Convection Connection Project
University of Colorado at Boulder
Department of Physics
Dr. Michael Dubson, Faculty
(Featured Scientist and Activity Guide Scientific Advisor)
Cooperative Institute for Research in Environmental Sciences
Dr. Alex Weaver, Director, K-12 Outreach Program
(Featured Scientist and Activity Guide Scientific Advisor)
Program in Atmospheric and Oceanic Sciences
Scott Kittelman, Faculty
(Technical Support)
Department of University Communications
Bobbi Barrow, Executive Director
Monteith Mitchell, Project Manager
Wynn Martens, Community Affairs, Director
Dirk Martin, Broadcast Services Coordinator
Science Discovery
Carol McLaren, Director
(Project Advisor and Activity Guide Consulting Editor)
Tara Chace, Special Projects Coordinator
(Activity Guide Editor)
Check out the Convection Connection website
http://Colorado.EDU/ScienceDiscovery
NEWS 4 Staff
Marv Rockford, General Manager
Angie Kucharski, News Director
Larry Green, Colorado's Weatherman
Jeff Gurney, Producer
Logan Smith, Photographer
Mike Porras, Photographer
Tom Marès, Graphic Design
(Illustrator/Designer: Activity Guide and Poster Producer)
Vikki Olesen, Marketing Account Executive
Check out the NEWS 4 website at www.kcncnews4.com
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Convection Connection
Activity Guide
Day 1 - Overview
Take a good look at the
Convection Connection poster (pictured in
black and white on the cover of this guide)! Hot air
balloons and floating raisins, lava lamps and whales, palm
trees and pots of boiling water - how in the world are all
these things connected?
You've got it: CONVECTION! Convection is found in the oceans, atmosphere
and even the earth's mantle and sun. Convection explains many phenomena in
the environment, and can be demonstrated in myriad fun experiments, some
of which are included in this activity guide.
So join us as we consider the density of fluids - air, water, and molten
rock - and how density relates to convection; it should prove to be an
exciting journey of learning!
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Day 2 - Density
Concepts:
Density is mass divided by volume. More mass in a space makes for a more
dense object. Imagine three cubes of the same size: one is granite, one is wood, and one is
styrofoam. The granite has more mass, and is the most dense; the wood does not have as much
mass, and is not as dense; and the styrofoam, with the least mass, is the least dense of the
three cubes.
Fluids also have different densities. Imagine a cup of plain water. If we dissolve one tablespoon of
salt in the water, we still have the same volume -- one cup of fluid -- but the cup of fluid now has
more mass, because there are more molecules (salt and water) packed into the cup than there
were when we just had water in the cup. A cup of salt water is more dense than a cup of plain
water.
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Density Activity
Purpose:
To observe density of fluids and solids together
Materials:
Dark-colored pancake syrup
Blue food coloring
Water
Vegetable oil
600 ml beaker or glass jar (with straight sides)
Selection of objects to float (For example: corks, paper clips, grapes, marbles, small
plastic piece, little stick, pebble, etc)
Procedure:
1. Pour syrup into the container until it is about 1/4 full.
2. Slowly pour the same amount of vegetable oil into the container.
3. Put just enough food coloring in some water to make the water light blue.
4. Slowly pour the same amount of blue water into the container.
5. Observe how the liquids layer.
6. Now slowly add objects to see if they float or not, and if so on which liquids.
Explanation: The liquids layer because they have different
densities. A liquid that is more dense can hold up a liquid that is
less dense. The oil is less dense than the syrup so it floats on top
of the syrup. The water is also less dense than the syrup, but it is
more dense than the oil, so the oil floats on top of the water which
floats on top of the syrup. Solid objects have different densities
as well.
By observing where the solids float you can tell
whether they are more or less dense than the
various liquids, and each other.
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Day 3 - Heat
Concepts:
A fluid is anything that can flow, such as a liquid (water), a gas (air), and
molten rock. All fluids are made up of free flowing molecules. As the temperature of a fluid
increases, molecules move faster, bouncing off each other more vigorously, and thus moving
further apart from one another. As more space is created between the molecules -- there are
fewer molecules in a given volume -- the fluid becomes less dense. Likewise, as the temperature of
the fluid decreases, molecules move more slowly, and become closer to one another. When there is
less space between the molecules -there are more molecules in a given volume -- the fluid becomes
more dense.
