Anti-Gravity Water

The upside-down glass of water.

 

 

 

Category - Solids, Liquids & Gases

Key Idea - Air Pressure

 

Purpose - This shows the forces pushing down on us all the time under the weight of the air above us.
Nature -  Demonstration
Materials -  drinking glass, drink coaster (a rubber one works best), water
Method - 
  1. Fill the drinking glass with water and place the coaster on top of the glass.
  2. Hold the drink coaster against the mouth of the glass and turn the whole thing upside down.
  3. Carefully let go of the drink coaster and note what happens.
Safety - If not done carefully you might get wet. 
Explanation -

Air is pushing down on everything due to the effect of gravity.  This pressure pushes against the the coaster holding it back against the weight of the water.

Another way to think about it is this.  If the water was to fall out as one "lump" then it would keep the glass sealed as it fell creating a vacuum.  So the suction of this potential vacuum keeps the water in.  
Notes - It may be best to first try this over a sink or outside.