If you have ever been hard at work, trying to keep sweat from dripping into your eyes or onto your work, you might have wondered why we have to sweat.
To find out, you will need:
- your hand
- water
- rubbing alcohol
- cooking oil
First, blow on the back of your hand. Notice how it feels. Now, dip a finger in some water and rub it across the back of your hand to wet it. Blow on your hand again. Do you notice a difference? You should notice that it is cooler. Dry the back of your hand and try the experiment again, this time with rubbing alcohol instead of the water. Notice the temperature change when you blow on it. Dry your hand and try it once more, this time with cooking oil. Again, blow and notice the temperature sensation.
What did you discover? When you blew on the wet skin, it felt cooler than dry skin. When you blew on the skin with alcohol, it was much cooler. When you blew on the skin with oil, you did not notice much of a difference from dry skin. The cooling sensation is due to evaporation. As a liquid evaporates, it absorbs heat from its surroundings. This produces a cooling sensation on your skin. The faster the liquid evaporates; the cooler it feels. Since the oil does not evaporate, it does not produce a cooling sensation.
What does this have to do with sweating? When you get hot, you sweat. As the perspiration evaporates, it cools your skin. The humidity already in the air also has an impact on how fast water evaporates. High humidity causes perspiration to evaporate more slowly, causing you to feel hot and sticky. Low humidity lets the moisture evaporate quickly, leaving you feeling cooler and dry, leading people to say that the American southwest is more comfortable because "it's a dry heat."
Have a wonder-filled week.