Heat Activity #1
Purpose:
To see how temperature affects the speed of molecules
Materials:
Two small clear glass jars (baby food jars work well)
Red and blue food coloring (can use any two colors)
Two eye droppers
Paper and pencil
Hot water
Cold water
Procedure:
1. Fill one glass half full with very cold water, and one half
full with very hot (not boiling)
2. Draw about 4 drops of blue food coloring into one
eyedropper, and 4 drops of red food coloring into the
other eyedropper. Try to have the same amount in each.
3. Hold the blue dropper over the cold water, and the red
over the hot water near the surface of the water, but not
touching it, and squeeze to empty the droppers at exactly the same time.
4. Compare how the food coloring moves in each container. Did the color spread more
rapidly in one glass than the other? If so, what was the temperature in that glass
in relation to the other glass?
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Heat Activity #2
Purpose:
To observe how temperature affects density
Materials:
4 small, clear, identical glass jars (baby food jars work well)
Hot water (not quite boiling)
Cold water
Red food coloring
Blue food coloring
Stir stick
2 thin stiff clear plastic squares that will cover the opening of the jars
Shallow baking pans or pie pans to catch spills
Procedure:
1. Place the four jars in the shallow pan. Fill two with hot
water, and fill two with cold water. Fill the jars to the
brim - the very top!
2. Place a drop or two of red food coloring in the two
jars with hot water. Stir. Place a drop or two of blue
food coloring in the two jars with cold water. Stir.
3. Place one plastic square on a hot water jar, and flip it
over (carefully holding the middle of the plastic). Place
it on top of a cold water jar. Place one plastic square on
a cold water jar, and flip it over (carefully holding the
middle of the plastic). Place it on top of a hot water jar.
You should now have a hot jar on top of a cold jar, and a cold jar on top of a hot jar.
4. Now for the tricky part! Carefully line up the edges of one set of jars, and applying a bit of
pressure to the top jar, slide the plastic out from between the two jars. Do the same to the
other set of jars.
5. What happens in each pair of jars?
Explanation:
When the cold water is in the top jar, the cold water sinks
down, displacing the hot water. This happens because the cold water is more dense
than the hot water, causing the cold water to flow to the bottom of the liquid column,
while the hot water flows to the top. When the hot water is in the top jar, the hot
water remains on top of the cold water. This happens because the hot water is less
dense than the cold water, allowing it to remain at the top of the column of liquid.
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Day 4 - Air Pressure
Concepts: Air exerts pressure on whatever it touches.
The Earth is surrounded by an atmosphere which is about 80 miles thick. All this air produces a
pressure of about 14.7 pounds per square inch at sea level. This pressure is called atmospheric
pressure, and everything on Earth experiences this pressure - including you! An empty can does
not collapse, because there is air inside as well as outside of the can. But if the air inside the can
is removed, there is no pressure inside, and the outside air pressure will cause the can to collapse.
Air pressure changes with temperature. If the volume of air is kept constant, and the
temperature is increased, the speed of the air molecules increases, as does the pressure. If the
temperature is decreased, the air pressure also decreases.
Air Pressure Activity ____________
Purpose: To see the effects of air pressure
Materials:
2 Empty aluminum soda cans
Water
Hot plate
Pan with about 1 1/2" of cold water
Safety goggles
Tongs
Procedure:
Trial #1
1. Put on safety goggles.
2. Put about 1/2 inch of water into one can and place it on the hot plate.
3. The moment a wisp of steam is visible coming out of the top of the can, remove the soda can
with tongs, and quickly turn it upside down in the pan with cold water.
4. What do you observe?
Trial #2
1. Keep your safety goggles on.
2. Put about 1/2 inch of water into the other can and place it on the hot plate.
3. When the water is boiling well (steam will be coming out of the top of the can), remove the soda
can with tongs, and quickly turn it upside down in the pan with cold water.
