Science Unit 4 (Glencoe Red 2002)

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44How Are

Air & AdvertisingConnected?

How AreAir & Advertising

Connected?

Earth’s Air and Water

SCIENCE CONNECTIONSCIENCE CONNECTION

NOBLE GASES Neon is one of six elements known as the noble gases. These gases make up a tiny fraction of the atmosphere. Conduct research to find outmore about this group. What other gases belong to the group? What do theyall have in common? Why are they called “noble”? Create a chart that showswhen each of the noble gases was discovered and what distinctive characteris-tics and uses it has.

In the late 1800s, two scientists were studyingthe composition of air when they discovered an

element that hadn’t been known before. Theynamed it “neon,” and soon this new element, rep-resented by the chemical symbol Ne, had beenassigned a spot in the periodic table (right). Ittook a few years for people to figure out some-thing useful to do with neon! In 1910, a Frenchengineer experimented with passing an electricalcurrent through neon gas in a vacuum tube. Theresult was a spectacular orange-red light. Neon’sadvertising possibilities were quickly realized, andsoon the first neon sign blazed on a boulevard inParis. Today, neon signs in a wide range of colorsadvertise shops and services all over the world.The other colors are made by mixing neon withother gases and by using tinted tubes.

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Atmosphere1010

Why is it difficult to breatheat high elevations? Whyare some mountain peaks

permanently covered with snow?These mountain climbers aren’t sup-plementing oxygen just because theactivity is physically demanding. Atelevations like this, the amount ofoxygen available in the air is so smallthat the climbers’ bodily functionsmight not be supported. In this chap-ter, you’ll learn about the composi-tion and structure of the atmosphere.You also will learn how energy istransferred in the atmosphere. Inaddition, you’ll examine the watercycle and major wind systems.

What do you think?Science Journal Look at the picturebelow with a classmate. Discuss whatthis might be. Here’s a hint: It “pops”in thin air. Write your answer or bestguess in your Science Journal.

The air around you is made of billions of molecules.These molecules are constantly moving in all

directions and bouncing into every object in the room,including you. Air pressure is the result of the billionsof collisions of molecules into these objects. Because

you usually do not feel molecules in air hitting you, do the activity below tosee the effect of air pressure.

Observe air pressure1. Cut out a square of cardboard about

10 cm on a side from a cereal box.

2. Fill a glass to the brim with water.

3. Hold the cardboard firmly over the top of the glass, covering the water,and invert the glass.

4. Slowly remove your hand holding the cardboard in place and observe.

ObserveWrite a paragraph in your Science Journal describing what happened to thecardboard when you inverted the glass and removed your hand. How does airpressure explain what happened?

EXPLOREACTIVITY

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Making a Sequence Study Fold Make the following Foldable to help you visualize the layers of Earth’s atmosphere.

1. Stack three sheets of paper in front of you so the shortsides are at the top.

2. Slide the top sheet up so that about four centimeters ofthe middle sheet show. Slide the middle sheet up sothat about four centimeters of the bottom sheet show.

3. Fold the sheets top to bottom to form six tabs and sta-ple along the topfold. Turn the Foldable so the staplesare at the bottom.

4. Label the flaps Earth’s Atmosphere, Troposphere, Stratosphere, Mesosphere,Thermosphere, and Exosphere, as shown.

5. As you read the chapter, write information about each layer of Earth’s atmosphere under the tabs.

FOLDABLESReading & StudySkills

FOLDABLESReading & Study Skills

ThermosphereMesosphere

StratosphereTroposphere

Exosphere

Earth's Atmosphere

282 CHAPTER 10 Atmosphere

Earth’s AtmosphereS E C T I O N

Importance of the Atmosphere Earth’s atmosphere, shown in Figure 1, is a thin layer of air

that forms a protective covering around the planet. If Earth hadno atmosphere, days would be extremely hot and nights wouldbe extremely cold. Earth’s atmosphere maintains a balancebetween the amount of heat absorbed from the Sun and theamount of heat that escapes back into space. It also protects life-forms from some of the Sun’s harmful rays.

Makeup of the AtmosphereEarth’s atmosphere is a mixture of gases, solids, and liquids

that surround the planet. It extends from Earth’s surface toouter space. The atmosphere is much different today from whatit was when Earth was young.

Earth’s early atmosphere, produced by erupting volcanoes,contained nitrogen and carbon dioxide, but little oxygen. Then,more than 2 billon years ago, Earth’s early organisms releasedoxygen into the atmosphere as they made food with the aid ofsunlight. These early organisms, however, were limited to layersof ocean water deep enough to be shielded from the Sun’s

harmful rays, yet closeenough to the surface toreceive sunlight. Eventu-ally, a layer rich in ozone(O3) that protects Earthfrom the Sun’s harmfulrays formed in the upperatmosphere. This protec-tive layer eventuallyallowed green plants toflourish all over Earth,releasing even more oxy-gen. Today, a variety oflife forms, including you,depends on a certainamount of oxygen inEarth’s atmosphere.

■ Identify the gases in Earth’satmosphere.

■ Describe the structure of Earth’satmosphere.

■ Explain what causes air pressure.

Vocabularyatmosphere ozone layertroposphere ultraviolet radiationionosphere chlorofluorocarbon

The atmosphere makes life on Earthpossible.

Figure 1 Earth’s atmosphere, as viewedfrom space, is a thin layer ofgases. The atmosphere keepsEarth’s temperature in a rangethat can support life.

Gases in the Atmosphere Today’satmosphere is a mixture of the gasesshown in Figure 2. Nitrogen is the mostabundant gas, making up 78 percent of theatmosphere. Oxygen actually makes uponly 21 percent of Earth’s atmosphere. Asmuch as four percent of the atmosphere iswater vapor. Other gases that make upEarth’s atmosphere include argon and car-bon dioxide.

The composition of the atmosphere ischanging in small but important ways. Forexample, car exhaust emits gases into theair. These pollutants mix with oxygen and other chemicals in thepresence of sunlight and form a brown haze called smog.Humans burn fuel for energy. As fuel is burned, carbon dioxideis released as a by-product into Earth’s atmosphere. Increasingenergy use may increase the amount of carbon dioxide in theatmosphere.

