Why does water vaporazing from a surface cools it?

Question

I’ve read that when someone is having a heat stroke just making them wet isn’t enough, you have to ventilate them so the water vaporazes, cooling them. But why does water vaporizing cools something?

In: 1

Answer 1

When water vaporizes it takes energy – in this case, heat – from the surface it’s evaporating from. When this happens, the temperature of the surface decreases, thus cooling it. In the case of a heat stroke, it cools the affected person’s body when the water vaporizes from their skin.