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BSCS Middle School Science
Student Edition
Earth Science Unit:
Energy In Earth’s Systems
Sea Surface Temperature (°C)
August 2005
equator
key
Table of Contents
Chapter 3: Hot Water.................................................. ES3-2
Engage: Hurricanes—Heat Machines ....................................... ES3-5
Explore: Water Cycle and Heat Flow.........................................ES3-10
Explain: Hot Tropics, Cold Poles............................................... ES3-17
Elaborate: Wind and Water—Becoming Current...................... ES3-27
Evaluate: Polar Express—for Energy....................................... ES3-32
Spanish Vocabulary................................................................ ES3-36
ES3-1
BSCS Middle School Science
Student Edition
Earth Science Unit · Energy In Earth’s Systems
chapter 3:
Hot Water
a. January
b. July
H
ave you ever been to a tropical climate? These tend to be near the equator.
If you have not visited a tropical place, you have probably seen pictures
on TV or in a movie. You have seen images of warm beaches, turquoise
waters, and palm trees swaying in sea breezes.
In the last chapter, you studied some of the factors that affect the solar radiation
Figure 3.1: Global temperatures.
These maps show the average
temperature in (a) January and (b)
July. Oceans at the equator are hot all
year, regardless of whether it’s (a)
winter or (b) summer where you live.
The GLOBE Program
that reaches different parts of Earth. The angle of light energy is a key factor. And
for a round object like Earth, most solar radiation arrives at Earth near the equator.
That is why the equator is hot and tropical. The opening images (figure 3.1) show
the evidence of this. Look at where the hottest temperatures can be seen. In chapter
3, Hot Water, you will learn more about the radiation coming to Earth.
If days are sunny and warm for the tropics, do oceans near them keep getting
warmer and warmer? How hot could oceans become? What keeps the water
temperature from getting warmer and warmer? You will investigate questions
like these in this chapter.
An important teamwork skill is planning ahead to share responsibility. In this
chapter, you will have several chances to work on this skill.
Goals for the Chapter
You will see that chapter 3 includes some themes you’ve studied before. One
important theme is heat flow. Temperatures in Earth systems are an indicator of
how heat flows on Earth. By the end of this chapter, you will learn about
n
the flow of heated air and water from the equator to the poles,
n
the flow of matter and heat in the water cycle,
n
how patterns of heat flow over Earth affect the climate where you live,
n
how energy is transferred from the ocean to the atmosphere, and
n
how to use models to represent the transfer of energy.
ES3-2
Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
This chapter will help you understand how heat and water move over Earth’s
surface. Often they flow together. This helps shape the climate where you live. In a
sense, your climate is the result of events happening all over Earth. You will do the
following activities to explore these ideas in this chapter:
Engage—Hurricanes—Heat Machines
Explore—Water Cycle and Heat Flow
Explain—Hot Tropics, Cold Poles
Elaborate—Wind and Water—Becoming Current
Evaluate—Polar Express—for Energy
In previous chapters, a chapter organizer showed you the flow of a chapter.
Look at the organizer for an overview of this chapter.
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Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Hot Water
Engage—Hurricanes—
Heat Machines
key idea: Tropical cyclones
move heat quickly between
the ocean and the air.
Linking Question:
What does a model show
about the transfer of heat
from the ocean to the air?
Explore—Water Cycle and
Heat Flow
Part I: Steam Heat
Part II: Heat Flow in Fluids
key idea: You can simulate the
transfer of heat from the ocean
to the air in a beaker.
Linking Question:
How does the model relate
to the water cycle and
climate patterns on Earth?
major CONCEPTS
• Matter and energy transfer
between the ocean and the
atmosphere.
• Heat is transferred from
the equator to the poles,
and then out to space.
• The patterns of heat flow
in the ocean and the
atmosphere affect the
regional climate and the
local weather.
• Both water (matter) and
heat are transferred in the
water cycle.
• Models help you understand processes that are
hard to see.
Explain—Hot Tropics,
Cold Poles
key idea: The pattern of solar
radiation on Earth leads to
tropics and colder poles. Energy
is transferred from the equator
to the poles, yet it also escapes
to space.
Evaluate —Polar Express—
for Energy
Part I: Chapter Review
Part II: Polar Express
Part III: Revising Your Ideas
key idea: An important part
of gaining new knowledge is
learning from mistakes.
Linking Question:
What are the major
concepts of this chapter?
Elaborate—Wind and
Water— Becoming Current
key idea: Global wind patterns
are connected to ocean currents.
Linking Question:
How do winds in the
atmosphere relate to
ocean currents?
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Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Engage
Hurricanes—Heat Machines
What do you think happens when there is heating of the ocean? Sometimes
there are no problems from this heating—it just means a nice, warm ocean to
swim in. Other times, though, heating of the ocean can cause serious problems.
This heating can lead to tropical cyclones. In the Atlantic Ocean, tropical cyclones
are called hurricanes. These violent storms change ecosystems, and they can result
in massive property damage and loss of life. In 2005, the Atlantic Ocean saw
about 27 hurricanes—way above the number for average years.
At the global scale, tropical cyclones are “heat machines.” They are a key part
of the flow of heat on Earth. In this Engage activity, Hurricanes—Heat Machines,
you will share some of what you know about hurricanes, thermal energy in the
ocean, and the water cycle. Start by investigating some features of hurricanes.
Materials
For each team of 3 students
access to a computer
Process and Procedure
Join with two teammates to start thinking about some features of hurricanes. Work
together to complete the steps of this activity.
1.Look at the opening images again (figure 3.1). Investigate them by following
Steps 1a–b.
a. Which region on Earth receives the most solar energy?
What is your evidence?
Did you remember to go to a new page in your science notebook?