Solids and Liquids in Earth’s Atmosphere In additionto gases, Earth’s atmosphere contains small, solid particles suchas dust, salt, and pollen. Dust particles get into the atmospherewhen wind picks them up off the ground and carries themalong. Salt is picked up from ocean spray. Plants give off pollenthat becomes mixed throughout part of the atmosphere.

The atmosphere also contains small liquid droplets otherthan water droplets in clouds. The atmosphere constantly movesthese liquid droplets and solids from one region to another. Forexample, the atmosphere above you may contain liquid dropletsand solids from an erupting volcano thousands of kilometersfrom your home, as illustrated in Figure 3.

SECTION 1 Earth’s Atmosphere 283

–

–

–––– ––––

Argon(0.93%)Carbondioxide

(0.03%)

NeonHelium

MethaneKrypton

XenonHydrogen

Ozone

21%Oxygen

78%Nitrogen

Trace 1%

Figure 2This graph shows the percent-ages of the gases, excludingwater vapor, that make upEarth’s atmosphere.

Figure 3Solids and liquids can travel largedistances in Earth’s atmosphere,affecting regions far from theirsource.

Droplets of sulfuric acid from volcanoescan produce spectacular sunrises.

On June 12, 1991, Mount Pinatubo inthe Philippines erupted, causing liquiddroplets to form in Earth’s atmosphere.

Layers of the AtmosphereWhat would happen if you left a glass of chocolate milk on

the kitchen counter for a while? Eventually, you would see alower layer with more chocolate separating from upper layerswith less chocolate. Like a glass of chocolate milk, Earth’s atmo-sphere has layers. There are five layers in Earth’s atmosphere,each with its own properties, as shown in Figure 4. The lowerlayers include the troposphere and stratosphere. The upperatmospheric layers are the mesosphere, thermosphere, and exo-sphere. The troposphere and stratosphere contain most of the air.

Lower Layers of the Atmosphere You study, eat, sleep,and play in the troposphere, which is the lowest of Earth’satmospheric layers. It contains 99 percent of the water vaporand 75 percent of the atmospheric gases. Rain, snow, and cloudsoccur in the troposphere, which extends up to about 10 km.

The stratosphere, the layer directly above the troposphere,extends from 10 km above Earth’s surface to about 50 km. AsFigure 4 shows, a portion of the stratosphere contains higherlevels of a gas called ozone. Each molecule of ozone is made upof three oxygen atoms bonded together. Later in this section youwill learn how ozone protects Earth from the Sun’s harmful rays.

Research Visit the Glencoe Science Web site atscience.glencoe.comfor more information aboutlayers of Earth’s atmosphere.Communicate to your classwhat you learn.

500 km

85 km

50 km

Earth

10 kmJet

Ozone layer

Troposphere

Stratosphere

Mesosphere

Thermosphere

Exosphere

Meteor trails

Satellite

Space shuttle

Figure 4Earth’s atmosphere is dividedinto five layers. Which layer of theatmosphere do you live in?

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Upper Layers of the Atmosphere Beyond the strato-sphere are the mesosphere, thermosphere, and exosphere. Themesosphere extends from the top of the stratosphere to about85 km above Earth. If you’ve ever seen a shooting star, youmight have witnessed a meteor in the mesosphere.

The thermosphere is named for its high temperatures. Thisis the thickest atmospheric layer and is found between 85 kmand 500 km above Earth’s surface.

Within the mesosphere and thermosphere is a layer of elec-trically charged particles called the ionosphere (i AHN uh sfir).If you live in New Jersey and listen to the radio at night, youmight pick up a station from Boise, Idaho. The ionosphereallows radio waves to travel across the country to another city, asshown in Figure 5. During the day, energy from the Sun inter-acts with the particles in the ionosphere, causing them to absorbAM radio frequencies. At night, without solar energy, AM radiotransmissions reflect off the ionosphere, allowing radio trans-missions to be received at greater distances.

The space shuttle in Figure 6 orbits Earth in the exosphere.In contrast to the troposphere, the layer you live in, the exo-sphere has so few molecules that the wings of the shuttle areuseless. In the exosphere, the spacecraft relies on bursts fromsmall rocket thrusters to move around. Beyond the exosphere isouter space.

How does the space shuttle maneuver in theexosphere?


Figure 6Wings help move aircraft in lowerlayers of the atmosphere. Thespace shuttle can’t use its wingsto maneuver in the exospherebecause so few molecules arepresent.

Boise

New Jersey

Day

AM radio transmitter

Night

Radio waves

Receiving antenna

Ionosphere

Figure 5During the day, the ionosphereabsorbs radio transmissions. Thisprevents you from hearing distant radio stations. At night,the ionosphere reflects radiowaves. The reflected waves cantravel to distant cities.

Atmospheric gases extend hundreds ofkilometers above Earth’s surface, but the

molecules that make up these gases arefewer and fewer in number as you go higher.This means that air pressure decreases withaltitude.

Identifying the ProblemThe graph on the right shows these

changes in air pressure. Note that altitudeon the graph goes up only to 50 km. Thetroposphere and the stratosphere are repre-sented on the graph, but other layers of theatmosphere are not. By examining thegraph, can you understand the relationshipbetween altitude and pressure?

Solving the Problem1. Estimate the air pressure at an altitude of

5 km.2. Does air pressure change more quickly at

higher altitudes or at lower altitudes?

How does altitude affect air pressure?

Problem-Solving Activity

Atmospheric Pressure Imagine you’re a football player running with

the ball. Six players tackle you and pile one on topof the other. Who feels the weight more—you orthe player on top? Like molecules anywhere else,atmospheric gases have mass. Atmospheric gasesextend hundreds of kilometers above Earth’s sur-face. As Earth’s gravity pulls the gases toward itssurface, the weight of these gases presses down onthe air below. As a result, the molecules nearerEarth’s surface are closer together. This dense airexerts more force than the less dense air near thetop of the atmosphere. Force exerted on an area isknown as pressure.

