also changes. But while a substancechanges state, its temperature does not change until the changeof state is complete, as shown in Figure 19.

States of Matter 73

Boiling point

Melting point

Time

Tem

pera

ture

( C

)

100

0

o

ENER

GY

ADDED ENER

GY ADDED

ENER

GY ADDED ENERGY

ADD

ED

1. Compare endothermic and exothermic changes.

2. Classify each change of state (melting, freezing, vapor-ization, condensation, and sublimation) as endothermicor exothermic.

3. Describe how the motion and arrangement of particleschange as a substance freezes.

4. Comparing Concepts How are evaporation and boilingdifferent? How are they similar?

REVIEW

Figure 19 Changing the State of Water

Temperature remains atthe melting point until allof the solid has melted.

Temperature remains atthe boiling point until allof the liquid has boiled.

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TOPIC: Changes of StateGO TO: www.scilinks.orgsciLINKS NUMBER: HSTP070