lesson planner and worksheets—all on cd-rom! lesson...

Lesson Planner

CHAPTER 10 Lesson Planner

D26•a UNIT D Astronomy, Weather, and Climate

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Vocabulary Resources and TechnologyObjectivesLesson

Atmosphere and AirTemperature, pp. D28–D35

■ Explore how the angle oflight affects temperature.

■ Identify factors that affecttemperatures on Earth.

■ Explain how theatmosphere changes withelevation.

■ Identify conditions thatmake up the weather.

insolationatmospheretroposphereair pressureweatherbarometer

■ Activity Resources, pp. 130–134■ Reading in Science Resources, pp. 215–220■ Vocabulary Cards■ School to Home Activities,pp. 24–25■ Reading Aid Transparency D3■ Explore Activity Video

Water Vapor andHumidity, pp. D36–D41

■ Explore how waterchanges as a result ofheating and cooling.

■ Relate humidity to theprocesses of evaporation.

■ Explain what happens towater vapor with cooling.

■ Describe a series ofchanges that water goesthrough.

water vaporhumidityevaporationcondensationrelative

humidity

■ Activity Resources, pp. 135–139■ Reading in Science Resources, pp. 221–226■ Vocabulary Cards ■ Reading Aid Transparency D4■ Explore Activity Video

Clouds and Precipitation,pp. D42–D49

■ Explore how clouds form.■ Identify causes and types

of clouds and precipitation.■ Put in sequence the

processes of the watercycle.

■ Describe how to compareamounts of rainfall andcloud cover.

stratus cloudcumulus cloudcirrus cloudfogprecipitation

■ Activity Resources, pp. 140–144■ Reading in Science Resources, pp. 227–232■ Vocabulary Cards■ School to Home Activities, p. 26■ Grade-Level Science Book, The Great

Johnstown Flood■ Reading Aid Transparency D5 ■ Visual Aid Transparencies 22, 23■ Explore Activity Video■ Science Newsroom CD-ROM

On the Vapor Trail

Air Pressure andWind, pp. D52–D61

■ Explore what causes airpressure to change.

■ Explain how air pressure isrelated to winds.

■ Describe the paths ofwinds in global windzones.

■ Identify how wind ismeasured and recorded atweather stations.

windconvection cellsea breezeland breezeCoriolis effectisobar

■ Activity Resources,pp. 145–149■ Reading in Science Resources, pp. 233–238■ Vocabulary Cards■ School to Home Activities, p. 28■ Grade-Level Science Book, The Sky-Watchers■ Reading Aid Transparency D6■ Explore Activity Video

Teacher Works Teacher Edition, interactive lesson planner and worksheets—all on CD-ROM!

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CHAPTER 10 Weather D26•b

Activity Planner

Activity Planner

Explore Materials Other ActivitiesExplore Activities

Lesson 3 Explore Activity

Does the Sun’s Angle Matter? p. D29

observe, predict, communi-cate, use variables, infer, experimentINQUIRY SKILLS

3 thermometers, triangular blocks,black paper, white paper, centimeterruler, scissors, tape, 150-W clear-bulblamp, stopwatch, foam bowl, clay


Where Does the Puddle ComeFrom? p. D37

form a hypothesis, experi-ment, communicate, infer, use variablesINQUIRY SKILLS

plastic cups, ice, paper towels, foodcoloring, thermometer, goggles


How Do Clouds Form? p. D43

make a model, observe,communicate, inferINQUIRY SKILLS

hot tap water, 2 identical clearcontainers, mug, 3 ice cubes, foodcoloring

Lesson 5 Quick Lab with Foldables™ by Dinah Zike

Feel the Humidity p. D48

observe, inferMaterials: thermometer, clothINQUIRY SKILLS


What Can Change Air Pressure?p. D53

make a model, experiment,observe, infer, use variablesINQUIRY SKILLS

plastic jar with hole in bottom, plasticsandwich bag, rubber band, maskingtape

Lesson 6 Inquiry Skill Builder

A Weather Station Model p. D60

interpret data, use numbers,communicateMaterials: none

INQUIRY SKILLS


Transpiration p. D39

observe, communicate, draw conclusions, predictMaterials: plastic bag, house plant

INQUIRY SKILLS


Investigating Angles p. D31

use variables, measure, inferMaterials: flashlight, graph paper, 3 small lumps ofclay, 3 toothpicks

INQUIRY SKILLS

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Unit D · Astronomy, Weather and Climate Use with textbook pages D28–D35

Atmosphere and Air TemperatureFill in the blanks. Reading Skill: Main Idea - questions 1, 2, 16

Does the Sun’s Angle Matter?

1. The hottest parts of Earth are the areas near , while

the coldest are the areas .

2. The angle of the Sun’s rays is the cause of differences in temperatures at the

and the .

3. Combining parts of the words “incoming,” “solar,” “radiation,” forms the

term “ .”

4. The greater the angle of insolation, the a place

will be.

What Affects Insolation?

5. The Sun is highest in the sky at .

6. The angle of insolation can be measured by examining the angles created by

.

Why Do You Cool Down as You Go Up?

7. Air temperatures drop as you go higher up a mountain because you are

traveling higher above .

8. Temperatures drop about degrees for every

in altitude.

9. The troposphere is the lowest layer of Earth’s .atmosphere

305 meters/1,000 feet

2˚C/3.6˚F

sea level

shadows

midday

warmer

insolation

polesequator

around the North and South poles

the equator

Lesson 3

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Unit D · Astronomy, Weather and Climate Use with textbook page D30

Does the Sun’s Angle Matter?Diagrams like this one take careful study. Notice the direction of the arrows, whichshow how Earth moves around the Sun during a year. Then notice that the diagramshows Earth’s position and tilt relative to the Sun at different times of the year. To understand the diagram, look carefully at the changes from season to season.Observe the differences in the angle at which the Sun’s rays fall on different partsof Earth.

Answer these questions about the diagram above.

1. In December, which half of Earth, northern or southern, is tilted away from the Sun?

northern

Are the Sun’s rays more or less concentrated in that half in December?

less concentrated

2. In June, is the southern half of Earth tilted toward or away from the Sun?

away

3. What part of Earth receives concentrated sunlight all year round?

the equator

4. Where on Earth are the Sun’s rays spread out thinly all the time?

North and South Poles

Lesson 3

Sun

North Pole

Earth

South Pole

Concentrated

Spread out

North Pole

Earth

South Pole

Concentrated

Spread out

June(summer)

December(winter)

Lesson Outline

Reading in Science Resources,pp. 215–216, 221–222, 227–228,

233–234

Lesson Vocabulary andCloze Test


237–238

Interpret Illustrations


235–236

Macmillan/McGraw-Hill Science Reading in Science Resources provides the followingBlackline Master worksheets for this chapter.

Macmillan/McGraw-Hill Science Reading in Science Resources provides the followingBlackline Master worksheets for every lesson in this chapter.

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WeatherFind the main idea of this activity about weather. Fill in the circles and the blankswith the correct processes and supporting details. Then describe the main idea inthe space provided.

Chapter 10

heating cooling

Droplets ofwater form around

dust and other particles in the air.

What kinds of water particles fall from the sky?

Where does water that

reaches thesurface of Earth go?

Plants release water into

the air.Liquid waterchanges intowater vapor.

What is the main idea?

plants

Three Basic Clouds

1.

2.

3.

1.

2.

3.

4.

Bodies of Water

1.

2.

3.

4.

Describe the main idea.

Evaporation

Condensation

Transpiration

The Water Cycle

Earth's water moves continuosly

from place to place through the

processes of evaporation,

condensation, and precipitation.

Water can follow many paths

in a cycle that has no

beginning or end.

stratus

cumulus

cirrusoceans

lakes

rivers

streams

rain, drizzle

snow

sleet

hail

Precipitation

runoff

groundwater

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Main IdeaEvery story has a main idea, a sentence that tells what the story’s mostly about.Other facts in the story are details that support, or tell more about, the main idea. Read the following paragraphs, based on information from this chapter of your textbook. Then circle the main idea and underline the supporting details in each paragraph.

Now reread the Science Magazine article “Flood: Good News or Bad?” Then writethe main idea of the article, and list at least four supporting details.

Main Idea:

Supporting Details:

1.

holds back the waters, forcing farmers to use fertilizer that threaten fish.

2.

3.

4.

Details include that the flooding once enriched the land, but today a dam

was once good news, but the stopping of the flooding is bad news.

Wording may vary, but the main idea is that flooding of the Nile

Chapter 10

1. What happens to the Sun as time goes by each day?

2. Air temperature drops with altitude at about 2°C (3.5°F) every 305 meters (1,000 feet).

meters (6,288 feet), it’s only 1°C (34°F).(70°F). Two hours away in Mount Washington, New Hampshire, elevation 1,917For example, in Lewiston, Maine, elevation 34 meters (110 feet), it’s a pleasant 21°C

disappear below the horizon.day. After noon the Sun begins to get lower and lower in the sky until it seems toto the horizon. By noon the Sun is high in the sky above you, as high as it gets all

In the morning the Sun is close

To the Teacher: Remind students that supporting details often answer the 5Ws and an H–who, what,why, where, when, and how. After students have donethe first half of the exercise, have them reread the

Science Magazine article. Then have them complete theworksheet, and invite volunteers to read their mainidea and supporting details aloud.

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WeatherCircle the letter of the best answer.

1. As you get higher in altitude, air pressure

a. increases. b. remains the same.

c. decreases. d. rises.

2. The layer of atmosphere closest to Earth’s surface is the

a. mesosphere. b. stratosphere.

c. troposphere. d. ozone.

3. When weather is described as overcast

a. there are no clouds.

b. the entire sky is covered by clouds.

c. there are a few clouds in the sky.

d. the sky is half covered by clouds.

4. Insolation is

a. the amount of the Sun’s rays that reach Earth.

b. the angle at which the Sun’s rays hit Earth.

c. the insulating effect of the atmosphere.

d. another name for the mesosphere.

5. Humidity is

a. found mostly along shorelines.

b. how much moisture the air could hold if it was warm.

c. the amount of water vapor in the air.

d. the amount of water vapor at ground level.

6. An instrument used to measure air pressure is a(n)

a. barometer.

b. thermometer.

c. gauge.

d. balance.

Chapter 10

Chapter Vocabulary

Reading in Science Resources,p. 212

Reading in Science Resources,pp. 213–214

Reading in Science Resources,pp. 239–240

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Atmosphere and Air TemperatureFill in the blanks.

1. The air that surrounds the Earth is the .

2. Ninety-nine percent of the air we breathe is made up of

and .

3. Air pressure is measured by a(n) .

4. The levels of the four layers of the atmosphere are

determined by sudden changes in

at each level.

5. The amount of the Sun’s energy that reaches Earth at a

given place and time is .

6. All the moisture around Earth is in the .

7. The force put on a given area by the weight of the air above it is

.

8. The conditions present in the troposphere at any given time determine

the .

Answer each question.

9. How does air pressure change with altitude? Why?

Air pressure decreases with altitude because the height of the

air column gets shorter so the weight of that column decreases.

10. What happens to temperature as the angle at which the Sun’s rays strikeEarth’s surface increases? As the angle decreases? What happens to the lengthof shadows at the same time?

The temperature increases as the angle increases. At the same

time, the length of shadows decrease. The temperature drops

and shadows lengthen as the angle decreases.

weather

air pressure

troposphere

insolation

temperature

barometer

oxygennitrogen

atmosphere

Lesson 3

insolation

weather

nitrogen

air pressure

troposphere

barometer

oxygen

atmosphere

temperature

D26•c UNIT D Astronomy, Weather, and Climate

CHAPTER 10 Teaching Resources

Reading in Science Resources

Chapter Graphic Organizer Chapter Reading Skill

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Chapter Test

Macmillan/McGraw-Hill Science Assessment Book provides the following Blackline Masterworksheets for this chapter.

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Unit D · Astronomy, Weather, and Climate Use with textbook pages D26–D65

Name Date

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Weather Section 1: Vocabulary Each item is worth 2 points.

Mark true or false. If false, underline the word or words that make the statement false.

1. Air that moves vertically is called wind.

2. Puffy clouds that appear to rise from a flat bottom are

called cumulus clouds.

3. The layer closest to Earth’s surface is the troposphere.

4. A cloud at ground level is called precipitation.

5. Relative humidity is a comparison of how much water

vapor is in the air, and how much the air can hold.

6. The amount of water vapor in the air is called humidity.

7. A sea breeze blows from the land toward the sea.

8. Air pressure is measured with an anemometer.

9. Stratus clouds form in blanketlike layers.

10. The curving of the wind to the right in the Northern

Hemisphere is a result of the Coriolis effect.

true

true

false

false

true

true

false

true

true

false

Chapter 10

Macmillan/McGraw-Hill Science Activity Resources provides the following Blackline Masterworksheets for every lesson in this chapter.

Teaching Resources

CHAPTER 10 Weather D26•d

Activities and Assessment

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Interpret DataA Weather Station Model

A weather station model includes temperature, cloud cover, air pressure, pressuretendency, wind speed, and wind direction. The circle is at the location of the station. You will interpret the data—use the information—from the weather use station models to answer questions and solve problems.

Procedure

1. Use Numbers Look carefully at the Dallas weather station model. How fast isthe wind blowing? What is the wind direction? Record your answers.

Wind speed: 33–57 km/h (19–31 knots); wind direction: from southwest

2. Interpret Data What other information does this weather station model give you?

Amount of cloud cover, air temperature, and air pressure

3. Look at the other weather station models. On the next page, make a tablerecording weather conditions for each city.

Remind students that tables consist of columns and rows, with space for

appropriate headings. They should construct a 6-column by 5-row chart with

the following column labels: city, wind speed, wind direction, cloud cover,

temperature, and pressure.

Lesson 6

Dallas

100434

Charlotte

980 28

Tampa

99630

Wind speed(knots or

km/h)

Air temperature(°C)

(It may also be recorded in °F.)

Air pressure(mb)

Winddirection

(from north)

Pressure change

Cloud cover

13 1014

Oakland

101214

Inquiry Skill Builder

Activity Resources, pp. 148–149

Explore Activity and Alternative Explore Activity

Activity Resources, pp. 130–132,135–137, 140–142, 145–147

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Does the Sun’s Angle Matter?How does the angle at which the Sun’s energy

hits Earth affect the warming of Earth? Write a Hypothesis:

Possible hypothesis: The more directly sunlight hits Earth, the

warmer Earth gets.

Procedure

Do not look into the lamplight. Prop up a foam

bowl, using a plate or clay, to shield your eyes from the light.

1. Place a thermometer ontoeach of the three blocks, asshown. Cover each with blackpaper. Put blocks 20 cm fromthe light bulb, level with its filament (curly wire).

2. Observe Measure the starting temperature at each block.Record the temperatures.

Answers will vary.

3. Predict What will happen when the lamp is turned on? Turn the lamp on.Record the temperature at each block every two minutes for ten minutes, in adata table on another sheet of paper.

Students might predict that when the light is turned on, the

temperature at the surface of the blocks will increase.

4. Communicate On another sheet of paper, make a line graph showing thechange in temperature at each block over time.

Graphs should have “Time (mins)“ as x-axis and “Temperature” as y-axis. Theline associated with each block will be different.

5. Use Variables Repeat the activity with white paper.

Lesson 3

• 3 ther-mometers

• centimeterruler

• stopwatch

• triangularblocks

• scissors

• foam bowl

• black paper

• tape

• clay

• white paper

• 150-W clear-bulb lamp

F

0 - 10- 20

- 30- 40

- 50

5040

3020

10

10090

8070

60

F

0- 10

- 20- 30

- 40- 50

5040

3020

10

10090

8070

60F

0- 10

- 20- 30

- 40- 50

5040

3020

10

10090

8070

60

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Investigating Angles

Why does the angle of insolation cause a difference in warming? Write a Hypothesis:

Possible hypothesis: The angle of insolation determines how

much direct sunlight a location receives: the greater the

angle of insolation, the warmer it is; the smaller the angle of

insolation, the colder it is because the Sun’s rays are more

spread out.

Procedure

1. Fold a sheet of graph paper lengthwise in three equal parts. Put a small lumpof clay in the middle of each part. Stand a toothpick straight up in each lumpof clay.

2. Hold a flashlight directly over the first toothpick. Have a partner trace a linearound the circle of light and trace the toothpick shadow.

3. Use Variables Repeat step 2 for the other two toothpicks, changing only theangle of the flashlight. Keep distance of flashlight constant.

4. Measure Count the number of boxes in each circle. Measure the lengths ofthe toothpick shadows. Record your results in the table below.

The number of boxes should increase as the angle is decreased. The lengths ofthe toothpick shadows should increase as the angle is decreased.

Lesson 3

• flashlight

• modeling clay

• 3 toothpicks

• sheet of graphpaper

• ruler

Toothpick Number of Boxes Length of Shadow

1

2

3

Quick Lab for School or Home

Activity Resources, pp. 133–134,138–139, 143–144

Assessment Book, pp. 53–56

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LESSON 3

Atmosphere and AirTemperature, D28

LESSON 4

Water Vapor andHumidity, D36

LESSON 5

Clouds andPrecipitation, D42

LESSON 6

Air Pressure and Wind, D52

WeatherCHAPTER

What causes frost to form? Frost forms when it is cold enough for water vapor in the air to change from gas to ice crystals on grass and other objects. In warmer weather dew would form instead of frost.

