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Name: Christine P.
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Age: 10
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Date: 2001 - 2002

How does evaporation work?

The molecules in a liquid or solid are in motion -- they bounce around at different speeds and directions -- some faster, some slower than average. That average depends upon the temperature of the liquid or solid. If the temperature is high enough, some of the molecules near or at the surface will be kicked so hard that they end up in the space above the liquid or solid. There will be other molecules in this space that will collide and move the molecule further from the liquid or solid boundary, or bounce the molecule back into the liquid or solid. The number of molecules in this gas (also called vapor) depends on this average temperature.

If the conditions are correct and the evaporated molecules are swept away somehow the amount of liquid or solid will get smaller as more of the molecules get kicked into the gas space above the surface. That is evaporation.

Vince Calder

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