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Science Unit 4 (Glencoe Red 2002)

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  • 1. UNIT 4 Earth’s Air and Water How Are Air & Advertising Connected?278
  • 2. I n the late 1800s, two scientists were studying the composition of air when they discovered anelement 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. SCIENCE 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 out more about this group. What other gases belong to the group? What do they all have in common? Why are they called “noble”? Create a chart that shows when each of the noble gases was discovered and what distinctive characteris- tics and uses it has.
  • 3. 10 AtmosphereW hy is it difficult to breathe at high elevations? Why are some mountain peakspermanently 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.280
  • 4. EXPLORE T he air around you is made of billions of molecules. These molecules are constantly moving in all ACTIVITY directions and bouncing into every object in the room, including you. Air pressure is the result of the billions of collisions of molecules into these objects. Because you usually do not feel molecules in air hitting you, do the activity below to see the effect of air pressure. Observe air pressure 1. 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. Observe Write a paragraph in your Science Journal describing what happened to the cardboard when you inverted the glass and removed your hand. How does air pressure explain what happened?FOLDABLESReading &Study & Study Making a Sequence Study Fold Make the following FoldableSkills to help you visualize the layers of Earth’s atmosphere.1. Stack three sheets of paper in front of you so the short Exosphere sides are at the top. Thermosphere Mesosphere2. Slide the top sheet up so that about four centimeters of Stratosphere the middle sheet show. Slide the middle sheet up so Troposphere that about four centimeters of the bottom sheet show. Earths3. Fold the sheets top to bottom to form six tabs and sta- Atmosphere ple along the topfold. Turn the Foldable so the staples are 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. 281
  • 5. SECTION Earth’s Atmosphere Importance of the Atmosphere Earth’s atmosphere, shown in Figure 1, is a thin layer of airs Identify the gases in Earth’s that forms a protective covering around the planet. If Earth had atmosphere. no atmosphere, days would be extremely hot and nights woulds Describe the structure of Earth’s be extremely cold. Earth’s atmosphere maintains a balance atmosphere. between the amount of heat absorbed from the Sun and thes Explain what causes air pressure. amount of heat that escapes back into space. It also protects life-Vocabulary forms from some of the Sun’s harmful rays.atmosphere ozone layertroposphere ultraviolet radiationionosphere chlorofluorocarbon Makeup of the Atmosphere Earth’s atmosphere is a mixture of gases, solids, and liquids that surround the planet. It extends from Earth’s surface toThe atmosphere makes life on Earthpossible. outer space. The atmosphere is much different today from what it was when Earth was young.Figure 1 Earth’s early atmosphere, produced by erupting volcanoes,Earth’s atmosphere, as viewed contained nitrogen and carbon dioxide, but little oxygen. Then,from space, is a thin layer of more than 2 billon years ago, Earth’s early organisms releasedgases. The atmosphere keeps oxygen into the atmosphere as they made food with the aid ofEarth’s temperature in a range sunlight. These early organisms, however, were limited to layersthat can support life. of ocean water deep enough to be shielded from the Sun’s harmful rays, yet close enough to the surface to receive sunlight. Eventu- ally, a layer rich in ozone (O3) that protects Earth from the Sun’s harmful rays formed in the upper atmosphere. This protec- tive layer eventually allowed green plants to flourish all over Earth, releasing even more oxy- gen. Today, a variety of life forms, including you, depends on a certain amount of oxygen in Earth’s atmosphere.282 CHAPTER 10 Atmosphere
  • 6. Gases in the Atmosphere Today’satmosphere is a mixture of the gases Argon (0.93%)–shown in Figure 2. Nitrogen is the most Carbonabundant gas, making up 78 percent of the dioxide–atmosphere. Oxygen actually makes up (0.03%) 21% 78%only 21 percent of Earth’s atmosphere. As Oxygen Nitrogen Neon–much as four percent of the atmosphere is Helium–water vapor. Other gases that make up Methane–Earth’s atmosphere include argon and car- Krypton– – Trace 1%bon dioxide. Xenon – Hydrogen– The composition of the atmosphere is Ozone–changing in small but important ways. Forexample, car exhaust emits gases into theair. These pollutants mix with oxygen and other chemicals in the Figure 2presence of sunlight and form a brown haze called smog. This graph shows the percent-Humans burn fuel for energy. As fuel is burned, carbon dioxide ages of the gases, excludingis released as a by-product into Earth’s atmosphere. Increasing water vapor, that make upenergy use may increase the amount of carbon dioxide in the Earth’s atmosphere.atmosphere.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 moves Figure 3these liquid droplets and solids from one region to another. For Solids and liquids can travel largeexample, the atmosphere above you may contain liquid droplets distances in Earth’s atmosphere,and solids from an erupting volcano thousands of kilometers affecting regions far from theirfrom your home, as illustrated in Figure 3. source. On June 12, 1991, Mount Pinatubo inthe Philippines erupted, causing liquiddroplets to form in Earth’s atmosphere. Droplets of sulfuric acid from volcanoes can produce spectacular sunrises. SECTION 1 Earth’s Atmosphere 283