Like the pile of football players, air pressure isgreater near Earth’s surface and decreases higherin the atmosphere, as shown in Figure 7. Peoplefind it difficult to breathe in high mountains

because fewer molecules of air exist there. Jets that fly in thestratosphere must maintain pressurized cabins so that peoplecan breathe.

Where is air pressure greater—in the exosphere or in the troposphere?


Figure 7 Air pressure decreases as you gohigher in Earth’s atmosphere.

Air Pressure Changes with Altitude1000

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5040302010Altitude (km)


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20 400 600 8000-20-40-60-80-100Temperature (ºC)

Troposphere

Stratosphere

Mesosphere

Thermosphere

Exosphere

Altit

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(km

)

Temperature of the Atmosphere at Various Altitudes

Highest concentration of ozone

Determining if air has massProcedure1. On a pan balance, find the

mass of an inflatable ballthat is completely deflated.

2. Hypothesize about thechange in the mass of theball when it is inflated.

3. Inflate the ball to its maximum recommendedinflation pressure.

4. Determine the mass of thefully inflated ball.

Analysis1. What change occurs in the

mass of the ball when it isinflated?

2. Infer from your datawhether air has mass.

Figure 8The division of the atmosphereinto layers is based mainly on dif-ferences in temperature. Does thetemperature increase or decreasewith altitude in the mesosphere?

Temperature in Atmospheric Layers The Sun is the source of most of the energy on Earth. Before

it reaches Earth’s surface, energy from the Sun must passthrough the atmosphere. Because some layers contain gases thateasily absorb the Sun’s energy while other layers do not, the vari-ous layers have different temperatures, illustrated by the red linein Figure 8.

Molecules that make up air in the troposphere are warmedmostly by heat from Earth’s surface. The Sun warms Earth’s sur-face, which then warms the air above it. When you climb amountain, the air at the top is usually cooler than the air at thebottom. Every kilometer you climb, the air temperaturedecreases about 6.5°C.

Molecules of ozone in the stratosphere absorb some of theSun’s energy. Energy absorbed by ozone molecules raises thetemperature. Because more ozone molecules are in the upperportion of the stratosphere, the temperature in this layer riseswith increasing altitude.

Like the troposphere, the temperature in the mesospheredecreases with altitude. The thermosphere and exosphere arethe first layers to receive the Sun’s rays. Few molecules are inthese layers, but each molecule has a great deal of energy. Tem-peratures here are high.

The Ozone LayerWithin the stratosphere, about 19 km to 48 km above your

head, lies an atmospheric layer called the ozone layer. Ozone ismade of oxygen. Although you cannot see the ozone layer, yourlife depends on it.

The oxygen you breathe has two atoms per molecule, but anozone molecule is made up of three oxygen atoms boundtogether. The ozone layer contains a high concentration ofozone and shields you from the Sun’s harmful energy. Ozoneabsorbs most of the ultraviolet radiation that enters the atmo-sphere. Ultraviolet radiation is one of the many types of energythat come to Earth from the Sun. Too much exposure to ultravi-olet radiation can damage your skin and cause cancer.

CFCs Evidence exists that some air pollutants are destroying theozone layer. Blame has fallen on chlorofluorocarbons (CFCs),chemical compounds used in some refrigerators, air conditioners,and aerosol sprays, and in the production of some foam packaging.CFCs can enter the atmosphere if these appliances leak or if theyand other products containing CFCs are improperly discarded.

Recall that an ozone molecule is made of three oxygen atomsbonded together. Chlorofluorocarbon molecules, shown in Figure 9, destroy ozone. When a chlorine atom from achlorofluorocarbon molecule comes near a molecule of ozone, theozone molecule breaks apart. One of the oxygen atoms combineswith the chlorine atom, and the rest form a regular, two-atommolecule. These compounds don’t absorb ultraviolet radiationthe way ozone can. In addition, the original chlorine atom cancontinue to break apart thousands of ozone molecules. Theresult is that more ultraviolet radiation reaches Earth’s surface.


Ultraviolet lightbreaks up CFC molecule.

A releasedchlorine atom breaksup ozone (O3) molecule.

A free oxygenatom breaks the

chlorine-oxygen bond.

Oxygen atomsrejoin to form a normaloxygen (O2) molecule.

The chlorine atom joinswith an oxygen atom,leaving behind a molecule of oxygen (O2).

Releasedchlorine atom breaks up anotherozone (O3) molecule.

A. B. C.

D. E. F.

Cl

Cl

Cl

Cl ClO

OO

OO

O

O

O

O

O

Cl

ClO

OO

F

C

UVlight

Figure 9Chlorofluorocarbon (CFC) mole-cules were used in refrigeratorsand air conditioners. Each CFCmolecule has three chlorineatoms. One atom of chlorine candestroy approximately 100,000ozone molecules.

Algae are organisms thatuse sunlight to make theirown food. This processreleases oxygen to Earth’satmosphere. Some scien-tists suggest that growth isreduced when algae areexposed to ultraviolet radiation. Infer what mighthappen to the oxygen levelof the atmosphere ifincreased ultraviolet radia-tion damages some algae.

Ozone Holes Each year, morethan 1.3 million Americans developskin cancer, and more than 9,500 die

from it. Exposure to ultraviolet radiation can cause skin cancer. Ifthe ozone layer disappeared, skin cancer rates might increase. In1986, scientists found areas in the stratosphere with extremelylow amounts of ozone. One large hole was found over Antarc-tica. A smaller hole was discovered over the north pole. Figure 10shows how the ozone layer has thinned and developed holes.

In the mid 1990s, many governments banned the produc-tion and use of CFCs. Perhaps over time, the areas where theozone layer is thinning will recover.


