Convection Connection Project

University of Colorado at Boulder

Department of PhysicsDr. Michael Dubson, Faculty

(Featured Scientist and Activity Guide Scientific Advisor)

Cooperative Institute for Research in Environmental SciencesDr. Alex Weaver, Director, K-12 Outreach Program

(Featured Scientist and Activity Guide Scientific Advisor)

Program in Atmospheric and Oceanic SciencesScott Kittelman, Faculty

(Technical Support)

Department of University CommunicationsBobbi Barrow, Executive Director

Monteith Mitchell, Project ManagerWynn Martens, Community Affairs, DirectorDirk Martin, Broadcast Services Coordinator

Science DiscoveryCarol McLaren, Director

(Project Advisor and Activity Guide Consulting Editor)Tara Chace, Special Projects Coordinator

(Activity Guide Editor)

Check out the Convection Connection websitehttp://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 ConnectionActivity Guide

Day 1 - Overview Take a good look at the

Convection Connection poster (pictured inblack and white on the cover of this guide)! Hot air

balloons and floating raisins, lava lamps and whales, palmtrees 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, atmosphereand even the earth's mantle and sun. Convection explains many phenomena inthe environment, and can be demonstrated in myriad fun experiments, someof which are included in this activity guide.

So join us as we consider the density of fluids - air, water, and moltenrock - and how density relates to convection; it should prove to be an

exciting journey of learning!

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Day 2 - DensityConcepts: Density is mass divided by volume. More mass in a space makes for a moredense object. Imagine three cubes of the same size: one is granite, one is wood, and one isstyrofoam. The granite has more mass, and is the most dense; the wood does not have as muchmass, and is not as dense; and the styrofoam, with the least mass, is the least dense of thethree cubes.

Fluids also have different densities. Imagine a cup of plain water. If we dissolve one tablespoon ofsalt in the water, we still have the same volume -- one cup of fluid -- but the cup of fluid now hasmore mass, because there are more molecules (salt and water) packed into the cup than therewere when we just had water in the cup. A cup of salt water is more dense than a cup of plainwater.

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Density Activity

Purpose: To observe density of fluids and solids together

Materials:Dark-colored pancake syrupBlue food coloringWaterVegetable oil600 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.

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Explanation: The liquids layer because they have differentdensities. A liquid that is more dense can hold up a liquid that isless dense. The oil is less dense than the syrup so it floats on topof the syrup. The water is also less dense than the syrup, but it ismore dense than the oil, so the oil floats on top of the water whichfloats on top of the syrup. Solid objects have different densitiesas well.

By observing where the solids float you can tellwhether they are more or less dense than thevarious liquids, and each other.

Day 3 - HeatConcepts: A fluid is anything that can flow, such as a liquid (water), a gas (air), andmolten rock. All fluids are made up of free flowing molecules. As the temperature of a fluidincreases, molecules move faster, bouncing off each other more vigorously, and thus movingfurther apart from one another. As more space is created between the molecules -- there arefewer molecules in a given volume -- the fluid becomes less dense. Likewise, as the temperature ofthe fluid decreases, molecules move more slowly, and become closer to one another. When there isless space between the molecules -there are more molecules in a given volume -- the fluid becomesmore 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 droppersPaper and pencilHot waterCold water

Procedure: 1. Fill one glass half full with very cold water, and one halffull with very hot (not boiling)2. Draw about 4 drops of blue food coloring into oneeyedropper, and 4 drops of red food coloring into theother eyedropper. Try to have the same amount in each.3. Hold the blue dropper over the cold water, and the redover the hot water near the surface of the water, but nottouching 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 morerapidly in one glass than the other? If so, what was the temperature in that glassin relation to the other glass? PAGE

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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 waterRed food coloringBlue food coloringStir stick2 thin stiff clear plastic squares that will cover the opening of the jarsShallow baking pans or pie pans to catch spills

Procedure:1. Place the four jars in the shallow pan. Fill two with hotwater, and fill two with cold water. Fill the jars to thebrim - the very top! 2. Place a drop or two of red food coloring in the twojars with hot water. Stir. Place a drop or two of bluefood coloring in the two jars with cold water. Stir.3. Place one plastic square on a hot water jar, and flip itover (carefully holding the middle of the plastic). Placeit on top of a cold water jar. Place one plastic square ona cold water jar, and flip it over (carefully holding themiddle 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 ofpressure to the top jar, slide the plastic out from between the two jars. Do the same to theother set of jars.5. What happens in each pair of jars?

Explanation: When the cold water is in the top jar, the cold water sinksdown, displacing the hot water. This happens because the cold water is more densethan 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 hotwater remains on top of the cold water. This happens because the hot water is lessdense than the cold water, allowing it to remain at the top of the column of liquid.

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Day 4 - Air PressureConcepts: Air exerts pressure on whatever it touches.