  • 7. Layers of the Atmosphere What would happen if you left a glass of chocolate milk on the kitchen counter for a while? Eventually, you would see a lower layer with more chocolate separating from upper layers with 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 lower Research Visit the layers include the troposphere and stratosphere. The upper Glencoe Science Web site at atmospheric layers are the mesosphere, thermosphere, and exo- science.glencoe.com sphere. The troposphere and stratosphere contain most of the air. for more information about layers of Earth’s atmosphere. Lower Layers of the Atmosphere You study, eat, sleep, Communicate to your class and play in the troposphere, which is the lowest of Earth’s what you learn. atmospheric layers. It contains 99 percent of the water vapor and 75 percent of the atmospheric gases. Rain, snow, and clouds occur 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. As Figure 4 shows, a portion of the stratosphere contains higher levels of a gas called ozone. Each molecule of ozone is made up of three oxygen atoms bonded together. Later in this section you will learn how ozone protects Earth from the Sun’s harmful rays.Figure 4 Satellite ExosphereEarth’s atmosphere is divided 500 kminto five layers. Which layer of theatmosphere do you live in? Space shuttle Meteor trails Thermosphere 85 km Mesosphere 50 km Ozone layer Stratosphere Jet 10 km Troposphere284 Earth
  • 8. Figure 5 During the day, the ionosphere Day Night absorbs radio transmissions. This prevents you from hearing distant radio stations. At night, the ionosphere reflects radio AM radio transmitter Radio waves waves. The reflected waves can travel to distant cities. Receiving antenna ere Ionosph Boise New JerseyUpper 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, you Figure 6might have witnessed a meteor in the mesosphere. Wings help move aircraft in lower The thermosphere is named for its high temperatures. This layers of the atmosphere. Theis the thickest atmospheric layer and is found between 85 km space shuttle can’t use its wingsand 500 km above Earth’s surface. to maneuver in the exosphere Within the mesosphere and thermosphere is a layer of elec- because so few molecules aretrically charged particles called the ionosphere (i AHN uh sfir). present.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 the exosphere? SECTION 1 Earth’s Atmosphere 285
  • 9. Atmospheric Pressure Imagine you’re a football player running with the ball. Six players tackle you and pile one on top of the other. Who feels the weight more—you or the player on top? Like molecules anywhere else, atmospheric gases have mass. Atmospheric gases extend hundreds of kilometers above Earth’s sur- face. As Earth’s gravity pulls the gases toward its surface, the weight of these gases presses down on the air below. As a result, the molecules nearer Earth’s surface are closer together. This dense air exerts more force than the less dense air near the top of the atmosphere. Force exerted on an area is known as pressure. Like the pile of football players, air pressure is greater near Earth’s surface and decreases higher in the atmosphere, as shown in Figure 7. People find it difficult to breathe in high mountainsFigure 7 because fewer molecules of air exist there. Jets that fly in theAir pressure decreases as you go stratosphere must maintain pressurized cabins so that peoplehigher in Earth’s atmosphere. can breathe. Where is air pressure greater—in the exosphere or in the troposphere? Problem-Solving Activity How does altitude affect air pressure? tmospheric gases extend hundreds of A kilometers above Earth’s surface, but the molecules that make up these gases are Air Pressure Changes with Altitude 1000 Pressure (millibars) 800 fewer and fewer in number as you go higher. This means that air pressure decreases with 600 altitude. 400 Identifying the Problem 200 The graph on the right shows these 0 10 20 30 40 50 changes in air pressure. Note that altitude Altitude (km) on the graph goes up only to 50 km. The troposphere and the stratosphere are repre- Solving the Problem sented on the graph, but other layers of the 1. Estimate the air pressure at an altitude of atmosphere are not. By examining the 5 km. graph, can you understand the relationship 2. Does air pressure change more quickly at between altitude and pressure? higher altitudes or at lower altitudes? 286 CHAPTER 10 Atmosphere
  • 10. Temperature in Atmospheric Layers The Sun is the source of most of the energy on Earth. Beforeit reaches Earth’s surface, energy from the Sun must passthrough the atmosphere. Because some layers contain gases that Determining if aireasily absorb the Sun’s energy while other layers do not, the vari- has massous layers have different temperatures, illustrated by the red linein Figure 8. Procedure 1. On a pan balance, find the Molecules that make up air in the troposphere are warmed mass of an inflatable ballmostly by heat from Earth’s surface. The Sun warms Earth’s sur- that is completely deflated.face, which then warms the air above it. When you climb a 2. Hypothesize about themountain, the air at the top is usually cooler than the air at the change in the mass of thebottom. Every kilometer you climb, the air temperature ball when it is inflated.decreases about 6.5°C. 3. Inflate the ball to its maximum recommended Molecules of ozone in the stratosphere absorb some of the inflation pressure.Sun’s energy. Energy absorbed by ozone molecules raises the 4. Determine the mass of thetemperature. Because more ozone molecules are in the upper fully inflated ball.portion of the stratosphere, the temperature in this layer rises Analysiswith increasing altitude. 1. What change occurs in the Like the troposphere, the temperature in the mesosphere mass of the ball when it isdecreases with altitude. The thermosphere and exosphere are inflated?the first layers to receive the Sun’s rays. Few molecules are in 2. Infer from your datathese layers, but each molecule has a great deal of energy. Tem- whether air has mass.peratures here are high. Temperature of the Atmosphere at Various Altitudes Exosphere 500 Figure 8 Thermosphere 120 The division of the atmosphere 110 into layers is based mainly on dif- ferences in temperature. Does the 100 temperature increase or decrease 90 with altitude in the mesosphere?Altitude (km) 80 Mesosphere 70 60 50 Stratosphere 40 Highest concentration of ozone 30 20 10 Troposphere 0 -100 -80 -60 -40 -20 0 20 400 600 800 Temperature (ºC) SECTION 1 Earth’s Atmosphere 287
