Convection is the transfer of heat by the movement or flow of a substance from one position to another.

Make a hot air balloon!

The purpose of this experiment is to observe convection.

Tissue paper (16 sheets, 24" x 30", various colors except black)

Cutting pattern

Straight 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

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 five foot long panel and use the glue stick or rubber cement to glue the two pieces together. Repeat for seven more panels. You should finish this stepwith eight 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: Take two 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 to glue the panels together on opposite edges. When all are glued together they will be in one long line, folded like a fan. Check that the panels are folded this way, but don't open them 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 and position the wire on the inside about one inch up from the edge.
c. Fold the tissue over the wire and glue it 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 a name and address tag to the balloon.

10. To launch the balloon, go outdoors. Hold the bottom (open end) of the balloon over the hot air rising from a burning camp stove and allow the balloon to fill with hot air. When the balloon begins to float, give it a gentle push, and WATCH IT FLY!!

Hot air is not as dense as cool air. That makes a parcel of warm air rise. See the "Ingredients of Weather" to see why this is true.

Which time of day would this activity like work better?

The coolest time of day, probably morning, is best. This allows there to be a big difference between the air temperature and the temperature of the air inside the balloon and the air around it. The balloon will rise faster this way.

What season is best?

Well, this depends on where you live. Why don't you think up a good answer to this question yourself?

If your balloon didn't fly well, what do you think went wrong?

Here are some problems that can occur. Did your balloon leak, so that the hot air escaped from it? Did you not get enough hot air inside the balloon? Was it too windy? Was there not enough difference between the air temperature and the hot air inside the balloon?

If your balloon flew, why did it eventually come down?

The longer the balloon is in the air, the cooler the air inside it becomes. When the air inside the balloon is the same temperature, or cooler, than the air outside, the balloon will come down.

Check out some fun these students had with this project! (You need a way to run "mpeg" video clips on your computer like Microsoft's ActionMovie Player.)

Thanks go out to Bowlus School Supply, Inc., Pittsburg, Kansas; Raven Industries, Inc., Applied Technology Division in Sioux Falls, South Dakota; and to Zimmerman, Presentation at NSTA Regional Convention, Little Rock, Arkansas, November 1988.