Liquids & Vapours
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Evaporation is what happens when a liquid changes into a gas below its boiling point. Evaporation only happens on the surface and happens when some particles have more energy and are able to escape from the surface to form a gas.
There are a few methods to increase the rate of evaporation:
- Increase temperature
- Increase surface area
- Reduce humidity
- Increase wind
Cooling effect of evaporation
Evaporation has a cooling effect because it takes thermal energy away from the surface. This is because the faster particles escape from the liquids surface leaving behind the slower ones, and that the faster ones have more energy, the temperature of the liquid drops.
Using Evaporation
Sweating uses the cooling effect that comes from evaporation. The sweat, which is secreted from pores on the skin, can evaporate very easily. As the sweat evaporates, it takes away thermal energy from the skin to the surrounding air.
Refrigerators also use the cooling effect from evaporation. The process is as follows.