  • 11. The Ozone Layer Within the stratosphere, about 19 km to 48 km above your Algae are organisms that head, lies an atmospheric layer called the ozone layer. Ozone is use sunlight to make their made of oxygen. Although you cannot see the ozone layer, your own food. This process life depends on it. releases oxygen to Earth’s The oxygen you breathe has two atoms per molecule, but an atmosphere. Some scien- ozone molecule is made up of three oxygen atoms bound tists suggest that growth is together. The ozone layer contains a high concentration of reduced when algae are exposed to ultraviolet ozone and shields you from the Sun’s harmful energy. Ozone radiation. Infer what might absorbs most of the ultraviolet radiation that enters the atmo- happen to the oxygen level sphere. Ultraviolet radiation is one of the many types of energy of the atmosphere if that come to Earth from the Sun. Too much exposure to ultravi- increased ultraviolet radia- olet radiation can damage your skin and cause cancer. tion damages some algae. CFCs Evidence exists that some air pollutants are destroying the ozone 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 they and other products containing CFCs are improperly discarded. Recall that an ozone molecule is made of three oxygen atoms bonded together. Chlorofluorocarbon molecules, shown in Figure 9, destroy ozone. When a chlorine atom from a chlorofluorocarbon molecule comes near a molecule of ozone, the ozone molecule breaks apart. One of the oxygen atoms combines with the chlorine atom, and the rest form a regular, two-atom molecule. These compounds don’t absorb ultraviolet radiation the way ozone can. In addition, the original chlorine atom can continue to break apart thousands of ozone molecules. The result is that more ultraviolet radiation reaches Earth’s surface. A. B. C. Ultraviolet light Cl Cl O breaks up CFC O O O UV molecule. light O O The chlorine atom joins Cl A released with an oxygen atom, F chlorine atom breaks leaving behind a Cl Cl up ozone (O3) molecule. molecule of oxygen (O2). CFigure 9 D. E. F.Chlorofluorocarbon (CFC) mole- O Clcules were used in refrigerators O O Cl O Oand air conditioners. Each CFC O Released Omolecule has three chlorine A free oxygen Oxygen atoms chlorine atomatoms. One atom of chlorine can atom breaks the rejoin to form a normal breaks up anotherdestroy approximately 100,000 chlorine-oxygen bond. oxygen (O2) molecule. ozone (O3) molecule.ozone molecules.288 CHAPTER 10 Atmosphere
  • 12. October 1980 October 1988 October 1990 September 1999 Ozone Holes Each year, more Figure 10 than 1.3 million Americans develop These images of Antarctica were skin cancer, and more than 9,500 die produced using data from a NASA from it. Exposure to ultraviolet radiation can cause skin cancer. If satellite. The purple color shows the ozone layer disappeared, skin cancer rates might increase. In how the ozone hole has grown 1986, scientists found areas in the stratosphere with extremely bigger over time. low amounts of ozone. One large hole was found over Antarc- tica. A smaller hole was discovered over the north pole. Figure 10 shows 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 the ozone layer is thinning will recover. Section Assessment 1. Earth’s early atmosphere had little oxygen. How did oxygen come to make up 21 per- 6. Interpreting Scientific Illustrations Using cent of Earth’s present atmosphere? Figure 2, determine the total percentage of 2. List the layers of the atmosphere in order nitrogen and oxygen in the atmosphere. What beginning at Earth’s surface. is the total percentage of argon and carbon 3. While hiking in the mountains, you notice dioxide? For more help, refer to the Science that it is harder to breathe as you climb Skill Handbook. higher. Explain why this is so. 7. Communicating The names of the atmo- 4. What are some effects from a thinning spheric layers end with the suffix -sphere a word ozone layer? that means “ball.” Use a dictionary to find out 5. Think Critically During the day, the radio what tropo-, meso-, thermo-, and exo- mean. only receives AM stations from a city near In your Science Journal, write the meaning of you. At night, you are able to listen to an these prefixes and explain if the layers are AM radio station from a distant city. appropriately named. For more help, refer to Explain why this is possible. the Science Skill Handbook. SECTION 1 Earth’s Atmosphere 289
