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
Sweat doesn’t always cool our bodies- sweating is only effective when equilibrium vapor pressure holds or favors condensation. Basically, if the environmental air is depleted of moisture, when the sweat from your body hits the dry environmental air, the sweat from your body experiences net evaporation. This is because the water vapor molecules have less mass than diatomic oxygen and nitrogen (primary constituents of dry air). In this specific case, a person can be unaware that they’re even sweating and if that person continues physical exertion, it will lead to heat exhaustion because their perspiration is immediately being wicked away from their skin. Now, if a person is sweating and their surrounding environmental air has a water vapor pressure in equilibrium or greater than equilibrium, that person’s sweat will enter an environment where it contains too much water vapor molecules. To try to reach equilibrium vapor pressure, the water vapor in your sweat will condense on your skin, changing phase into liquid water. When water vapor condenses, energy (heat) is released which lowers the temperature of the water molecules on your skin, essentially working to cool you down by releasing heat into the air that surrounds you and simultaneously cooling you in the process.
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