Blowing Bottle

It blows back!

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Purpose -

To show the effects of compressing air.

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 - 

Rig the retort stand to hold the boiling flask in a horizontal position.

Place the Styrofoam ball (or paper) just inside the mouth of the flask.

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.

Apparatus set up ready for blowing bottle

I can’t do it!

Neither can Ariel!