1. Fill container 2/3 full with room temperature water.

2. Let the water sit for 30 seconds until completely still.

3. Place a blue ice cube at one end of the plastic container.

4. Add two drops of red food coloring to the water at the opposite end of the plastic container. Be careful not to disturb the water.

5. Observe where the red and blue food coloring goes.

6. Using the red and blue pencils draw what you see happening.

What's happenin'?

It's all about convection! The cold water sinks while the warmer red water rises, or stays higher than the blue. Convection is the action of warm air rising and cold air sinking. You probably guessed that the blue water represents a cold air mass and the red water represents the warm, unstable air mass. A thunderstorm is caused by unstable air and convection plays an important part. A body of warm air is forced to rise by an approaching cold front. Other things can cause warm air to rise, like a mountain slope. 

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A strong, persistent updraft of warm moist air is formed and lifted by the approaching cold front. Speeds in an updraft can be as fast as 90 miles per hour! The air cools as it rises, condenses, and forms cumulus clouds. When condensation occurs, heat is released and helps the thunderstorm grow.

The cumulus cloud has grown into a cumulonimbus cloud at above about 30,000 feet (about 9 km).

At some point, condensation high in the cloud (now in the form of water droplets and ice) falls to the ground as rain. A cold downdraft forms as the rain falls.

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Activity #2: Make it rain!
Stuff you need

Large, wide-mouth container, such as a mayonnaise jar

Hot water

Ice cubes   

Small plate to hold ice cubes

Index cards   

 

Make it happen

1. Pour two inches of very hot tap water into the glass container and cover with the dish. Allow to sit for a few  minutes.

2. Place ice cubes on plate.

3. Watch what happens.

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Think about it 

How does this relate to the formation of the thundercloud in Activity 1?

What's happenin'?

The cold plate caused the moisture in the warm air to condense and form water droplets. This is the same thing that happens in the atmosphere as warm, moist air rises and meets colder temperatures high in the atmosphere. Water vapor condenses and forms precipitation that falls to the earth.

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Activity #3: Make a hot air balloon!
Stuff you need

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

Propane stove and chimney apparatus

Flight data sheet

Tag with name and address - optional

Make it happen

1. Using the tissue balloon pattern instructions, draw and cut out a pattern and set it aside.

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.   Repeat for 7 more panels (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. To glue the tissue panels together to make the balloon:

Take 2 panels off the stack. (Panels 1 and 2) Place them together so one side of the bottom panel extends 1" past the edge of the top panel. Fold that 1" margin over the edge of the top sheet and glue it along the edge of the top sheet.

Glue the next panel (3) to the bottom panel (2) in the same way, except along the opposite edge.

Continue glueing the panels together on opposite edges. When all are glued together it will be in one long line, folded like a fan. Check that the panels are folded this way, but don't open it up yet.

Glue the first and last panels together as you did the other panels along their unglued sides.

7. Lay the balloon flat. 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:

a. Form the wire or the pipe cleaner into a circle the size of the bottom opening
b. Gently open the bottom edge of the balloon, position the wire on the inside about one inch up from the edge
c. Fold the tissue over the wire and glue in place

9. Gently open the finished balloon and check for large holes. (Be careful not to make any new ones!) Patch them with pieces of tissue paper cut to fit. Small holes are ok. They won't keep the balloon from flying. If desired, attach the tether line and name and address tag.

10. To launch the balloon, hold the bottom, open end of the balloon over the hot stove and allow it to fill with hot air. When the balloon begins to float, give it a gentle push and WATCH IT FLY!!

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What's happenin'?

Again, it's all about convection! The cold air is more dense and sinks while the warmer, less dense air in the balloon rises. Convection is the action of warm air rising and cold air sinking. The balloon will stay afloat as long as the air in the balloon stays warmer than the air around it.