Experiment Make frost in your classroom! Layer saltand ice in a metal container. Observe the outside of the container.INQUIRY SKILL

Did You Ever Wonder?

D 26

D26 UNIT D Astronomy, Weather, and Climate

Resources■ Reading in Science Resources,

pp. 212–241

■ Assessment Book, pp. 53–56

GUIDED Soup cans are good-sized cans.Remove the label. Make sure the top edge of thecan is not sharp. If it is, cover it with masking tape.Use a wooden spoon to pack the salt and ice. A stu-dent should hold the top of the can while it is beingpacked. In approximately 5 minutes, frost will formon the outside of the can. The outside of the can isnow cold. Water vapor in the air will condense onthe outside of the can. The water vapor (a gas)changes to a liquid on the can. Since the can is cold,the liquid changes to a solid, which is the ice.

INQUIRY

Did You Ever Wonder?

Weather

CHAPTERSC

IENCE

Reading Strategy

This chapter provides MiniLessons and other opportunities fordeveloping and practicing the following reading skills:

Cause and Effect: p. D48Compare and Contrast:pp. D38, D45Draw ConclusionsFind the Main Idea: pp. D34,D47, D59Sequence of Events: p. D50Summarize: pp. D48, D49,D51, D58Ask QuestionsReread

Retell (paraphrase)Interpret Graphic Sourcesof Information: pp. D31, D32,D33Build on Prior Knowledge:pp. D28, D36, D42, D50, D52Organize Information:pp. D31, D48, D57, D62

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WeatherFind the main idea of this activity about weather. Fill in the circles and the blankswith the correct processes and supporting details. Then describe the main idea inthe space provided.

Chapter 10

heating cooling

Droplets ofwater form around

dust and other particles in the air.

What kinds of water particles fall from the sky?

Where does water that

reaches thesurface of Earth go?

Plants release water into

the air.Liquid waterchanges intowater vapor.

What is the main idea?

plants

Three Basic Clouds

1.

2.

3.

1.

2.

3.

4.

Bodies of Water

1.

2.

3.

4.

Describe the main idea.

Evaporation

Condensation

Transpiration

The Water Cycle

Earth's water moves continuosly

from place to place through the

processes of evaporation,

condensation, and precipitation.

Water can follow many paths

in a cycle that has no

beginning or end.

stratus

cumulus

cirrusoceans

lakes

rivers

streams

rain, drizzle

snow

sleet

hail

Precipitation

runoff

groundwater

BL

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Graphic Organizer

Reading in Science Resources, p. 212

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D 27

CHAPTER 10 Weather D27

Encourage students to keep a Science Dictionary.Remind them to add the Vocabulary words for eachlesson in this chapter to their Dictionary as theycomplete each lesson.

insolation, D30

atmosphere, D32

troposphere, D32

air pressure, D33

weather, D34

barometer, D34

water vapor, D38

humidity, D38

evaporation, D38

condensation, D39

relative humidity, D39

stratus cloud, D44

cumulus cloud, D44

cirrus cloud, D44

fog, D44

precipitation, D46

wind, D55

convection cell, D55

sea breeze, D56

land breeze, D56

Coriolis effect, D57

isobar, D59

Vocabulary Preview

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4. Insolation is





5. Humidity is






a. barometer.

b. thermometer.

c. gauge.

d. balance.

Chapter 10

BL

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Vocabulary

Reading in Science Resources, pp. 239–240

Visit www.amnh.org/resources/mhscience to discover more about what causes changes in weatherand how scientists track and monitor storms.

Syllables Ask students to lookat the Vocabulary list as you readit. Then ask them to repeat thewords as you read it again.Explain that dividing words intosyllables helps us to learn pro-nunciation. Assign students twowords each and ask them to usedictionaries to divide the wordsinto syllables.

Beginning Ask students to writetheir words on the board, drawinglines between the syllables.

Intermediate Ask students howmany syllables are in theirwords. Invite them to read thewords syllable by syllable.

Advanced Ask students toshare their results. Challengethem to divide the rest of thewords into syllables. Linguistic;Logical

English Language Learners

SCIENCE

F O R A L L

Getting Familiar with Vocabulary

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http://www.amnh.org/resources/mhscience

If it’s summer, is it always hot?These animals may find it warmerin summer than in winter.However, it isn’t exactly hot hereon this beautiful summer day.How can summer be hot in someplaces and so cold in others?

How does the angle atwhich the Sun’s energy hits

Earth affect the warming of Earth?

Atmosphereand AirTemperature

insolation, D30

atmosphere, D32

troposphere, D32

air pressure, D33

weather, D34

barometer, D34

Vocabulary

Inquiry SkillYou experiment when you

perform a test to support or

disprove a hypothesis.

D 28


Build on Prior KnowledgeHave students discuss temperature changes thatoccur with different seasons. Have them determinethe current temperature. Then ask:

■ What are temperatures usually like threemonths from now? Six months? (Answers willvary depending on area’s elevation and latitude.)

Developing the Main IdeaHave students discuss how two places on Earth canhave such different temperatures on the same day.(Places closer to the equator have higher tempera-tures than those closer to the poles; places are athigher elevations; seasons are reversed north andsouth of the equator. The higher the angle at whichthe Sun’s energy hits Earth, the more concentratedthe energy.)

Objectives

■ Explore how the angle of lightaffects temperature.

■ Identify factors that affect tem-peratures on Earth.

■ Explain how the atmospherechanges with elevation.

■ Identify conditions that make upthe weather.

Resources■ Activity Resources, pp. 130–134

■ Reading in Science Resources,

pp. 215–220

■ Vocabulary Cards

■ Reading Aid Transparency D3

■ School to Home Activities,

pp. 24–25

Atmosphereand AirTemperature

Our SunThe Sun is Earth’s source ofenergy and light. The Sun’sheat comes from continuallyoccurring nuclear reactions. Asmatter is converted to energy,the Sun’s mass decreases byabout four million tons per sec-ond. However, scientists pre-dict that the Sun will still warmEarth for another 6 billionyears.

Science Background

Additional Outside Reading

To order, see page D1•b.

Cross Curricular Books

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D 29


Procedure

Do not look into the lamplight.

Place a thermometer onto each of the threeblocks, as shown. Cover each with black paper. Put the blocks 20 cm from the light bulb, levelwith its filament (curly wire).

Observe Measure the starting temperature at each block. Record the temperatures.

Predict What will happen when the lamp isturned on? Turn the lamp on. Record the temperature at each block every two minutes for ten minutes.

Communicate Make a line graph showing thechange in temperature at each block over time.

Use Variables Repeat the activity with white paper.

Drawing Conclusions

Communicate Which block’s surface was warmed most by the lamplight? Which block’s surface was warmed the least?

Infer How does the angle atwhich light hits a surface affecthow much the surface is heated?How does the surface color affecthow much it is heated?

ExperimentWhat other factors might affecthow much a surface is warmed bysunlight? How would you testyour ideas?

FURTHER INQUIRY3

2

1

5

4

3

2

1

Materials

3 thermometers

triangular blocks

black paper

white paper

centimeter ruler

scissors

tape

150-W clear-bulblamp

stopwatch

foam bowl

clay


Science Inquiry Skills observe, predict, communi-cate, use variables, infer, experiment

Resources Activity Resources, pp. 130–131

Pacing 30–40 minutes

Grouping small groups

Procedure

STRUCTURED

Be Careful! Warn students not to look into the lamp-light. Have them use a foam bowl to shield their eyesfrom the light.

Students might predict that when the light isturned on, the temperature on the surface of theblocks will increase; they may recognize that theangle that the light hits will be a factor in deter-mining how warm each block gets.

Answers to Drawing Conclusions

The block whose surface was most vertical waswarmed the most. The block with the lowestangle was least affected.

The more vertically the light hits the surface, themore it is warmed. Students should infer thatdarker colors absorb more light, warming the sur-face more.

GUIDED Possible answers might includehow rough or smooth a surface is, how shiny ordull it is, or what the material is made of. They canset up a controlled experiment for each.

STUDENT-INITIATED Students can ask theirown questions to explore, such as: Does the time ofyear affect temperature on different parts of Earth?

INQUIRY

INQUIRY3

2

1

3

INQUIRY

CHAPTER 10 Lesson 3 D29

Materials globe, flashlight

Cold at the Poles Demonstratefor students how the angle ofsunlight affects temperature.Darken the classroom, thenshine a flashlight onto the globefrom the side, so that the beamis directly striking the equator.Encourage students to describethe way in which the lightstrikes the poles. (The rays strikethe poles at an angle, and arespread out and less intense.)Spatial

Activity Resources, p. 132

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Cold at the Poles

Procedure

1. Darken the classroom by shutting off the lights and closing the blinds.

2. Place a globe on your desk.

3. Holding a flashlight, stand one or two paces from theglobe.

4. Turn on the flashlight and shine it onto the globe.

5. Hold the flashlight level with the equator. Observe how the light strikes the equator and record your observations.

The light strikes the equator perpendicular to it or straight on, so it

looks bright.

6. Observe How does the light strike the north and south poles? Record yourobservations.

The light strikes the poles at an angle, so it does not look very bright.

Drawing Conclusions

1. What do the globe and flashlight represent?

The globe represents Earth and the flashlight represents the Sun.

2. Compare and Contrast How does sunlight strike Earth at the equator and atthe poles?

It strikes at different angles, hitting perpendicular at the equator

and at an angle at the poles.

3. Why do you think temperatures near the equator are warmer than those near the poles?

At the equator, the angle at which sunlight strikes causes the light

to be more intense and the surface to get warmer.

Lesson 3

• globe

• flashlight

Alternative Explore Activity

Technology

When time is short, preview the activity with the Explore Activity Video.

SC05_T5D_Les_L03_PgsD028-035 5/6/04 8:30 AM Page D29

D 30

June(summer in Northern Hemisphere)

Sun

December(winter in Northern Hemisphere)

EarthEarth

South Pole South Pole

Concentrated

Concentrated

North Pole

Spread out

Spread out North Pole

The Sun’s rays hit Earth’s surface at alow angle. The strength of the rays ismuch weaker at this angle.

The angle at which sunlight strikesEarth’s surface is called the angle of

. Insolation is short forincoming solar radiation. It means theamount of the Sun’s energy thatreaches Earth at a given place and time.

The diagram shows how sunlightwarms Earth in summer and winter.The amount of warming depends onthe angle of insolation. The greater theangle, the warmer it gets. The angle ofinsolation is always smaller near thepoles than near the equator. Thatmeans while it’s freezing cold in onepart of the world, it’s hot in another.

insolationDoes the Sun’s Angle Matter?

Where do you think you might findwarm temperatures all year long?Where would you find very coldweather? That depends a lot on theangle at which sunlight hits a region.Angles make a difference in how muchthe Sun warms an area. The areasaround the equator are hottest. That’sbecause the Sun’s path is high over-head at midday. In those areas theSun’s rays hit Earth at their strongest.

The areas around the North andSouth Poles are coldest. In those areasthe Sun is much lower at midday.

How do differing angles of insolation

cause differences in warming?

The Sun’s rays strike the surface at differentangles as Earth travels around the Sun.

Angles count! Earth is actually closer to the Sunwhen it’s winter in the Northern Hemisphere.

How Sunlight Warms Earth

Main Idea The Sun warms Earth’s

surface, which transmits heat to the

air above it.

Areas with a higher angle of insolationreceive more direct sunlight.



Before ReadingHave students try to answer the red question at thetop of the page.

Exploring the Main IdeaDemonstrate why the equator is always hotter thanthe North Pole by shining a flashlight straight downonto a tabletop in front of the class, directing them toobserve the circle of light formed. Tilt the flashlight sothat the beam hits the tabletop at an angle; againencourage students to observe the shape that thelight forms. Ask:

� What does the flashlight represent? (the Sun)

Point out that the first demonstration representedthe manner in which the Sun reaches Earth at theequator, while the second demonstration representedthe way in which the Sun reaches Earth at the poles.

� How was the sunlight different at the poles?(The light was spread over a larger area; therewas a larger, dimmer oval.)

� How do you think the sunlight the polesreceived compared to what the equatorreceived? How were they different? (The angleof incoming sunlight is low and it was spreadover a larger area at the poles.)

� If the poles receive the same amount of lightas the equator, why is it so much colderthere? (The energy from slanted rays of the Sunis spread out and less intense than the energyfrom direct sunlight.)

After ReadingHave students answer the red question in thestudent book as ongoing assessment.

The word insolation is a combi-nation of three words—incoming solar radi-ation. Sol is Latin for Sun. Ask students to listsome other words that contain sol.

insolation

Developing Vocabulary

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Atmosphere and Air Temperature

Fill in the blanks. Reading Skill: Main Idea - questions 1, 2, 16


1. The hottest parts of Earth are the areas near , while

the coldest are the areas .

2. The angle of the Sun’s rays is the cause of differences in temperatures at the

and the .

3. Combining parts of the words “incoming,” “solar,” “radiation,” forms the

term “ .”

4. The greater the angle of insolation, the a place

will be.


5. The Sun is highest in the sky at .

6. The angle of insolation can be measured by examining the angles created by

.


7. Air temperatures drop as you go higher up a mountain because you are

traveling higher above .

8. Temperatures drop about degrees for every

in altitude.

9. The troposphere is the lowest layer of Earth’s .atmosphere

305 meters/1,000 feet

2˚C/3.6˚F

sea level

shadows

midday

warmer

insolation

polesequator

around the North and South poles

the equator

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Lesson Outline


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Does the Sun’s Angle Matter?Diagrams like this one take careful study. Notice the direction of the arrows, whichshow how Earth moves around the Sun during a year. Then notice that the diagramshows Earth’s position and tilt relative to the Sun at different times of the year. To understand the diagram, look carefully at the changes from season to season.Observe the differences in the angle at which the Sun’s rays fall on different partsof Earth.


1. In December, which half of Earth, northern or southern, is tilted away from the Sun?

northern

Are the Sun’s rays more or less concentrated in that half in December?

less concentrated

2. In June, is the southern half of Earth tilted toward or away from the Sun?

away

3. What part of Earth receives concentrated sunlight all year round?

the equator

4. Where on Earth are the Sun’s rays spread out thinly all the time?

North and South Poles

Lesson 3

Sun

North Pole

Earth

South Pole

Concentrated

Spread out

North Pole

Earth

South Pole

Concentrated

Spread out

June(summer)

December(winter)

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D 31

Investigating AnglesMake a Trifold Book.

(See p. R 42.)

1. Fold a sheet of graph

paper lengthwise in

three equal parts. Put

a small lump of clay

in the middle of

each part. Stand a toothpick

straight up in each lump of clay.

2. Hold a flashlight directly over the

first toothpick. Have a partner trace

a line around the circle of light and

trace the toothpick’s shadow.

3. Use Variables Repeat step 2 for the

other two toothpicks, changing only

the angle of the flashlight.

4. Measure Count the number of

boxes in each circle. Measure the

lengths of the toothpick shadows.

Record your results.

5. Infer Use the Trifold Book to

record how the length of the

shadow is related to the angle.

6. Infer Record how the number

of boxes in the circle is related to

the angle.

QUICK LABWhat Affects Insolation?

In the morning the Sun is close tothe horizon. What happens as timegoes by? At midday the Sun is high upin the sky, as high as it gets during theday. After midday the Sun is lower andlower in the sky.

How does this affect the angle ofinsolation? How do we measure it?Look at the shadows cast by objectsthey strike! The lower the angle of thelight rays, the longer the shadows. Asyou can see in the diagram, the angleof insolation is the same as the anglebetween the ground and the line fromthe tip of the shadow to the top of the wall.

30°30°30°

Tip of shadow

Sun’s ray

Angle of insolation

Wall

Ground

The angle of insolationcan be measured byexamining the anglescreated by shadows.

Angle of Insolation

Shadow of wall

How does the time of day affect the

angle of insolation?

What will happen to the angle asthe Sun gets higher in the sky? Howwill this affect the temperature?

Sunlight is most direct at midday; the angleof insolation is less before and after noon.



Exploring the Main IdeaWith the class, locate a flagpole or lamppost on theschool grounds. Point out that the length of shadowschange as the angle of insolation changes during theday. Have a student volunteer measure the length ofthe shadow cast by the flagpole or lamppost, record-ing the time and date. Ask another student to recordthe temperature. Return to the site at different timesto repeat the measurements. Ask:

■ What do the shadows tell you about the Sun?(They tell you the position of the Sun in the sky;the higher the Sun is in the sky, the shorter theshadows.)

Materials graph paper, 3 small lumps of modelingclay, 3 toothpicks, flashlight, ruler

Science Inquiry Skills use variables, measure, infer


Step 3 Encourage students to compare and contrastthe circles of light and shadows cast for eachof the three toothpicks.

Step 5 When the Sun is directly overhead (at a 90°angle), its shadow is shortest. As the angledecreases, the shadow lengthens.

Step 6 When the light is overhead, the fewest squaresare covered with light, but it is direct. Whenthe angle decreases, light is spread out overmore boxes.

After ReadingHave students answer the red question in the student book as ongoing assessment.


Develop Temperatures can bemeasured in degrees Fahrenheit(°F) or degrees Celsius (°C).

You can use these formulas toconvert temperatures betweenthe two scales.

C � �59

� � (F � 32)Complete. 68°F � °C

�59

� � (68 � 32) � �59

� � 36 � 20

So, 68°F is about 20°C.

F � (1.8 � C) � 32Complete. 8°C � °F

Practice Complete.

