4E10.15-Balloon on a Flask


Video: Watch this demo

Instructor’s video

Description: This demonstration shows that the pressure increases as water is heated up and changed to steam.


  • Glass Flask
  • Stopper with balloon on top
  • Bunsen burner and stand
  • Matches

Setup Procedure:

  1. Fill the flask with some water.
  2. Connect the Bunsen burner to the gas valve and make sure it works.
  3. Place the flask on the stand over the Bunsen burner.
  4. When the professor is done, use caution as the apparatus may still be very hot.

Demonstration Procedure:

  1. Note the balloon is not blown up.
  2. Turn on the gas valve and lite the Bunsen burner.
  3. Wait a few minutes until the water starts to change into a gas.
  4. Note that the balloon gets blown up. This happens because the water is changing to a gas and increases the pressure inside the balloon.
  5. Turn off the gas valve before the balloon explodes.
  6. Note that the balloon deflates. This is because the steam is changing back to a liquid and the pressure inside the balloon decreases.

Open Flame Open Flame
Keep away from flammable materials.