Section Assessment

1. Earth’s early atmosphere had little oxygen.How did oxygen come to make up 21 per-cent of Earth’s present atmosphere?

2. List the layers of the atmosphere in orderbeginning at Earth’s surface.

3. While hiking in the mountains, you noticethat it is harder to breathe as you climbhigher. Explain why this is so.

4. What are some effects from a thinningozone layer?

5. Think Critically During the day, the radioonly receives AM stations from a city nearyou. At night, you are able to listen to anAM radio station from a distant city.Explain why this is possible.

6. Interpreting Scientific Illustrations UsingFigure 2, determine the total percentage ofnitrogen and oxygen in the atmosphere. What is the total percentage of argon and carbondioxide? For more help, refer to the ScienceSkill Handbook.

7. Communicating The names of the atmo-spheric layers end with the suffix -sphere a wordthat means “ball.” Use a dictionary to find outwhat tropo-, meso-, thermo-, and exo- mean.In your Science Journal, write the meaning ofthese prefixes and explain if the layers areappropriately named. For more help, refer tothe Science Skill Handbook.

Figure 10These images of Antarctica wereproduced using data from a NASAsatellite. The purple color showshow the ozone hole has grownbigger over time.

October 1980 October 1988 October 1990 September 1999

Create a poster on the proper use of sun-screens, and provide guidelines for selectingthe safest product. For more help, refer tothe Science Skill Handbook.

Evaluating Sunscreens


Conclude and Apply1. Explain why you need to use sunscreen.

2. A minimum of SPF 15 is considered adequateprotection for a sunscreen. Sunscreens withan SPF greater than 30 are considered bygovernment guidelines to be misleadingbecause sunscreens will wash or wear off.Evaluate the SPF of each brand of sunscreen.

3. Considering the cost and effectiveness of allthe sunscreen brands, discuss which brandyou consider to be the best buy.

W ithout protection, sun exposure can dam-age your health. Sunscreens protect your

skin from ultraviolet radiation. In this activity, youwill draw inferences using the labels of differentsunscreens.

What You’ll InvestigateHow effective are various brands of sunscreens?

Materialsvariety of sunscreens of different brand names

Goals■ Draw inferences based on labels on sun-

screen brands.■ Compare the effectiveness of different sun-

screen brands for protection against the Sun.■ Compare the cost of several sunscreen brands.

Safety Precautions

Procedure1. Make a data table in your Science Journal

using the following terms: brand name, SPF,misleading terms, and cost per milliliter.

2. The Sun Protection Factor (SPF) tells you howlong the sunscreen will protect you. For exam-ple, an SPF of 4 allows you to stay in the Sunfour times longer than if you did not use sun-screen. Record the SPF of each sunscreen onyour data table.

3. Calculate the cost per milliliter of each sun-screen brand.

4. Government guidelines say that terms likesunblock and waterproof are misleadingbecause sunscreens cannot block the Sun, andthey wash off in water. List the misleadingterms in your data table for each brand.

Brand Name

SPF

Cost per Milliliter

Misleading Terms

Sunscreen Assessment

6% reflected by the atmosphere

25% reflected from clouds

50% directly or indirectly absorbed by Earth’s surface

15% absorbed by the atmosphere

4% reflected from Earth’s surface

■ Describe what happens to theenergy Earth receives from theSun.

■ Compare and contrast radiation,conduction, and convection.

■ Explain the water cycle.

Vocabularyradiation hydrosphereconduction condensationconvection

The Sun provides energy to Earth’satmosphere, allowing life to exist.

Energy Transfer in the Atmosphere

S E C T I O N

Figure 11The Sun is the source of energyfor Earth’s atmosphere. Thirty-five percent of incoming solarradiation is reflected back intospace. How much is absorbed byEarth’s surface and atmosphere?

Energy from the SunThe Sun provides most of the energy on Earth. This energy

drives winds and ocean currents and allows plants to grow andproduce food, providing nutrition for many animals. WhenEarth receives energy from the Sun, three different things canhappen to that energy, as shown in Figure 11. Some energy isreflected back into space by clouds, atmospheric particles, andEarth’s surface. Some is absorbed by the atmosphere. The rest isabsorbed by land and water on Earth’s surface.

Heat Heat is energy that flows from an object with a higher tem-

perature to an object with a lower temperature. Energy from theSun reaches Earth’s surface and heats objects such as roads,rocks, and water. Heat then is transferred through the atmo-sphere in three ways—radiation, conduction, and convection, asshown in Figure 12.

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Radiation Sitting on the beach, you feel the Sun’s warmth onyour face. How can you feel the Sun’s heat even though youaren’t in direct contact with it? Energy from the Sun reachesEarth in the form of radiant energy, or radiation. Radiation isenergy that is transferred in the form of rays or waves. Earthradiates some of the energy it absorbs from the Sun back towardspace. Radiant energy from the Sun warms your face.

How does the Sun warm your skin?

Conduction If you walk barefoot on a hot beach, your feetheat up because of conduction. Conduction is the transfer ofenergy that occurs when molecules bump into one another.Molecules are always in motion, but molecules in warmerobjects move faster than molecules in cooler objects. Whenobjects are in contact, energy is transferred from warmer objectsto cooler objects.

Radiation from the Sun heated the beach sand, but directcontact with the sand warmed your feet. In a similar way, Earth’ssurface conducts energy directly to the atmosphere. As airmoves over warm land or water, molecules in air are heated bydirect contact.

Convection After the atmosphere is warmed by radiation orconduction, the heat is transferred by a third process called con-vection. Convection is the transfer of heat by the flow of mate-rial. Convection circulates heat throughout the atmosphere.How does this happen?


Specific heat is the amountof heat required to changethe temperature of a sub-stance one degree. Sub-stances with high specificheat absorb a lot of heat fora small increase in temper-ature. Land warms fasterthan water does. Inferwhether soil or water has ahigher specific heat value.

Figure 12Heat is transferred within Earth’satmosphere by radiation, con-duction, and convection.

Radiation warms the surface.

Cooler air pushes warm air upward, creating a convection current.

The air near Earth's surface is heated by conduction.