The Earth is surrounded by an atmosphere which is about 80 miles thick. All this air produces apressure of about 14.7 pounds per square inch at sea level. This pressure is called atmosphericpressure, and everything on Earth experiences this pressure - including you! An empty can doesnot collapse, because there is air inside as well as outside of the can. But if the air inside the canis 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 thetemperature is increased, the speed of the air molecules increases, as does the pressure. If thetemperature is decreased, the air pressure also decreases.

Air Pressure Activity ____________

Purpose: To see the effects of air pressure

Materials:2 Empty aluminum soda cansWaterHot platePan with about 1 1/2" of cold waterSafety gogglesTongs

Procedure:Trial #11. 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 canwith tongs, and quickly turn it upside down in the pan with cold water.4. What do you observe?Trial #21. 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 sodacan with tongs, and quickly turn it upside down in the pan with cold water.BE VERY CAREFUL TO KEEP HANDS AND FACE AWAY FROM THE STEAM!4. What do you observe?

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Day 5 - BuoyancyConcepts: Whether something sinks or floats depends on its density relative to thedensity of the surrounding medium. The ability to float is called buoyancy, and there are differentdegrees of buoyancy. For example: a solid block of granite sinks in water because granite is moredense than water - it is not buoyant in water; a helium balloon floats on air because the ballooncontaining 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 jarAbout 25 raisins (2 oz. Box)2 cups of water1/4 cup vinegar1 teaspoon baking soda

Procedure:1. Put the raisins into a container of water and removeany that float. Put those back in the box.2. Pour out the water, and set the raisins that didn'tfloat aside for the next steps.3. Put 2 cups of water and 1/4 cup of vinegar in thelarge jar4. 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 theforce of gravity pulling them down is greater than theupward buoyant force exerted by the liquid. The gasbubbles act like tiny balloons that make the raisinslight 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 - ConvectionConcepts:Convection is the transfer ofheat by the movement of asubstance from one positionto another. Convection canbe forced, such as occurs inthe heating systems ofmany houses, or natural,such as occurs in thetransfer of heat in fluids -air, water and molten rock --due to density differences.A hot air balloon is awonderful place to "see"convection due todifferences in the density ofair. As the lowest layer ofair in the balloon is heated, itbecomes less dense andrises. As that layer nearsthe top of the balloon it hasbecome cooler than the layernow being heated, and thussinks, becomes heated andrises again. This process iscalled convection. The overalltemperature of the air in theballoon increases, andeventually makes the balloonbuoyant (less dense thanthe air around it), and itrises 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 patternTissue paper (16 sheets, 24" x 30", various colors except black)Cutting patternPins (about 6 per balloon)Scissors (2)Rubber cement or glue sticks (2)Fishing line for tether (50 foot roll) - optionalWire (24", 16 gauge, or use pipe cleaners)Wire cuttersDryer 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 orrubber cement to glue the 2 pieces together along the 24" edge. Repeat using 16 pieces oftissue paper. You will have a total of 8 long panels. Be creative with colors. Plan how your balloonwill 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 thetissue paper.5. Cut out the tissue paper along the pattern. Carefully remove the pins and the pattern and savethem. 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.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 ofpanel 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 circle7. Lay the balloon flat again. Cut a circle of tissue to cover the top opening and glue it over the tophole in the balloon.8. To hold the bottom of the balloon open: Form the wire or the pipe cleaner into a circle the sizeof the bottom opening; gently open the bottom edge of the balloon and position the wire on theinside 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 newones! 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 acouple of students, WITH A TEACHER, help to hold the balloon over the dryer duct. Turn on thestove and allow the balloon to fill with hot air. When the balloon begins to feel warm, and as if it canfloat, it is ready to be launched. Count down, give it a gentle push and WATCH IT FLY!!

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Important Safety Note: An adult shouldbe in control of the stove and the hotdryer duct. Use hot pads if you musthandle the dryer duct after it has beenheated.

Explanation: Again, it's all aboutconvection! Convection occurs in theballoon as the warm air rises and thecooler air sinks. The balloon fills with airthat is warmer than the air surroundingthe balloon, and as it does so the balloonbecomes less dense than the surroundingair. The balloon will stay afloat as long asthe air in the balloon stays warmer (lessdense) than the air around it.

Day 7 - Convection in theAtmosphereConcepts: We expect that convection occurs in the atmosphere because air is a fluid -- airmolecules are free to move -- and because there are areas of warm air and areas of cool air. Cloudsare visible proof of convection: hot moist air rises; eventually it cools down and condenses (waterdroplets form). The clouds we see are these tiny water droplets. A thunderstorm, also called aconvective 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 warmair is forced to rise quickly by an approaching (sinking) cold front. A strong persistent updraft ofwarm, moist air is formed. The approaching cold front helps build the updraft into a cumuluscloud, which eventually builds into a cumulonimbus cloud up above 30,000 feet. Then a downdraftforms 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)PencilScissors or sharp knife for cutting cardboardWide transparent tape (package tape works well)Transparent plastic wrapMatchesIncense to produce smokeTongsOne cup of steaming hot water

Procedure:1. Cut off the flaps of the cardboard box top2. Position the box so that the opening makes one "side" of the box, and the top is a long-side ofcardboard.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 thetransparent 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 lampchimney.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 tostay very still while observing the smoke in the box; any drafts will interfere with the convectivecurrents.

