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

The short answer is that the water molecules that leave the liquid into the gas (the vaporized molecules) are the ones with the most energy (that’s why they are able to escape the liquid). You take the most energetic molecules out, and the remaining molecules are on average less energetic (i.e. colder).