Make sure you write your name, the activity title, and the date at
the top. Add the activity to your table of contents.
b. Will regions near the equator keep getting hotter over
the next 20 years? Can they ever overheat?
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Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Engage
2. Now you will watch a video with your team. Follow Steps 2a–e as you watch
and work with your team to answer questions about the video.
a. With your team, review the bulleted list below. These are important
points you should watch for in the video:
n Hurricane (cyclone) paths in the Atlantic Ocean
n How hurricanes affect sea surface temperatures (SSTs)
n The month, located in the upper right
The phrase “sea surface temperatures” refers to the temperature
of the ocean near the surface of Earth.
b. Watch the video 27 Storms: Arlene to Zeta. Record important ideas
from the video in your science notebook.
Notice that SSTs warmer than about 82 degrees Fahrenheit (°F)
appear as yellow, orange, or red (hottest) on the map. The SSTs
colder than about 82°F appear as light blue or blue on the map.
c. How do SSTs change over the time shown in the video? Why do you
think that happens?
d. W
atch the video again. This time, try to answer the question, What can
happen to SSTs as a hurricane passes over hot water? If you need to,
pause the video so you can record your observations. Be sure to list the
hurricane names and their month with the observations.
Pay special attention Hurricanes Dennis, Emily, Katrina, and Rita.
e. What general path do hurricanes tend to take?
In other words, in what region or regions of Earth do hurricanes
usually begin? In what region or regions do they end?
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Chapter 3 · Hot Water
Engage
3. All hurricanes from 2005 are shown in figure 3.2. The legend shows increasing
hurricane winds from green to red. Red shows the most violent winds. Use the
map to answer the questions in Steps 3a–b.
Figure 3.2: Atlantic hurricanes,
2005. This diagram shows the
paths and strengths of all 2005
hurricanes. Hurricane wind
velocities increase from green to
red. Red indicates violent storms.
a. What happens when powerful hurricanes move to colder water?
You can use figure 3.1 or 3.10 to estimate SSTs.
b. What happens to the most powerful hurricanes as they move
over land?
120°
NOAA
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NATIONAL HURRICANE CENTER
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ATLANTIC • CARIBBEAN • GULF OF MEXICO • HURRICANE TRACK CHART
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+ + + Extratropical
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Katrina
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Philippe
Rita
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Unname
Tammy
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EJG
062306
4.You have looked at the paths and the strengths of hurricanes. You also studied
the SSTs related to hurricanes. Next look at the rainfall pattern by following
Steps 4a–b.
a. As you watch the 2 videos, answer these questions:
n What rainfall pattern do you see as a hurricane moves over land?
n Does rainfall generally increase or decrease?
b. Watch the 2 videos called Hurricane Katrina Rain Accumulation and
Hurricane Rita Rain Accumulation. Figure 3.3 is an image from
Hurricane Rita.
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Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Engage
5.Where do you think hurricanes get their power? In other words, what do you
think “drives” or “fuels” hurricanes? In explaining your ideas, use evidence
from the figures you’ve seen.
Figure 3.3: Hurricane Rita rainfall.
This image shows the total amount
of rainfall for Hurricane Rita. The
storm path is from the ocean to
land (clockwise). The scale shows
millimeters (mm) of rain. Some areas
in red received over 300 mm of rain
(>12 inches).
NASA/Goddard Space Flight Center Scientific
Visualization Studio
Reflect and Connect
Continue to work with your team to answer the questions below. Since you are
just beginning to learn about these topics, don’t worry that you don’t know all the
correct answers to these questions.
1.You may have studied the water cycle in science classes before this one. Write
some of your ideas about the water cycle.
Some words that might help you think about the water cycle are
“evaporation,” “rainfall,” “river,” and “precipitation.”
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Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Engage
2. How do you think tropical cyclones and the water cycle might be similar?
How are they different? Follow Questions 2a–c to answer these questions.
a. Turn your science notebook to a landscape orientation.
Draw a large Venn diagram outline (figure 3.4). Label one
side “tropical cyclones” and the other “water cycle.”
b. Use the large overlapping area in the center to show how
you think cyclones and the water cycle are similar.
c. U
se the other areas to show how you think cyclones and
the water cycle are different.
If you need more help with Venn diagrams, see I Can Develop
a Venn Diagram.
Figure 3.4: Venn diagram.
Use a Venn diagram like this to
show your ideas for how tropical
cyclones and the water cycle are
similar and different.
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Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Explore
Water Cycle and Heat Flow
Tropical cyclones are extreme weather events. They are also heat machines. This
is because they move massive amounts of heat from warm oceans to the
atmosphere above. Yet hot surface water does not automatically result in a
cyclone. For example, you viewed the paths of 27 storms that occurred in 2005.
A lot of hot water remained in the space between those storms.
What then happens to the thermal energy in oceans when there are no cyclones
in the neighborhood? Or what if the sea surface temperatures (SSTs) are warm, but
not quite hot enough to sustain a cyclone? In this Explore activity, Water Cycle and
Heat Flow, you will study the processes that move heat away from hot water—
without having to be in a cyclone!
Part I—Steam Heat
Materials
For each team of 3 students 1 hot plate or heat source
1 1-L beaker
400 mL of water
3 rubber bands
1 piece of thick plastic from a resealable bag (to cover beaker)
scissors
1 pencil or craft stick
1 clear straw
1 thermometer
1 ruler
1 hot pad or rags to hold a hot beaker
1 long sheet of plastic wrap
1 test tube
access to ice water
1 pair of safety goggles for each student
different-colored pens or pencils
Caution
This activity uses boiling water and hot plates. Use caution around
these materials and wear eye protection at all times.
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Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Explore
Process and Procedure
1.Write this focus question in your science notebook. Use a colored pen or pencil
to make a box around it.
Focus Question: “How is heat transferred from hot water to the
air above?”
