Balloon Bottle

1. Get a medium-sized plastic soda bottle and a party balloon.
2. Puncture a hole in the side of the bottle near the bottom.  It’s easy if you use a nail heated with a match or a candle.
3. Dangle the balloon inside the bottle and open it over the bottle’s lip.  (See photo.)
4. Inflate the balloon inside the bottle.
5. With your mouth still on the bottle, place a finger snugly over the hole in the side.
6. The balloon stays open on it’s own!  Fill it with water from a faucet.
7. Bring it outside, and take your finger off of the hole…

Science! To quote Zap Science (see section “Soda Bottle Science”), we live at the bottom of an ocean of air.  Air pushes in upon everything.  The weight of the atmosphere pushes down and outward on the balloon but, when the hole is covered, there is not much air pushing back.  The pressure of the atmosphere – all the air piled up over your head – is working to hold the balloon open.  When you uncover the hole, you let the atmosphere back in (so to speak) and – splash! – the balloon is free to shrink again.

Stray tips. It’s best if you use a normal rubber party balloon, not a small water balloon.  Also, 1-liter bottles are best.  2-liters tend to fold in on themselves to easily under pressure.