  • 13. Evaluating Sunscreens W ithout protection, sun exposure can dam- age your health. Sunscreens protect your skin from ultraviolet radiation. In this activity, you will draw inferences using the labels of different sunscreens. What You’ll Investigate How effective are various brands of sunscreens? Materials variety of sunscreens of different brand names Goals Sunscreen Assessment s Draw inferences based on labels on sun- Brand Name screen brands. SPF s Compare the effectiveness of different sun- screen brands for protection against the Sun. Cost per Milliliter s Compare the cost of several sunscreen brands. Misleading Terms Safety Precautions Conclude and Apply 1. Explain why you need to use sunscreen. Procedure 2. A minimum of SPF 15 is considered adequate protection for a sunscreen. Sunscreens with 1. Make a data table in your Science Journal an SPF greater than 30 are considered by using the following terms: brand name, SPF, government guidelines to be misleading misleading terms, and cost per milliliter. because sunscreens will wash or wear off. 2. The Sun Protection Factor (SPF) tells you how Evaluate the SPF of each brand of sunscreen. long the sunscreen will protect you. For exam- 3. Considering the cost and effectiveness of all ple, an SPF of 4 allows you to stay in the Sun the sunscreen brands, discuss which brand four times longer than if you did not use sun- you consider to be the best buy. screen. Record the SPF of each sunscreen on your data table. 3. Calculate the cost per milliliter of each sun- screen brand. 4. Government guidelines say that terms like Create a poster on the proper use of sun- sunblock and waterproof are misleading screens, and provide guidelines for selecting because sunscreens cannot block the Sun, and the safest product. For more help, refer to they wash off in water. List the misleading the Science Skill Handbook. terms in your data table for each brand.290 CHAPTER 10 Atmosphere
  • 14. SECTION Energy Transfer in the AtmosphereEnergy from the Sun The Sun provides most of the energy on Earth. This energydrives winds and ocean currents and allows plants to grow and s Describe what happens to theproduce food, providing nutrition for many animals. When energy Earth receives from theEarth receives energy from the Sun, three different things can Sun. s Compare and contrast radiation,happen to that energy, as shown in Figure 11. Some energy is conduction, and convection.reflected back into space by clouds, atmospheric particles, and s Explain the water cycle.Earth’s surface. Some is absorbed by the atmosphere. The rest isabsorbed by land and water on Earth’s surface. Vocabulary radiation hydrosphere conduction condensationHeat convection 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, The Sun provides energy to Earth’s atmosphere, allowing life to exist.rocks, and water. Heat then is transferred through the atmo-sphere in three ways—radiation, conduction, and convection, asshown in Figure 12. Figure 11 6% reflected by The Sun is the source of energy the atmosphere for Earth’s atmosphere. Thirty- five percent of incoming solar radiation is reflected back into space. How much is absorbed by Earth’s surface and atmosphere? 25% reflected from clouds 15% absorbed by the atmosphere 4% reflected from Earth’s surface 50% directly or indirectly absorbed by Earth’s surface 291
  • 15. Radiation warms the surface. Cooler air pushes warm air upward, The air near creating a Earths surface convection current. is heated by conduction.Figure 12 Radiation Sitting on the beach, you feel the Sun’s warmth onHeat is transferred within Earth’s your face. How can you feel the Sun’s heat even though youatmosphere by radiation, con- aren’t in direct contact with it? Energy from the Sun reachesduction, and convection. Earth in the form of radiant energy, or radiation. Radiation is energy that is transferred in the form of rays or waves. Earth radiates some of the energy it absorbs from the Sun back toward space. 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 feet heat up because of conduction. Conduction is the transfer of energy that occurs when molecules bump into one another. Specific heat is the amount Molecules are always in motion, but molecules in warmer of heat required to change the temperature of a sub- objects move faster than molecules in cooler objects. When stance one degree. Sub- objects are in contact, energy is transferred from warmer objects stances with high specific to cooler objects. heat absorb a lot of heat for Radiation from the Sun heated the beach sand, but direct a small increase in temper- contact with the sand warmed your feet. In a similar way, Earth’s ature. Land warms faster surface conducts energy directly to the atmosphere. As air than water does. Infer whether soil or water has a moves over warm land or water, molecules in air are heated by higher specific heat value. direct contact. Convection After the atmosphere is warmed by radiation or conduction, 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?292 CHAPTER 10 Atmosphere
  • 16. 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- Modeling Heattion, conduction, and convection together distribute the Sun’s Transferheat throughout Earth’s atmosphere. Procedure 1. Cover the outside of an empty soup can with blackThe Water Cycle construction paper. Hydrosphere is a term that describes all the water on Earth’s 2. Fill the can with cold watersurface. Water moves constantly between the atmosphere and and feel it with your fingers.the hydrosphere in the water cycle, shown in Figure 13. 3. Place the can in sunlight for 1 h then pour the water If you watch a puddle in the Sun, you’ll notice that over time over your fingers.the puddle gets smaller and smaller. Energy from the Sun causes Analysisthe water in the puddle to change from a liquid to a gas by a 1. Does the water in the canprocess called evaporation. Water that evaporates from lakes, feel warmer or cooler afterstreams, and oceans enters Earth’s atmosphere. placing the can in sunlight? If water vapor in the atmosphere cools enough, it changes 2. What types of heat transferback into a liquid. This process of water vapor changing to a liq- did you model?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- Figure 13lide to form larger drops. As the drops grow, they fall to Earth as In the water cycle, water movesprecipitation, which completes the cycle by returning water to from Earth to the atmospherethe hydrosphere. and back to Earth again. Precipitation Condensation Evaporation Runoff SECTION 2 Energy Transfer in the Atmosphere 293
