Balloon in a Bottle Experiment

A balloon in a jar
Getty/Matt Meadows

The Balloon in a Bottle Experiment follows up on some of the fun of the Bottle Balloon Blow-Up Experiment, but instead of using a chemical reaction to make changes it shows that using heat to change air pressure inside a bottle can make change the position of a water-filled balloon set on the top of the bottle.  

It’s an experiment that requires precise timing, so it’s better for an older child or one who is happy to just observe.

  

What Your Child Will Learn (or Practice)

  • The power of air pressure

Materials Needed:

  • A large glass jar  
  • A medium-sized balloon
  • Water
  • Facial tissue (Kleenex)
  • A pair of tongs
  • Matches

The Balloon in a Bottle Experiment  

  1. Stretch the neck of the balloon over your kitchen or bathroom faucet. Turn the water just high enough to fill the balloon with enough water to make it a little bigger than the mouth of the jar. Tie off  the balloon.

  2. Use the tongs to pick up a tissue, then use the matches to light it on fire.

  3. Drop the flaming tissue into the jar.

  4. Quickly place the water balloon on top of the jar.  The balloon should sort of dance and will be sucked into the jar.

What’s Going On

At first  the air pressure inside and outside the jar is equal. As the tissue burns in the jar, it heats up the air inside.. The air expands and takes up more room, but can’t get out of the jar because the balloon is blocking its exit route..

As the heated air pushes around the balloon, it makes the balloon “dance” out of the way.

When the fire extinguishes, the air in the jar cools down again. However, the water balloon is still in the way and no new air can get into the jar.  At that point, the air pressure in the jar is lower than the air pressure outside the jar.

The outside air exerts force on the balloon and pushes it into the jar.