1. 77°F � °C (34.7)

2. 15°C � °F (25)

Activity Have students estimatethe temperatures for the fourseasons in both degrees Celsiusand degrees Fahrenheit.

Math MiniLesson

Temperatures

1.8 8 32 46.4So, 8°C is about 46.4°F.

��

The angle will increase. The temperature willrise.

QUICK LAB

M�

QUICK LABby Dinah Zike


D 32

Why Do You Cool Down

As You Go Up?Did you ever climb a high

mountain? As you go higher and higherabove sea level, air temperatures drop.The natural drop in air temperaturewith altitude is about 2°C (3.6°F) forevery 305 meters (1,000 ft).

Climbing up a mountain is really ajourney up into the , the airthat surrounds Earth. The atmospherereaches from Earth’s surface to the edgeof space. What if you could travel to thetop part of the atmosphere? Thediagram of the atmosphere shows whatyou would find.

atmosphere

You would find that the temperaturedoes not fall steadily with altitude. Itchanges abruptly several times. Thesechanges mark the boundaries of fourmain layers. These layers surroundEarth like huge shells.

The layer closest to Earth’s surface isthe (TROP·uh·sfeer). It’sthe narrowest layer—between 8 and 18 kilometers (5–11 miles) thick—but itcontains most of the air in the atmos-phere. All life on Earth exists here. Inthis layer all moisture is found and allclouds, rain, snow, and thunderstormsform. Above this layer the air graduallythins out to the near-emptiness of space,with no exact upper boundary.

troposphere

Mt. EverestLow Temperature High

8–18 km

50 km

80 km

0 km

Ozone

Troposphere

Stratosphere

Mesosphere

ThermosphereIonized gas

Radio waves

–100°C –50°C 0°C 50°C

Layers of the Atmosphere

Most weather occurs in the troposphere. The ozone layer in the stratosphere helpsshield us from the Sun’s ultraviolet light. Auroras (the northern and southern lights)may form in the ionized (electrically charged) gas in the thermosphere.

What is the relationship between

altitude and temperature?Describe how the temperature changesin each layer of the atmosphere.

In the troposphere, asaltitude increases,temperature decreases.



Developing the Main IdeaAsk students:

■ What happens to air as it warms? (Remind stu-dents of what they have learned about thebehavior of molecules, and guide them toanswer that the molecules move faster, movingapart so that the air expands and rises.)

■ If air rises when it’s warmed, why does it getcooler as you climb a mountain? (Encouragestudents to speculate, and tell them that theywill learn more about how altitude affects tem-perature.)

■ How does air temperature change with alti-tude? (Air temperature decreases about 3.5°Ffor every 1,000 feet in altitude.)



Students may know frommath that a sphere is a geometric shape usedto describe a ball or globe. Atmos- is fromGreek for “gas” or “vapor.” So the word liter-ally means a ball or sphere of gases — sur-rounding Earth.

Tropos- means “turning” Thisprefix attached to sphere may indicate theancient belief that the sky turned aroundEarth while Earth remained stationary.

troposphere

atmosphere


Students should describe a pattern ofdecreasing and increasing temperatures thatalternates with each layer of the atmosphere.

Interpret Graphic Sources ofInformation

Developing Reading SkillsHave students interpret thediagram on page D32, summa-rizing the layers of the atmos-phere. They can also interpretthe chart on p. D33 to summa-rize the composition of the air.

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Why Do You Cool Down as You Go Up?The two parts of this diagram show different, but related, kinds of information. To understand it, you need to look carefully at how the two parts are related. The left-hand part shows the layers of the atmosphere and their heights above the Earth. The other part is a graph of temperature change in each layer. Read it as you would read a line graph.


1. In what layer of the atmosphere do people live and clouds form?

troposphere

At about what height is the top of that layer?

2. Describe the location of the ozone layer.

It is at the boundary between the stratosphere and the mesosphere.

3. Do temperatures get warmer or colder as you move from the lower

stratosphere to the top of that layer?

How big is the change?

4. The topmost layer of the atmosphere is the .

How high above Earth does this layer begin?

5. Which layer has the greatest temperature change? thermosphere

80 km

thermosphere

from about –50°C to about 25°C

warmer

8–18 km

The Layers of the Atmosphere

Ozone

80 km

50 km

8–18 km

0 km

Mesosphere

Stratosphere

Troposphere

Mt. EverestTemperatureLow High

–100°C –50°C 0°C 50°C

Ionized gas

Radio w

aves

Thermosphere

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D 33

What Happens to

the Air Pressure?

As you go higher in altitude, decreases steadily. Air

pressure is the force put on a given areaby the weight of the air above it. Air is amixture of gases. It is made up mostlyof molecules of nitrogen and oxygen.Molecules are the smallest pieces that asubstance can be broken into withoutchanging what the substance is.

The molecules have mass. They areattracted to Earth by gravity, so theyhave weight.

Normal air pressure is greatest at sealevel. There the column of air extendingabove the surface to the top of theatmosphere is tallest. Sea level airpressure is about 1.04 kilograms persquare centimeter (14.7 pounds persquare inch). As you go higher inaltitude, the height of the air columnabove you becomes shorter. Thereforethe weight of that column—or airpressure—becomes less.

air pressureIn the lower atmosphere, the

composition of air varies very little. Upto an altitude of about 100 km (62 mi),air consists of a mixture of gases, watervapor, and dust particles. Nitrogen andoxygen make up 99 percent of thegases in dry air.

Water vapor is a gas. It should notbe confused with clouds or fog, whichare made of liquid or solid water. Theamount of water vapor in air variesfrom of air in dry arctic regions to

of air in moist equatorial regions.The dust in air is made of particles

so tiny that 100,000 lined up wouldonly form a row 1 cm (0.4 in.) long.Some of it comes from Earth’s surface,from fires and volcanic eruptions, orfrom tiny crystals of salt.

125

110,000

2,000 m

10,000 m

Sea level

Argon, carbon dioxide, and other trace gases 1%

Oxygen 21%

Nitrogen 78% Lower altitudes have alarger air columnabove them, whichcreates greater airpressure.

Air in theAtmosphere

How does air pressure change

with altitude?

Composition of Dry Air by Volume

1. What is meant by trace?

2. Which gas is the most abun-dant in the atmosphere?

As altitude increases, air pressure decreases.

What Happens to the Air Pressure?


Exploring the Main IdeaAs students observe, place an index card over the topof a drinking glass filled to the brim with water, mak-ing sure that the opening is completely covered. Holdthe card in place as you turn the glass over, thenremove your hand from the card. Ask:

■ Why didn’t the water spill out of the glass?(The air pressure pushing upward against thecard was greater than the gravity pulling down.)

■ What do you think will happen when watersoaks into the card? (Encourage speculation;students might suggest that as the cardbecomes heavier with water, the force of gravitywill become stronger than the air pressure, caus-ing the card to fall and the water to spill.)

Discussing the Main IdeaAsk:

■ How does altitude affect air pressure? (As altitude increases, air pressure decreases.)



Remind students that air is amixture of gases and the weight of the gasesexerts a force on the area below the gases.

air pressure


Temperature Changes in the Atmosphere

Temperature steadily decreaseswith altitude in the troposphere,the lowest layer of the atmos-phere. Temperatures increasewith altitude in the strato-sphere, which extends to about30 miles above Earth’s surface.They drop with altitude in themesosphere, which extends toabout 50 miles above the sur-face. They increase with alti-tude in the thermosphere.

Science Background

Hero’s DemonstrationThough the idea was scoffed atin the first century, the Greekengineer Hero was among thefirst scientists to theorize thatair exerts pressure. He demon-strated this theory by placingan open-ended container of airon the surface of water, show-ing that air must escape asbubbles in order for the waterto rise in the vessel. He con-cluded that air is matter, andthat it has weight.

Science Background

1. A trace is a very small amount of some-thing.

2. Nitrogen is most abundant.


D 34

What Is Weather?

When you say, “It sure is hottoday!” the it is the air. You reallymean that the air around you is hot.The same is true if you say, “It iswindy, ” or “It is cloudy,” or give any other similar description of the

. The weather is simply whatthe lower atmosphere, or troposphere,is like at any given place and time.

The conditions that make upweather are the characteristics thatchange. They are air temperature, airpressure, amount of moisture in the air,wind, clouds, and rain or snow.

Measuring Temperature

You can measure temperature witha thermometer. Thermometers can use two different temperature scales.The Celsius scale is marked with theletter C. The Fahrenheit scale is shownby the letter F.

Measuring Air Pressure

Air pressure is measured with a(buh·ROM·i·tuhr). Two

common types of barometers are themercury barometer and the aneroidbarometer.

Mercury barometers use a mercury-filled glass tube with one closed end.The open end is submerged in liquidmercury. Air pressure on the mercurypushes it up into the tube. When theweight of the mercury column equalsthe air pressure, the mercury stopsrising.

barometer

weather

An aneroid (AN·uh·royd) barometeris an accordion-like metal can withmost of the air removed. Inside, aspring balances the outside airpressure. When outside air pressureincreases, the can squeezes the spring.When air pressure decreases, thespring pushes outward. A needleinside indicates changes in pressure.

You can monitor and recordweather conditions for your ownweather station. Measure and recordair temperature several times a day.Record daily air pressure by using abarometer or by getting air pressurereadings from weather reports.

Two commontypes ofbarometers

Aneroidbarometer

Mercurybarometer

Main Idea

What conditions make up weather?

air temperature, air pressure, wind, amount ofmoisture in the air, clouds, and rain or snow

What Is Weather?


Developing the Main IdeaAsk students to define weather based on what theyalready know. Encourage discussion; students may listweather conditions such as rain, snow, and so on.

Ask students to brainstorm, listing as many conditionsthat make up weather as they can. Write theresponses on the chalkboard, and guide students toinfer that the term weather describes a number ofconditions that, together, describe the lower atmos-phere. Ask:

■ Do any of these conditions exist alone? (No;weather includes a number of conditions at anyone time.)

Encourage students to identify conditions that com-monly occur together, such as cold and snow, warmand humid, and so on.

After Reading

Have students answer the red question in the student book as ongoing assessment.


To help students understand thatweather is the total of conditions in theatmosphere, ask them to list words that theywould use to describe what it is like outsideat any given time.

The suffix “-meter” is used todescribe an instrument that measures some-thing. Ask students if they can list otherwords that end in “-meter”.

barometer

weather


Develop Discuss with studentshow every story, poem, play,article, and even a paragraphhas a main idea—what the writ-ten material is mostly about.Other facts in the document aredetails that support, or tell moreabout, the main idea. Point outthat in paragraph 3, the mainidea is stated in the first sen-tence. Discuss how the othersentences in that paragraphsupport the main idea that ther-mometers measure temperature.

Practice Ask students to sug-gest supporting facts thatwould back up the main idea ofthe fifth paragraph—that a tubeof liquid mercury can be used tomeasure air pressure. (Answersshould include statements ofhow air pressure pushes mer-cury up the column of a tubethat’s submerged in it and stopsrising when the pressure andweight of the mercury areequal.)

Main Idea and Supporting Details

Reading MiniLesson

SC

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D 35

MATH LINKSolve this problem. The sunniest placeon Earth is in the eastern Sahara Desert,where sunlight shines an average of4,300 hours per year. Calculate thepercentage of possible sunlight hours ayear this number represents. (Assume 12hours of daylight per day.)

WRITING LINKWriting a Poem Write a poem abouthow the weather affects your life. Usewords, such as splash, that imitate thesound of the weather.

SOCIAL STUDIES LINKResearch the history of thethermometer. The maximum-and-minimum thermometer wasinvented in 1780 by Englishscientist James Six. A column ofmercury moves up and down a U-shaped tube. An index moveswith it, recording the highest andlowest temperatures. Researchthe history of the thermometer,and write a report for the class.

TECHNOLOGY LINKVisit www.science.mmhschool.com

for more links.LOG

Why It MattersHave you ever heard a day

called a “scorcher”? That means areally hot day. On really hot days,your body can lose a lot of moisture.Your body gives off sweat graduallymost of the time. On a hot day, yourbody tends to give off more andmore. That’s why it’s important tohave plenty of drinking waterhandy on a hot day.

On really cold days, manypeople have other problems—suchas frostbite. You have to cover yourface, ears, and hands to avoidcontact with air at extremely lowtemperatures.

Think and Write1. How do temperatures on

Earth depend on angles?

2. List factors that affect temperatures of places on Earth.

3. What is air pressure? How does it change in the atmosphere?

4. What is the troposphere?What happens there?

5. Critical Thinking Is the weatherone or more than just onething? Defend your answer.

-JournalJournal Visit our Web sitewww.science.mmhschool.com to do aresearch project on the atmosphere.

Answers to Think and Write1. The angle at which rays of the Sun strike a sur-

face affects how much heat it will receive. Themore vertical the rays the greater the heat.(pp. D29–D31)

2. angle of insolation, water, plants, altitude(pp. D31–D32)

3. Air pressure is the force on an area caused bythe weight of air above it. It is greatest at sealevel and decreases with increasing altitude.(pp. D32–D33)

4. The troposphere is the lowest part of theatmosphere. Most air is found and mostweather occurs in the troposphere. (p. D32)

5. Critical Thinking Weather is made up of manyconditions that describe what the lower atmos-phere is like at any given time. (p. D34)

SummarizeCheck students’ understanding by having them writea brief summary of the lesson in their own words.

MATH LINKStudents first calculate the number of possible sun-light hours in a year: 365 days/year � 12 hours/day �4,380 hours/year. Then calculate the percent of timethe Sun is actually shining: �

44

,,33

08

00

� � 0.981, or 98 percent.

WRITING LINKWriting a poem Tell students that when they usewords that imitate a sound, like splash, they are usinga poetic device known as onomatopoeia.

SOCIAL STUDIES LINKStudents’ research should focus on information aboutSix’s thermometer, as well as Galileo and GabrielFahrenheit’s.


Easy/Average Have smallgroups create posters showingEarth, its atmosphere, and howrays of the Sun reach Earth. Havethem add labels describing howangle of insolation, altitude,water, air, pressure, and temper-ature affect weather. Display theposters in the classroom.

Challenge Have studentsexplore Ben Franklin’s forays intometeorology. Urge students toconsider whether modern tech-nology is essential to further ourknowledge, or if Franklin pos-sessed the necessary tools forweather exploration. Have stu-dents write reports to defendtheir positions.

Informal Assessment

Technology

Internet Research Project Have students visit www.science.mmhschool.com to conduct aresearch project on the atmosphere. Theywill find a suggested outline for the project,questions to research, and links to Internetreference sites.


http://www.science.mmhschool.com



What if you were walking on this bridge? What wouldyou see and feel all around you? It’s fog. What is fog

made of? Here’s a hint. What if you put a cold glassof lemonade outside on a table on a hot, humid

day? What would you see and feel on theoutside of the glass?

What is a humid day like? Whereis the moisture on a humid day?

Inquiry SkillYou use variables when you identify

and separate things in an experiment

that can be changed or controlled.

water vapor, D38

humidity, D38

evaporation, D38

condensation, D39

relative humidity, D39

Vocabulary

D 36

Water Vaporand Humidity


Build on Prior KnowledgeHave students discuss what they know about water inthe air. Ask:

■ Where does rain come from? (clouds)■ Where does the moisture that forms clouds

come from? (air)■ How does water get into the air? (It evaporates

from oceans, lakes, and other water sources.)

Using the IllustrationsHave students discuss how they might feel if theywere walking across the bridge in the photograph.(They might feel the moisture from the fog on theirskin.) Fog is water vapor in the air. Water on the out-side of a cold lemonade glass does not come frominside the glass but from water vapor that condensesoutside the glass.

Have students describe how they feel on a humid day.(Students may answer that they feel sticky or dampand hot.) Point out that the stickiness they feel on ahumid day is from moisture in the air.

Water Vaporand Humidity

Objectives

■ Explore how water changes as aresult of heating and cooling.

■ Relate humidity to the processesof evaporation.

■ Explain what happens to watervapor with cooling.

■ Describe a series of changes thatwater goes through.



pp. 221–226



HygrometerJohn Frederic Daniell (1790-1845), a British chemist,invented the dew-pointhygrometer. Dew point is thetemperature at which watervapor of a certain percentagein air condenses. A hygrometercools air to its dew point, thencompares that temperaturewith the actual temperature toshow relative humidity.

Science Background

Unseen HabitsTeacher Awareness Teacherswork hard to create balancedlearning environments, yet canunintentionally favor some students. Check yourself as youteach about weather: Do youask certain students to supporttheir answers but simply praiseothers for a correct response?Challenge all students to elaborate their answers.Linguistic


Materials

plastic cups

ice

paper towels

food coloring

thermometer

goggles

Where Does the Puddle Come From?

Procedure: Design Your Own

Wear goggles.

Form a Hypothesis Write down your idea about why apuddle forms around a frosty drink. Where do youthink the puddle came from?

Experiment Describe what you would do to test youridea. How would your test support or reject your idea?

Communicate Draw a diagram showing how you woulduse the materials. Keep a record of your observations.

Drawing Conclusions

Communicate Describe the results of your investigation.

Communicate What evidence did you gather? Explain what happened.

Infer How does this evidence support or reject your explanation?

Use Variables Doyou get the same results on a cool day as on a warm day? Do you get the same results on a humid day as on a dry day? Investigate to test your hypothesis.

FURTHER INQUIRY4

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Where Does the Puddle Come From?