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Explanation: This is called a convection box. When hot water isplaced 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 risingout of the box. The smoke from the incense shows the convection current.

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Day 8 - Convection in the OceansConcepts: 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 continuousmotion 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 thepoles, where cold, salty water sinks to the bottom of the sea; because the world is not still thiswater 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 "globalconveyor belt," takes about 1,000 years to complete one cycle.

E. Greenland

Norweigan

N. Atlantic Drift

Gulf Stream

Canary

N. Equatorial

Brazil

Benguela

West Wind DriftWest Wind Drift

West Wind Drift

Peru

S. Equatorial

E. Australian

Equatorial Counter

N. Equatorial

California

N. Pacific

AlaskaOyashio

Kuroshio

N. Equatorial

S. Equatorial

Agulhas

W. Austrialian

S.W. Monsoon Equatorial Counter

S. Equatorial

Labrador

Somali

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Convection in the Ocean Activity #1 ____________

Purpose: To discover how salinity affects the density of water.

Materials:Aluminum pie panSmall piece of clayClear, colorless plastic straw (only clear will work well)Blue, green and red food coloring3 600 ml beakers, each filled with 500 ml of waterSaltEye droppers, one for each solutionPaper towels for cleanupDensity 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 dropsof blue food coloring.3. "Brackish water:" 500 ml of water with 30 ml of salt. Stir until dissolved and then add 20drops 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 throughthe 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 andsalinity. The students job is to figure out which is the fresh water, brackish water (found at themouth of rivers), and ocean water. The students should hypothesize which type of water is themost dense, least dense, and in between, and why.7. Using the worksheet provided, have the students document their trials until they have layeredthe three liquids successfully. To test the liquids, the students should drop about 10-15 drops ofthe first color they plan to use slowly down the straw with an eye dropper - it works best to tipthe straw slightly. Repeat the procedure with the second and third color. If the liquids mix, thestudents should start over with a new trial. If they layer perfectly on the first trial, have themtry different orders to compare the difference. After each trial the straw should be emptied intothe 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 samevolume 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) watermaking it the most dense of the three. Less salt was dissolved in the brackish (red) water. Nosalt was dissolved in the fresh (green) water, making it the least dense of the three. Whenlayered ocean, brackish, fresh -- with ocean on the bottom -- the layers stayed distinct. Densitycurrents 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 warmedNote: To warm put container of food coloring in a cup of hot - not boiling - water.Blue and red colored pencilsIndex cards

Procedure:1. Fill the container two-thirds full of room temperature water. Make sure the water is completelystill 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 seehappening .

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Explanation: Convection is apparent as theblue (cold) water sinks, and the red (warm) water rises,or stays higher. If this cold water was also salty (like seawater at the poles) can you see that it would be evenmore dense?!

Day 9 - Convection in the Sun andEarth's MantleConcepts: We think of the earth as a solid, but really the solid crust is riding on top ofthe earth's mantle. The mantle is a viscoelastic fluid, like Silly Putty®. If you hit Silly Putty® witha hammer, it breaks like a rock. If you slowly pull Silly Putty®, it will stretch. If you leave SillyPutty® 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 ironand magnesium rocks of the mantle. Beneath the mantle is the extremely hot core withtemperatures greater than 6,000 degrees Celsius. The Earth's crust is not one solid piece ofrock, but is made up of what scientists call plates. These plates are not stationary. It is theirmovement and resulting seismic activity that indicates convection currents in the Earth'smantle. Convection also occurs in the Sun which is made up of a fluid called gas plasma. There is alayer 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 theEarth's mantle occurs VERY slowly - over millions of years!

Materials:Piece of paper Four Styrofoam cupsHot and cold water Food coloring (any color)Eye dropperClear 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 outeredge of the saucer.3. Fill the plastic saucer 3/4 full with room temperature water. Wait until the water is perfectlystill 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.7. Observe and record what the color does PAGE

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8. Dump out the water in the saucer and repeat steps 2 through 7 with the followingvariation: 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.

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Explanation:The hot wa ter causes the food

color to warm and move upwa rdthrough the liquid, simulating the

co n ve ction current in theEarth's mantle.

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You've now made the convection connection!!

“Balloon on the Rise” “Balloon on its way Down”

Day 1O - Wrap-upAssessment: Hot air balloons have been prominent throughout the television series,and in this activity guide. Clearly convection enables hot air balloons to work. On thisAssessment Worksheet label what is enabling the "Balloon on the Rise" to go up, and what isenabling the "Balloon on its Way Down" to sink. Consider the temperature and density of the airinside the balloon; consider air pressure inside the balloon; and consider the buoyancy of theballoon. How do these things change in relation to the air outside of the balloon as the balloongoes up, and as the balloon sinks?

notes