2.Decide who in your team will get the materials for the activity. Listen to
your teacher for directions.
3.You and your team will use a special system (shown
in figure 3.5) for the investigation. Steps 3a–e will
explain how to build the system.
a. Get the materials you need for the
pencil to
anchor the
straw
clear straw at
45º angle
investigation. Put on safety goggles.
Add 400 milliliters (mL) of water to
1000 mL
beaker
the beaker.
b. Cut a piece of plastic bag so that the
cut piece fits over the beaker. Have one
person hold the piece of plastic bag
over the beaker, while another stretches
plastic
wrap
500 mL
hot
plate
1 rubber band to fasten the plastic on
top of the beaker (figure 3.5).
c. Put another rubber band tightly around
the plastic. Use scissors to trim off extra
plastic that may hang down below the lip of the beaker.
d. Use a rubber band to attach the clear straw to the pencil
(or craft stick), as in figure 3.5. Your teacher will help
you with this step.
e. Use a pencil or pen to poke the smallest possible hole in
Figure 3.5: Beaker setup. This
diagram shows the setup that you
will use to investigate heat flow from
hot water to air. During the activity,
think about how this relates to heat
flow from warm oceans to the
atmosphere above.
the plastic. Push the straw through so that the fit is tight.
Place the system on the hot plate.
Be sure that the plastic is not touching the hot plate or
other heat source.
4.Investigate heat flow from the hot plate to the water, and then to the air above
the water, by using Steps 4a–c.
a. Turn the hot plate to “on.” Turn it high enough to boil the water.
b. While the water is heating, turn to a new page in your science notebook.
Draw the setup for this investigation. Label the key parts of the system,
as in figure 3.5.
c. Finish your sketch by showing the system with the water boiling.
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Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Explore
5.Once the system has reached a steady boil, use the following questions to help
you make observations. Answer them in your science notebook.
a. In your diagram, label any areas where you see steam in the system.
Look carefully inside the beaker. Do you see steam there?
Be careful not to confuse steam inside the beaker with fine water
droplets on the inside of the beaker.
b. Where would you expect to find water in the gas state (water vapor)?
Label this in the diagram you made in Step 4.
Caution
You will be making several measurements near or in the steam from the
boiling water. Be careful when you are working near steam. Steam can
cause severe burns.
c. Get a thermometer. Measure the temperature at several locations.
Use these suggested locations, although you can add more:
n A place in the classroom away from the beaker
n The steam about 20 centimeters (cm) from the tip of the straw
n The steam about 4 cm from the tip of the straw
n The steam about 1 cm from the tip of the straw
Have one teammate carefully hold the thermometer at the spot
where you want to collect the data. Wait until the temperature is
steady. Another teammate should read the temperature.
d.Record the temperature data on your diagram (for example,
“T = 40 degrees Celsius, or °C”). You can write the measurements
with a different color.
e.Do another measurement if you have a long thermometer. Poke a
small hole (2–3 millimeters, or mm, in diameter) in the plastic at
the top of the beaker. Gently push the bulb of the thermometer
2–3 cm inside the beaker and measure the temperature. Add this
measurement to your diagram.
f.If possible, gently push the thermometer far enough into the beaker
so that it is in the boiling water. The thermometer should touch only
the water and not the glass. Add this measurement to your diagram.
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Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Explore
6.Get a long sheet of plastic wrap and a test tube with
ice water. Have 2 teammates hold the plastic wrap.
Have a third teammate hold the test tube at the end
of the plastic wrap. Alternately, a ring stand may be
used to hold the materials. Direct the steam toward
the test tube (figure 3.6). What do you observe at the
test tube?
path of steam
under plastic
wrap
Caution
1000 mL
Be careful working near steam. Steam can cause
severe burns.
500 mL
7.Imagine a water particle in the boiling water. It ends
up in a drop on the countertop beneath the test tube.
a. Get a colored pen or pencil. Draw on your
diagram a possible path of that water
particle as it moves out of the beaker and
to the counter.
b. Label on the diagram where the water is in the vapor state. Label on
the diagram where the water is in the liquid state.
8.Compare clouds and steam. How are they similar and different? Discuss this
with your team. Write your ideas in your science notebook.
Figure 3.6: Water leaving
a beaker. This diagram shows
the setup that you will use to
investigate heat flow from hot
water to air. During the activity,
think about how this relates to
the ocean and the atmosphere.
Stop and Think—Part I
1.Answer the questions below about the temperature data.
a. How does temperature change between the inside of the beaker
and 20 cm beyond the tip of the straw?
b. Changes in temperature indicate the transfer of thermal energy.
The temperature of steam decreases as it moves into the air.
Where do you think the energy went?
Part II—Heat Flow in Fluids
Process and Procedure
You saw evidence of the flow of water and heated air in Part I, Steam Heat.
A change in temperature told you that heat moved. But if heat and water
move away from the beaker, does anything move toward the beaker? Watch the
demonstration your teacher does to help answer this question.
ES3-13
Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Explore
1.Look at the demonstration your teacher has set up. Investigation 1 uses a jar
of hot water (colored red) above a jar of cold water (clear; see figure 3.7).
Make a sketch of this setup in your science notebook. Label the key parts of
the setup.
Remember to set up your science notebook and label this section
“Part II, Heat Flow in Fluids.” You should also indicate that this is
investigation 1.
2.What do you think you would observe if you removed the plastic sheet from
between the 2 jars? You will have a chance to observe this, but for now
complete Steps 2a–c.
a. Write in your science notebook your idea of what you think will
happen. Also write your reason.
You may use sketches or words to answer. Label this “prediction.”
b. Share your answer for Step 2a in a class discussion. Listen to the
reasons of other students.
c. A volunteer will keep track of ideas on the board. A good way
to do this is with a 2-column table with the headings “outcome”
and “reasons.” Record these in your science notebook, too.