Science Inquiry Skills form a hypothesis, experi-ment, communicate, infer, use variables



Grouping individual

Procedure

STRUCTURED

Be Careful! Have students wear goggles to preventgetting food coloring in their eyes.

Students might describe placing ice and tintedwater into a cup, adding a straw, marking thewater level on the straw, measuring and record-ing the temperature of the water and the air atintervals, and comparing the conditions whenwater droplets form with those at the beginningof the experiment.


The water level does not go down, and the waterdroplets are not tinted.

Answers will vary, but might include that the tem-perature of the water increased, that the temper-ature of the air decreased, untinted waterdroplets formed, and the water level in the cupdid not change.

The untinted water droplets that formed supportthe hypothesis that the water comes from the air.

GUIDED On a cool day, less water willform on the glass. Students might suggest testingthis by using the apparatus they used in theExplore Activity, and cooling the area with a fanor placing the setup in the refrigerator.

STUDENT-INITIATED Students can ask their ownquestions to explore, such as whether anything hap-pens when a container holding a hot liquid is placedin cool surroundings.

INQUIRY

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Materials two jars, one with alid, wax pencil, and water

Where’d It Go? Have studentspour an equal amount of waterinto the jars, tightly screwing thelid onto one. Have them markthe water level with a wax pencil.Leave the jars undisturbedovernight. Direct students tocheck the water level in each.Challenge them to explain whatoccurred. (There is less water inthe open jar because watermoved into the air by evapora-tion; the closed jar may have con-densation on its sides.) Spatial



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Where’d It Go?

Procedure

1. Pour an equal amount of water into each of the jars.

2. Tightly screw the lid onto one of the jars.

3. With a wax pencil, mark the level of water in each jar.

4. Leave the jars where they will be undisturbed overnight.

5. The next day, observe the water level in each jar and record your observations.

The water level in the open jar dropped. That of the closed jar

dropped slightly at first and then leveled off.

6. Record any other observations you made.

The closed jar may have condensation on its sides.

Drawing Conclusions

1. What do you think happened to the water in the open jar?

Some of it moved into the air by evaporation.

2. Did you observe the same results in both jars? Explain why or why not.

In the open jar, evaporation from the water was greater than condensation

back into the water, so the water level dropped. In the closed jar, condensa-

tion increased until it equaled evaporation, at which point the water level

remained the same.

Lesson 4

• two jars, onewith a lid

• wax pencil

• water


Technology

When time is short, preview the activity with theExplore Activity Video.


gas. Water vapor is invisible, colorless,odorless, and tasteless. The amount of water vapor in the air is called

. Do not confuse humiditywith droplets of liquid water you seein rain, fog, or clouds.

How does water vapor get into the airin the first place? More than two-thirdsof planet Earth is covered with liquidwater—oceans, rivers, and lakes. Thereis also water in the ground and in plants.To get into the air, this liquid water mustbe changed into water vapor.

The changing of a liquid into a gas iscalled . This takes lots ofenergy. The main energy source forEarth is the Sun. Each day the Sunturns trillions of tons of ocean waterinto water vapor.

Water molecules absorb the Sun’senergy and speed up. “Speedy” water molecules near the surface of the liquid“escape” or evaporate into the atmos-

evaporation

humidity

D 38

Where Does Water Vapor

Come From?

Put a frosty glass of lemonade on atable on a hot day. What happens? Apuddle forms on the table. Wheredoes the puddle come from? The waterlevel in the glass does not drop as thepuddle forms. The water in the puddleisn’t lemonade.

The water in the puddle comes fromthe air around the glass. When thewarm air touches the cold glass, the aircools. Droplets of water form, run downthe side of the glass, and make a puddleon the table.

The water in the air is .Water vapor is water in the form of a

water vapor

Arctic Circle

Tropic of Cancer

Antarctic Circle

Tropic of Capricorn

Mexico City•

Cape Town •

Olekminsk•

Madrid•

Tuamotu•

Mt. Kenya•

Main Idea Water on Earth’s surface

and in the atmosphere changes form and

affects the weather.

How could you prove that over two-thirdsof the planet is covered with water?

Earth’s Water

Where Does Water Vapor

Come From?


Exploring the Main IdeaWork with students to make a hygrometer to measurethe water in the air. Punch a hole in an index card,about halfway down the short side and an inch fromthe edge. Then cut a thin lengthwise strip from a sec-ond card, cutting one end diagonally to form a point.Attach the unpointed end of the strip to the indexcard (through the hole) with a brass brad-type fas-tener. To the pointed end of the strip, tape a strand ofhair that is at least 4 inches long. Tape the other endof the hair to the top of the card so that the pointedstrip hangs in the middle of the card. Draw a line onthe card indicating where the pointed arrow reaches.Tell students that certain materials, including hair,soak up water on humid days.


By looking at a map or a globe and compar-ing the amount of Earth’s land with theamount of Earth’s waters

Have students look up the sci-ence meaning of vapor in the dictionary tocome up with a definition of water vapor. (agaseous state of a substance that is usually aliquid or a solid; water in the gaseous state)

Students may be able to seehumid in this word. Have them describe theuncomfortable feeling they may have onhumid days.

Students may find vapor inthis word. See water vapor above. The prefixe- means “to become” or “to leave” — that is,“to become a gas” or “to leave the ground asa gas.”

evaporation

humidity

water vapor

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Water Vapor and Humidity


Where Does Water Vapor Come From?

1. When water drops form on a cold glass, the water comes from the

.

2. Water vapor is water in the form of a(n) .

3. The amount of water vapor in the air is .

4. Water covers more than of Earth’s surface.

5. Liquid water becomes a gas called water vapor through the process

of .

6. The Sun’s energy enables from the water’s surface to

escape into the atmosphere.

7. The change from a gas to a liquid is called .

8. The second-largest source of water vapor is from

plant leaves.

transpiration

condensation

water molecules

evaporation

two-thirds

humidity

gas

air around the glass

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Lesson Outline


Compare and ContrastDeveloping Reading SkillsHave students compare andcontrast the movement ofwater into the air as a vaporwith the formation of waterdroplets by condensation.

Reading StrategySC

IENCE


D 39

phere as water vapor. Some hit othermolecules and return to the liquid.When air is cooled, molecules in the airslow down. The molecules of watervapor in the air also slow down. If theyslow enough, water vapor moleculeschange to molecules of liquid water that collide and stick together to form droplets on cool surfaces.

is the changing of a gasinto a liquid. You see condensation onshower doors, on cold drink glasses, andas dew on grass in the early morning.

Plants’ roots absorb water that hasseeped into the ground. Plants transportthe liquid water through their roots andstems to their leaves. The leaves thengive off water in the process calledtranspiration. This is the second-largestsource of water vapor in the atmosphere.

Two factors determine the amount ofhumidity in the air. First, there has to bewater available to evaporate. Second,the warmer the temperature, the fasterthe water evaporates. This means that ifwater is available, warm air will take onmore water vapor than cold air.

is a comparisonbetween how much water vapor is inthe air and how much the air couldhold—at a given temperature.

Relative humidity can affect how aperson feels. The higher the relativehumidity, the less water can evaporateinto the air. The less water, such assweat, can evaporate from our skin, thewarmer and “stickier” we feel.

Relative humidity

Condensation

TranspirationMake a Two-Column

Table. (See p. R 41.) Label as shown.

1. Place a clear-plastic bag completely

over a houseplant. Tie the bag tightly

around the base of the stem. Do not

put the soil-filled pot in the bag.

2. Observe Place the plant in a sunny

location. Observe it several times a

day. When you are done, remove the

plastic bag from the plant.

3. Communicate Use the table to

describe what you see inside the bag.

Explain what happened.

4. Draw Conclusions Transpirationsounds like perspiration—sweating.

How might the two processes be

alike?

5. Predict How would your results

vary if you put the plant in the

shade?

QUICK LAB

Main Idea

How does water get into the air?

#3Communicate

#5Predict

The water in the air comes from the evaporation of water from oceans, lakes,rivers; from water in the ground; and from plants giving off water vapor.

Exploring the Main IdeaReinforce the concept that evaporation requires heat,and point out that places where evaporation takesplace become cooler as a result. As students observe,dampen a cotton ball with water and wrap it aroundthe bulb of a thermometer. Place a second ther-mometer, without damp cotton, next to the first.Direct the breeze from a fan onto the two thermome-ters. Leave them undisturbed for 10 minutes. Have astudent volunteer read both. Ask:

■ What happened? Why? (The wet thermometerregisters a lower temperature because, as thewater from the cotton ball evaporated, heatenergy was removed from the thermometer.)


Materials potted houseplant (such as geranium),clear plastic bag, string

Science Inquiry Skills observe, communicate, drawconclusions, predict


Step 2 Students will observe moisture forming in thebag.

Step 3 Water droplets form on the inside of the bagas a result of transpiration. The plant absorbswater through its roots, then gives off waterthrough its leaves.

Step 4 Both transpiration and perspiration areprocesses where water is given off by a plantor an animal, respectively.

Step 5 The transpiration process would be slower.


HygrometerBenjamin Franklin (1706–1790)was among the first to notethat on humid days, certainmaterials absorb water. Basedon observations, Franklindeveloped the hygrometer tomeasure humidity. Ask stu-dents to bring in a picture of ahygrometer.

Science Background

Students may see the worddense, “thick, packed together,” in condensa-tion and infer the word means “the act orprocess of making something dense.” Themolecules of gas are compacted into asmaller volume when the gas becomes liquid.

Ask students to findrelative in a dictionary, and then discusswhich meaning applies to its use in relativehumidity.

relative humidity

condensation


QUICK LABby Dinah Zike

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Where Does Water Vapor Come From?A map is a kind of diagram. This map shows Earth’s water and land. Notice how theareas of water compare with the areas of land.

Lesson 2


1. What is the title of the diagram?

Earth’s Water

2. What do the lighter gray areas represent?

water

3. What do the darker gray areas represent?

land

4. More than two-thirds of Earth is covered with water. Do you think the diagram shows this accurately? Explain.

possible answer: Yes, because it looks like there is more light gray than dark

gray in the diagram.

Earth’s Water

Mexico City•

Olekminsk•

Tropic of Cancer

Cape Town•

Tropic of Capricorn

Mt. Kenya•

Madrid•

Tuamotu•

Antarctic Circle

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D 40

What Happens When Warm,

Moist Air Cools?How can warm, moist air cool off?

In the lower atmosphere, the air getscolder with increasing altitude.

• Air can cool by being pushedupward over mountains by winds.

• Heating the air also causes it to rise.When the Sun heats the ground, airabove the ground warms and rises.As it rises, it expands and cools.

• Air can also be pushed upwardwhen cooler air and warmer airmeet. When the two meet, theydon’t mix. The lighter, warm air ispushed up over the heavier, cold air.As a result, the warm air, pushedhigher into the atmosphere, cools.

In each case the end result is thesame. As the air rises and cools, thewater vapor in it condenses into tinywater droplets, forming clouds.

If the temperature is below thefreezing point of water, its water vaporwill form a cloud of tiny ice crystals.

In order for water vapor tocondense, it must have a surface onwhich the liquid droplet or ice crystalwill form. This surface is provided bytiny dust particles in the air. You willlearn more about clouds in the nextlesson.

Cloud forms

Cloud forms

Warm air

Warm air

Cool air

Warm air

Cloud forms

How Clouds Form

How can warm air rise and cool? 1. What can cause air to rise?

2. What happens to the air temperature as air rises?

Warm air can be pushed upward over mountainsby winds or pushed upward when warm and coolair meet, and can rise when heated by the Sun.

What Happens When Warm, Moist Air Cools?


Developing the Main IdeaAsk:

� How can warm air become cool? (It can bepushed upward by winds, it can be pushed up bycool air, and it can cool by rising and expanding.)

� What part of the water cycle did the ExploreActivity illustrate? (condensation)

� How did the condensation that occurred relyon evaporation? (For condensation to occur,there must have been water, formed by evapo-ration, in the air.)

After ReadingHave students answer the red question in the stu-dent book as ongoing assessment.


1. Air can rise by being pushed over moun-tains, by being displaced by cooler air, orby being heated by the Sun.

2. As air rises, it expands and cools.

Erasmus Darwin, an eighteenthcentury British physician, wasthe first scientist to hypothesizethat the rising of air is an impor-tant method of cooling. To testhis hypothesis, he charged anunloaded pellet gun andallowed it to reach room tem-perature before discharging it,releasing air under pressure ontothe bulb of the thermometer.

When the thermometer regis-tered a drop in temperature,Darwin concluded that the cool-ing mechanism was the abruptexpansion of air as it wasreleased from the gun. Ask stu-dents to describe how Darwin’sexperiment produced cool air.(release of pressured air expandsit, causing cooling)

Science Background

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How Clouds FormThese three diagrams show three ways in which clouds are formed when watervapor in the air condenses. When air moves higher, it cools. Because the tempera-ture decreases, condensation from water droplets is greater than evaporation from the droplet. As a result, the droplets grow. The diagrams show what can happen next.


1. In diagram 1, does the air get warmer or cooler when the wind pushes it up

over the mountain?

2. What happens to the water vapor in the air when the air cools?

It condenses and forms a cloud.

3. In diagram 2, the Sun warms the ground. What happens to the warm air near

the ground?

It rises and cools and then forms a cloud.

4. In diagram 3, the warm air is pushed up by the below it.cool air

cooler

1 Cloud forms

Warm air

3 Cloud forms

Warm air

Cool air

2 Cloud forms

Warm air

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D 41

WRITING LINKPersonal Narrative Why are you lesscomfortable in higher relative humidity?Write about a day in your life whenhigher relative humidity affected you.

MATH LINKFind the heat index. Use an almanac tofind a heat index prepared by the weatherservice. This chart tells how warm aperson feels at a particular temperatureand humidity level. Using the chart, findthe heat index for each of the days in thetable below. Then use newspaper weatherreports for one week last summer. Findthe heat index for each of those days.

ART LINKMake a poster. Very hot, humid weathercan be dangerous. Make a poster warningabout the dangers of very hot, humidweather. Include a list of safety tips.


for more links.LOG

Mon Tues Wed Thurs Fri

High25ºC 35ºC 30ºC 35ºC 25ºCtemp.

Relative90% 97% 89% 48% 45%humidity

Why It MattersHave you ever had sweat trickle

down your face on a hot day? Peoplesweat every day. Sweating is a wayour bodies release wastes. We don’talways feel the sweat because wesweat gradually, and it evaporates.

As sweat evaporates, the waterdroplets absorb heat from the skin’ssurface, cooling it. In this way yourbody controls surface temperature.

On very hot days and when youare physically active, you may sweata lot. The sweat builds up, does notevaporate fast, and collects. On ahigh-humidity day, you feel even“stickier.” On a low-humidity day,the sweat evaporates more quickly.

Think and Write1. Where does water vapor in

the air come from? Whatprocess produces it?

2. How is relative humidity dif-ferent from humidity?

3. What causes water vapor tochange into droplets of liquidwater?

4. How does water vapor getcooled in the atmosphere?

5. Critical Thinking Would you saythat the Sun is a cause ofclouds? Defend your answer.

-JournalJournal Visit our Web sitewww.science.mmhschool.com to do aresearch project on humidity.

Answers to Think and Write1. water vapor from the water that covers the sur-

face of Earth; evaporation (pp. D38–D39)

2. Both describe water in the air. Humidity is ameasure of the amount of water in the air.Relative humidity compares the amount ofwater in the air with the amount of water thatthe air could hold at a given temperature.(p. D38–D39)

3. Water vapor must be cooled and have some-thing on which to condense. (p. D39)

4. by being pushed upward and expanding(p. D40)

5. Critical Thinking The Sun heats air, causing it torise. As air rises, it expands and cools.Condensation then occurs, forming clouds.(p. D40)


WRITING LINKPersonal Narrative When relative humidity is high,more moisture is held in the air. The higher the rela-tive humidity, the less water can evaporate into theair. Thus, the sweat on your skin does not evaporateas quickly as on a day with low relative humidity. On ahumid day, your skin feels damp and sticky, and youare less comfortable.

MATH LINKThe heat index is the combined effect of temperatureand relative humidity. The heat index temperaturetells you how warm the weather feels to you regard-less of the actual temperature. The heat index for thefollowing days is: Mon—87; Tues—140; Wed—105;Thurs—90; and Fri—79.

ART LINKMake a wall display of students’ posters.


Easy/Average Have studentsexplore methods elephants useto cool off and explain whythese methods are effective.(Elephants spray themselveswith water. They also use theirears as fans to cause the water toevaporate and cool themselves.)

Challenge Have small groupsfind out more about evaporationand condensation. Challengestudents to make posters show-ing how evaporation and con-densation move water from thesurface of Earth to the atmos-phere and back. Display theposters in the classroom.

Informal Assessment

Technology

Internet Research Project Have studentsvisit www.science.mmhschool.com to do aresearch project on humidity. They can compare humidity and relative humidity.They will find a suggested outline for theproject, questions to research, and links toInternet reference sites.





How can you predict the weatherwithout using the instrumentsweather forecasters use? Look atthe sky. There are clues up there.They’re called clouds. Differentkinds of clouds bring differentkinds of weather. What is a cloud?What makes a cloud form? Whatdo evaporation and condensation

have to do with it?

Inquiry SkillYou infer when you form an

idea from facts or observations.

