Why does evaporation cause cooling

Evaporation causes cooling because the process requires energy, which it takes from its surroundings. This phenomenon is known as evaporative cooling.

Here’s the step-by-step reason:

1. Energy Requirement: To change from a liquid to a gas, a water molecule must gain a specific amount of energy, called the latent heat of vaporization.
2. "Hottest" Molecules Leave: Within any liquid, molecules are moving at different speeds (different kinetic energies). The molecules with the highest kinetic energy (the "hottest" ones) are the first to gain enough energy to break their bonds and escape from the surface as vapor.
3. Energy Taken from Surroundings: These escaping molecules take this energy (heat) from their immediate environment. This environment can be the remaining liquid, the surface they are on, or the surrounding air.
4. Average Energy Drops: Since the most energetic molecules have left, the average kinetic energy of the molecules that remain in the liquid decreases.
5. Cooling Sensation: Temperature is a measure of the average kinetic energy of molecules. Because the average energy has dropped, the temperature of the remaining liquid (or the surface) also drops, which we feel as cooling.

A common example is sweating: when sweat evaporates from your skin, it draws heat from your body, which cools you down.