Atmospheric Pressure
Properties of Matter

Impossible Straws

Enrichment Activity for 5-11 11-14


What you need

  • Three straws
  • A glass of drinking water
  • A drawing pin (for making a small hole in one of the straws)

Instructions

  1. Bet your friend that they can't suck up any of the water with two straws in their mouth
  2. The catch is that they have to have one straw outside of the glass, and one inside. What happens?
  3. Make a small hole 3 cm from the top of the other straw
  4. What happens when your friend tries to suck water using just this straw?

Results and Explanation

It's impossible to suck water through the straws. In order for the water to be forced into your mouth, the pressure outside your mouth (atmospheric pressure) needs to be greater than the pressure inside. This means that no matter how you suck, a straw won't work if air can get into your mouth.

These experiments have not been specifically safety tested for home use but we believe them to be safe if the instructions are followed. Adult supervision or direction is recommended as appropriate. All experiments are carried out at your own risk.

Atmospheric Pressure
is a special case of Pressure
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