Materials
- 5 sheets of tissue paper per student or group
- one glue stick per student
- markers for decorating (optional)
- dry fuel tablets
- 2′ tall stove pipe
- 3 hair dryers (alternate material to replace fuel tablets and stove pipe)
- scissors
Procedure
- Have students pick out five sheets of tissue paper and a glue stick. It is best if students work in groups of two or three.
- Have students lay the first sheet of tissue paper on a clean flat surface and apply a solid line of glue stick to one of the long edges of the tissue paper
- Immediately have students place their next sheet of tissue paper on top of the line of glue so that the two sheets overlap about ¾”.
- Continue this process until you have one large sheet made up of four sheets of tissue paper glued long side to long side as shown in the diagram below.
- Then glue the short end of the fifth sheet to the top of first sheet, short side to short side as shown in the diagram below.
- Glue edge one to edge two with about ¾” overlap so that the tissue paper forms a box shape that is open on both ends.
- Cover the top edge of the box with the fifth sheet of the tissue paper, gluing heavily around the edge and covering over top of the box to form a seal with no leaks. The bottom of the hot air balloon should remain open.
- Have student decorate their balloon if they wish, being careful not to rip the balloon. Even the smallest hole may cause the balloon not to fly.
- Take the balloons outside and have the students hold the bottom edge of the balloon over the heat source. Have student be careful not to touch the heat source, or allow the tissue paper to touch the heat source as the tissue paper might catch on fire. Be ready to extinguish any fires by having water and an extinguisher ready.
- After the inside of the balloon has heated up, have the students count down from three and all let go of the balloon. On a good day the balloons with fly three stories high before losing their air and coming back down.
SAFETY PRECAUTIONS
Make sure that students do not run after the balloon, especially younger children will be looking up and not in front of them and my trip or bash into other students doing the same.
Make sure that students do not try to have the balloons land over their heads, even when the balloon is falling, the air inside the balloon can be very warm
Explanation
As the air inside the balloon is replaced by the hotter air from the fuel tablet or hair dryer, the density of air inside the balloon becomes less dense then the air outside the balloon. Since warm air rises, the air attempts to rise, thus pushing the balloon upward until the air inside the balloon cools down.
This can also be looked at in terms of buoyancy. The buoyant force needs to be greater than the gravitational force of the balloon in order for the balloon to rise. The density of the balloon changes when the air in the balloon heats up. When the weight of air that the balloon displaces is equal in weight to the amount of gravitational force on the balloon and the air inside the balloon, the balloon will begin to float.
Reinforcement Activities
It is often difficult to get the balloons to launch correctly and it takes up class time to have the students build the balloons. There is a simpler, easier, more durable way to perform this experiment, by buying the pre-made kit listed below.
A similar and quite amazing activity is the Giant Solar Bag. This 50 foot bag when filled with air will magically rise off the ground if placed in a direct sunlight and allowed to heat up. This is a very impressive and inexpensive demonstration that illustrates the same concepts above.
Related Products
- Hot Air Balloon Kits (12′, 9′ and 6′ models available)
- Dry Fuel Tablets
- Giant Solar Bag
- 45M Thick Braided Cord for Solar Bag
