Staying Cool This Summer

We all know heat, and with summer right around the corner, the only thing most people are thinking of is having fun in the sun. But unfortunately with heat comes sweat. Sweat is the body's natural reaction to a rise in temperature. But have you ever thought about the physics of staying cool?

Sweat happens when there is an increase in the body's temperature. When temperature increases, the molecules in the substance excite. When this happens, the kinetic energy of the substance increases. So, when you cool something down, you lower its average kinetic energy.

So how does sweat cool you off? It works through the evaporation of water. Suppose we have some water at room temperature. This means that the water molecules in this group of water has an average kinetic energy of some value. But not all water molecules are the same. Instead there is a distribution of kinetic energies. Some molecules are moving quite slow and some are moving very fast. It’s possible that these very fast molecules can escape the liquid water and become gas water. What’s left is a water but now with a lower average kinetic energy since the highest KE molecules have evaporated. If this is a bead of sweat on a human, the water will be cooler than the actual skin, helping the human to cool off.