3.Watch as your teacher holds the jars. A volunteer will gently remove the
cardboard or plastic sheet. Answer the questions in Steps 3a–c about what
you observe.
a. Carefully record any patterns that you see. For example, what do
you see where the 2 waters meet?
Figure 3.7: Investigation 1.
This diagram shows the setup for
investigation 1. Hot water (red) is
above cold water (clear). Investigation
2 reverses the hot and cold water.
You can use a speech bubble like the
one in this figure to sketch a close-up
view of what you see.
You could use speech
bubbles to show what
you see at specific
locations. An example
of a blank speech
hot water
bubble is shown in
figure 3.7. Remember to
label which jar held hot
water and which jar
held cold water in this
clear,
wide-mouthed
jars
demonstration.
b. Describe any movement
you see.
c. What parts of the
cold water
thin plastic sheet
to separate jars
tray or
cookie sheet
system are heated
or cooled?
If there is movement in
the system, then arrows in your sketch are a good way
to show that.
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Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Explore
4.Investigation 2 uses a jar of cold water (clear) above a jar of hot water (red). This
is the opposite of investigation 1. Sketch this setup in your science notebook.
Be sure to label your sketch “investigation 2.”
5.What do you think will happen when the sheet is slipped out from between
the 2 jars?
a. In your science notebook, write what you think will happen.
Also write your reason.
b. Share your thinking in a class discussion.
c. A volunteer will record ideas on the board.
6. Watch as your teacher holds the 2 jars. A volunteer will carefully remove
the sheet.
a. Carefully sketch any patterns that you see. For example, what do you see
where the 2 waters meet?
You could use a speech bubble to show what you see at specific
locations. An example of a blank speech bubble is shown in figure
3.7. Remember to label which jar held hot water and which jar held
cold water in this demonstration.
b. Describe the water, its temperature, and whether it moves. If so, how
does it move?
c. Describe the transfer of heat in the system. In other words, what parts
are heated or cooled?
If there is movement in the system, then arrows in your sketch can
help you show that.
7.You saw 2 liquids at different temperatures that were next to each other.
Write a statement for how heat moved in the system of liquids.
Reflect and Connect
Answer the questions below in your science notebook.
1.
Think again about the focus question: “How is heat transferred from
hot water to the air above?” From your investigations in Part I, answer the
focus question.
2.Imagine that you did investigation 2 with a jar of cold air above a jar of hot
air. Do you think the pattern you obtained would be similar to or different
from what happened with the water? Discuss your ideas with your team,
and then write your best ideas in your science notebook. A sketch is also a
good way to show your answer.
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Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Explore
3.Think back to the last chapter. You thought about seasons and about solar
energy coming to Earth. Now think about what you have learned so far in
this chapter. For example, you have learned that ocean waters are warm
along the equator (figure 3.1). Draw a diagram like the one in figure 3.8.
Show how the tilt of Earth’s axis relates to the warm, equatorial waters.
Select a season like winter or summer. Then add the season
to this diagram.
Figure 3.8: Earth and Sun
diagram. Add to a diagram like
this to show your understanding
of the warm regions on Earth.
The season shown is
The reason is
Earth
Sun
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Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Explain
Hot Tropics, Cold Poles
You saw in the Engage activity that tropical cyclones are large and powerful. At
first glance, tropical cyclones seem rather different from the two models in the
Explore activity. Or are they? Perhaps there are some similarities. In this Explain
activity, Hot Tropics, Cold Poles, you will think more about some of the maps and
models of Earth that you’ve been exploring. How do processes in the models help
explain the processes on Earth? An important idea is how these processes relate to
heat flow from the equator to the poles. This transfer of thermal energy drives the
climate where you live.
Materials
For each team of 3 students
3 Cloud and Beaker Diagram handouts
different-colored pens or pencils
tape or glue
access to a computer
Process and Procedure
Meet with two teammates for the following reading.
1.Preview the reading Hot Tropics, Cold Poles by looking at the figures in the
reading. You used these steps in the last chapter.
a. Teammate 1 describes to the team what he or she sees in the figure.
b. Teammate 2 reads the figure caption to the team.
c. Teammate 3 describes to the team how the caption relates to the figure.
2.Complete the reading Hot Tropics, Cold Poles as a team by using a pattern of
read-summarize-restate. Write the key concept of each paragraph in a 2-column
table in your science notebook. Title the columns “paragraph” and “key idea.”
You used this strategy in the last chapter. The steps of the
strategy follow:
• Teammate 1 reads.
• Teammate 2 summarizes the paragraph, in his or her own words.
• Teammate 3 states the key idea of the paragraph, in his or her
own words.
• Write in your science notebook the key idea for each paragraph.
Be sure to write which paragraph you are writing about.
• Switch roles for the next paragraph.
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Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Explain
Reading: Hot Tropics, Cold Poles
Water Cycling
In the last chapter, you investigated factors affecting the amount of solar
energy received. You have learned about the heating of Earth’s surface by
solar radiation. The opening images in this chapter show the result of
this heating for Earth (figure 3.1). Only a small amount of land lies along
the equator. Thus, oceans absorb most of this energy at the equator.
Climates there are hot and tropical (figure 3.9). At higher latitudes, solar
energy reaches Earth’s surface at an angle. These regions are located both
north and south of the equator. Solar energy hitting at an angle leads to
less heating during the year. Of course, the exact amount depends on the
season and whether the axis is pointed toward or away from the Sun.
Figure 3.9: Earth’s climate zones.
Earth has several climate zones. Their
characteristics depend on their
latitude. Most parts of the United
States are in the midlatitudes. Hawaii
and some parts of the Southeast
such as Florida are subtropical.