  • 17. Sunlight Earth’sSunlight t Atmosphere HeaSunlight is Unique On Earth, radiation atSunlight He from the Sun can be reflected into space, ab- t Hea Heat sorbed by the atmo- Earths sphere, or absorbed by atmosphere land and water. Once it is absorbed, heat can be transferred by radi-Figure 14 ation, conduction, or convection. Earth’s atmosphere, shown inEarth’s atmosphere creates Figure 14, helps control how much of the Sun’s radiation isa delicate balance between absorbed or lost.energy received and energy 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 to hold much of the Sun’s heat. Temperatures on the surface of Mars range from 35°C to –170°C. On the other hand, gases in Venus’s dense atmosphere trap heat coming from the Sun. The temperature on the surface of Venus is 470°C. Living things would burn instantly if they were placed on Venus’s surface. Life on Earth exists because the atmosphere holds just the right amount of the Sun’s energy. Section Assessment 1. How does the Sun transfer energy to Earth? 2. How is Earth’s atmosphere different from 6. Concept Mapping Make a concept map that the atmosphere on Mars? explains what happens to radiant energy that 3. How is heat transferred from the stove to reaches Earth. For more help, refer to the the water when you boil a pot of water? Science Skill Handbook. 4. Briefly describe the steps included in the 7. Solving One-Step Equations Earth is about water cycle. 150 million km from the Sun. The radiation 5. Think Critically What would happen to coming from the Sun travels at 300,000 km/s. temperatures on Earth if the Sun’s heat How long does it take for radiation from the Sun were not distributed throughout the to reach Earth? For more help, refer to the atmosphere? Math Skill Handbook.294 CHAPTER 10 Atmosphere
  • 18. SECTION Air MovementForming Wind Uneven heating of Earth’s surface by the Sun causes someareas to be warmer than others. Recall from Section 2 that s Explain why different latitudes onwarmer air expands, becoming less dense than colder air. This Earth receive different amounts ofcauses air pressure to be generally lower where air is heated. solar energy. s Describe the Coriolis effect.Wind is the movement of air from an area of higher pressure to s Locate doldrums, trade winds,an area of lower pressure. prevailing westerlies, polar easter- lies, and jet streams.Heated Air Areas of Earth receive different amounts of radia-tion from the Sun because Earth is curved. Figure 15 illustrates Vocabulary Coriolis effect sea breezewhy the equator receives more radiation than areas to the north jet stream land breezeor 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 less Wind systems determine majorradiation from the Sun, making air at the poles much cooler. The weather patterns on Earth.resulting dense, high-pressure air sinks and moves along Earth’ssurface. However, dense air sinking as less-dense air rises doesnot explain everything about wind. Figure 15 Because of Earth’s curved surface, the Sun’s rays strike the equator more directly than Near the poles, North Pole areas toward the north or south poles. the Suns energy strikes Earth at an angle, spreading Suns Rays out the energy received over a larger area than near the equator. Suns Rays Equator Each square meter of Suns Rays area at the equator receives more energy from the Sun than each square meter at the poles does. South Pole SECTION 3 Air Movement 295
  • 19. Figure 16 NThe Coriolis effect causes movingair to turn to the right in thenorthern hemisphere and to theleft in the southern hemisphere. Equ ator Actual path of wind Path of wind without Coriolis effect S The Coriolis Effect What would happen if you threw a ball to someone sitting directly across from you on a moving merry- go-round? Would the ball go to your friend? By the time the ball got to the opposite side, your friend would have moved and the ball 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 the equator and to the left south of the equator. This is called the Coriolis (kohr ee OH lus) effect. It is illustrated in Figure 16. The flow of air caused by differences in the amount of solar radiation received on Earth’s surface and by the Coriolis effect creates distinct wind patterns on Earth’s surface. These wind systems not only influence the weather, they also determine when and where ships and planes travel most efficiently. Global Winds How did Christopher Columbus get from Spain to the Americas? The Nina, the Pinta, and the Santa Maria had no Research Visit the source of power other than the wind in their sails. Early sailors Glencoe Science Web site at discovered that the wind patterns on Earth helped them navi- science.glencoe.com to gate the oceans. These wind systems are shown in Figure 17. learn more about global Sometimes sailors found little or no wind to move their sail- winds. Communicate to your ing ships near the equator. It also rained nearly every afternoon. class what you’ve learned. This windless, rainy zone near the equator is called the dol- drums. Look again at Figure 17. Near the equator, the Sun heats the air and causes it to rise, creating low pressure and little wind. The rising air then cools, causing rain. What are the doldrums?296 CHAPTER 10 Atmosphere