When air is warmed, the molecules in it move apart and theair becomes less dense. Air pressure decreases because fewermolecules are in the same space. In cold air, molecules movecloser together. The air becomes more dense and air pressureincreases. Cooler, denser air sinks while warmer, less dense airrises, forming a convection current. As Figure 12 shows, radia-tion, conduction, and convection together distribute the Sun’sheat throughout Earth’s atmosphere.

The Water Cycle Hydrosphere is a term that describes all the water on Earth’s

surface. Water moves constantly between the atmosphere andthe hydrosphere in the water cycle, shown in Figure 13.

If you watch a puddle in the Sun, you’ll notice that over timethe puddle gets smaller and smaller. Energy from the Sun causesthe water in the puddle to change from a liquid to a gas by aprocess called evaporation. Water that evaporates from lakes,streams, and oceans enters Earth’s atmosphere.

If water vapor in the atmosphere cools enough, it changesback into a liquid. This process of water vapor changing to a liq-uid is called condensation.

Clouds form when condensation occurs high in the atmo-sphere. Clouds are made up of tiny water droplets that can col-lide to form larger drops. As the drops grow, they fall to Earth asprecipitation, which completes the cycle by returning water tothe hydrosphere.

SECTION 2 Energy Transfer in the Atmosphere 293

Evaporation

Condensation

Precipitation

Runoff

Figure 13In the water cycle, water movesfrom Earth to the atmosphereand back to Earth again.

Modeling Heat TransferProcedure1. Cover the outside of an

empty soup can with blackconstruction paper.

2. Fill the can with cold waterand feel it with your fingers.

3. Place the can in sunlight for1 h then pour the waterover your fingers.

Analysis1. Does the water in the can

feel warmer or cooler afterplacing the can in sunlight?

2. What types of heat transferdid you model?


Section Assessment

1. How does the Sun transfer energy to Earth?

2. How is Earth’s atmosphere different fromthe atmosphere on Mars?

3. How is heat transferred from the stove tothe water when you boil a pot of water?

4. Briefly describe the steps included in thewater cycle.

5. Think Critically What would happen totemperatures on Earth if the Sun’s heatwere not distributed throughout theatmosphere?

6. Concept Mapping Make a concept map thatexplains what happens to radiant energy thatreaches Earth. For more help, refer to the Science Skill Handbook.

7. Solving One-Step Equations Earth is about150 million km from the Sun. The radiationcoming from the Sun travels at 300,000 km/s.How long does it take for radiation from the Sunto reach Earth? For more help, refer to theMath Skill Handbook.

Earth’s Atmosphere is Unique

On Earth, radiationfrom the Sun can bereflected into space, ab-sorbed by the atmo-sphere, or absorbed byland and water. Once itis absorbed, heat canbe transferred by radi-

ation, conduction, or convection. Earth’s atmosphere, shown inFigure 14, helps control how much of the Sun’s radiation isabsorbed or lost.

What helps control how much of the Sun’s radiation is absorbed on Earth?

Why doesn’t life exist on Mars or Venus? Mars is a cold, life-less world because its atmosphere is too thin to support life or tohold much of the Sun’s heat. Temperatures on the surface ofMars range from 35°C to –170°C. On the other hand, gases inVenus’s dense atmosphere trap heat coming from the Sun. Thetemperature on the surface of Venus is 470°C. Living thingswould burn instantly if they were placed on Venus’s surface. Lifeon Earth exists because the atmosphere holds just the rightamount of the Sun’s energy.

Heat

Heat

Heat

Hea

t

Earth'satmosphere

Sunlight

Sunlight

Sunlight

Sunlight

Figure 14Earth’s atmosphere creates a delicate balance betweenenergy received and energy lost.

Suns Rays

Suns Rays

Suns Rays

Equator

North Pole

South Pole

SECTION 3 Air Movement 295

Forming Wind Uneven heating of Earth’s surface by the Sun causes some

areas to be warmer than others. Recall from Section 2 thatwarmer air expands, becoming less dense than colder air. Thiscauses air pressure to be generally lower where air is heated.Wind is the movement of air from an area of higher pressure toan area of lower pressure.

Heated Air Areas of Earth receive different amounts of radia-tion from the Sun because Earth is curved. Figure 15 illustrateswhy the equator receives more radiation than areas to the northor south. The heated air at the equator is less dense, so it is dis-placed by denser, colder air, creating convection currents.

This cold, denser air comes from the poles, which receive lessradiation from the Sun, making air at the poles much cooler. Theresulting dense, high-pressure air sinks and moves along Earth’ssurface. However, dense air sinking as less-dense air rises doesnot explain everything about wind.

■ Explain why different latitudes onEarth receive different amounts ofsolar energy.

■ Describe the Coriolis effect.■ Locate doldrums, trade winds,

prevailing westerlies, polar easter-lies, and jet streams.

VocabularyCoriolis effect sea breezejet stream land breeze

Wind systems determine majorweather patterns on Earth.

Air MovementS E C T I O N

Figure 15Because of Earth’s curved surface, the Sun’srays strike the equator more directly thanareas toward the north or south poles.

Near the poles, the Sun's energy strikes Earth at an angle, spreading out the energy received over a larger area than near the equator.

Each square meter of area at the equator receives more energy from the Sun than each square meter at the poles does.

The Coriolis Effect What would happen if you threw a ballto someone sitting directly across from you on a moving merry-go-round? Would the ball go to your friend? By the time the ballgot to the opposite side, your friend would have moved and theball would appear to have curved.

Like the merry-go-round, the rotation of Earth causes mov-ing air and water to appear to turn to the right north of theequator and to the left south of the equator. This is called theCoriolis (kohr ee OH lus) effect. It is illustrated in Figure 16.The flow of air caused by differences in the amount of solarradiation received on Earth’s surface and by the Coriolis effectcreates distinct wind patterns on Earth’s surface. These windsystems not only influence the weather, they also determinewhen and where ships and planes travel most efficiently.

Global WindsHow did Christopher Columbus get from Spain to the

Americas? The Nina, the Pinta, and the Santa Maria had nosource of power other than the wind in their sails. Early sailorsdiscovered that the wind patterns on Earth helped them navi-gate the oceans. These wind systems are shown in Figure 17.