Generalized Climate Zones on Earth
polar
subpolar
midlatitudes
subtropical
equatorial, tropical
(equator)
subtropical
midlatitudes
subpolar
polar
Solar energy is responsible for many patterns on Earth. A climate pattern
is one of these patterns. Climate is the average temperature or air
conditions that you would expect in a region over long periods of time.
This is different from weather, which is the condition on any given day.
Weather can include temperature, clouds, rain, snow, or whatever else is
reported. For example, if you call a family member on the phone, you
might ask, “How’s your weather today?” Weather changes from day to
day, or at times even hour to hour. You wouldn’t bother to ask, “How’s
continued
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Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Explain
your climate been the past 30 years?” This is because seasonal climate
for a region is stable over time.
Look again at figure 3.10. It shows that solar heating leads to high water
temperatures near the equator. Water is always evaporating, but warmer
water evaporates more. Evaporation occurs when liquid water absorbs
heat and changes from liquid water to water vapor—a gas. This process
transfers thermal energy from the ocean to the air above. Still, most air
consists of nitrogen and oxygen. Humid air is about 3 percent water
mixed with about 77 percent nitrogen and 20 percent oxygen.
Figure 3.10: Hot water. Energy
from the Sun heats the Pacific,
Indian, and Atlantic Oceans at the
equator. Heating of the atmosphere
over the hot water drives convection
at the equator.
Sea Surface Temperature (°C)
August 2005
equator
key
In your investigation, you made water vapor quickly by boiling liquid
water. Tropical oceans are warm, but they do not continue to get warmer
and warmer like the beaker of water. This is because evaporation
transfers both water and energy to the air above.
continued
ES3-19
Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Explain
What happens to the water vapor as it rises? You measured in the
Explore activity how the humid air cools. With enough cooling, the
water vapor condenses to form tiny droplets of liquid water in the air.
Condensation is the change of water vapor to liquid water. Rather than
absorb energy, condensation releases energy to the surrounding air.
Water vapor has carried thermal energy from the ocean to the air above.
What do you call these tiny droplets of water in the air? You may be
thinking “rain,” but these droplets are smaller than raindrops. These tiny
droplets of water form clouds. Clouds are visible because we can see
liquid water. Water vapor is not visible. Clouds also have nitrogen,
oxygen, and water vapor between condensing droplets of liquid water.
When the tiny droplets continue to condense more water vapor, they
develop into large drops inside of a cloud. The drops are too big and
heavy to stay in the cloud, so they fall as rain.
You may have seen something similar to a cloud in your kitchen. When
liquid water boils and water vapor is above the hot water, a “cloud” may
form. This happens when the water vapor cools and condenses into tiny
droplets of water. This cloud that you can see is steam. The steam that
you see is liquid water.
Most of the evaporation on Earth occurs where the warmest water is
found—at the oceans near the equator. Likewise, most condensation and
rain occur over the same equatorial oceans. About 80 percent of rain
falls right back to the ocean. This is the biggest part of the water cycle.
The rest of the rain moves to continents. When it affects your soccer
game or a picnic, then that’s where the water cycle becomes a part of
your daily weather!
continued
Stop and Think
Work with your team to answer the following questions.
1.Figure 3.9 shows a general image of climate zones on Earth. Compare this
image of Earth’s climates with the chapter opener images of global temperatures (figure 3.1).
a. How are the images similar?
b. How are the images different?
c. How are the images related?
In other words, what can you learn from one of the images that
will help you understand the other?
ES3-20
Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Explain
Hot Tropics, Cold Poles (continued)
Convection Connections
Why does warm air rise? It rises because cooler air must move into
position to fill the space. This also happens with heated liquids. You
observed this with the hot (red) and cold water investigation. The circular
pattern of movement forms a convection cell (figure 3.12). Convection is
a process where hot fluids (air and liquid are fluids) move upward as
cooler fluids move downward. Convection is driven by a difference in
density. Warm air is less dense than the cold air around it. In a growing
cloud, hot air rises because it is less dense than the surrounding, cooler air.
Convection also transfers thermal energy with the fluid, whether the fluid
is water or air. Compare the two investigations you did in the Explore
activity to warm oceans along the equator. Both investigations transferred
warm fluid (water or steam) and thermal energy up. Warm, humid air
above warm oceans also rises. This transfers thermal energy out of oceans
and into the atmosphere. An example is shown in figure 3.11.
Figure 3.11: Towering clouds.
This photo shows a towering,
growing cloud over warm ocean
waters. How are the paths of water
and thermal energy similar to, or
different from, your activity with
the beaker?
PhotoDisc
continued
ES3-21
Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Explain
In the early 1700s, George Hadley, an English scientist, was interested in
the heating at the equator. He reasoned that this heating should result in
a large convection cell. As you have seen, warm air at the equator rises.
In Hadley’s model, this warm air would then flow toward the North and
South Poles because heat always moves from warmer areas to cooler
areas. This would transfer thermal energy toward the poles. The air
would cool as it moved toward the poles. It would then be denser, so it
would sink back toward the surface of Earth. This air would then be
pushed back toward the equator as warm air rose there (figure 3.12).
However, Hadley’s model did not address a few things. For example, his
model did not show the observed winds at the equator that move from
east to west. Similarly, Earth is not blanketed by surface winds moving
from the poles to the equator. Some revisions to the model were needed.
The model was a good start, but not correct.
Slow Planet Rotation
sinking
cold air
cold
solar
radiation
su
convection
cell
Figure 3.12: Convection model.
In the 1700s, English scientist George
Hadley suggested a model like this
for global convection. Warm air rises
at the equator and sinks at the poles.
