View Single Post
Nugatory
#9
Feb4-13, 01:01 PM
Mentor
P: 3,949
Quote Quote by sgstudent View Post
Oh but could you explain how the particles gain enough energy to evaporate? Since heat transfers from a region of high temperature to a region of low temperature how would it apply to the heat transfer to allow evaporation? I'm having trouble understanding how the heat energy can accumulate at the surface of the liquid.
Heat energy doesn't "accumulate" at the surface of the liquid.

Temperature measures the average speed of the molecules, so even when the temperature is uniform throughout the liquid, some of the molecules are moving a bit faster than average and others a bit slower. At the surface of liquid, if one of the "bit faster" ones happens to moving in an upwards direction, it can escape.

The effect is to slightly cool the surface; the faster-moving molecules are more likely to escape so the average energy of the ones left behind goes down. But as you say... heat moves from areas of high temperature to lower, so as the surface cools, heat flows from the warmer interior of the liquid and eliminates the temperature differential again.