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
The water isn’t especially important in this question, it’s only acting as a heat battery. The water absorbs some heat, but too much and it evaporates. The important thing here is how you frame the sources of heat in your heat. When you dip your finger in wax, you remove a portion of wax from the candle, and with it comes an equal portion of the heat energy in the ENTIRE CANDLE(this is important).
Think of it like this. You have a burning candle with a pool of wax in the center. You dip your finger into the wax, and when you pull it out, let’s say 1% of the wax came with it. Now, for a moment, that 1% of wax also holds 1% of the heat stored collectively in the rest of that wax pool. So you’re getting 1% of the heat of the entire candle. The layer of water can pretty easily absorb most of that heat, bringing it down to safe temperatures before it reaches your nerves.
Now lets move on to the pan. So you have a wet oven mitt, and a VERY hot pan. Much larger layer of water, but not that much hotter heat source. What’s the difference? Well first off, the metal pan can store a lot more heat than the wax, but that’s not the really important bit. When you touch the metal pan, you’re not removing 1% of the pan and taking that heat. You’re taking the heat of the ENTIRE pan. No 1% stuff here. This is equivalent to dipping your entire hand into a pool of 400 degree candle wax AND LEAVING IT.
In one case, the heat source is liquid, and when you dip into it and pull out, you’re only dealing with a portion of the total heat in the system.
In the second case the heat source is solid, and you are forced to deal with the entirety of the heat stored in the heat source.
In both cases, the water serves as both a store of energy and a conductor of energy. In the first, the energy is sufficiently low that the water can take it. In the second, there is too much energy, and the water is thermally massive enough to take it without evaporating, but also not massive enough to avoid heating up to scalding temperatures.
Your mistaking thermal energy and heat.
A flame may be very HOT but only a thin layer of gas on the outside of the flame is generating that heat. Reduce the heat of those gas particles and the flame goes out, and because the liquid on your fingers has a much higher heat capacity than the gas, you don’t feel the burn.
A hot pan may not be as HOT, but the thermal energy is way bigger. You have a fuck ton of particles through the entire metal pan that are hot and will give off their heat very easily. The layer of water that could absorb the heat soaks it all up, and now the rest of the water in the towel has no where to evaporate into so it keeps spreading the heat, eventually to your hand.
A dry cloth is safe again because the thermal capacity. It doesn’t transfer heat very well, so you could also use that to put out an candle at the risk of getting it dirty OR putting it in contact with something hot enough to light it on fire (another property of heat)
Imagine you take a few ounces of water to put out the flame of a candle. It will extinguish it right away. The water will still be cold because not much heat energy was stored in the wick.
Now imagine a cast iron pan heated to 400 degree. Toss the water in the pan or dip the handle in the water for 5 seconds. The water will flash boil. If you put your face near the steam that rises you might even burn your skin.
When your oven mitt is wet, the water it contains will steam out hotter than boiling water and burn your hand very quickly.
This is a scale and mass issue.
The candle wick has a relatively small mass, so the small amount of water on your fingers absorbs almost all of the heat energy without much turning to steam, and a layer around your finger stays below 100C.
The pan has a relatively large mass, so it can transfer a large amount of heat energy into your wet oven mitt. The water absorbs enough to turn into steam, which then expands to fill the space around your dry hand. That steam then imparts all of that heat energy to your hand before condensing back into water, which burns you.
TLDR: Specific heat of transformation is a bitch.
Candle = small heat.
Hot pan = big heat.
Small heat smaller than wet fingers.
Big heat bigger than wet oven mitt.
Fire needs oxygen, hot metal doesn’t. Fire don’t burn long if you pinch it fast enough. And by not for long I mean you’ll hear a *tsss* sound.
You’ll get the same sound with a pan, but thats you’re skin frying not the water sizzling.
This dude wants to know why you can’t just blow out a bonfire but you can a birthday candle
Because the heat stored energy in the pan is magnitudes greater than that in a candle, and the conductivity of metal is vastly greater than a wick.
If you take an iron pan out of the oven and throw water on it, it will immediately will turn to steam. FWOSSH! The same thing happens when you put a damp mitt on it. The water in contact with the metal will turn to steam very quickly and hit your fingers super hot. It depends on the ratio of the metal type, how hot it is and how much water the mitt is holding. If you have a lot of water and low heat, you are fine as the water can take it without turning too hot or even flash into steam. But if you have lots of heat and low water, the water will be “overwhelmed” and burn you.
Oh dude. I was drunk and stoned a few weekends ago and grabbed a red hot cast iron pan with my bare fucking hand. The skin is still peeling off
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