Surface winds return cool air to the
equator, where they warm up again.
r
fa
ce
flo
w
hot
rising
warm air
fa
ce
flo
w
hot
su
cold
r
convection
cell
Later, scientists saw two main reasons why Hadley’s model was too
simple. One was that Earth rotates. This rotation has an effect on the
direction winds blow. Away from the equator, Earth’s rotation causes
surface winds to curve. The second reason is that Earth’s surface is made
up of water (70 percent) plus land (30 percent). Land and water heat up
and cool down at different rates. This interferes with wind patterns.
continued
ES3-22
Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Explain
Scientists now know more about convection in Earth’s atmosphere. The
global pattern has warm, moist air rising at the equator (figure 3.13).
Rain falls from the air as it cools. The air becomes drier and cooler as it
moves away from the equator. The air also gets more dense. This air then
Figure 3.13: Convection at the
equator. Heat flow to the poles
starts with convection at the equator
(0° latitude). There, air is warm and
moist. The air moves toward the
poles and cools. The condensation of
vapor transfers thermal energy to the
air. The cooler, drier air sinks to Earth
at latitudes of about 30° north.
sinks back to Earth at latitudes of about 30° north and 30° south.
Sometimes the winds are violent and result in a tightly spinning storm.
This is the case in tropical cyclones. These storms are also important
vehicles for moving heat to higher latitudes. Warmer waters make these
storms get stronger and stronger. When they hit land or colder water,
they weaken quickly. The storm energy decreases.
n
Air Flow By Latitude
30 –
altitude (km)
stratosphere
20 –
au
t ro p o p
tropopause
se
10 –
troposphere
polar
front
0 –|
90 o
|
60
|
o
latitude north or south
30
|
o
0o
equator
Process and Procedure (continued)
3.What new science words did you learn? Review the reading by adding bold or
unfamiliar words to your personal glossary.
ES3-23
Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Explain
4.Watch a video of water vapor in the atmosphere. This is the water vapor
available to make rain in the water cycle. A frame from the video is shown
in figure 3.14.
a. Check that each member on your team under-
Precipitable Water
Dec
stands the color scale (figure 3.14). Can each
team member say what color represents the
most water vapor in the atmosphere?
b. Where is most of the water vapor found?
Describe this in your science notebook.
c. Compare the map of water vapor and rain with
the map of average SSTs (figure 3.10). Describe
how these are similar, or different.
d. View the video titled Precipitable Water Vapor.
e. Does your team see evidence of seasons in the video? If so, write
your evidence.
It can help to compare months such as January and July.
5.Figure 3.11 shows a cloud growing above warm water. Use this image to help
you compare the beaker investigation (Explore activity, Part I) and the Hot
Tropics, Cold Poles reading to features on Earth.
Figure 3.14: Global water vapor.
This map shows the amount of
water vapor in the atmosphere in
December. This vapor leads to rain.
Where is the vapor concentrated?
Where will it rain the most?
Data: NCEP/NCAR Reanalysis Project, 1959–1997
Climatologies; Animation: Department of Geography,
University of Oregon, March 2000
a. Obtain the handout Cloud and Beaker Diagram from your teacher.
Review each feature in the images, or systems, with your team.
b. Neatly add to the systems these labels. Use arrows or brackets to show
where a substance is or where a process occurs.
n Water vapor (gas)
n Clouds
n Liquid water
n Evaporation
n Condensation
n Fine water droplets in air
n Sun
c. G
et a different-colored pen or pencil. Draw on each system the
path of water (matter). Add any labels to help you explain what
you have drawn.
d. G
et a pen or pencil of a different color. Write on each system the
path of energy transfer. Add labels to help you explain what you
have drawn. Start at the Sun or the hot plate in each case.
Water cycles back to the surface of Earth. Does the thermal energy
also return to Earth, or does it remain in the atmosphere? How
would you show that?
e. Make a legend that shows the colors you used for the path of water
and the path of energy transfer. Put this legend on the bottom right of
your diagram. Tape or glue your work into your science notebook.
ES3-24
Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Explain
Reflect and Connect
Answer the questions below in your science notebook.
1.Think about polar climates to help you answer the following questions. Use
the consider, contribute, consult, revise (CCCR) strategy in Steps 1a–d to help
you answer them:
n
If heated air from the tropics flows to the poles, will polar climates
eventually become tropical?
n Can the poles keep warming or will they reach a point where they
won’t continue to get warmer?
n If not all the heat goes to the poles, where might some of it go?
Refer to figure 3.13.
a. First, work by yourself and write your answers to the questions.
Consider many pieces of evidence from your work to answer
this question.
b. Contribute your ideas within your team. Each of you should read
what you wrote in Question 1a, word for word.
c. Consult your team and get its advice for revising your answers.
d. Revise your ideas based on the best ideas from your team.
2.Sometimes airplanes leave white “lines” in the sky behind them. These are
called contrails. Some people refer to contrails as “vapor trails.”
a. Is this accurate? Explain your thinking.
b. Can your team think of a better name for them?
ES3-25
Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Explain
3.To show the water cycle, many texts use a diagram like figure 3.15. The
diagram shows water evaporating over an ocean, clouds and rain forming
over nearby mountains, and rivers flowing back to the ocean. Use your global
view of the water cycle to critique this figure.
“To critique” means “to analyze or evaluate, noting strengths and
weaknesses.” Make suggestions on how to improve the diagram.
H2O
condensation
clouds
Figure 3.15: Water cycle. This
diagram shows an image of the
water cycle. Water (H2O) evaporates
from an ocean, rains or snows onto
mountains, and then flows through
rivers back to the ocean.
H2O vapor
rain • snow
evaporation
precipitation
runoff
stream flow
OCEAN
infiltration
groundwater discharge
4. Answer the following questions about where you live.
a. Describe the weather today. How do think it compares with the
weather for the same day one year ago?
b. Describe the seasonal climate for today. How do think it compares
with the seasonal climate for the same day one year ago?