Sometimes sailors found little or no wind to move their sail-ing ships near the equator. It also rained nearly every afternoon.This windless, rainy zone near the equator is called the dol-drums. Look again at Figure 17. Near the equator, the Sun heatsthe air and causes it to rise, creating low pressure and little wind.The rising air then cools, causing rain.

What are the doldrums?


Actual path of wind

N

S

Path of wind without Coriolis effect

Equator

Research Visit the Glencoe Science Web site atscience.glencoe.com tolearn more about globalwinds. Communicate to yourclass what you’ve learned.

Figure 16The Coriolis effect causes movingair to turn to the right in thenorthern hemisphere and to theleft in the southern hemisphere.


TRADE WINDSAir warmed near the equator travelstoward the polesbut gradually coolsand sinks. As the airflows back towardthe low pressure of the doldrums, the Coriolis effectdeflects the surface wind to the west. Early sailors,in ships like the one above, relied on these windsto navigate global trade routes.

C

Figure 17

VISUALIZINGGLOBAL WINDS

The Sun’s uneven heating of Earth’s surfaceforms giant loops, or cells, of moving air. The Coriolis effect deflects the surface winds

to the west or east, setting up belts of prevailingwinds that distribute heat and moisture aroundthe globe.

30° N

0°

60° N

30° S

60°S

Equatorial doldrums

Trade winds

Westerlies

Westerlies

Polar easterlies

Trade winds

Polar easterlies

DOLDRUMS Along the equator, heating causes air toexpand, creating a zone of lowpressure. Cloudy, rainy weather,as shown here, develops almostevery afternoon.

B

POLAR EASTERLIESIn the polar regions,cold, dense air sinksand moves away fromthe poles. Earth’s rota-tion deflects this windfrom east to west.

D

WESTERLIES Near 30° north and south latitude, Earth’s rotation deflects air from westto east as air moves toward the polar regions.In the United States, the westerlies moveweather systems, such as this one along theOklahoma-Texas border, from west to east.

A

Equatorial doldrums

Trade winds

Westerlies

Westerlies

Polar easterlies

Trade winds

Polar easterlies


Warm air

Cold air

Polar jet stream

Surface Winds Air descending to Earth’s surface near 30°north and south latitude creates steady winds that blow in tropi-cal regions. These are called trade winds because early sailorsused their dependability to establish trade routes.

Between 30° and 60° latitude, winds called the prevailingwesterlies blow in the opposite direction from the trade winds.Prevailing westerlies are responsible for much of the movementof weather across North America.

Polar easterlies are found near the poles. Near the northpole, easterlies blow from northeast to southwest. Near thesouth pole, polar easterlies blow from the southeast to thenorthwest.

Winds in the Upper Troposphere Narrow belts of strongwinds, called jet streams, blow near the top of the troposphere.The polar jet stream forms at the boundary of cold, dry polar airto the north and warmer, more moist tropical air to the south,as shown in Figure 18. The jet stream moves faster in the winterbecause the difference between cold air and warm air is greater.The jet stream helps move storms across the country.

Jet pilots take advantage of the jet streams. When flying east-ward, planes save time and fuel. Going west, planes fly at differ-ent altitudes to avoid the jet streams.

Local Wind Systems Global wind systems determine the major weather patterns

for the entire planet. Smaller wind systems affect local weather.If you live near a large body of water, you’re familiar with twosuch wind systems—sea breezes and land breezes.


Figure 18A strong current of air, called thejet stream, forms between cold,polar air and warm, tropical air.

Flying from Boston to Seattlemay take 30 min longer than fly-ing from Seattle to Boston.

The polar jet stream in North America usually isfound between 10 km and 15 km above Earth’s surface.

Sea Breezes Convection currents over areas where the landmeets the sea can cause wind. A sea breeze, shown in Figure 19,is created during the day because solar radiation warms the landmore than the water. Air over the land is heated by conduction.This heated air is less dense and has lower pressure. Cooler,denser air over the water has higher pressure and flows towardthe warmer, less dense air. A convection current results, andwind blows from the sea toward the land.

How does a sea breeze form?

Land Breezes At night, land cools much more rapidly thanocean water. Air over the land becomes cooler than air over theocean. Cooler, denser air above the land moves over the water, asthe warm air over the water rises. Movement of air toward thewater from the land is called a land breeze.


Figure 19 These daily winds occur becauseland heats up and cools off fasterthan water does. During theday, cool air from the watermoves over the land, creating asea breeze. At night, cool airover the land moves toward thewarmer air over the water, creat-ing a land breeze.

Section Assessment

1. Why do some parts of Earth’s surface,suchas the equator, receive more of the Sun’sheat than other regions?

2. How does the Coriolis effect influence windcirculation on Earth?

3. Why does little wind and lots of afternoonrain occur in the doldrums?

4. Which wind system helped early sailorsnavigate Earth’s oceans?

5. Think Critically How does the jet streamhelp move storms across North America?

6. Comparing and Contrasting Compare andcontrast sea breezes and land breezes. For morehelp, refer to the Science Skill Handbook.

7. Using Graphics Software Use graphics soft-ware and Figure 17 to draw the wind systems onEarth. Make a separate graphic of major wind cir-culation cells shown by black arrows. On anothergraphic, show major surface winds. Print yourgraphics and share them with your class. For morehelp, refer to the Technology Skill Handbook.

Warm air

Warm air

Land breeze

Cool air

Cool air

Sea breeze

Sometimes, a plunge in a pool or lake on a hot summer day feels cool and refresh-ing. Why does the beach sand get so hot when the water remains cool? A few

hours later, the water feels warmer than the land does. In this activity, you’ll explorehow water and land absorb heat.

Recognize the ProblemHow do soil and water compare in their abilities to absorb and emit heat?

Form a HypothesisForm a hypothesis about how soil and water compare in their abilities to absorb andrelease heat. Write another hypothesis about how air temperatures above soil andabove water differ during the day and night.

