Why is it that if we wet our fingers before putting out a candle, we don’t get burned, but if we grab a hot pan out of the oven with a wet oven mitt, we get burned?
In: Physics
So THAT is why I burned my hand 5 minutes ago making pizza. The glove was wet. I didn’t know you get burnt that way. Thanks
A good mental thought experiment that could help with understanding is to ask “How much volume of water will it take to cool down this hot object?” Framing a question like that makes you begin to consider the energy content of the hot object, not necessarily its temperature.
In fact, it is known that the temperature at the hottest part of a candle’s flame can be up to 2,500 °F, yet the flame could be put out by a single drop of water. Hence a wet finger is protected when touching a candle flame. But you can imagine that a hot pan out of the oven will be barely affected by a drop of water. The hot pan has tremendously more energy content than a flaming candle.
Warmth and temperature are not the same thing.
A candle might be a few hundred degrees, but it doesn’t radiate (much) thermal energy. The wet on your hand will be enough to quell that intense – but small- energy source.
But the hot pan, despite having a lower temperature, is larger, and had more thermal energy in its metal/Pyrex structure. That abundance of heat is enough to shluck through a wet mitt through conduction. The heat from the over pan cannot be quelled by a soggy mitt, so instead that thermal energy agitates the water, making it hot, and soon enough the heat conducts through.
You don’t even need to wet your finger to put out a candle. I never did and it barely feels warm.
I learned a similar lesson after bringing socks to the beach to help walk across the hot sand. I went back to our house at one point and thought it would be “really smart” if I dipped the socks in the cool pool water before heading back on the burning sand to our site. Big mistake.
This is two different things: thermal mass and conductivity.
The moisture you give your fingers to put out the candle provides them with enough thermal mass to absorb the energy from the candle, without dramatically changing the temperature of the water (the water can absorb a lot of energy without changing temperature) Also the water is a better conductor than your skin, so it spreads the energy across the liquid much better.
When you wet an oven mitt, you turn what should be insulating you from the heat into a better conductor, and the heat travels through the water in the glove to burn your hand.
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the candle side seems to have been covered pretty well at least. As for the oven mitt, think of snowboarders. Most of them, rather than wear one big puffy coat, will wear multiple layers of thinner material. That’s because the trapped air between layers is itself actually a really good insulator, meaning it takes a while to change temperature, so it’s a good material to keep a hot space hot, or a cold space cold.
Actually, they tried to use this principle for houses too, by making air filled walls sealed in plastic sheets. It worked great for temperature, but eventually some really toxic mold grew in the air pockets, so it didn’t take off.
But yeah, your hot pad is made (usually) of something with air trapped in it. Because it takes so long for that trapped air to get warmer, you have time to do what you’re doing with the really hot thing, then put it back down before a dangerous amount of heat reaches your hand. But the water is a much better conductor… it gets hot or cold really fast and then spreads that temperature on to the next thing. So if you’re out in the snow and sweat through your wool jacket, now you’re also in tons of danger because your body heat gets out through the damp stuff way way faster than before. Same concept with the oven mitt getting wet, and transferring heat.
[https://www.youtube.com/watch?v=yTOCAd2QhGg](https://www.youtube.com/watch?v=yTOCAd2QhGg)
Mythbusters did it first.
As others have pointed out, the tip of a burning wick doesn’t contain very much energy. A hot metal pan is insanely energetic by comparison. In either case, you need enough water so that it’s not instantly converted to steam.
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