Blowing Bottle

It blows back!

 

 

 

Category - Solids, Liquids & Gases

Key Idea - Air Pressure

 

Purpose - To show the effects of compressing air.

Set up, ready to go.

 

I can’t do it.

 

Ariel can’t do it either!
Nature -  Demonstration or Experiment
Materials -  Boiling flask (or soft drink bottle), a small Styrofoam ball a bit smaller than the mouth of the flask (or a small piece of screwed up paper), a retort stand
Method - 
  1. Rig the retort stand to hold the boiling flask in a horizontal position.
  2. Place the Styrofoam ball (or paper) just inside the mouth of the flask.
  3. Challenge members of the class to blow the ball into the flask (with out touching the arrangement). They will find it impossible; in fact the ball actually pops out of the bottle.
Safety - Nil 
Explanation - When you blow into the mouth of the flask you are increasing the air pressure inside compared with the atmospheric pressure outside. This causes the air inside to push outwards blowing the ball with it.
Notes - Students love trying different strengths of blowing or different angles and refuse to believe that it cannot be done.