D 42

Clouds andPrecipitationstratus cloud, D44

cumulus cloud, D44

cirrus cloud, D44

fog, D44

precipitation, D46

Vocabulary


Build on Prior KnowledgeHave students discuss what they know about cloudsand precipitation. Have students look at the cloudsoutside the classroom. Ask them if they think there isa good chance of rain or snow and then have themexplain their ideas. (Possible answers: Gray clouds mayproduce rain or snow depending on the day’s tempera-ture; a nearly cloudless sky may mean a rainless day.)

Developing the Main IdeaReview cloud formation from the previous lesson:when rising warm air cools, water vapor in the air con-denses into tiny water droplets or ice crystals. The for-mation of clouds depends on air temperature and theamount of water vapor in the air.

Clouds andPrecipitation

Objectives

■ Explore how clouds form.■ Identify causes and types of

clouds and precipitation.■ Describe how to compare

amounts of rainfall and cloudcover.



pp. 227–232



■ Visual Aid Transparencies

22, 23

■ Grade-Level Science Book,

The Great Johnstown Flood

■ School to Home Activities, p. 26

Cloud ClassificationThe English chemist LukeHoward (1722–1864) createdthe basic system of cloud clas-sification. Though he didn’tunderstand how the differentkinds of clouds formed, heassigned them Latin namesbased on their appearance.Cirrus clouds, for example,resemble curls of hair, whilecumulus clouds look like heaps,and stratus clouds lie flat. Stillin use today, these categoriesnow have further subdivisions.

Science Background


D 43

How Do Clouds Form?

Procedure

Be careful handling the hot water.

Chill container 1 by putting it in a refrigerator or on ice for about ten minutes.

Fill a mug with hot water.

Make a Model Fill container 2 with the hot water.Place empty cold container 1 upside down on top ofcontainer 2 with the water. Fit the mouths togethercarefully. Place the ice cubes on top of container 1.

Observe Record your observations.

Drawing Conclusions

Communicate What did you observe?

Communicate Where did this take place?

Infer Where did the water come from?Explain what made it happen.

InferDo clouds form better in dryor moist air? Conduct anexperiment to test your inference. What materials willyou need? What will youdo?

FURTHER INQUIRY4

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Materials

hot tap water

2 identical clearcontainers

mug

3 ice cubes How Do Clouds Form?

Science Inquiry Skills make a model, observe, communicate, infer



Grouping pairs

Procedure

STRUCTURED

Be Careful! Be sure the tap water is not so hot that itcould cause scalding.

Ask students to predict what will happen to thehot water. (Some of the water will evaporate intothe air and the warm, moist air will rise into thecold container.)


Droplets of water collected on the inside bottomof the container holding the ice.

Invisible water vapor moved upward from the hotwater, cooling as it rose; droplets formed on thebottom inside of the container holding ice.

The water evaporated from the hot water into theair. Then as the air was cooled, some of the watervapor in the air condensed. Students might inferthat the upper container cooled the air contain-ing water vapor rising from below. As it cooled,the air couldn’t hold as much water as it hadbefore, so the water condensed, forming dropletson the underside of the cool container.

GUIDED Setup should be similar toExplore Activity with warm water in a cup. Therewill be moist air above the water. To test dry air,use sand instead of water. Clouds form better inmoist air.

STUDENT-INITIATED Students can ask theirown questions to explore, such as whether the waterin clouds evaporates.

INQUIRY

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Materials electric tea kettle,water, metal pie plate, tongs,oven mitt

Make a Cloud Boil water in thekettle. As students observe, holda metal pie plate in the cloudabove the spout. (Hold yourhand away from the steam toprevent burns.) Have studentsexplain how the result confirmsthat clouds are formed by con-densation. (Heated air holdingwater vapor cools as it rises, andcondenses forming a cloud ofvisible water droplets on thepie plate.) Spatial

Activity Resources, p.142


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Unit D · Astronomy, Weather and Climate Use with TE textbook page D43

Make a Cloud

Procedure

Keep away from the tea kettle spout and steam

to avoid getting burned. Wait until the tea kettle cools before

handling it.

1. Fill the tea kettle about half way with water.

2. Plug in the tea kettle, turn it on (if necessary), and waitfor the water to start boiling.

3. Observe Observe the spout of the tea kettle and recordyour observations.

Teachers should do this as a demonstration as students watch from a safe

distance. Steam can cause burns! Steam or water droplets form above the spout.

4. Use the mitt and tongs to hold the metal pie plate above the spout.

5. Observe Observe what happens and record your observations.

Many tiny water droplets form on the underside of the metal pie plate

where the steam hits it.

6. Turn off and unplug the tea kettle

Drawing Conclusions

1. What happened when the water in the kettle boiled? Explain yourobservations.

Liquid water in the kettle evaporated and moved into the air and out of

the spout. As the warm water vapor rose, it cooled and formed steam,

or tiny water droplets, in the air.

2. When you held up the pie pan, where did a “cloud” form? Why did it form there?

A “cloud” of tiny water droplets formed where the steam hit the pie pan.

As warm water in the air rose from the spout, it hit the colder

metal surface, cooled, and condensed.

Lesson 5

• electric teakettle

• water

• metal pie plate

• tongs

• oven mitt


Technology

When time is short, preview activity with theExplore Activity Video.


D 44

How Do Clouds Form?What has to happen for a cloud to

form? Clouds are made up of tiny waterdroplets or ice crystals. The air is filledwith water vapor. When the air iscooled, the water vapor condenses. Thatis, the water molecules clump togetheraround dust and other particles in theair. They form droplets of water.

Clouds look different depending onwhat they are made of. Water-dropletclouds tend to have sharp, well-definededges. If the cloud is very thick, it maylook gray, or even black. That’s becausesunlight is unable to pass through. Ice-crystal clouds tend to have fuzzy, lessdistinct edges. They also look whiter.

All clouds form in the troposphere.There are three basic cloud forms.

form in blanketlikelayers. are puffyclouds that appear to rise up from aflat bottom. form atvery high altitudes out of ice crystalsand have a wispy, featherlike shape. Ifrain or snow falls from a cloud, theterm nimbo or nimbus—for “rain”—isadded to the cloud’s name.

Clouds are further grouped intofamilies by height and form. There arelow clouds, middle clouds, high clouds,and clouds that develop upward—clouds of vertical development.Cumulonimbus clouds develop upward.These clouds bring thunderstorms.

Cirrus clouds

Cumulus cloudsStratus clouds

Stratus clouds

Cirrus clouds

Cumulus clouds

They can start as low clouds and reachup to the highest clouds. If moist air atground level cools, a cloud can formright there. A cloud at ground level iscalled .fog

What are three basic cloud forms?

Main Idea Water vapor and ice form

clouds that produce precipitation.

stratus—blanketlike clouds; cumulus—puffy clouds; cirrus—featherlike clouds

How Do Clouds Form?


Developing the Main IdeaPoint out that historically, sophisticated weatherinstruments are very new, but that people have pre-dicted weather since ancient times by noting theshapes, sizes, colors, and movements of clouds.



Stratus comes from a Latinword meaning “to spread out.” A stratuscloud looks spread out in a layer, coveringmost of the sky overhead. Students may alsothink of a similar word, a rock layer, a rockstratum.

An everyday meaning ofthis word is “heap, pile, accumulation.” Thiscloud looks like many fluffy mounds or heapsone over the other.

In biology, cirrus means “athreadlike, flexible appendage of an animal,such as a feeler or tentacle.” Students can seewispy curls in the picture of cirrus clouds.

The word fog comes from a Danishword meaning “driving snow” Thick groundfog may resemble piles of snow on theground.

cirrus cloud

cumulus cloud

stratus cloud


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Clouds and PrecipitationFill in the blanks. Reading Skill: Main Idea - questions 2, 5

How Do Clouds Form?

1. Clouds are made up of or .

2. All clouds form when the air cools and water vapor

around dust and other particles.

3. A thick, sharp-edged gray cloud is probably made of ,

not .

4. All clouds form in the lower atmosphere, or .

5. The three basic cloud forms are:

a. blanketlike layers, or ,

b. puffy, flat-based , and

c. high-altitude, feathery .

6. The prefix “nimbo-,” or nimbus, as in nimbostratus, refers to a cloud that

brings or .

7. A cloud at ground level is called .

What Is Precipitation?

8. Any form of water particles that falls to the ground from the atmosphere is

.

9. Precipitation occurs when water droplets or ice crystals join together and

become .

10. A dust particle is the around which water

molecules condense.

11. The type of precipitation formed from ice crystals that occurs when the ground

temperature is cold is .

12. When cloud droplets collect and freeze around an ice crystal, and the process

repeats over and over, is formed.hail

snow

nucleus

too heavy

precipitation

fog

snowrain

cirrus

cumulus

stratus

troposphere

ice crystals

water droplets

condenses

ice crystalswater droplets

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Lesson Outline


fog

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Lesson 5How Do Clouds Form?Some diagrams show parts of a whole. The diagram below shows the basic types ofclouds found in the atmosphere. Notice how the cloud forms are related to eachother.

Types of Clouds

Cirrus

Anvil top

Cirrocumulus

CirrostratusAltocumulus

5 km

2 km

0 km

Altostratus

Stratus

Nimbostratus Stratocumulus

Cumulus

Fog

Cumulonimbus(vertical development)

Hig

h c

lou

ds

Clo

ud

s o

f ve

rtic

al d

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Mid

dle

clo

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sLo

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1. What are the four general families of clouds shown in the diagram?

low clouds, middle clouds, high clouds, and clouds of vertical development

2. What is the upper height range for low clouds?

2 km

3. Which two cloud forms are found in the middle cloud family?

Altostratus and Stratus

4. What are ground-level clouds called?

fog

5. How are clouds of vertical development different from the other three families

of clouds?

possible answer: These clouds are not grouped horizontally, like low,

middle, and high clouds.

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Fog

2 km

0 km

5 km

Cumulus

Cumulonimbus(vertical development)

Altostratus

Altocumulus

Stratus

Cirrus

Cirrocumulus

Cirrostratus

Anvil top

Nimbostratus Stratocumulus

Low

clo

ud

sM

idd

le c

lou

ds

Clo

ud

s o

f ve

rtic

al d

evel

op

men

t

Hig

h c

lou

ds

Types of Clouds

D 45

1. How are low, middle, and high clouds different?

2. Why are clouds of vertical development not groupedtogether with any of the other cloud families?

Using the IllustrationsEncourage students to compare and contrast the dif-ferent kinds of clouds. Ask:

■ How are cumulus, cirrus, and stratus cloudsalike? How are they different? (They are allformed from water in one of its forms. Stratusclouds form in blanket-like layers, cumulus areflat-bottomed and globular, and cirrus cloudsare wispy and feather-like.)


SnowflakesMany of us have heard thephrase “no two snowflakes arealike.” Wilson A. Bentley(1865–1931) of Jericho,Vermont, discovered that notwo snowflakes are alike.Bentley is known for his pho-tomicrograph work. Headapted a microscope to a bel-lows camera and became thefirst person to photograph asingle snow crystal in 1885.Bentley captured over 5,000snowflakes on film, never find-ing any two alike.

Science Background

1. Low clouds have bases that are lowerthan 2 km above Earth; middle cloudshave bases that are between 2 and 6 kmabove Earth; high clouds have bases thatare higher than 6 km above Earth.

2. Because their bases are usually onlyabout 1 km above Earth, but their topscan extend beyond 20 km in altitude.

Compare and ContrastDeveloping Reading SkillsHave students compare andcontrast the different kinds ofclouds. They can organize atable by cloud type–level, thatis, low, middle, and high clouds,based on the illustration on p. D45.

Reading StrategySC

IENCE

Technology

Visual Aid Transparency 22:Types of Clouds


1. Classify the types of precipitation into two groups—solids and liquids.

2. Which types of precipitationform in similar ways?

What Is Precipitation?How do rain and snow form and

fall? is any form ofwater particles that falls from theatmosphere and reaches the ground.Precipitation can be liquid (rain) orsolid (such as snow).

Clouds are made up of tiny waterdroplets or ice crystals—only aboutof a millimeter across. These tiny parti-cles are so light that they remain“hanging” in the air. This is why manyclouds do not form precipitation.

Precipitation occurs when clouddroplets or ice crystals join together

150

Precipitation

and become heavy enough to fall. Theyclump around particles of dust in theair. Each particle is like a nucleus thatthe water molecules condense around.The chart shows the different types ofprecipitation and how they form.

Condensationaround nucleus

Cloud droplets collect.

Fall throughwarm air


Cloud droplets collect.

Raindrop

Fall through airat freezing

temperature

Condensationaround ice nucleus

Supercooled water

freezes around ice nucleus,

or water vapor changes

to ice crystals.

Ice crystals grow larger.

Snowflakes

Cold ground temperature


Cloud droplet

Freezing

Cloud droplets collectaround ice crystal.

Freezing

Repeats over and over

Warm ground temperature

Rain Sleet Snow Hail

Types of Precipitation

D 46

When does precipitation occur?when cloud droplets becomeheavy enough to fall

What Is Precipitation?


Using the IllustrationsAsk:

� Which two types of precipitation are themost similar? Why? (Rain and drizzle are themost similar because they are both made up ofwater droplets that form when cloud dropletscollide and combine.)

� How are sleet, snow, and hail alike? How dothey differ? (They are all made of ice. Sleet ismade of clear pellets of ice, snow is made up ofice crystals, and hail is layered balls of ice.)



To reinforce the meaning ofthe word, have students list or describe anyform of water particles that fall from theatmosphere, that is, hail, rain, snow.

precipitation


1. Rain falls as liquid; snow, sleet, and hailare solids, because they fall as ice.

2. Rain forms when cloud droplets collideand combine; sleet and hail both formfrom cloud droplets that freeze (thoughhail is thrust upward so that more layersform).

Technology

Visual Aid Transparency 23:Types of Precipitation

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What Is Precipitation?Charts like this one organize information. This chart shows four different types of precipitation and how each one forms. To understand the chart, read the labels on each column. Then follow the arrows to see the steps in forming eachkind of precipitation.


1. What first step do all types of precipitation have in common?

condensation around a nucleus

2. When raindrops fall through air at freezing temperatures, they become

sleet

3. What two things can happen after condensation forms around an ice nucleus?

Either supercooled water freezes around the ice nucleus, or water vapor

changes to ice crystals.

4. A snowflake forms when grow larger.ice crystals

Types of Precipitation


Cloud dropletscollect.

Fall throughwarm air


Cloud dropletscollect.

Raindrop

Fall through air atfreezing temperature


Cloud droplets collectaround ice crystal

Cloud droplet

Freezing

Warm groundtemperature

Repeats over and over.

Freezing

Condensationaround ice nucleus

Supercooled water freezes around ice

nucleus or watervapor changes to

ice crystals.

Ice crystalsgrow larger.

Cold groundtemperature

Snowflakes

Rain Sleet Snow Hail

Lesson 5

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Are Cloud Type and

Precipitation Related?

Do certain kinds of clouds givecertain kinds of precipitation? Yes.

• In tall clouds there is more chance fordroplets to run into one another andcombine, making larger raindrops.

• Precipitation from large cumulusclouds is often heavy rain or snowshowers that don’t last too long.

• Precipitation from stratus clouds isusually long lasting, with smallerdrops of rain or snowflakes.

• Clouds with great vertical develop-ment hold a lot of water. Theseclouds are very turbulent, or violent.Their tops often reach heights whereit is below freezing. They often pro-duce great downpours. They alsosometimes produce hail. Hail is pel-lets or lumps of ice.

These clouds have updrafts—strong winds that move up inside.Hail forms when updrafts in thesehuge clouds hurl ice pellets upwardagain and again. As the pellets fall,they become coated with water. Asthey rise, the water freezes into anicy outer shell. This process usuallyhappens over and over, adding moreand more layers to the hailstones.The more violent the updrafts, thebigger the hailstones can get beforethey fall to the ground.

Strong winds

Strong windsin cloud

Hailstones form inlayers and cansometimes growvery large.Hailstormscan be verydangerous.

Path of Growing Hailstone

D 47

Main Idea

What kind of cloud can produce hail? Why?

Clouds of vertical development; they have updrafts—winds that can hurl ice crystals upward again andagain, creating hailstones.

Are Cloud Type and

Precipitation Related?



■ How does the size of a cloud affect theamount of precipitation that it can form?(Encourage speculation; students might respondthat larger clouds can hold more water, so theycan produce more precipitation.)

■ What type of precipitation do stratus cloudsusually produce? (Longer-lasting steady rainwith small drops. The cloud shape does notcause the type of precipitation. Other factorscause the cloud shape and precipitation.)

■ What type of clouds tend to produce hail?Why? (Hail tends to form in clouds with greatvertical development. These clouds are very tall,with the tops often reaching above the pointwhere water freezes. Their turbulence can forcepellets of ice up again and again, forming hail.)



Develop Discuss with studentshow a diagram title usuallystates the main idea, and sup-porting details are illustrated inthe diagram. Review the dia-gram on page D47 and notehow the diagram labels andarrows explain how, where, andwhen a hailstone grows.

Practice Have students illus-trate the main idea of the rela-tionship between “cloud typeand precipitation” by writingthose words in one large circle,then drawing a tall cloud, alarge cumulus cloud, stratuscloud, and a cumulonimbuscloud around it. Inside the cloudshapes, students shoulddescribe the precipitation fromthat type of cloud.