ES3-26
Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Elaborate
Wind and Water—
Becoming Current
Some winds are local. Other winds span the globe. Winds are like river currents,
but in the atmosphere. Winds move heated air, just as rivers move water. At the
global scale, heating at the equator and convection above hot ocean waters causes
the winds. When winds move moisture away from the equator to higher latitudes,
they are, in effect, atmospheric rivers.
But what about oceans—do they have currents? If so, are currents in the
oceans like wind in the atmosphere? You’ll use a focus question in the first step
of this Elaborate activity, Wind and Water—Becoming Current, to answer this
scientific question.
Materials
For each team of 3 students
1 pencil
1 plate (Styrofoam or waxed paper) or aluminum pie tin
clay to make continents
1 metric ruler
3 straws
water
3–4 paper dots (punched-out pieces)
1 paper towel or rag (for spills and to blot off wet clay)
different-colored pens or pencils
Process and Procedure
Work with two partners to explore the effect of wind on water. How does this
relate to ocean currents? You will start with some observations, and then discuss
your ideas with your class.
1.Write this focus question in your science notebook. Use a colored pen or
pencil to make a box around it.
Focus Question: “What is the relationship between patterns of
global winds and ocean currents?”
ES3-27
Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Elaborate
2.Look at figure 3.16. It shows patterns of winds on Earth. Use Steps 2a–c to
analyze the figure.
a. Discuss some of these global features as a class:
n Oceans
n Continents
n Equatorial regions
n High latitude, low latitude
Figure 3.16: Global wind patterns.
Winds of the Northern and Southern
Hemispheres come together and
meet (dashed line) near the equator.
Winds at the equator blow from right
to left (east to west).
n Tropics
b. What direction do winds travel around the equator?
c. What happens where ocean winds meet a continent?
Global Atmospheric Winds
N
80O –
latitude
40O –
0O –
40 O –
S
80 O –|
180O
W
|
|
|
|
|
|
|
|
|
|
|
|
150 O
120O
90O
60O
30O
0O
30O
60O
90O
120O
150O
180O
longitude
E
ES3-28
Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Elaborate
3.Participate in a class discussion for this step. Look at the map of ocean currents
in figure 3.17, then complete the following tasks.
a. Discuss some of the patterns that you see. Note these features:
n
Oceans
n
Continents
n
Equatorial regions
n
Gyre
n
Ocean current patterns
n
Tropics
b. Based on the map, how would you describe a gyre? Discuss this
with your class.
4.What happens to ocean currents when they meet a continent? Use these steps
to explore that question.
Figure 3.17: Global ocean
currents. Large-scale circulation
occurs in gyres. Red arrows show
relatively warm currents in the
gyres. Blue arrows show relatively
cold currents. How do these currents
relate to atmospheric wind?
a. Look at figure 3.17. In your science notebook, describe specific
examples of what happens when the ocean currents meet a continent.
b. Form a team with 2 other students.
c. Compare your answer for Step 4a with your partners’ answers.
Global Ocean Currents
80O –
La
b
ra
dor
C.
Alaskan
C.
fic C.
or
a
C.
N. A
tlan
tic D
rift
North
Atlantic
Gyre
r
Ku
os
hio
C.
N. Equatorial C.
N. Equatorial C.
N. Equatorial C.
0O –
S. Equatorial C.
C.
az
Br
40 O –
C
Indian
Ocean
Gyre
gu ela C.
C.
South
Atlantic
Gyre
.
A us t r al i an
Ben
Peru
South
Pacific
Gyre
S. Equatorial C.
E.
S. Equatorial C.
il
latitude
lif
ni
North
Pacific
Gyre
m
rea
St
Gr
.
stralian C
Ca
Gulf
40O – N. Paci
E.
.
dC
lan
n
ee
Au
N
.
W
West Wind Drift
West Wind Drift
East Wind Drift
East Wind Drift
S
80 O –|
180O
W
|
|
|
|
|
|
|
|
|
|
|
|
150 O
120O
90O
60O
30O
0O
30O
60O
90O
120O
150O
180O
longitude
E
ES3-29
Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Elaborate
5.In the next few steps, you will make a model of wind and water currents. You
can do this for 1 of the examples your team identified in Step 4a. Your teacher
may provide additional instructions.
a. Use a pencil to draw the outline of 1 or more continents on a plate.
b. Add an arrow showing “N” for north or “S” for south.
c. M
old clay into the shape of the continent. The continent should be
about 1 cm high at the shoreline.
d. Show your work to your teacher.
e. Prepare a flat work area. Move books and papers away from this
work area.
f. Let your teacher know when you are ready for the water.
6.Use the points below to conduct tests of your model. Record your findings
with sketches for each trial.
n
Add paper dots to trace the water current.
n
Use a straw to create wind. Blow winds in the direction shown
in figure 3.16 for the location you are modeling.
n
Take turns blowing. Use your own straw.
n
Blow with different speeds. Does this change the speed of the
water current?
n
Blow with different wind directions. How does this change the pattern
of ocean currents at that location (compared with figure 3.17)?
n
If your map includes the equator, create a wind at the equator
blowing from west to east. If your map does not include the equator,
join with a team that has the equator to do this test.
n
Record your results in your science notebook.
7.Is it possible to move wind over water without causing a current in the water?
Test this question with your team’s model.
8.Decide as a team the best way that you could improve your team’s model.
Write the heading “model revisions” in your science notebook, and then write
your ideas about how to improve the model.
9. Be prepared to share with the class your answers for these questions:
n
What continents did you model?
n
What wind currents did you model?
n
What water currents did you model?
n
What is one way you could improve your team’s model?
n
Show the class how your team’s model works.
10. Listen to your teacher for directions on how to clean up the materials.
ES3-30
Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Elaborate
Reflect and Connect
Answer the questions below in your science notebook with your team.