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BE VERY CAREFUL TO KEEP HANDS AND FACE AWAY FROM THE STEAM!
4. What do you observe?
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Day 5 - Buoyancy
Concepts: Whether something sinks or floats depends on its density relative to the
density of the surrounding medium. The ability to float is called buoyancy, and there are different
degrees of buoyancy. For example: a solid block of granite sinks in water because granite is more
dense than water - it is not buoyant in water; a helium balloon floats on air because the balloon
containing helium is less dense than the air below - it is buoyant in air.
Buoyancy Activity ____________
Purpose: To observe the buoyancy of raisins, and how their buoyancy can change.
Materials:
600 ml beaker or other large glass jar
About 25 raisins (2 oz. Box)
2 cups of water
1/4 cup vinegar
1 teaspoon baking soda
Procedure:
1. Put the raisins into a container of water and remove
any that float. Put those back in the box.
2. Pour out the water, and set the raisins that didn't
float aside for the next steps.
3. Put 2 cups of water and 1/4 cup of vinegar in the
large jar
4. Add 5 to 10 raisins to the jar.
5. Add one teaspoon of baking soda to the jar.
6. Observe the raisins.
Explanation: The raisins sink because the
force of gravity pulling them down is greater than the
upward buoyant force exerted by the liquid. The gas
bubbles act like tiny balloons that make the raisins
light enough to float to the surface. At the surface the gas bubbles are knocked off,
and the raisins sink to the bottom until more bubbles attach. The bubbles change
the raisins' buoyancy causing them to rise and sink.
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Day 6 - Convection
Concepts:
Convection is the transfer of
heat by the movement of a
substance from one position
to another. Convection can
be forced, such as occurs in
the heating systems of
many houses, or natural,
such as occurs in the
transfer of heat in fluids air, water and molten rock -due to density differences.
A hot air balloon is a
wonderful place to "see"
convection due to
differences in the density of
air. As the lowest layer of
air in the balloon is heated, it
becomes less dense and
rises. As that layer nears
the top of the balloon it has
become cooler than the layer
now being heated, and thus
sinks, becomes heated and
rises again. This process is
called convection. The overall
temperature of the air in the
balloon increases, and
eventually makes the balloon
buoyant (less dense than
the air around it), and it
rises from the ground.
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Convection Activity ____________
Purpose:
To "see" convection by building and launching a hot air balloon.
Materials:
One 60” x 20” piece of stiff paper for pattern
Tissue paper (16 sheets, 24" x 30", various colors except black)
Cutting pattern
Pins (about 6 per balloon)
Scissors (2)
Rubber cement or glue sticks (2)
Fishing line for tether (50 foot roll) - optional
Wire (24", 16 gauge, or use pipe cleaners)
Wire cutters
Dryer duct chimney apparatus (about 24")
Propane stove
Procedure:
1. Using the tissue balloon pattern instructions, draw and cut out a
pattern and set it aside.
Tissue Balloon Pattern Instructions:
a. Fold a piece of paper (60" x 20") lengthwise.
b. Measure and mark points as shown.
c. Connect the dots.
d. Cut out the pattern, so that the fold is in the middle.
2. Overlap two pieces of tissue paper to make one 5 foot long panel and use the glue stick or
rubber cement to glue the 2 pieces together along the 24" edge. Repeat using 16 pieces of
tissue paper. You will have a total of 8 long panels. Be creative with colors. Plan how your balloon
will look.
3. Place the long panels in an even stack. Straighten them and smooth them out.
4. Fit the pattern made in step 1 over the sheets and pin it in place. Be careful not to tear the
tissue paper.
5. Cut out the tissue paper along the pattern. Carefully remove the pins and the pattern and save
them. Keep the tissue sheets in a stack.
6. Glue the tissue panels together to make the balloon:
a. Take panel 1 off the stack, and lay it flat on a table.
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b. Lay panel 2 on top of panel 1, so that one side of the bottom panel extends 1"
past the edge of the top panel.