  • 20. VISUALIZING GLOBAL WINDSFigure 17 he Sun’s uneven heating of Earth’s surfaceT forms giant loops, or cells, of moving air. The Coriolis effect deflects the surface windsto the west or east, setting up belts of prevailingwinds that distribute heat and moisture around A WESTERLIES Near 30 ° north and souththe globe. latitude, Earth’s rotation deflects air from west to east as air moves toward the polar regions. In the United States, the westerlies move weather systems, such as this one along the Oklahoma-Texas border, from west to east. 60° N Polar easterlies Westerlies 30° N Trade winds B DOLDRUMS Along theequator, heating causes air toexpand, creating a zone of low 0° Equatorial doldrumspressure. Cloudy, rainy weather,as shown here, develops almostevery afternoon. Trade winds 30° S Westerlies C TRADE WINDSAir warmed near 60°Sthe equator travels Polar easterliestoward the polesbut gradually coolsand sinks. As the airflows back toward D POLAR EASTERLIESthe low pressure In the polar regions,of the doldrums, cold, dense air sinksthe Coriolis effect and moves away fromdeflects the surface wind to the west. Early sailors, the poles. Earth’s rota-in ships like the one above, relied on these winds tion deflects this windto navigate global trade routes. from east to west. SECTION 3 Air Movement 297
  • 21. 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 sailors used their dependability to establish trade routes. Between 30° and 60° latitude, winds called the prevailing westerlies blow in the opposite direction from the trade winds. Prevailing westerlies are responsible for much of the movement of weather across North America. Polar easterlies are found near the poles. Near the north pole, easterlies blow from northeast to southwest. Near the south pole, polar easterlies blow from the southeast to the northwest. Winds in the Upper Troposphere Narrow belts of strong winds, called jet streams, blow near the top of the troposphere. The polar jet stream forms at the boundary of cold, dry polar air to the north and warmer, more moist tropical air to the south, as shown in Figure 18. The jet stream moves faster in the winter because 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-Figure 18 ent altitudes to avoid the jet streams.A strong current of air, called thejet stream, forms between cold,polar air and warm, tropical air. Local Wind Systems Global wind systems determine the major weather patterns Flying from Boston to Seattle for the entire planet. Smaller wind systems affect local weather.may take 30 min longer than fly- If you live near a large body of water, you’re familiar with twoing from Seattle to Boston. such wind systems—sea breezes and land breezes. Cold air Polar je t stream The polar jet stream Warm air in North America usually is found between 10 km and 15 km above Earth’s surface.298 CHAPTER 10 Atmosphere
  • 22. Warm Warm air air Cool air Cool air Land breeze Sea breezeSea Breezes Convection currents over areas where the land Figure 19meets the sea can cause wind. A sea breeze, shown in Figure 19, These daily winds occur becauseis created during the day because solar radiation warms the land land heats up and cools off fastermore than the water. Air over the land is heated by conduction. than water does. During theThis heated air is less dense and has lower pressure. Cooler, day, cool air from the water moves over the land, creating adenser air over the water has higher pressure and flows toward sea breeze. At night, cool airthe warmer, less dense air. A convection current results, and over the land moves toward thewind blows from the sea toward the land. warmer air over the water, creat- ing a land breeze. 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. Section Assessment 1. Why do some parts of Earth’s surface,such as the equator, receive more of the Sun’s 6. Comparing and Contrasting Compare and heat than other regions? contrast sea breezes and land breezes. For more 2. How does the Coriolis effect influence wind help, refer to the Science Skill Handbook. circulation on Earth? 7. Using Graphics Software Use graphics soft- 3. Why does little wind and lots of afternoon ware and Figure 17 to draw the wind systems on rain occur in the doldrums? Earth. Make a separate graphic of major wind cir- 4. Which wind system helped early sailors culation cells shown by black arrows. On another navigate Earth’s oceans? graphic, show major surface winds. Print your 5. Think Critically How does the jet stream graphics and share them with your class. For more help move storms across North America? help, refer to the Technology Skill Handbook. SECTION 3 Air Movement 299
  • 23. The Heat Is On S ometimes, 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 explore how water and land absorb heat. Recognize the Problem How do soil and water compare in their abilities to absorb and emit heat? Form a Hypothesis Form a hypothesis about how soil and water compare in their abilities to absorb and release heat. Write another hypothesis about how air temperatures above soil and above water differ during the day and night. Safety Precautions WARNING: Be careful when handling the hot overhead light. Do not let the light or its cord make contact with water. Possible Materials ring stand clear plastic boxes (2) soil overhead light metric ruler with reflector water thermometers (4) masking tape colored pencils (4) Goals s Design an experiment to compare heat absorption and release for soil and water. s Observe how heat release affects the air above soil and above water.300
