For this activity you will need the following materials:

  • Wide-necked bottle or jar with an air-tight lid
  • Soda straw
  • Modeling clay
  • Small balloon
  • Thread
  1. Blow the balloon up just enough to fit very loosely in the bottle
  2. Tie a thread around the neck of the balloon so the air will not escape.
  3. Drop the balloon into the bottle.
  4. Punch a hole in the lid and insert the straw; seal the straw with modeling clay.
  5. Screw the lid on the bottle.
  6. Suck some of the air out of the bottle through the straw and clamp your finger over the top of the straw to prevent air from rushing back into the bottle.
  7. The balloon will increase in size because the air inside the balloon expands as the air pressure decreases in the bottle.
A balloon in a sealed jar with a straw sticking through the top of the jar.