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c. Fold that 1" margin of the bottom sheet over the edge of the top sheet and glue it down.
d. Lay panel 3 on top of panel 2, so that the unglued side of panel 2 extends 1" past the edge of
panel 3.
e. Fold that 1" margin of panel 2 over the edge of panel 3 and glue it down.
f. Continue gluing the panels together on opposite edges.
g. When all are glued together it will be in one long line, folded like a fan.
h. Check that the panels are folded this way, but don't open it up yet.
i. Glue the first and last panels together as you did the other panels along their unglued sides.
Now you can open the balloon to see that you have a circle
7. Lay the balloon flat again. Cut a circle of tissue to cover the top opening and glue it over the top
hole in the balloon.
8. To hold the bottom of the balloon open: Form the wire or the pipe cleaner into a circle the size
of the bottom opening; gently open the bottom edge of the balloon and position the wire on the
inside about one inch up from the edge; fold the tissue over the wire and glue in place.
9. Gently open the finished balloon and check for large holes, being careful not to make any new
ones! Patch any holes with pieces of tissue paper cut to fit. Tiny holes are ok.
10. To launch the balloon, place the dryer duct on the propane stove to form a chimney. Have a
couple of students, WITH A TEACHER, help to hold the balloon over the dryer duct. Turn on the
stove and allow the balloon to fill with hot air. When the balloon begins to feel warm, and as if it can
float, it is ready to be launched. Count down, give it a gentle push and WATCH IT FLY!!
Important Safety Note: An adult should
be in control of the stove and the hot
dryer duct. Use hot pads if you must
handle the dryer duct after it has been
heated.
Explanation: Again, it's all about
convection! Convection occurs in the
balloon as the warm air rises and the
cooler air sinks. The balloon fills with air
that is warmer than the air surrounding
the balloon, and as it does so the balloon
becomes less dense than the surrounding
air. The balloon will stay afloat as long as
the air in the balloon stays warmer (less
dense) than the air around it.
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Day 7 - Convection in the
Atmosphere
Concepts: We expect that convection occurs in the atmosphere because air is a fluid -- air
molecules are free to move -- and because there are areas of warm air and areas of cool air. Clouds
are visible proof of convection: hot moist air rises; eventually it cools down and condenses (water
droplets form). The clouds we see are these tiny water droplets. A thunderstorm, also called a
convective storm, is the most dramatic example of convection in the atmosphere.
Thunderstorms build due to a variety of weather conditions. One example is when a body of warm
air is forced to rise quickly by an approaching (sinking) cold front. A strong persistent updraft of
warm, moist air is formed. The approaching cold front helps build the updraft into a cumulus
cloud, which eventually builds into a cumulonimbus cloud up above 30,000 feet. Then a downdraft
forms bringing cold air and precipitation from high in the cloud to the ground.
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Convection in the Atmosphere Activity ____________
Purpose: To observe how changes in air temperature cause convection currents.
Materials:
Cardboard box about the size of a 10-gallon aquarium
(Note: A 10-gallon aquarium can be used. If it is, then you just need a piece of
card board that snugly fits on the top.)
Two glass lamp chimneys (clear plastic bottles such as Gatorade ® bottles also work)
Pencil
Scissors or sharp knife for cutting cardboard
Wide transparent tape (package tape works well)
Transparent plastic wrap
Matches
Incense to produce smoke
Tongs
One cup of steaming hot water
Procedure:
1. Cut off the flaps of the cardboard box top
2. Position the box so that the opening makes one "side" of the box, and the top is a long-side of
cardboard.
3. In one short end of the box cut a door that can be opened and closed.
4. Position the chimney lamps about an inch from the two short edges of the box top.
5. Trace a snug circle on the cardboard around the bottom of each chimney lamp.
6. Cut out the circles and fit a chimney lamp into each.
7. Seal around the chimney lamps with transparent tape.
8. Use the plastic wrap to cover the front of the box; seal it well to the cardboard using the
transparent tape.
9. With tongs, carefully put the cup of steaming hot water in the box under one lamp chimney.
Shut the cardboard door.
