Exhibit Models Vapor Pressure and Energy Transfer Demonstration
	In this demonstration an airtight jar 75% full of water is evacuated before hand. The jar is heated to a safely hot temperature. The visitor is asked what they think will happen when ice is placed on the jar lid. Most correctly deduce the ice will melt. The visitor is then asked to "do the experiment" and place the ice on the jar to see what happens. The ice causes the pressure to drop inside the jar and the water begins to boil. How can ice make water boil? Doesn't water boil when it is heated, not cooled? Energy is going out of the water and melting the ice on the lid. The cool lid provides a place for the water vapor to condense, causing drops to fall down (observe). Contact us Back to home page Copyright Phil Rossoni 12/2004