Why does aluminum foil never get hot to the touch. You can leave it in the oven and touch it directly out of the oven without it feeling hot. Why is this?
In: Physics
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The reasons are twofold.
On the materials side, a lot of people are getting at the gist of it: a thin sheet of aluminum doesn’t have a lot of thermal energy. That’s just a property of aluminum, and also due to the fact that there’s not a lot.
The biological side is being neglected, though. You have nerve endings that measure the *movement* of thermal energy; they don’t measure raw temperature. That’s why a hot shower turns warm, and that’s where the saying about a frog in a pot comes from. Since aluminum foil doesn’t have a lot of energy to transfer, it’s hardly gonna register in your nerves.
A lot of FANTASTIC explanations here, but none are ELI5.
The aluminum that the foil is made of is special because it can go from hot to cold SUPER fast, so as soon as the oven door opens up, it starts to get cool enough to not burn you.
Plus small things that have a lot of air nearby can cool down faster, so the foil being so thin means the air touches almost all of it at once and helps it cool even faster so when your finger made mostly of water touches it, there’s not enough heat in the special aluminum left over to burn you.
So those two reasons together are why mommy and daddy can touch foil, but don’t ever ever ever touch the oven when we’re cooking, it’s VERY dangerous and I wouldn’t want you getting hurt.
Actually, if you use heavy duty foil, it *does* stay hot to the touch for a good 20 or 30 seconds.
it can most definitely get hot as fuck, it’s just likely to do so because of the thinness & material.
It’s really thin, and aluminum can get hot really fast, but also get cold really fast. This means it has what is known as good thermal conductivity.
Back when I was about 12 (looong time ago) Mr. Ireland (known, inevitably, as Paddy) was trying to get across to a new class the difference between heat and temperature. He heated a needle to white heat, dropped it in a liter of cold water, had us all feel that the water was still cold. He heated a lump of steel in boiling water, dropped it into his liter and it had an easily discernable effect on the temperature. There you go, he said, the needle was at a much higher temperature the steel contained more heat energy. The foil may be very hot but it doesn’t contain much heat, and it cools quickly, so your fingers can’t detect it. edman007-work probably explains it better
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