1.Answer the focus question for this activity, “What is the relationship between
patterns of global winds and ocean currents?” Use specific geographic examples
in your answer.
2.Look at figure 3.17 with your team. Give an example of an ocean current that
is not blocked by a continent. What direction does it go? How far does it go?
ES3-31
Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Evaluate
Polar Express—for Energy
In the last chapter, you investigated factors affecting solar energy at the surface of
Earth. Most energy reaches Earth in equatorial regions. That’s why the tropics
have the highest average temperatures. From there, the heat flows toward regions
of lower temperature at the North and South Poles. This heat flow is closely linked
to the water cycle.
In this Evaluate activity, Polar Express—for Energy, you’ll get to show what
you’ve learned about heat flow on Earth from the equator to the poles. This heat
flow affects your local climate (figure 3.9) and even your weather. First you and
your team will review the major concepts of the chapter. Next you’ll answer questions by yourself. Then you’ll get to review and revise your answers with a team.
Explaining your revisions helps you learn the science better.
Part I—Chapter Review
Materials
For each team of 3 students
tape or glue
different-colored pens or pencils
1 Polar Express—for Energy Rubric handout
3 Global Average Temperatures, July handouts
3 Airflow by Latitude handouts
Process and Procedure
Join with two partners to review what you’ve learned about heat flow on Earth,
the water cycle, and climate zones. This is the first of three parts to this activity.
1.Get the handout Polar Express—for Energy Rubric. Note the weights for
different parts of the activity. A final score isn’t just from Part III, Revising
Your Ideas.
Remember the features to add to your science notebook to help
with organization (activity title, date, page number, entry for table
of contents, etc.).
ES3-32
Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Evaluate
2.Work with your team to make a list of science ideas from this chapter. Write
these ideas in your science notebook. Examples include science ideas such
as tropical cyclone, evaporation, water cycling, and convection. Use these
resources to help you:
n
Your science notebook
n
The chapter organizer
n
The text of the chapter
n
Visual prompts in your room
3.Get 1 copy per person of the Global Average Temperatures, July and the
Airflow by Latitude handouts. Tape or glue each to its own blank page in
your science notebook. Leave lots of blank room around them.
4.
Follow these steps to connect your science ideas with the images on
the handouts.
a. Work with your team to review your list of science ideas.
ook for evidence of the ideas on the images. Write the science
b. L
ideas next to the evidence you see.
c. U
se arrows or lines to connect the ideas you wrote in words with
the evidence of the science idea in the images.
d. A
dd other words to help explain how the evidence in the images
connects to the ideas.
5.When you are finished, have a team member write your team’s names on a list
at the front of the class. Wait for your teacher to come review your handouts
and record a score for Part I, Chapter Review.
Part II—Polar Express
Materials
For each student
1 Questions for Chapter 3: Hot Water handout
Process and Procedure
You will work individually on the following questions.
1.Listen as your teacher reviews each step in Part II, Polar Express. When you
get the Questions for Chapter 3: Hot Water handout, write your name on
each page.
2.Take about 20 minutes to complete the chapter questions. Take the handout
to your teacher when you are finished.
3.Read the steps in Learn from Mistakes (LFM) Protocol. You will use this in
Part III.
ES3-33
Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Evaluate
4.Your teacher will return your scored questions to you. Write your score on the
top of the page and circle it. Near your score, list the numbers to the questions
you missed. These are the questions that you’ll work on.
5. As you wait for others to finish, start reviewing the questions that you missed.
Learn from Mistakes Protocol
School is a place to learn. But sometimes we make mistakes. Remember
when you learned how to ride a bicycle or use a skateboard? Did you make
mistakes? You likely fell off or crashed—you may even have scars on your
knees as evidence. But you learned from these mistakes, and now you may
be able to ride easily. Making mistakes happens a lot when the subject is
difficult or new. If you learn to identify and explain what’s incorrect about a
wrong answer, you have a better chance of avoiding that mistake next time.
This makes learning easier.
Go through the steps below for every question you missed on the test.
1. Reword the original question from the test and write the new
wording in your science notebook. Try to highlight the specific
things you think the question is looking for. You can use pictures
or sketches in addition to words.
2. Find the mistake you made in your answer. Try to explain why
you made the mistake. Even if you read the question wrong the
first time, make sure you list that as your explanation. Focus on
the concepts and big ideas you didn’t understand.
3. Write the correct answer. Include a description of why you
changed your answer and why the new answer makes sense.
If you answered only in words the first time, you might consider
adding a sketch or graph.
Part III—Revising Your Ideas
Materials
For each team of 3 students
scored copy of each team member’s chapter questions
Process and Procedure
In Part III, you will get to build on what you know to improve your understanding.
You’ll use the same process that scientists often have to use to learn about Earth
systems—learning from mistakes. Look over your results.
ES3-34
Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Evaluate
1.Participate in a class discussion of how you will get to improve your answers
and show that you learned from mistakes. The discussion will also include
some review of the major concepts of this unit. You may want to take notes
about the concepts where you made mistakes.
2.Use the steps in the LFM Protocol for each question you answered incorrectly.
Do your corrections and revisions in a different color.
3. Turn in all your work.
ES3-35
Earth Science Unit · Energy In Earth’s Systems
Chapter 3 · Hot Water
Spanish Vocabulary
Spanish Vocabulary
atmosphere: atmósfera
climate: clima
clouds: nubes
condensation: condensación
convection: convección
cyclone: ciclón
equator: ecuador
evaporation: evaporación
hurricane: huracán
North Pole: Polo Norte
ocean: océano
ocean current: corriente oceánica
South Pole: Polo Sur
steam: vapor
tropics: trópicos
Venn diagram: diagrama de Venn
water cycle: ciclo del agua
water vapor: vapor de agua
ES3-36