Science project

Floating Balloons


  • Balloon
  • Air conditioner
  • Hot water
  • Towel
  • Notebook
  • Pen


  1. Inflate the balloon using your mouth and tie the end of it.
  2. Turn on the air conditioner. Wait until the room gets fairly chilly.
  3. Wet the towel in the hot water.
  4. Wrap the balloon in the towel for 10 minutes.
  5. Do you this will cause the balloon to float? If so, explain why. Use this time to write down your guess, also called a hypothesis, in your notebook.
  6. Take the towel off of the balloon and release it back into the room.


The balloon should float after you heated it with the wet towel.


Helium-filled balloons float because helium is much less dense than air. This means that a cubic centimeter of helium weighs less than a cubic centimeter of air, allowing a balloon inflated with helium to float on top of the cold, heavier air. Because we used normal air to fill our balloon, the change in temperature is what made our balloon float. Cold air is heavier than hot air because the molecules in cold air are much more densely packed. The warm air in the balloon got pushed up by the cold air we created with our air conditioner.

What if you used different gasses? Or experimented with different temperatures? This experiment can be altered in a variety of ways in order to produce some cool results.

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