Reading MiniLesson

SC

IENCE

Hail DamageHailstones are usually small,with a diameter below 0.4inches (10 mm). Sometimes,however, they are much larger,and very destructive. On May 8,1926, baseball-sized hailstonescaused $2 million worth ofdamage in Dallas, Texas, in just15 minutes. During a 1979 foot-ball game in Fort Collins,Colorado, grapefruit-sized hailpounded the field. Luckily, theplayers were wearing helmets,but a spectator died from askull fracture.

Science Background


D 48

How Do You Record

How Cloudy It Is?As you observe the weather each day,

you might wish to record the types ofclouds you see in the sky. You can usethe charts in this lesson to indicate thecloud family and the types of clouds.

Try to estimate the cloud cover—that is, the amount of the sky coveredby clouds. Use the terms clear, scatteredclouds, partly cloudy, mostly cloudy, orovercast to describe cloud cover.

One way to record cloud cover is tomake a weather station model. Start bydrawing a circle for each day. An emptycircle means “clear skies.” A fully shadedcircle means “completely overcast.”Portions of a circle are shaded to showdifferent amounts of cloud cover.

Precipitation is measured with a raingauge. You can make a simple rain gaugefrom an empty coffee can. Place it outside,open end up, away from buildings or trees.When the precipitation stops, measure itsdepth in the can. Keep track of the typeof precipitation and how much falls.

Feel the HumidityMake an

Eight-Row Chart. (See p.R 44.) Label as shown.

1. Observe Use athermometer to determine the airtemperature. Use the chart to recordthe air temperature.

2. Put the thermometer in coldwater. Slowly add warmwater until the water temper-ature matches the air tempera-ture.

3. Wrap a 5-cm-square piece of oldcotton cloth around the bulb ofthe thermometer. Gently hold itwith a rubber band. Dampen thecloth in the water.

4. Observe Gently wave the thermometer in the air. Note thetemperatures every 30 seconds for 3minutes. Record them on your chart.

5. Infer What happened to the tem-perature of the wet cloth? How doesthe cloth feel? Explain on the bottomof your chart.

6. Infer If you try this experiment ona day that is humid and on a day thatis dry will you get the same results?

Symbols areused to showcloud coveron a weatherstation model.

Clear

Overcast

Scattered clouds

Partly cloudy

Mostly cloudy

What are the terms used

to record cloud cover?

QUICK LAB

Time Humid Day Dry Day

3 m

in.

2 m

in.

1 m

in.

30 s

30 s

30 s

30 s

30 s

30 s

#5 Infer

clear, scatteredclouds, partlycloudy, mostlycloudy andovercast

How Do You Record How Cloudy It Is?

Before ReadingHave students try to answer the red question at thetop right of the page.

Developing the Main IdeaOn the chalkboard, draw the circular symbols forsunny, partly cloudy, mostly cloudy, and overcast. Askstudents to describe the amount of cloud cover foreach. Ask:

Why do you think scientists use symbols like theseto describe weather? (Symbols are a sort of univer-sal language that can be understood by all scientists,no matter where they’re from.)


Materials thermometer, �12

� cup cold water in a foam cup, 1 cup warm water, 5-cm-square piece ofcotton cloth, rubber band

Science Inquiry Skills observe, infer

Resources Activity Resources pp. 143–144

Be Careful! Tell students to be careful when han-dling hot water.

Step 1 Remind students to handle thermometers withcare to prevent breakage and to avoid touch-ing them should breakage occur.

Step 5 The temperature of the wet cloth drops. Whenthe cloth is touched, it feels cool.

Step 6 Because water evaporates more slowly whenthe air is moist and more rapidly on a dry day,the difference between the two temperatureswould be greater on a dry day than on ahumid day.


Making RainRemind students that untilrecently, people did not knowwhy some clouds producedrain, while others did not.Encourage students to useencyclopedias to learn moreabout how people in differenttimes and cultures have tried to“make rain” during times ofdrought. For example, manyNative American groups heldrain dances, while Americanpioneers attempted to inducethe clouds to release rain bybuilding smoky fires.

Cultural Perspective

SummarizeDeveloping Reading SkillsHave students summarize inwriting the effect that humidityhas on evaporation. (Thegreater the humidity, theslower the evaporation canoccur.)

Reading StrategySC

IENCE

QUICK LABQUICK LABby Dinah Zike


D 49

LITERATURE LINKRead The Great JohnstownFlood, the story of the stormthat destroyed a town. Whenyou finish reading, thinkabout how you would preparefor a flood. Try the activitiesat the end of the book.

MATH LINKCalculate accuracy. Observe clouds inyour area each day for a week. Predictweather based on precipitation thoseclouds are likely to produce. Record howaccurate your predictions are. Then,calculate your accuracy in percent.

WRITING LINKWriting a Story The Inuit have morethan 20 different words for snow. Why doyou think this is so? Write a “how” or“why” story about why the Inuit have somany words for snow.

TECHNOLOGY LINK Science Newsroom CD-ROMChoose On the Vapor Trail tolearn more about how warm,moist air reacts when it cools.

Visit www.science.mmhschool.com

for more links.LOG

Why It MattersIf you ever had a baseball game

rained out, you know how rain canruin your day.

Rain may ruin your plans for aday, and flooding can sometimescause disasters. However, rain is vitalfor life on Earth. Rain helps cropsgrow. Rain helps build the amount ofwater in wells and water-collectingareas, such as reservoirs. If you everhad a drought in your area, a timewhen there is little or no precipitation,you know how scarce water can be.

Think and Write1. How do clouds form?

2. What are some different typesof precipitation? Why arethere different types?

3. Explain the differencebetween the way hail formsand the way sleet forms.

4. How can you measure anddescribe the amount of precip-itation and cloud cover on agiven day?

5. Critical Thinking “Sun showers”are sudden rainfalls on a sunnyday. How can a sun showerhappen?

-JournalJournal Visit our Web sitewww.science.mmhschool.com to do aresearch project on clouds.

Answers to Think and Write1. Clouds form by water vapor in the air condens-

ing into droplets. (p. D44)

2. Different types of precipitation form in differentconditions. Cold air forms sleet and snow; coldturbulent clouds form hail; and rain and drizzlefall as liquids. (pp. D46–D47)

3. Sleet: condensation around nucleus; clouddroplets collect; raindrop; fall through air atfreezing temperature. Hail: condensation aroundnucleus; cloud droplet; freezing; cloud dropletscollect around ice crystal; freezing; repeats overand over; warm ground temperature (p. D46)

4. Precipitation is measured with a rain gauge;cloud cover is described by the amount of skythat is covered by clouds. (p. D48)

5. Critical Thinking Sun showers can happen ifcloud cover is so low that the Sun shinesbetween the rain clouds. (pp. D42–D44, D48)


LITERATURE LINKHave students read the Grade-Level Science Book, TheGreat Johnstown Flood. Additional books to read canbe found on TE p. D1•b.

MATH LINKStudents should record their predictions in the samenotebook each day. A description of actual weathershould follow each prediction. Percent correct is cal-culated using this formula: Days Correct/TotalNumber of Days Predicted � 100% � Percent Correct.For example, �

57

� � 100% � 71.4% correct predictions.

WRITING LINKWriting a Story Students should understand thatthere are many different types of snow: wet; packed;slushy. Their stories should be set in the past withcharacters who decide how and why to name the dif-ferent types of snow.


Easy/Average Have smallgroups create word search puz-zles using lesson vocabularywords. Have students writeclues describing the words hid-den in a grid of letters. Allowtime for groups to exchangeand solve the puzzles.

Challenge Provide studentswith materials for making vari-ous cloud types. Have themdesign dioramas showingcloud types, heights, and theprecipitation that can comefrom them.

Informal Assessment

Technology

Internet Research Project Have students visit www.science.mmhschool.com to conducta research project on clouds.





Can you imagine a flood beinggood news? It was to many

ancient Egyptians living near the NileRiver. They looked forward to itsannual summer flood. Land that wasflooded was better for crops!

D 50

Summerwinds

EGYPT

MEDITERRANEANSEA

RED SEA

SAUDIARABIA

SUDAN

ETHIOPIA

NILERIVER

No one knew for sure why the floodcame. Some people believed that greatrains fell near the source of the Nile tostart the flood. Much of the wateractually comes from rains that fall inthe mountains of Ethiopia.

Ethiopia has many mountains over4,000 meters (13,000 feet) tall. In Junethe monsoons blow from the SouthAtlantic over the rain forests of Africa.When the winds reach the mountainsof Ethiopia, giant rain clouds let loosetheir water in great thunderstorms.Rain-filled mountain streams join toform a great river. The river carries thewater to the Nile. By July the waterreaches Egypt and produces the flood.


Build on Prior KnowledgeAsk:

■ What are the advantages of flood preven-tion? The disadvantages? (Restraining waterprotects buildings and other structures fromdamage, but prevents the distribution of rich,fertile soil that is caused by flooding.)

Flood: Good News or Bad?

Developing the Main IdeaWhen students have read the article, ask:

■ What did ancient Egyptians think caused theannual flooding of the Nile? How did theirbeliefs differ from what actually occurs?(Ancient Egyptians believed that great rainsnear the source of the Nile caused flooding.Actually, the rains originate in Ethiopia, whererain-filled streams join to form a river that carrieswater to the Nile, causing flooding in Egypt.)

■ How has the annual flood been controlled?(A high dam holds back the water, forming alarge lake.)

■ What are the benefits of the high dam atAswan? The drawbacks? (The dam preventsflooding, so that structures stay in place, andfarmers can plant two crops each year ratherthan one. On the other hand, farmers must nowuse fertilizer, fish that were once common arenow gone, and snails that thrive in the now-slowwater cause the spread of a serious disease.)

Objective

■ Describe causes and effects offloods.

Mississippi DeltaPoint out to students thatdespite the problems caused byflooding, people have histori-cally tended to settle in areaswhere flooding is common inorder to satisfy their need forfertile land for their crops. Onesuch region is the MississippiDelta in the United States.Encourage interested studentsto use encyclopedias to learnabout the crops produced, andthe flooding that occurs, in theMississippi Delta, comparingthis region with the Nile delta.

Cultural Perspective

Sequence of EventsDraw students’ attention to themap on this page. Encouragethem to list the sequence ofevents in the movement of theJune–July winds that result inflooding rains. Have themreread the last paragraph on p. D50 to be sure they have thedetails correct. Linguistic

Reading StrategySC

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SC05_T5D_Les_TechSoc 1_D50-51 7/1/04 9:01 PM Page D50

D 51

Today the flood waters are stoppedsoon after they reach Egypt. A highdam holds back the water to form agreat lake. The good news is thatbuildings on the shore are no longerswept away. Farmers no longerdepend on floods to plant one cropeach year. Now they have water toplant during summer and winter.

Stopping the flood has changed theenvironment, and that’s bad news. Theflood kept the fields fertile; but nowfarmers must use fertilizer. TheMediterranean Sea was nourished bymud from the Nile. Now fish that werecommon are gone, and a seriousdisease is spread by snails thriving inthe Nile’s slow waters.

1. Where did the Nile flooding start?

A in the Red SeaB in the Mediterranean SeaC in the mountains of EthiopiaD in Saudi Arabia

2. Stopping the Nile flooding

F kept the fields fertile.G increased the fish population.H killed off the snails.J changed the environment.

What Did I Learn?

Aswan Dam, Egypt

Visit www.science.mmhschool.com to learn more about floods.

LOG

■ Was it important to gain an understanding ofthe source of the flooding before trying toprevent it? Explain. (Knowing the source offlooding can help people decide where to builda dam. While it wasn’t really necessary to knowthat the rains originate in Ethiopia, it was neces-sary to build the dam at a location far enoughupriver to prevent the flooding.)

■ Why might the people regret that the damwas built? Why might they be grateful for it?(Flooding enriched the soil, making the use offertilizers unnecessary. On the other hand, prop-erty is no longer destroyed by floodwaters.)

Test Prep:

1. C

2. J

SummarizeCheck students’ understanding by having them writea brief summary of the magazine in their own words.

What Did I Learn?


One of the earliest damsdesigned to prevent one kind offlooding was a predecessor ofthe Suez Canal. Built by PtolemyII, the dam prevented water fromthe Red Sea from overflowinginto the Mediterranean Sea. Theearliest dam for pure flood con-trol, however, was built byChryses of Alexandria in A.D. 550.

Near the eastern border of theRoman Empire, this dam con-sisted of an arch pointingupstream in a small river. In con-trast, the regular, extensiveflooding of the Nile River wasnot controlled until the highdam at Aswan was built in the1960s.

Science Background

Very Early Dams

SC05_T5D_Les_TechSoc 1_D50-51 5/6/04 9:18 AM Page D51


What makes the air move? What causes wind? Winds make these kites fly. Some winds move sofast and powerfully, they can knock down trees oreven lift trucks into the air. Some winds can be sogentle, they hardly ruffle your hair. Air moves fromone place to another because of differences in air

pressure. What causes these differences?

Inquiry SkillYou use variables when you identify

and separate things in an experiment

that can be changed or controlled.

Air Pressureand Windwind, D55

convection cell, D55

sea breeze, D56

land breeze, D56

Coriolis effect, D57

isobar, D59

Vocabulary

D 52


Build on Prior KnowledgeHave students discuss what they know about howwind affects things. Turn on a fan. Then ask:

■ What effect does the movement of air have?(Possible answers: cools the air; moves lightthings such as paper)

■ What effect might the air movement have if itwere ten times stronger? (Possible answers:could knock things over, blow them away, orcause other damage)

Developing the Main IdeaHave students discuss how different places have dif-ferent air pressure. These differences in air pressureare the result of variations in altitude or elevationabove Earth’s surface, air temperature, and theamount of water vapor.

Air Pressureand Wind

Objectives

■ Explore what causes air pressureto change.

■ Explain how air pressure isrelated to winds.

■ Describe the paths of winds inglobal wind zones.

■ Identify how wind is measuredand recorded at weather stations.



pp. 233–238



■ Grade-Level Science Book,

The Sky-Watchers

■ School to Home Activities, p. 28

Human Bodies and Air Pressure

Air pressure is the weight of allthe air above a certain placepressing down. The averagecolumn of air above Earthexerts 106 dynes of pressureper sq cm. Our bodies containair that exerts pressure outwardequal to the atmospheric airpressure exerted on our bodies.

Science Background


D 53

Materials

plastic jar withhole in bottom

plasticsandwich bag

rubber band

masking tape

What Can Change AirPressure?

Procedure

Make a Model Set up a bag-and-jar system asshown. Make sure the masking tape covers thehole in the jar. Have a partner place bothhands on the jar and hold it firmly. Reach inand slowly pull up on the bottom of the bag.Describe what happens.

Experiment Pull the small piece of tape off thehole in the bottom of the jar. Repeat step 1.Push in on the bag. Record your results.

Observe Place some small bits of paper on thetable. Hold the jar close to the table. Point thehole toward the bits of paper. Pull up on thebag, and observe and record what happens.

Experiment Do just the opposite. Push the bag back into the jar. What happened?

Drawing Conclusions

Observe What differences did you observe with the hole taped and with the tape removed?

Infer Explain what happened each time you pushed the bag back into the jar. How does this model show air pressure changes?

Use VariablesWhat happens to the amount of space air takes up if it is warmed? Use the model to test your hypothesis.

FURTHER INQUIRY3

2

1

4

3

2

1

Plasticsandwich

bag

Hole

Plasticjar

Rubberband

Step 1

What Can Change Air Pressure?

Science Inquiry Skills make a model, experiment,observe, infer, use variables



Grouping pairs

Procedure

STRUCTURED

When an attempt is made to pull up the bag, itcannot be done successfully.

The bag can be pulled up. When the bag ispushed in, air moves out of the hole in the jar.

The bits of paper are drawn to the hole.

The paper bits are blown away by the air leavingthe jar.


When the hole was taped, air pressure inside thebag kept it from being pulled out of the jar. Whenthe hole was opened, air was able to move intothe jar.

When the bag was pushed into the jar, air waspushed out of the bottom of the jar. The air wasbeing squeezed into a smaller space so it escapedout the hole. The model shows that volumeaffects air pressure; when more space is available,pressure is lower, but when air is confined in asmaller volume, air pressure increases.

GUIDED Warm the jar by putting it inwarm water. Air in a closed container will expandwhen warmed. Air expands when it gets warm.

STUDENT-INITIATED Students can ask theirown questions to explore, such as whether air temperature affects air pressure. (Warm air has lowerpressure than cold air.)

INQUIRY

INQUIRY3

2

1

4

3

2

1

INQUIRY


new EPS to come

Materials large suction cup

Pushing Air Demonstrate dif-ferences in air pressure bypressing a large suction cup or“plumber’s helper” against theboard. Point out to studentsthat pushing in on the suctioncup forces air out of the cup.When the rubber (or plastic)springs back, it causes a lowpressure under the cup. Thehigher air pressure on the out-side of the cup makes it stick tothe board. Spatial



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Unit D · Astronomy, Weather and Climate Use with TE textbook page D53

Pushing Air

Procedure

1. Place the open end of the large suction cup against thechalkboard.

2. Push the stick attached to the cup as far as you cantoward the chalkboard. Observe what happens and record your observations.

The cup collapses and air may be heard rushing out of

the suction cup.

3. Let go of the stick. Observe what happens and record your observations.

The stick springs back and the suction cup sticks to the chalkboard.

Drawing Conclusions

1. What happened to the air inside the suction cup when you pushed the stick in?

It was forced out of the cup.

2. How did the pressure of the air inside the suction cup change after you pushedin and released the stick? Explain your answer.