Safety Precautions

WARNING: Be careful when handling thehot overhead light. Do not let the light orits cord make contact with water.

Possible Materialsring stand clear plastic boxes (2)soil overhead light metric ruler with reflectorwater thermometers (4)masking tape colored pencils (4)

Goals■ Design an experiment to compare

heat absorption and release for soiland water.

■ Observe how heat release affectsthe air above soil and above water.

The Heat Is On

300

Test Your Hypothesis

Analyze Your Data

Draw Conclusions

Do1. Make sure your teacher approves

your plan and your data table beforeyou start.

2. Carry out the experiment as planned.

3. During the experiment, record yourobservations and complete the datatable in your Science Journal.

4. Include the temperatures of the soiland the water in your measurements.Also compare heat release for waterand soil. Include the temperatures ofthe air immediately above both ofthe substances. Allow 15 min foreach test.

Plan1. As a group, agree upon and write

your hypothesis.

2. List the steps that you need to taketo test your hypothesis. Include inyour plan a description of how youwill use your equipment to compareheat absorption and release forwater and soil.

3. Design a data table in your ScienceJournal for both parts of your exper-iment—when the light is on andenergy can be absorbed and whenthe light is off and energy is releasedto the environment.

2. Analyze your graphs. When thelight was on, which heated upfaster—the soil or the water?

3. Compare how fast the air temper-ture over the water changed withhow fast the temperature over theland changed after the light wasturned off.

1. Use your colored pencils and theinformation in your data tables tomake line graphs. Show the rate oftemperature increase for soil andwater. Graph the rate of tempera-ture decrease for soil and water afteryou turn the light off.

1. Were your hypotheses supported or not? Explain.

2. Infer from your graphs which cooled faster—the water or the soil.

3. Compare the temperatures of the air above the water and above the soil 15 minutes after the light was turned off. How do water and soil compare in their abilities to absorb andrelease heat?

ACTIVITY 301

Make a poster showing the steps you followed for your experiment. Include graphs of your data. Display your poster in the classroom. For more help, refer to theScience Skill Handbook.

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Science & Language ArtsandandandScience Language Arts

Respond to the ReadingRespond to the Reading

1. Why do the wordsMother Earth andFather Sky appear oneither side and aboveand below the rest ofthe words?

2. Why does the songuse the image of agarment to describeEarth’s atmosphere?

This Native American prayer probably comes from theTewa-speaking Pueblo village of San Juan, New Mexico. Thepoem is actually a chanted prayer used in ceremonial rituals.

Mother Earth Father Sky

we are your children

With tired backs we bring you gifts you love

Then weave for us a garment of brightnessits warp2 the white light of morning,

weft3 the red light of evening,fringes the falling rain,

its border the standing rainbow.

Thus weave for us a garment of brightnessSo we may walk fittingly where birds sing,So we may walk fittingly where grass is green.

Mother Earth Father Sky

1 a machine or device from

which cloth is produced2 threads that run lengthwise

in a piece of cloth3 horizontal threads inter-

laced through the warp in a

piece of cloth

Song of the Sky Loom1

Brian Swann, ed.


m grat on compound d chotomous greenhoexoskeleton permafrost magma isotopes plat

cellgymmaionthekidproignparzonmoorpetalalloomogeproacctabnoleathtemsolahavdim

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Creating a Metaphor Write afour-line poem that uses ametaphor to describe rain. Youcan choose to write about a gen-tle spring rain or a thunderousrainstorm. Remember that ametaphor does not use the wordslike or as. Therefore,your poemshould begin with something like“Rain is . . .” or “Heavy rain is . . .”

andandandLinking Science Linking Science

Kim Perez is an on-air meteorologist for The Weather Channel, anational cable television network. She became interested in theweather when she was living in Cincinnati, Ohio. There, in 1974, shewitnessed the largest tornado on record. Ms.Perez now broadcastsweather reports to millions of television viewers. Meteorologistsstudy computer models of Earth’s atmosphere. These models helpthem predict short-term and long-term weather conditions for theUnited States and the world.

To learn more about careers in meteorology,visit the Glencoe Science Web site at science.glencoe.com.

Meteorologist �

CareerCareer ConnectionConnection

Understanding LiteratureMetaphor A metaphor is a figure of speech that com-pares seemingly unlike things. Unlike a simile, ametaphor does not use the connecting words like or as.For instance, in the song you just read, Father Sky is aloom. A loom is a machine or device that weaves cloth.The song describes the relationship between Earth andsky as being a woven garment. Lines such as “weave forus a garment of brightness” serve as metaphors forhow Mother Earth and Father Sky together create anatmosphere in which their “children,” or humans, canthrive.

Science Connection In this chapter, you learned aboutthe composition of Earth’s atmosphere. The atmo-sphere maintains the proper balance between theamount of heat absorbed from the Sun and the amountof heat that escapes back into space. You also learnedabout the water cycle and how water evaporates fromEarth’s surface back into the atmosphere. Usingmetaphor instead of scientific facts, the Tewa song con-veys to the reader how the relationship between Earthand its atmosphere is important to all living things.

Metaphor

SCIENCE AND LANGUAGE ARTS 303


304 CHAPTER STUDY GUIDE

4. Unlike the atmosphere on Mars or Venus,Earth’s unique atmosphere maintains a balance between energy received and energylost that keeps temperatures mild. This deli-cate balance allows life on Earth to exist.

Section 3 Air Movement 1. Because Earth’s surface is curved, not all

areas receive the same amount of solar radiation. This uneven heating causes temperature differences at Earth’s surface.

2. Convection currents modified by the Coriolis effect produce Earth’s global winds.

3. The polar jet stream is a strong current of wind found in the upper troposphere.It forms at the boundary between cold,polar air and warm, tropical air.

4. Land breezesand sea breezesoccur near theocean. Why dowinds changedirection fromday to night?

Section 1 Earth’s Atmosphere1. Earth’s atmosphere is made up mostly

of gases, with some suspended solids andliquids. The unique atmosphere allows life on Earth to exist.

