What is evaporation? Why does evaporation cause cooling?
The process in which a liquid changes into its vapour state at a temperature below the boiling point is called evaporation. Evaporation is an endothermic process i.e., the liquid absorbs heat during evaporation. This heat may be provided either by the surrounding or by the liquid itself. When the evaporating liquid takes the required heat from other parts of the liquid, the rest of the liquid cools down. On the other hand, if the liquid takes heat from the surroundings, it causes cooling of the surroundings. For example, on a hot day (sunny day) we perspire. When this sweat evaporates, it absorbs the required heat from our body, and we feel cool.