  • 24. Test Your HypothesisPlan Do1. As a group, agree upon and write 1. Make sure your teacher approves your hypothesis. your plan and your data table before2. List the steps that you need to take you start. to test your hypothesis. Include in 2. Carry out the experiment as planned. your plan a description of how you 3. During the experiment, record your will use your equipment to compare observations and complete the data heat absorption and release for table in your Science Journal. water and soil. 4. Include the temperatures of the soil3. Design a data table in your Science and the water in your measurements. Journal for both parts of your exper- Also compare heat release for water iment—when the light is on and and soil.Include the temperatures of energy can be absorbed and when the air immediately above both of the light is off and energy is released the substances. Allow 15 min for to the environment. each test. Analyze Your Data1. Use your colored pencils and the 2. Analyze your graphs. When the information in your data tables to light was on, which heated up make line graphs. Show the rate of faster—the soil or the water? temperature increase for soil and 3. Compare how fast the air temper- water. Graph the rate of tempera- ture over the water changed with ture decrease for soil and water after how fast the temperature over the you turn the light off. land changed after the light was turned off. Draw Conclusions1. Were your hypotheses supported or not? Explain.2. Infer from your graphs which cooled faster— the water or the soil. Make a poster showing the steps you3. Compare the temperatures of the air above followed for your experiment. Include the water and above the soil 15 minutes after graphs of your data. Display your poster in the light was turned off. How do water and the classroom. For more help, refer to the soil compare in their abilities to absorb and Science Skill Handbook. release heat? ACTIVITY 301
  • 25. marsup alnucleus organelle marsupial mantle element ibosome primate sea otter hypertension jet ici Science & Language Arts and orwa Song of the Sky Loom1no Brian Swann, ed.me This Native American prayer probably comes from the dRespond to the Reading Tewa-speaking Pueblo village of San Juan, New Mexico. The og 1. Why do the words Mother Earth and poem is actually a chanted prayer used in ceremonial rituals.ntu Father Sky appear on Mother Earth either side and above Father Sky m and below the rest of the words? we are your children cai 2. Why does the song use the image of a With tired backs we bring you gifts you love Then weave for us a garment of brightness ha garment to describe Earth’s atmosphere? 2 its warp the white light of morning,ppu 3 weft the red light of evening, fringes the falling rain,atim tim its border the standing rainbow. ou Thus weave for us a garment of brightness So we may walk fittingly where birds sing,dig So we may walk fittingly where grass is green. co Mother Earth Father Skyaga ga ni 1 a machine or device from which cloth is produced 2 threads that run lengthwise he 3 in a piece of cloth horizontal threads inter- enc laced through the warp in a piece of clothbre ozopopoi 302 CHAPTER 10 Atmosphereoem
  • 26. m grat on compound d chotomous greenhoexoskeleton permafrost magmaMetaphor plat isotopes cell gym Understanding Literature ma Metaphor A metaphor is a figure of speech that com- Linking Science pares seemingly unlike things. Unlike a simile, a and ion metaphor does not use the connecting words like or as. the For instance, in the song you just read, Father Sky is a loom. A loom is a machine or device that weaves cloth. Creating a Metaphor Write a kid The song describes the relationship between Earth and sky as being a woven garment. Lines such as “weave for four-line poem that uses a metaphor to describe rain. You us a garment of brightness” serve as metaphors for how Mother Earth and Father Sky together create an pro can choose to write about a gen- tle spring rain or a thunderous ign atmosphere in which their “children,” or humans, can rainstorm. Remember that a metaphor does not use the words thrive. par like or as. Therefore,your poem should begin with something like the composition of Earth’s atmosphere. The atmo- zon Science Connection In this chapter, you learned about “Rain is ...” or “Heavy rain is ...” sphere maintains the proper balance between the mo amount of heat absorbed from the Sun and the amount orp of heat that escapes back into space. You also learned about the water cycle and how water evaporates from Earth’s surface back into the atmosphere. Using eta etal metaphor instead of scientific facts, the Tewa song con- allo veys to the reader how the relationship between Earth and its atmosphere is important to all living things. om Career Connection Meteorologist oge pro Kim Perez is an on-air meteorologist for The Weather Channel, a acc national cable television network. She became interested in the weather when she was living in Cincinnati, Ohio. There, in 1974, she tab witnessed the largest tornado on record. Ms.Perez now broadcasts weather reports to millions of television viewers. Meteorologists nol study computer models of Earth’s atmosphere. These models help them predict short-term and long-term weather conditions for the eat eath United States and the world. tem To learn more about careers in meteorology, sol sola visit the Glencoe Science Web site at science.glencoe.com. 303 hav SCIENCE AND LANGUAGE ARTS dim
  • 27. Chapter 10 Study GuideSection 1 Earth’s Atmosphere 4. Unlike the atmosphere on Mars or Venus,1. Earth’s atmosphere is made up mostly Earth’s unique atmosphere maintains a of gases, with some suspended solids and balance between energy received and energy liquids. The unique atmosphere allows lost that keeps temperatures mild. This deli- life on Earth to exist. cate balance allows life on Earth to exist.2. The atmosphere is divided into five layers Section 3 Air Movement with different characteristics. 1. Because Earth’s surface is curved, not all3. The ozone layer areas receive the same amount of solar protects Earth radiation. This uneven heating causes from too much Cl temperature differences at Earth’s surface. F C ultraviolet radia- 2. Convection currents modified by the tion, which can Coriolis effect produce Earth’s global Cl be harmful. How Cl winds. do chlorofluoro- 3. The polar jet stream is a strong current carbon molecules of wind found in the upper troposphere. destroy ozone? It forms at the boundary between cold, polar air and warm, tropical air.Section 2 Energy Transferin the Atmosphere 4. Land breezes and sea breezes1. Earth receives its energy from the Sun. occur near the Some of this energy is reflected back into ocean. Why do space, and some is absorbed. winds change2. Heat is distributed in Earth’s atmosphere by direction from radiation, conduction, and convection. day to night?3. Energy from the Sun powers the water cycle between the atmosphere and Earth’s surface. Clouds form during which part of the water cycle? After You Read FOLDABLES Reading &Study & Study Draw pictures on the front Skills of your Foldable of things that you might find in each layer of Earth’s atmosphere.304 CHAPTER STUDY GUIDE