2. The atmosphere is divided into five layerswith different characteristics.

3. The ozone layerprotects Earthfrom too muchultraviolet radia-tion, which canbe harmful. Howdo chlorofluoro-carbon moleculesdestroy ozone?

Section 2 Energy Transfer in the Atmosphere

1. Earth receives its energy from the Sun.Some of this energy is reflected back intospace, and some is absorbed.

2. Heat is distributed in Earth’s atmosphere byradiation, conduction, and convection.

3. Energy from the Sun powers the water cycle between the atmosphere and Earth’ssurface. Clouds form during which part of the water cycle?

Cl

Cl

Cl

F C

Draw pictures on the frontof your Foldable of thingsthat you might find in each

layer of Earth’s atmosphere.

After You ReadFOLDABLESReading & StudySkills

FOLDABLESReading &Study Skills

Study GuideChapter Study GuideChapter 1010

Vocabulary Reviewa. atmosphere i. jet streamb. chlorofluorocarbon j. land breezec. condensation k. ozone layerd. conduction l. radiatione. convection m. sea breezef. Coriolis effect n. troposphereg. hydrosphere o. ultraviolet radiationh. ionosphere

Using VocabularyThe sentences below include terms that have

been used incorrectly. Change the incorrect termsso that the sentence reads correctly.

1. Chlorofluorocarbons are dangerous becausethey destroy the hydrosphere.

2. Narrow belts of strong winds called seabreezes blow near the top of the troposphere.

3. The thin layer of air that surrounds Earth iscalled the troposphere.

4. Heat energy transferred in the form ofwaves is called condensation.

5. The ozone layer helps protect us from theCoriolis effect.

CHAPTER STUDY GUIDE 305

Describe ways that you might design an experi-ment to prove scientific principles.

Study Tip

Complete the following cycle map on the water cycle.

Study GuideChapter

Cooled water vaporcondenses.

Energy from the Sun evaporates

water.

1010

Choose the word or phrase that best answersthe question.

1. What is the most abundant gas in theatmosphere?A) oxygen C) argonB) water vapor D) nitrogen

2. What causes a brown haze near cities?A) conduction C) car exhaustB) mud D) wind

3. Which is the uppermost layer of the atmo-sphere?A) troposphere C) exosphereB) stratosphere D) thermosphere

4. What layer of the atmosphere has the mostwater?A) troposphere C) mesosphereB) stratosphere D) exosphere

5. What protects living things from too muchultraviolet radiation?A) the ozone layer C) nitrogenB) oxygen D) argon

6. Where is air pressure least?A) troposphere C) exosphereB) stratosphere D) thermosphere

7. How is energy transferred when objects arein contact?A) trade winds C) radiationB) convection D) conduction

8. Which surface winds are responsible formost of the weather movement across theUnited States?A) polar easterlies C) prevailing westerlies B) sea breeze D) trade winds

9. What type of wind is a movement of airtoward water?A) sea breeze C) land breezeB) polar easterlies D) trade winds

10. What are narrow belts of strong winds nearthe top of the troposphere called?A) doldrums C) polar easterliesB) jet streams D) trade winds

11. Why are there few or no clouds in thestratosphere?

12. It is thought that life could not have existedon land until the ozone layer formed about2 billion years ago. Why does life on landrequire an ozone layer?

13. Why do sea breezes occur during the daybut not at night?

14. Describe what happens when water vaporrises and cools.

15. Why does air pressure decrease with anincrease in altitude?

16. Concept Mapping Complete the cycle con-cept map below using the following phrasesto explain how air moves to form a convec-tion current: Cool air moves toward warmair, warm air is lifted and cools, and cool airsinks.

306 CHAPTER ASSESSMENT

Cool air is warmed by conduction.

AssessmentChapter 1010

CHAPTER ASSESSMENT 307

17. Drawing Conclusions In an experiment, astudent measured the air temperature 1 mabove the ground on a sunny afternoon andagain in the same spot 1h after sunset. Thesecond reading was lower than the first.What can you infer from this?

18. Forming Hypotheses Carbon dioxide inthe atmosphere prevents some radiationfrom Earth’s surface from escaping to space.Hypothesize how the temperature on Earthmight change if more carbon dioxide werereleased from burning fossil fuels.

19. Identifying and Manipulating Variablesand Controls Design an experiment to findout how plants are affected by differingamounts of ultraviolet radiation. In thedesign, use filtering film made for car win-dows. What is the variable you are testing?What are your constants? Your controls?

20. Recognizing Cause and Effect Why is theinside of a car hotter than the outdoor temperature on a sunny summer day?

21. Poster Illustrate or find magazine photosof convection currents that occur in every-day life.

22. Experiment Design and conduct an experi-ment to find out how different surfacessuch as asphalt, soil, sand, and grass absorband reflect solar energy. Share the resultswith your class.

Go to the Glencoe Science Web site at science.glencoe.com or use theGlencoe Science CD-ROM for additionalchapter assessment.

TECHNOLOGY

AssessmentChapter AssessmentChapter

Each layer of Earth’s atmosphere has aunique composition and temperature. Thefour layers closest to Earth’s surface areshown in the diagram below.

Study the diagram and answer the following questions.

1. In which part of the atmosphere isozone located.A) Thermosphere C) StratosphereB) Troposphere D) Mesosphere

2. According to the diagram, how fardoes the mesosphere extend aboveEarth’s surface?F) 10 km H) 50 kmG) 85 km I) 60 km

3. What is the correct order of atmo-spheric layers that the space shuttlegoes through when landing on Earth?A) Mesosphere C) Stratosphere

Stratosphere TroposphereTroposphere Mesosphere

B) Troposphere D) MesosphereStratosphere TroposphereMesosphere Stratosphere

Thermosphere(85-500 km)

Mesosphere(50-85 km)

Stratosphere(10-50 km)

Troposphere(0-10km)

Earth

Ozone layer

1010

Test Practice


Documents

Science Unit 4 (Glencoe Red 2002)