Pushing the stick forces air out of the suction cup, so that the

same volume contains less air. As a result, the air pressure inside

the suction cup is decreased.

3. Explain what happened to the suction cup after you let go of the stick.

The suction cup sticks to the chalkboard because the air outside the cup

has greater pressure than the air inside the cup and pushes on it,

holding it in place.

Lesson 6

• large suctioncup


Technology

When time is short, preview activity with theExplore Activity Video.


Explain what happens to theair pressure inside the jar asyou push down on the bag.

Air Pressure

Out

side

Insi

de

D 54

How Can Air Pressure Change?

Many factors affect the pressure.

Volume

Pulling up on the bag in the diagrambelow increases the volume inside thebag-jar system. The amount of air insidestays the same. The air inside the jarspreads out into the larger volume. Theair pressure inside the bag-jar becomesless. The outside air pushes in harderthan the inside air pushes out. Thatextra force pushing in is what you pullagainst as you pull up on the bag.

Height Above Earth’s Surface

Air pressure depends on the weightof its molecules pressing down on a

Air pressure (in millibars, mb)

980

Main Idea Differences in air pressure

on Earth’s surface cause wind.

Showing Air Pressure on a Station Model

Air Pressure Models

Air Pressure

Out

side

Insi

de

How would an increase in

temperature affect air pressure?

given area. Molecules are closertogether, or more dense, at sea levelthan high in the atmosphere. Denser airweighs more than an equal volume ofless dense air and pushes down harder.That is why air pressure is higher at sealevel than high in the atmosphere.

Temperature

Air pressure also depends ontemperature. When air is heated, itsmolecules speed up and spread outinto a larger space. The same volumeof air weighs less, and the pressuredecreases.

Amount of Water Vapor

Air is a mixture of nitrogen, oxygen,and other gases. Adding water vaporto air also affects air pressure. Watervapor molecules weigh less thanoxygen or nitrogen molecules. Moistair exerts less pressure than dry air.

Line showing changein air pressure

Key:rising pressure

falling pressure

pressure is not changing

air pressure would decrease




� How do you increase the volume inside thebag? How does increasing the volume in thebag-jar system affect air pressure? (Pulling upon the bag increases the volume. The amount ofair inside stays the same. It spreads out into alarger volume, so pressure inside becomes less.)

� How does height above sea level affect airpressure? (At sea level, molecules are moredensely packed than higher above sea level. Thus,air pressure is greater at sea level than above.)

� How does temperature affect molecules ofair? How does this affect air pressure?(Warming causes the molecules to speed up andspread out. It lowers air pressure.)


As you push in on the bag, the volumedecreases and air pressure increases.

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How Can Air Pressure Change?This diagram illustrates an experiment showing that volume is one factor thatcauses changes in air pressure. It shows two jars with a plastic bag fastened overtheir tops. Look at the jars and notice the difference between the air moleculesinside them. Then study the smaller diagrams, which show the pressures inside andoutside the jars.


1. In the jar on the left, is the inside air pressure greater than, less than, or the

same as the outside air pressure?

2. Pulling up the plastic bag on the right-hand jar increases the

inside the bag-jar system.

3. Are the air molecules in the right-hand jar closer together or farther apart

than those in the other jar?

4. When the volume increases, the air pressure in the jar becomes

than the air pressure outside.less

farther apart

volume

the same

An Air Pressure Model

Air pressure

Air pressureInsi

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Insi

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side

Out

side

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Air Pressure and Wind



1. If the volume of a container increases, the air pressure inside the container will

.

2. Air pressure is at sea level, than high in the atmosphere.

3. When air is heated, air pressure decreases because the molecules

and .

4. The same volume of air less, and the pressure

.

5. Air contains the gases and , which

are heavier than molecules of water vapor. So, moist air exerts

pressure than dry air.

6. In a weather station model, a line slanting up and to the right shows that air

pressure is .

Why Do Winds Blow?

7. When denser air moves toward less dense air, it creates .

8. Warm air rises because it is , or less dense.

9. Rising air is a(n) , while sinking air is

a(n) .

10. Rising warm air and sinking cool air form a circular wind pattern called

a(n) .

11. Convection cells form because of unequal and

of the air.cooling

heating

convection cell

downdraft

updraft

lighter

wind

rising

less

oxygennitrogen

decreases

weighs

spread out in a larger spacemove faster

higher

decrease/becomes less

Lesson 6

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Lesson Outline



Why Do Winds Blow?Think of what happens if you put a

blob of soft clay on a table and pushdown on it, using a flat hand. The claysquishes out from under your fingers,where the pressure is high. It moves tothe spaces between your fingers, wherethe pressure is lower.

Air acts in a similar way. Denser airexerts a higher pressure than less denseair. Like the clay, denser air flowstoward less dense air. This flow of air iswind. Air that moves horizontally iscalled . Air that rises is an updraft.Air that sinks is a downdraft.

Convection CellsHow can air become more or less

dense? As the Sun’s rays hit an area,they transfer energy to the air. The airheats up. Because it is warmer, theheated air is less dense. Then, just likea cork in water, the warm air rises

wind

above the surrounding cooler, denserair. On the other hand, if a region of airis cooled, it becomes denser and sinks.

This unequal heating and cooling ofthe air often makes a pattern of risingair, sinking air, and winds, called a

(kuhn·VEK·shuhn) . A convection cell is a part of theatmosphere where air moves in acircular pattern because of unequalheating and cooling.

The drawing shows how a convec-tion cell forms. Cities A and B have thesame air pressure. Then direct sunlightheats city A. The air above it warmsand expands. It becomes less denseand rises, forming an updraft. The airpressure goes down. The unheated airon either side has a higher pressure.This air moves in toward the low-pressure area, making a surface wind.

cellconvection

Use the diagram to explain whathappens to city B during theformation of the convection cell.

How are winds produced?

D 55

Air flows from areas of higherpressure to areas of lower pressure.


Why Do Winds Blow?


Exploring the Main IdeaDemonstrate for students how temperature affectsthe movement of air. Remove the shade from a lamp,and sprinkle some talcum powder above the bulb.Then light the lamp and allow it to get warm. Again,sprinkle talcum powder from above. Have studentsdescribe what they observe. (When the lamp is unlit,the powder slowly drifts down; when it is lit, the pow-der rises.) Ask:

■ What happens? Why? (Warming the air causesthe air to move. As the warm air rises, it carriesthe powder with it.)

■ What is this kind of air movement called? (anupdraft)

■ What is a downdraft? What causes it? (Adowndraft is air that sinks. A downdraft occurswhen air pressure above is higher, and the airmoves downward to an area of lower pressure.)


Have students describe situationswhen they have experienced wind or usedwind to their advantage e.g., flying a kite.

Remind students from les-sons on heat in previous grades that convectionis the transfer of heat from one place toanother. This transfer can occur in a circular pat-tern. When this occurs in the atmosphere,winds are formed.

convection cell

wind


When direct sunlight heats city A, the airabove it warms, expands, and exerts less airpressure. The air rises, creating an updraft.The warm air cools as it rises and sinks overcity B, increasing the air pressure over thatcity. Surface winds blow from city B (higherpressure) to city A (lower pressure).

Saharan WindsThe Sahara Desert is located inone of the high-pressure beltsthat circle Earth, flanking theequator at about 30° north andsouth. The Saharan air is ordi-narily still, but when a low pres-sure system forms over theMediterranean Sea, nearly athousand miles to the north,the dry desert air is drawntoward the area of low pressureso rapidly that fierce siroccowinds are created.

Science Background


What Are Sea and

Land Breezes?An example of convection

is a breeze that occurs along acoastline. Land warms faster thanwater. On sunny days air over landwarms faster than air next to it overthe sea. The warm air expands andrises. Cooler air from over the oceanreplaces the rising warm air. A windblows onto the land. A wind thatblows from the sea toward the land iscalled a .

At night the reverse happens. The airover the land cools more rapidly thanthe air over the water. Ablows from land toward the water.

Convection cells also occur alongmountains. As the Sun shines on amountain during the day, the slopeheats up faster than the valley below.Air over the slope warms and rises.

land breeze

sea breeze Cooler air over the valley replaces therising warm air, creating a valley breezethat blows up the slope. At night themountain slope cools rapidly. Thiscauses a mountain breeze to blow downthe slope.

Cold air

How are sea and land

breezes produced?

Valley breeze

D 56

These pictures show what happensduring the day. How would youshow what happens at night?

Sea breeze

Cold air

Warm air

Warm air

Temperature differences between two areas causeair to move from a higher pressure, cooler area to alower pressure, warmer area.


What Are Sea and Land Breezes?

Before ReadingHave students try to answer the red question at thetop of the text column.


■ What causes a sea breeze to form? (When theair over the land gets hotter than the air overwater, it expands, becomes less dense and itrises. The cooler air from above the water movestoward land, causing a sea breeze.)

■ What air pressure differences cause the air tomove from one place to another? (Air movesfrom an area with higher pressure to an area oflower pressure.)

■ In conditions that give rise to a sea breeze,how does air pressure over the water com-pare with air pressure over land? (The air pres-sure over the sea is higher than the air pressureover the land.)


The name of the breeze indi-cates the direction the wind is coming from:the wind blows from the sea.

The wind blows from the land.

Have students describe situations when they have experienced breezes from theland or sea.

land breeze

sea breeze


At night air over land cools more rapidlythan air over water. A land breeze forms.Mountain breezes blow down the mountainslope during the night, with cool air andhigh pressure over the mountain slope andlow pressure over the valley. In short, thearrows would be reversed.

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What Are Sea and Land Breezes?Land temperatures change faster than water temperatures do. This diagram showshow those temperature changes can affect winds and wind directions along acoastline. This diagram shows how a sea breeze—a breeze that blows from theocean—is created during the day.


1. On a sunny day, does the air over land get warmer or cooler than the air over

the water?

2. In what direction does the warmer air move?

3. When a sea breeze blows, it brings air to the land.

4. This diagram shows why a sea breeze blows inland during the day. Now figureout what will happen to these wind patterns at night. Remember that landtemperatures change faster than water temperatures. Explain what you thinkwill happen.

The land cools off faster. Then the cooler air moves out from the

land to the water, causing a land breeze.

cooler

It rises.

warmer

Warm air

Cold air

Sea breeze

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D 57

What Is the Coriolis Effect?Earth’s rotation affects winds

blowing across its surface. As Earthrotates, every spot on its surface moveswith it. However, in the same 24-hourperiod, places near the poles travel ashorter distance than places near theequator. This means that places nearthe poles are moving slower!

Now what if you are in an airplaneflying in a straight line from theNorth Pole to Chicago? While youare in the air, Earth is rotating, orspinning, underneath you.Earth rotates counterclockwiseas seen from the North Pole.As Earth rotates, Chicago ismoving west to east. Tosomeone in Chicago, though,the plane’s flight path seemsto curve to the southwest.

The same thing happenswith winds blowing from theNorth Pole. Because Earth rotates,the winds seem to curve to the rightas they head southward.

No matter which way the windblows, it will curve to the right in theNorthern Hemisphere. This curving isknown as the . In theSouthern Hemisphere, the Corioliseffect causes winds to curve to the left.This is because, as viewed from theSouth Pole, Earth rotates clockwise. Theeffect works on other moving objects aswell, such as missiles and rockets.

Coriolis effect

R o t a t i o n

If you were standing at the NorthPole looking south, this arrowwould appear to curve to the right.

If you were standing at the SouthPole looking north, this arrowwould appear to curve to the left.

What causes the Coriolis effect?

Coriolis Effect

Earth’s rotation causes winds to curve to the right in theNorthern Hemisphere and to the left in the Southern Hemisphere.


What Is the Coriolis Effect?


Developing the Main IdeaThe rotation of Earth affects the winds blowing acrossits surface. Because Earth rotates, winds follow acurved path over its surface. No matter which way thewind blows, it curves to the right in the NorthernHemisphere, and to the left in the SouthernHemisphere. This is known as the Coriolis Effect.Winds and pressure belts (zones) around the globeare caused by huge convection cells.

Ask:

■ The Coriolis effect causes winds in theNorthern Hemisphere to curve to the right.Does it also cause changes in ocean currents?How? (Yes, the Coriolis effect also causes oceancurrents in the Northern Hemisphere to curve tothe right; it causes ocean currents in theSouthern Hemisphere to curve to the left.)


Use a globe to demonstrateto students how the rotation of the Earthcauses winds to curve in different directionsin each hemisphere. The effect is namedafter Gustave Gaspard Coriolis, the Frenchengineer/mathematician who described it in1835.

Coriolis effect


Ballot’s LawIn 1857, Buys Ballot was the firstscientist to note that a low pres-sure area lay to the left in theNorthern Hemisphere whenwind blew onto an observer’sback. He concluded that in theNorthern Hemisphere windalways blows counterclockwisearound the center of a low pres-sure system, and clockwisearound the center of a highpressure system. Ballot’s Lawbuilds upon the work of Frenchengineer/mathematicianCoriolis.

Science Background

Organize InformationDeveloping Reading SkillsStudents can organize informa-tion about global wind zonesinto a table. Linguistic

Reading StrategySC

IENCE


How Are Global Wind

Patterns Produced?

Year round the equator is heatedstrongly by sunlight. The air becomesvery warm. Heat also causes evapora-tion, so the air becomes moist. Warm,moist air over the equator creates a zoneof low pressure around the globe.

As the air at the equator warms, itbecomes less dense and rises. It rises tothe top of the troposphere and spreadsout, moving north and south. As the airmoves away from the equator, it coolsand becomes denser. At about 30° northand south latitudes, the cold air beginsto sink toward the surface. This sinkingair creates a high-pressure zone on bothsides of the equator at these latitudes.A belt of winds is set in motion aroundEarth by air moving from these high-pressure zones toward the low pressure

at the equator. These are the trade winds.The Coriolis effect curves these winds,as you see in the diagram.

The poles get very low-anglesunlight, and the air there is very cold.Cold, dense air can hold very littlewater vapor. Cold, dry air over thepoles has high pressure. Air at the polesmoves toward 60° latitude, formingwinds. Because of the Coriolis effect,the winds curve. These are the polareasterly winds. Easterly means the windblows “from the east.”

Other winds occur between 60°latitude and the poles as well as between30° and 60° latitudes. Between 30° and60° latitudes is the zone of westerly winds.The continental United States is in thezone of westerly winds.

60°N

Polareasterlies

Polareasterlies

Prevailing westerlies

Prevailing westerlies

Trade winds

Trade winds

60°S

30°N

30°S

0° equator

90°S

90°N

What causes the global

trade winds?

Make a table listingdifferent global windzones and a descriptionof the directions inwhich winds move ineach zone.

N

S

W E

Global Wind Zones

D 58

a belt of winds set in motion around Earth byair moving toward the equator


How Are Global Wind

Patterns Produced?



■ How do convection cells near the equatorcause the trade winds to form? (The air at theequator is warm and moist. It rises, spreadingout and cooling. As it cools, the air becomesmore dense, and at about 25° to 30° north andsouth of the equator, it starts to sink. High pres-sure zones are thus formed. The trade windsblow from these high pressure zones to thelower pressure zones near the equator.)

Exploring the Main IdeaAsk:

■ How would winds behave if Earth did notrotate on its axis? (Air would rise and travelaway from the equator, toward the poles, cool-ing along the way. At the poles, the air wouldsink, and move back toward the equator.)

A simple model can illustrate how winds wouldbehave in the absence of rotation. Form loops of tape,sticky-side-out, and affix them to a globe between thepoles and the equator.


Tables should include information such as:polar easterly winds move from the east,curving to the right in the NorthernHemisphere and to the left in the SouthernHemisphere; westerly winds move from thewest, between 30° latitude and 60° latitude.

Seed Carriers The seeds of many plants hitch-hike on the wind. Some havestructures, such as the featheryappendages of dandelionseeds, that are adaptations forwind dispersal. Have studentsuse references to make a list ofplants whose seeds are dis-persed by the wind. Logical;Linguistic

Inclusion

SCIENCE

F O R A L L

SummarizeDeveloping Reading SkillsHave students write to summa-rize how the Coriolis effectcauses the winds in each zoneto move in their particulardirection.

Reading StrategySC

IENCE



D 59

LHBA High pressure

Clockwisedirection

Low pressure

NE = Northeastwind

Full feather = 14–22 km/h(8–12 knots)

Half feather = 5–13 km/h (3–7 knots)

What Are Isobars?Why is it important to know

about air pressure? Knowingwhere the air pressure is high orlow allows you to predict whichway air will move. This is whyweather scientists make mapsshowing air pressure. They startby plotting the air pressure atmany different locations on a map.Then they connect all places with thesame air pressure with a line. A line ona map connecting places with equal airpressure is called an . Isobarsmake pressure patterns easier to see.

Find the series of circular isobars inthe west, surrounding a region of highpressure (H). This pattern is called ahigh-pressure system. Since the centerhas higher pressure than its surround-ings, winds blow outward from thecenter in a clockwise pattern.

A similar set of isobars in the eastmarks a low-pressure system (L). In alow-pressure system, the central regionis surrounded by higher pressure. Thewinds blow in toward the center in acounterclockwise pattern.

isobar

Isobars also help scientists predicthow fast air will move. Big differencesin air pressure over short distancescause strong winds. This is shown on a map by drawing closely spacedisobars. Small differences in airpressure cause gentle winds. This isshown by widely spaced isobars.

You show wind on a station modelwith a straight line touching the circle.The line tells where the wind isblowing from. “Feathers” are used toshow speed.

