I always assumed the way sweat cooled us was how the water on the outside of our skin cools off and in turn cools the skin down however I don’t get why the air that cools the sweat cant cool our bodies especially if our skin can heat that sweat just as fast or faster than the air can cool it.
In: Biology
Let’s say you have a class of kids with an average grade of B. Most have B. Some have A. Some have C. Now, let’s say all the A kids get moved to some special gifted child class. What’s the class average now? Probably a B-. Did the other kids in the class get dumber? No. The smart ones were just removed, lowering the average.
Temperature is due to the random motion of molecules and atoms. Basically, the higher their average motion, the higher the temperature.
Your skin is a solid. You can only cool when air molecules hit you and fly away from the collision with more energy than they came in with. This carries away your thermal energy, cooling you. This does happen, as you are colder that the air, so the average collision gives energy to the air. But it not very fast at moving this heat. Air is not very dense, and the rare collisions don’t take that much energy.
Water is a liquid that is quite volatile, that is it evaporates easily. It’s the same temperature as you on your skin, and this corresponds to a certain average energy for the water molecules. Now, this is just an average. Some have more energy, some have less. Now back to water being volatile. Some of the higher energy ones have enough energy to break away from their bonds to other water molecules. They evaporate into a gas.
What does the high energy water molecules leaving mean? Your average dropped. Just like the A kids leaving, the most energetic water molecules leaving leaves a lower average behind, that is cooler. Ypur body then transfer heat to this now colder water, cooling you. And water is dense as a liquid, and a lot of energy is lost when the water evaporates, so this is very good at cooling you.
All A/C and fridges work the same. We just do it with some gas other than water that is even more volatile. That is, boils at a colder temperature and evaporates more easily. We then use a compressor to undo it so we can do it again. A/C is sweating in a closed loop.
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