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Evaporation 7,895 views

Teacher/Instructor Matt Jones
Matt Jones

M.Ed., George Washington University
Dept. chair at a high school

Matt is currently the department chair at a high school in San Francisco. In his spare time, Matt enjoys spending time outdoors with his wife and two kids.

Evaporation is the vaporization of liquids at the surface. Evaporation is related to vapor pressure and when the surface of a liquid gets warm, the additional energy is enough for it to vaporize. Evaporation is seen in the water cycle, as water from rains vaporize from the surfaces of bodies of water.

Evaporation, evaporation is known as a phase change meaning we're going from one state of matter to another and in this case we're going from a liquid to a gas but this is only occurring at the surface of the liquid unlike boiling where the entire mass of liquid is converted to gas. This occurs just at the surface, so let's look at, at the Physics in the properties behind evaporation to try to understand it a little better.

So if I've got a liquid here and I've got it's a liquid so I've got molecules in motion and these are all this kinetic energy and there's an average kinetic energy so some of these molecules have a lot of kinetic energy some have a little but when at the surface with a lot of kinetic energy will actually become a gas and leave the liquid and that's what evaporation is but because that one had a lot of kinetic energy left the liquid that means the liquid now has lost some of its kinetic energy and the way we feel that is we feel that as a decrease in temperature its lost some of its energy and this is a principle we call evaporative cooling so when we have a lot of evaporation that energy that's being used to cause it to go from a liquid to a gas because gases have more kinetic energy than liquids that energy is decreasing the average kinetic energy in the liquid which is keeping it cool which is why when we sweat, it helps keep our bodies cool we're converting that kinetic energy from the sweat to a gas and conversely lowering the energy or the temperature of the sweat on our skin helping keep us cool so this is all some of the Physics behind evaporation.