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
short answer: evaporation.
experiment you can try at home: get a dropper or q-tip. then get a cup of water and some rubbing alcohol (higher concentration the better, go with 90%+ vs. 50%). now put a drop of water on the back of your hand or forearm while keeping your hand/forearm very still. note how warm/cool it feels. now note how long it takes to evaporate. repeat with a drop of alcohol. bonus: repeat with a drop of hand sanitizer (main ingredient is ethanol; rubbing alcohol is isopropyl alcohol–similar to each other, but different).
you’ll note the alcohol feels much cooler even though it came from a room temperature bottle.
your sweat works the same way. for molecules of a liquid to make the jump to becoming a gas takes energy. if it’s the drops of water or alcohol as well as sweat, it can get that energy from your skin’s surface. so each little drop takes a bit of energy to jump to being gas molecules (evaporation) and so that spot on your skin cools off just a bit.
repeat this by a larger surface area of sweaty skin and/or add a breeze which helps in that evaporation process and you can really feel that cooling off effect.
another way to visualize it is to put lots of marshmallows on a large shallow baking pan. jiggle them around slowly–not enough to knock them off the pan. that’s kind of like the movement of the molecules in a liquid. if you were to add more shaking, you’d see some marshmallows probably leave the pan. if you jiggle and shake a lot, you’ll see even more marshmallows leave the pan. see? it takes energy for those “molecules” to leave the pan and have enough movement to transition to the “gas phase.”
Latest Answers