10. Hold the smoking incense, with the smoking end right at the opening of the other lamp
chimney.
11. What happens to the incense smoke?
Please note: If the inside of the box is painted black, the smoke may be more visible. Be sure to
stay very still while observing the smoke in the box; any drafts will interfere with the convective
currents.
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Explanation: This is called a convection box.
When hot water is
placed under a lamp chimney, it will heat air that will then rise.
Thus, the air outside the box will be drawn down to replace the air that is rising
out of the box. The smoke from the incense shows the convection current.
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Day 8 - Convection in the Oceans
Concepts: Oceans are never still; the Coriolis Effect, the gravitational pull of the moon,
surface winds, variations in salinity and water temperature all play a part in the continuous
motion of ocean water. There are areas of warm water and areas of cool water in the oceans,
indicating that convection is taking place. The most dense water in the oceans is found at the
poles, where cold, salty water sinks to the bottom of the sea; because the world is not still this
water starts to flow towards equator. As it moves, surface currents (including the Gulf Stream)
move warmer, fresher water in to take the place of the sinking more salty, cold water. This "global
conveyor belt," takes about 1,000 years to complete one cycle.
E. Greenland
Labrador
Alaska
Oyashio
N. Atlantic Drift
N. Pacific
Canary
California
Gulf Stream
Kuroshio
Somali
N. Equatorial
N. Equatorial
N. Equatorial
S.W. Monsoon
Norweigan
Equatorial Counter
Equatorial Counter
S. Equatorial
S. Equatorial
S. Equatorial
Brazil
Agulhas
W. Austrialian
E. Australian
West Wind Drift
West Wind Drift
Peru
Benguela
West Wind Drift
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Convection in the Ocean Activity #1 ____________
Purpose: To discover how salinity affects the density of water.
Materials:
Aluminum pie pan
Small piece of clay
Clear, colorless plastic straw (only clear will work well)
Blue, green and red food coloring
3 600 ml beakers, each filled with 500 ml of water
Salt
Eye droppers, one for each solution
Paper towels for cleanup
Density Currents Worksheet
Blue, green, and red colored pencils
Procedure:
1. Make the salt solutions:
2. "Ocean water:" 500 ml of water with 90 ml of salt. Stir until dissolved and then add 20 drops
of blue food coloring.
3. "Brackish water:" 500 ml of water with 30 ml of salt. Stir until dissolved and then add 20
drops of red food coloring.
4. "Fresh water:" Just 500 ml of water. Add 20 drops of green food coloring.
5. Stick the plastic straw in a square cube of clay. Make sure the straw doesn't quite go through
the bottom of the clay. Pour some tap water into the straw to make sure that it is leak proof.
To empty the straw, pick up the whole assembly.
6. Explain to the students that the difference between the three solutions is just color and
salinity. The students job is to figure out which is the fresh water, brackish water (found at the
mouth of rivers), and ocean water. The students should hypothesize which type of water is the
most dense, least dense, and in between, and why.
7. Using the worksheet provided, have the students document their trials until they have layered
the three liquids successfully. To test the liquids, the students should drop about 10-15 drops of
the first color they plan to use slowly down the straw with an eye dropper - it works best to tip
the straw slightly. Repeat the procedure with the second and third color. If the liquids mix, the
students should start over with a new trial. If they layer perfectly on the first trial, have them
try different orders to compare the difference. After each trial the straw should be emptied into
the pie pan.
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1. Hypothesize which type of water (ocean, fresh and brackish) is the most dense and
why?_________________________
Least dense:___________________
Middle:_______________________
2.
3. When the three colors layered which was on the
Top?__________________Middle?___________________Bottom?________________
4. Now label the fresh water, brackish water and ocean water.
Explain why they are layered as they are.
5. Experiment with making a density current in the straw.
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Explanation: Density is mass divided by volume. In this activity we used the same
volume of solution each time, but since there is a different mass of salt dissolved in each solution,
the density of the solutions are different. More salt was dissolved in the ocean (blue) water
making it the most dense of the three. Less salt was dissolved in the brackish (red) water. No
salt was dissolved in the fresh (green) water, making it the least dense of the three. When
layered ocean, brackish, fresh -- with ocean on the bottom -- the layers stayed distinct. Density
currents are visible if a more dense solution is added after a less dense solution (for example,
ocean after fresh).