  • 28. Chapter 10 Study GuideComplete the following cycle map on the water cycle. Cooled water vapor condenses. Energy from the Sun evaporates water.Vocabulary Review Using Vocabularya. atmosphere i. jet stream The sentences below include terms that haveb. chlorofluorocarbon j. land breeze been used incorrectly. Change the incorrect termsc. condensation k. ozone layer so that the sentence reads correctly.d. conduction l. radiation 1. Chlorofluorocarbons are dangerous becausee. convection m. sea breeze they destroy the hydrosphere.f. Coriolis effect n. troposphereg. hydrosphere o. ultraviolet radiation 2. Narrow belts of strong winds called seah. ionosphere breezes blow near the top of the troposphere. 3. The thin layer of air that surrounds Earth is called the troposphere. Study Tip 4. Heat energy transferred in the form of waves is called condensation. Describe ways that you might design an experi- ment to prove scientific principles. 5. The ozone layer helps protect us from the Coriolis effect. CHAPTER STUDY GUIDE 305
  • 29. Chapter 10 Assessment 10. What are narrow belts of strong winds near the top of the troposphere called? Choose the word or phrase that best answers A) doldrums C) polar easterliesthe question. B) jet streams D) trade winds 1. What is the most abundant gas in the atmosphere? A) oxygen C) argon B) water vapor D) nitrogen 11. Why are there few or no clouds in the 2. What causes a brown haze near cities? stratosphere? A) conduction C) car exhaust 12. It is thought that life could not have existed B) mud D) wind on land until the ozone layer formed about 3. Which is the uppermost layer of the atmo- 2 billion years ago. Why does life on land sphere? require an ozone layer? A) troposphere C) exosphere 13. Why do sea breezes occur during the day B) stratosphere D) thermosphere but not at night? 4. What layer of the atmosphere has the most 14. Describe what happens when water vapor water? rises and cools. A) troposphere C) mesosphere 15. Why does air pressure decrease with an B) stratosphere D) exosphere increase in altitude? 5. What protects living things from too much ultraviolet radiation? A) the ozone layer C) nitrogen B) oxygen D) argon 16. Concept Mapping Complete the cycle con- 6. Where is air pressure least? cept map below using the following phrases A) troposphere C) exosphere to explain how air moves to form a convec- B) stratosphere D) thermosphere tion current: Cool air moves toward warm 7. How is energy transferred when objects are air, warm air is lifted and cools, and cool air in contact? sinks. A) trade winds C) radiation B) convection D) conduction 8. Which surface winds are responsible for most of the weather movement across the United States? Cool air is warmed A) polar easterlies C) prevailing westerlies by conduction. B) sea breeze D) trade winds 9. What type of wind is a movement of air toward water? A) sea breeze C) land breeze B) polar easterlies D) trade winds306 CHAPTER ASSESSMENT
  • 30. Chapter 10 Assessment17. Drawing Conclusions In an experiment, a student measured the air temperature 1 m Test Practice above the ground on a sunny afternoon and again in the same spot 1h after sunset. The Each layer of Earth’s atmosphere has a second reading was lower than the first. unique composition and temperature. The What can you infer from this? four layers closest to Earth’s surface are shown in the diagram below.18. Forming Hypotheses Carbon dioxide in the atmosphere prevents some radiation Thermosphere from Earth’s surface from escaping to space. (85-500 km) Mesosphere Hypothesize how the temperature on Earth (50-85 km) might change if more carbon dioxide were Stratosphere released from burning fossil fuels. (10-50 km) Troposphere19. Identifying and Manipulating Variables (0-10km) and Controls Design an experiment to find Oz o out how plants are affected by differing ne lay amounts of ultraviolet radiation. In the er design, use filtering film made for car win- dows. What is the variable you are testing? Earth What are your constants? Your controls?20. Recognizing Cause and Effect Why is the Study the diagram and answer the inside of a car hotter than the outdoor following questions. temperature on a sunny summer day? 1. In which part of the atmosphere is ozone located. A) Thermosphere C) Stratosphere B) Troposphere D) Mesosphere21. Poster Illustrate or find magazine photos 2. According to the diagram, how far of convection currents that occur in every- does the mesosphere extend above day life. Earth’s surface?22. Experiment Design and conduct an experi- F) 10 km H) 50 km ment to find out how different surfaces G) 85 km I) 60 km such as asphalt, soil, sand, and grass absorb 3. What is the correct order of atmo- and reflect solar energy. Share the results spheric layers that the space shuttle with your class. goes through when landing on Earth? A) Mesosphere C) Stratosphere TECHNOLOGY Stratosphere Troposphere Go to the Glencoe Science Web site at Troposphere Mesosphere science.glencoe.com or use the B) Troposphere D) Mesosphere Glencoe Science CD-ROM for additional Stratosphere Troposphere chapter assessment. Mesosphere Stratosphere CHAPTER ASSESSMENT 307