Why when you step out the shower are you extremely cold for about 3 minutes but then you go back to normal temperature?
In: Biology
Our bodies cool by evaporating moisture off our skin, that’s what sweat does. When you step out of the shower you are covered in moisture and experience a lot of evaporation.
This is a little bit couterintuitive, but:
Warm water evaporates faster than cold water, yet pulls enough heat energy from your skin to make you feel colder as it does when it’s cold water. This is because the sensation of freezing or feeling warm isn’t prone to absolute temperature difference between your skin and another medium, but to how fast heat is transferred from your skin to the water. As I said, warm water is much more likely to evaporate and leave. The process of evaporation drags A LOT of energy from your skin really fast. Cold water just sits there and evaporates much slower, as it warms up un your skin, taking less energy in the same time.
OK. So vapor is a higher energy state than liquid. As the water evaporates, it needs to take in energy to go from liquid to vapor. That energy comes in the form of heat, specifically the heat of your body taken from the skin.
Evaporation is part of it, but it’s also because you don’t feel temperatures; you feel *differences* in temperature. When you’re standing around your house in 72° air, you get accustomed to it. Then you get into the shower and you’re surrounded by warm water and warm steam, and you feel that difference as being warm. Then you linger in the shower for a long enough time and get accustomed to it. Then you step back out into that 72° air in the rest of your house, and you feel that difference as being cold.
This is actually a physics question more than biology.
Water’s a liquid. There are a bunch of water molecules jostling around, but they stick to each other which means they tend to stay together as a mass.
Temperature is the average speed of the individual molecules. There are a few molecules that have way above-average speed. They’re moving fast enough to overcome the stickyness and escape into the air.
This process is called “evaporation.”
When only the highest-speed molecules can leave, the average speed of the remaining ones is lower. It’s a mathematical certainty.
So when you come out of the shower, the water on your skin starts evaporating. That makes you cold. Once the water’s mostly turned into gas, the evaporation process is no longer cooling you down.
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