Convection in the Ocean Activity #2 ____________
Purpose: To observe how changes in water temperature cause convection currents.
Materials:
Blue ice cubes (made ahead of time with blue food coloring)
One clear, colorless plastic container (about shoebox size)
Red food coloring warmed
Note: To warm put container of food coloring in a cup of hot - not boiling - water.
Blue and red colored pencils
Index cards
Procedure:
1. Fill the container two-thirds full of room temperature water. Make sure the water is completely
still before proceeding.
2. Place a blue ice cube at one end of the plastic container.
3. Add two drops of the warmed red food coloring at the other end of the container.
5. Observe, and use the blue and red pencils to illustrate, on the index card, what you see
happening .
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Explanation:
Convection is apparent as the
blue (cold) water sinks, and the red (warm) water rises,
or stays higher. If this cold water was also salty (like sea
water at the poles) can you see that it would be even
more dense?!
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Day 9 - Convection in the Sun and
Earth's Mantle
Concepts:
We think of the earth as a solid, but really the solid crust is riding on top of
the earth's mantle. The mantle is a viscoelastic fluid, like Silly Putty®. If you hit Silly Putty® with
a hammer, it breaks like a rock. If you slowly pull Silly Putty®, it will stretch. If you leave Silly
Putty® hanging slightly over the edge of a table, it will slowly flow downward.
The solid crust is mostly granitic and basaltic rock which "floats" on the more dense molten iron
and magnesium rocks of the mantle. Beneath the mantle is the extremely hot core with
temperatures greater than 6,000 degrees Celsius. The Earth's crust is not one solid piece of
rock, but is made up of what scientists call plates. These plates are not stationary. It is their
movement and resulting seismic activity that indicates convection currents in the Earth's
mantle. Convection also occurs in the Sun which is made up of a fluid called gas plasma. There is a
layer of the sun called the Convective Zone.
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Convection in the Earth’s Mantle Activity ____________
Purpose: To simulate convection in the Earth's mantle. Keep in mind convection in the
Earth's mantle occurs VERY slowly - over millions of years!
Materials:
Piece of paper
Four Styrofoam cups
Hot and cold water
Food coloring (any color)
Eye dropper
Clear plastic plant saucer
(8-10 inches. Ridges that are concentric circles won't work; radial rides are okay.)
Procedure:
1. Place three Styrofoam cups upside down on a piece of paper.
2. Put the plastic saucer on top of the cups. The cups should be evenly spaced near the outer
edge of the saucer.
3. Fill the plastic saucer 3/4 full with room temperature water. Wait until the water is perfectly
still before proceeding. The water should remain motionless throughout the experiment.
4. Fill the eyedropper with a few drops of food coloring.
5. Release the color in the water right at the bottom of the plastic saucer.
6. Slowly remove the dropper, being careful not to stir the water.
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7. Observe and record what the color does
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8. Dump out the water in the saucer and repeat steps 2 through 7 with the following
variation: Place a totally full cup of hot water under the center of the plastic saucer,
and then add a few drops of color in the water right at the bottom of the plastic saucer.
Explanation:
The hot water causes the food
color to warm and move upward
through the liquid, simulating the
convection current in the
Earth's mantle.
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Day 1O - Wrap-up
Assessment: Hot air balloons have been prominent throughout the television series,
and in this activity guide. Clearly convection enables hot air balloons to work. On this
Assessment Worksheet label what is enabling the "Balloon on the Rise" to go up, and what is
enabling the "Balloon on its Way Down" to sink. Consider the temperature and density of the air
inside the balloon; consider air pressure inside the balloon; and consider the buoyancy of the
balloon. How do these things change in relation to the air outside of the balloon as the balloon
goes up, and as the balloon sinks?
“Balloon on the Rise”
“Balloon on its way Down”
CONGRATULATIONS!
You've now made the convection connection!!
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notes