1008

1010

1012H

NE

The pressure on each isobar is inmillibars (mb).

Showing Wind ona Station Model

Main Idea

How do isobars help scientists

predict how air will move?

How Winds Blow

10021000

998

1004

They make it easier to see patterns ofhigh- and low-pressure areas.

What Are Isobars?


Using the IllustrationsDraw students attention to the map showing isobars.Remind students that when plotting air pressure, sci-entists begin by marking the air pressure at many dif-ferent places on the map. Ask:

■ Why do you think they go a step further anddraw isobars, when they already haverecorded the data? (Isobars show patterns thatare not as easily seen when numbers are plotted.)


Isobar is derived from two Greekwords meaning “equal weight.”isobar


Develop Discuss with studentsthat the main idea of page D59is the answer to the questionposed in the headline. Afterexpressing the main idea—thatisobars are lines connectingplaces of equal pressure—theauthors provide details to sup-port that idea.

Practice Have students listdetails from page D59 that sup-port the main idea that windshave different patterns in differ-ent air pressure systems.(Answers should include: windsin a high-pressure system blowclockwise outward from thecenter; winds in a low-pressuresystem blow counterclockwisein toward the center.)


Reading MiniLesson

SC

IENCE

Weather ForecastingForecasting the weather is likedetective work. Isobars aredrawn on the map. Areas ofhigh or low pressure are identi-fied, and drawn on the map.Next, the forecaster interpretscurrent weather conditionssuch as recent pressure ten-dencies, wind directionchanges, and precipitation.Fronts are added to the map.Other factors, such as warm airtraveling before a front, aretaken into consideration, aswell. The final result is theweather forecast.

Science Background



D 60

A Weather Station ModelA weather station model includes temperature,cloud cover, air pressure, pressure tendency,wind speed, and wind direction. The circle is at the location of the station. You will interpretthe data, using the information from the weather station models to answer questions and solve problems.

ProcedureUse Numbers Lookcarefully at the Dallasweather station model.How fast is the windblowing? What is the winddirection? Record your answers.

Interpret Data What other information does thisweather station model give you?

Look at the other weather station models. Make atable recording weather conditions for each city.

Drawing ConclusionsCompare the information in the table you madewith these station models. Which way is the information easier to interpret?

Interpret Data Where was wind fastest?Slowest? Which tells you this information morequickly, the table or the models?

Communicate Compare and contrast other weather conditions in the cities.

3

2

1

3

2

1

Interpret Data

Wind direction(from north)

Wind speed(knots or km/h)

Air temperature (°C)

(It may also be recorded in °F.)

13 1014

Cloud cover

Air pressure(mb)

Pressurechange

Dallas

Oakland

Charlotte

Tampa

34

14

28

30

1004

1012

980

996

B U I L D E R

A Weather Station Model

Science Inquiry Skills interpret data, use numbers,communicate



Grouping individuals

Procedure

The wind is blowing at 19–31 knots (33–57 km/h).The wind direction is from the southwest.

amount of cloud cover, air temperature, and airpressure and pressure change

Remind students that tables consist of columnsand rows, with space for appropriate headings.They should construct a 6 column by 4 row chartwith the following column labels: city, air pres-sure, wind speed, wind direction, cloud cover,and temperature. (Dallas: 34°C, 1004 mb, clearskies, southwest winds at 19–31 knots; Charlotte:28°C, 980 mb, mostly cloudy skies, northeastwinds at 11–19 knots; Tampa: 30°C, 996 mb,partly cloudy, southeast winds at 24–48 knots;Oakland: 14°C, 1012 mb, scattered clouds, southwinds at 16–24 knots.)


Tables are easier to interpret.

It was the fastest in Tampa, and the slowest inCharlotte. A chart gives this information morequickly.

Charlotte, North Carolina, had the most cloudcover, while Dallas had the clearest skies. Oaklandhad the lowest temperature, while Dallas had thehighest. Air pressure was highest in Oakland andlowest in Charlotte.

3

2

1

3

2

1

B U I L D E R

Develop This skill involvesstudying information in a table,chart, graph, paragraph, or pic-ture and looking for relation-ships, comparisons, or cause andeffect to solve a problem.

Practice Have students look atthe chart on page D17—“Comparing a Planet’s Radiuswith Earth’s.” Have them find theradii of each of the eight otherplanets listed by multiplying the

amount given by 1 centimeter(the assigned radius of Earth).Then lead a discussion about theresults they found.

A complete list of ScienceInquiry Skills appears on p. S1.

MiniLesson

Inquiry Skills

Interpret Data


D 61

LITERATURE LINKRead The Sky-Watchers,the story of how two studentsmaintained a weather station.When you finish reading, thinkabout how you would build aweather station. Try the activi-ties at the end of the book.

WRITING LINKExpository Writing Research and write areport on the Beaufort Wind Scale. Includeits history. Draw a conclusion about itsimportance.

MATH LINKCalculate weather factors. Collect aweek’s worth of national weather mapsfrom a newspaper. Select a region of thecountry, such as the Midwest or Southeast.Calculate its average temperature, windspeed, and air pressure.

SOCIAL STUDIES LINKWrite a report. Research the origin ofthe term “trade winds,” and write areport on your findings.


for more links.LOG

Think and Write1. What makes air pressure

change?

2. What causes wind to blow in aparticular direction?

3. Why are there zones of windsaround the world?

4. Interpret Data On a weathermap, how can you comparethe speed and direction ofwinds in different locations?

5. Critical Thinking How mighttemperatures near the oceancompare with those inland inwinter? In summer? Explain.

THESKY-WATCHERS

by Patricia Baehrillustrated by Eldon Doty

THESKY-WATCHERS

Why It MattersWind can be very useful.

It is often used as a source of power. Wind turns windmills, special machines that produceelectricity. They run the machinery that grinds grain.Windmills are also used to pump water.

Wind carries pollen to flowers. Seeds form as a result.Many kinds of seeds, in turn, are carried by wind to new places.

-JournalJournal Visit our Web sitewww.science.mmhschool.com

to do a research project on wind.

Answers to Think and Write1. changes in altitude, temperature, or humidity

(pp. D54–D55)

2. Winds blow in a particular direction because airmoves from an area of high pressure to an areaof lower pressure. (pp. D55–D57)

3. Huge convection cells cause winds and pressurebelts around the world. (p. D58)

4. STRUCTURED Organize the map’s infor-mation into a table so that it is easier to makecomparisons. (p. D60)

5. Critical Thinking Land warms and cools fasterthan water, so the air near the ocean will becooler in summer and warmer in winter. (p. D56)


LITERATURE LINKHave students read the Grade Level Science Book, TheSky-Watchers. Additional books to read can be foundon TE p. D1•b.

WRITING LINKExpository Writing Students’ writings shouldinclude facts about the Beaufort Wind Scale—its history, application, and importance.

MATH LINKTo calculate the average wind speed, temperature,and air pressure, students should add the week’sreadings of each measurement, then divide the totalof each by seven.

SOCIAL STUDIES LINKStudents’ reports should mention that trade winds arethe main east-west wind in two belts from the equa-tor to 30o north and 30o south latitude. Trade windsare so named because they were reliable enough formerchant sailors to count on them when sailing.

INQUIRY


Easy/Average Have studentsdraw diagrams showing air cir-culation in a convection cell.Have them indicate rising andsinking air, horizontal movementbetween areas of higher andlower pressure, and labels forupdraft and downdraft.

Challenge Make a model ofwind currents. Fill a small jarwith warm water and food color-ing. Cover the top tightly withplastic wrap. Place the small jarinside a large jar of cold water.Poke two small holes in the plas-tic wrap. Challenge students toexplain. (Warm water rises, thensinks as it cools.)

Informal Assessment

Technology

Internet Research Project Have students visit www.science.mmhschool.com to conducta research project on air pressure and wind.They will find a suggested outline for theproject, questions to research, and links toInternet reference sites.





D 62

Weather: It’s Instrumental!Weather: It’s Instrumental!You turn on the TV to catch the weather

forecast. The satellite image looks cool, butall you want to know is how warm it is,whether it’s windy, and if you’re going to get wet on your way to school. Wheredoes that information come from? Notfrom space, but from a set of instrumentsat a nearby weather station.

To find the temperature, you need a thermometer. To find how much rain has fallen, you need a rain gauge. Put astraight-sided bucket outside to collect rain water. Later, stick a ruler in the bucket to measure how much rain fell.

Wonder how much moisture is in theair? Your hair is a good indicator! It getsfrizzier when it’s raining or very humidoutside. That’s because hair lengthens (and kinks up) when the air is moist.Forecasters use “hairhygrometers” to measurehumidity. Hygrometershave pens that areattached to human or horse hairs. As thehair changes length,the pen graphs thechange in humidity.


Objective

■ Describe how weather instru-ments provide informationabout the weather.

Organize InformationDeveloping Reading SkillsHave students organize theinformation about eachweather instrument into achart that shows the name ofthe instrument, a drawing ofwhat it looks like, what eachinstrument measures, and how the data collected can beused to forecast the weather.

Reading StrategySC

IENCE

Build on Prior KnowledgeAsk:

■ What kinds of data can you collect that give you information about the weather?temperature, wind speed, humidity, air pressure,cloud formation

Weather—It’s Instrumental!


■ What does a thermometer tell you? (howwarm or cool the air is)

■ If someone has curly hair that is even curlierone day what does that tell you about thehumidity? (The humidity is high.)

■ How is the speed of wind measured? (Ananemometer spins faster as the wind movesfaster.)

Explore the Main IdeaHave students use newspaper weather maps to locatethe information collected by the tools mentioned onthis page. Discuss how meteorologists use weatherdata to prepare the weather forecast.

SC05_T5D_Les_SciMag_D062-063 5/7/04 2:10 PM Page D62

D 63

1. What weather informationdo you need before you gooutside? What instrumentshelp get that information?

2. What would it take to setup a weather station inyour neighborhood oroutside your window?

Which way’s the wind blowing? Aweather vane will tell you. An arrow pointsin the direction of the wind. The tail of thevane works like a sail to catch the wind.The vane spins until the wind is blowingequally on both sides of the tail. Then thearrow is pointing in the wind direction. If the wind is blowing from the west, thearrow points west. A wind blowing fromthe west is called a west wind.

How windy is it? The speed of the windis measured with an anemometer. It uses aset of cups attached to a central pole. As thecups catch the wind, they spin around likea pinwheel. The faster the wind, the fasterthey spin. Now you can set up a weatherstation right in your own backyard!

Visit www.science.mmhschool.comto learn more about measuringweather.

LOG


■ From what direction does a north wind blow?north

Thinking Further: Inferring

■ What kind of weather would you predict ifthe temperature is mild and humidity is low?low chance of rain

Answers to

1. Forecasters also provide information abouthumidity, rainfall, wind directions, and windspeed. Humidity is measured with a hygrometer.Rainfall is measured with a rain gauge. Winddirection is measured with a weather vane.Wind speed is measured with an anemometer.

2. A good way to start would include a ther-mometer, which you can buy for very littlemoney at a hardware store and put outsideyour window. You could also put a jar outsideto measure rainfall. A pinwheel could be usedto estimate the wind speed. For a hygrometer,you can always just observe how your hair looks!


Forecasting the WeatherSet up a weather station at yourschool with a thermometer and rain gauge. Have studentscut out the weather forecastfrom the local paper and then compare the forecast with the weather occurring at the school’s weather station.Ask students to identify howmeteorologists use similar toolsto forecast the weather. Logical

Inclusion

SCIENCE

F O R A L L

Beaufort Wind ScaleThis scale of 0 to 17 tells youhow fast the wind is blowing.The wind is measured 33 feetabove the ground. Calm air andgentle breezes rate from 0 to 3.Stronger breezes and winds aredesignated 4 to 7. A gale forcewind rates 8, a storm 10, and ahurricane 12. Beaufort ratings12 to 17 indicate how strong ahurricane is.

Science Background

SC05_T5D_Les_SciMag_D062-063 5/7/04 2:11 PM Page D63


D 64

Fill each blank with the best word orwords from the list.

barometer, D34cirrus cloud, D44condensation, D39Coriolis effect, D57evaporation, D38humidity, D38land breeze, D56precipitation, D46sea breeze, D56stratus cloud, D44

1. Rain, snow, and sleet are kindsof .

2. The causes winds tofollow a curved path overEarth’s surface.

3. A(n) forms in blanketlikelayers.

4. Liquid changes directly to a gasby the process called .

5. The amount of water vapor inthe air is called .

6. Wind blowing from the oceantoward the land is called a(n)

.

7. Wind blowing from the landtoward the ocean is called a(n)

.

8. The process that turns watervapor into raindrops is called

.

11. In a low-presure system .

A winds blow out

B winds blow clockwise

C winds blow west

D winds blow inward,counterclockwise

12. Weather takes place in the.

F thermosphere

G mesosphere

H troposphere

J stratosphere

13. Water drops that collect on acold glass of lemonade comefrom .

A the lemonade

B the air

C a puddle

D the glass itself

14. Isobars indicate .

F humidity

G temperature

H air pressure

J cloud cover

Vocabulary

Test Prep

9. A high, wispy cloud made of icecrystals is a(n) .

10. A(n) measures airpressure.


Answers to Vocabulary

1. precipitation 6. sea breeze

2. Coriolis effect 7. land breeze

3. stratus cloud 8. condensation

4. evaporation 9. cirrus cloud

5. humidity 10. barometer

Answers to Test Prep

11. D 14. H

12. H 15. A

13. B

Resources■ Reading in Science Resources,

pp. 239–240

■ Assessment Book, pp. 53–56

Chapter Review and Test Preparation

Name Date

239

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4. Insolation is





5. Humidity is






a. barometer.

b. thermometer.

c. gauge.

d. balance.

Chapter 10

BL

ACKLINE

Vocabulary


SC05_T5D_Les_C010_ChRev_D64-D65 7/2/04 12:55 PM Page D64

D 65

Concepts and Skills

19. Interpret Data

You are given this information on aweather map: What kind of weatheris city A having? What kind ofweather is city B having? Write aparagraph explaining your answer.

20. Critical Thinking What if therewere no plants? Do you think Earthwould still get as much rain as itdoes now? Write your ideas.Describe how you might test them.

Did You Ever Wonder?Infer You look up in

the sky and see clouds. Why don’tthose clouds fall to the ground?

Visit www.science.mmhschool.com

to boost your test scores.LOG

INQUIRY SKILL

INQUIRY SKILL15. On a hot day, a lake is likely tobe .

A cooler than nearby land

B hotter than nearby land

C the same temperature as theland

D the cause of the heat

16. Reading in Science Write aparagraph explaining why northwinds blow to the southwest.

17. Safety Why do you need to becareful on hot days when therelative humidity is high? Write aparagraph explaining your answer.

18. Scientific Methods How muchdoes humidity change over a day?Write a design for an experimentthat would test this.

City BCity A

Temperatures in Celsius

20261020 998

Answers to Concepts and Skills

16. Reading in Science The Coriolis effectcauses wind to curve to the right, so windsblowing from the north will travel to the southand west.

17. Safety When the relative humidity is high,less water can evaporate into the air. It isharder to cool off on a hot, humid day becauseless sweat evaporates.

18. Scientific Methods Students might use aglass of cold water, a thermometer, and atimer and might carry out an experiment similar to the Explore Activity in Lesson 4.

19. INTERPRET DATA A: clear, SEwinds, 26 degrees Centigrade, air pressure1020 mb; B: overcast, E winds, 20 degreesCentigrade, air pressure 998 mb.

20. Critical Thinking Because plants add watervapor to the atmosphere, a lack of plantswould result in less humidity. Students mightsuggest testing by placing a plant and anempty pot into separate plastic bags, toobserve differences in the amount of water.

Did You Ever Wonder?GUIDED Clouds are tiny water droplets or icecrystals. Because the water droplets or ice crystals areso small and so light, they can stay suspended in theair. Note that students learned that fog is stratusclouds that form near the ground.

STUDENT-INITIATED Students may have additional questions about the weather. For example,students may ask how observing cloud patterns canhelp in predicting the weather. Have students formu-late their questions as hypotheses that can be tested,then have them design an experimental procedure totest their hypotheses. Note that some questions maybe investigated through Internet or library research.Have students present the results of their research aswritten reports or oral presentations.

INQUIRY

INQUIRY

INQUIRY SKILL


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Unit D · Astronomy, Weather, and Climate Use with textbook pages D26–D65

Name Date

53

Weather

Section 1: Vocabulary Each item is worth 2 points.

Mark true or false. If false, underline the word or words that make the statement false.

1. Air that moves vertically is called wind.

2. Puffy clouds that appear to rise from a flat bottom are

called cumulus clouds.

3. The layer closest to Earth’s surface is the troposphere.

4. A cloud at ground level is called precipitation.

5. Relative humidity is a comparison of how much water

vapor is in the air, and how much the air can hold.

6. The amount of water vapor in the air is called humidity.

7. A sea breeze blows from the land toward the sea.

8. Air pressure is measured with an anemometer.

9. Stratus clouds form in blanketlike layers.

10. The curving of the wind to the right in the Northern

Hemisphere is a result of the Coriolis effect.

true

true

false

false

true

true

false

true

true

false

Chapter 10

Formal Assessment

Assessment Book, p. 53

CHAP

TER TEST

SC05_T5D_Les_C010_ChRev_D64-D65 5/6/04 9:39 AM Page D65


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