When I put say a blade over a fire it gets damn hot, right>? The other day I cooked some meat in the oven and layed the meat on some tin (aluminium) foil. When I removed the tin foil I did so with my bare hands and was surprised it hadnt absorbed heat, even though aluminium is classed as a metal (albeit a thin slice of it) howcome?
2006-06-13 10:29:15 · 10 answers · asked by supernovam13 3 in Science & Mathematics ➔ Physics
it does it is just too thin to hold the heat once the heat source has been removed
2006-06-13 10:32:56 · answer #1 · answered by Anonymous · 1⤊ 1⤋
Three reasons:
First, the aluminum reflects most light of the heat, and as a result, very little heat is actually absorbed by the metal. I ran into a problem with this once when I wrapped something in foil and tried to heat it in the oven - the food I was trying to heat stayed mostly frozen. This is the main reason why the foil is safe to touch just after removing it from the oven.
Second, the average mass of a sheet of foil is lower than that of, say, a knife or a pan - This means that it's able to HOLD much less heat. When the foil starts to cool, this fact causes it to cool more quickly. Furthermore, the fact that the mass to surface area ratio is so high (a lot of surface area, not a lot of mass) speeds this proccess even further.
Third, the foil conducts heat better than a lot of materials. As a result, what little heat that it HAS managed to acquire after being in the oven is radiated away quickly (and again, this is partialy a result of the large surface area combined with the small mass)
2006-06-13 17:47:00 · answer #2 · answered by Joe B 2 · 0⤊ 0⤋
The foil has a shiniy surface, which means the heat from light sources like infra red is reflected. So even a thin foil can reflect the heat coming with light. (Assume light has a wave behavior)
If heat comes as other wavs like conduction, the foil absorbs SOME. Al(Aluminium) is made out of Al atoms that are organised in a way thats called a metallic bond. It has a sea of electrons around each atom since all atoms are together, and the electrons are free to move around.
So, the electron sea is the place that absorbs energy and stores it and when they put the energy out, you feel it as heat.
Hope you got it.
2006-06-14 00:45:05 · answer #3 · answered by Tharaka D 2 · 0⤊ 0⤋
It is true that tin foil is not good in absorbing heat when the heat is in the form of radiation (it reflects). However, given enough time, the foil will heat up eventually at the same oven temperature.
Another thing is that the aluminum is a very good heat conductor that will release it's own heat so easily.
The aluminum foil have a small mass to hold large BTU of heat quantity. You can actually cool it the moment you touch it since there is just a little heat to be absorbed by your finger.
2006-06-13 23:57:56 · answer #4 · answered by asimovll 3 · 0⤊ 0⤋
It does get hot just as hot as the other metals but why you can use your hands is because it doesn't retain heat. It is very thin and has a huge surface area to mass ratio so it cools off very quickly. This is the same in all materials. For example, take a glass of hot water and put it in the freezer, then time how long it takes to freeze. Then take the same amount of hot water and put it in a baking pan and time how long it takes to freeze. The baking pan of water freezes much much faster because of much more surface area allowing a much faster cool down. If your tin foil were as thick as your knife it would stay hot for much longer (sort of like how a cookie sheet stays hot for a few minutes while the foil cools down after a few seconds)
So in short the fact that it's tin doesn't have much to do with it. Tin absorbs the heat just like anything else. The real issue here is the thickness, due to it's thickness it cools down very fast.
If you still don't believe me take two sheets of tinfoil. place one in the oven flat and then fold the other in half as many times as you can and place it in the oven next to it. heat them up to 300 degrees and pull them out with tongs. Touch each one after 10 seconds. you'll notice the flat foil is cool while the thicker folded foil is still quite hot.
2006-06-13 17:39:20 · answer #5 · answered by coxdebate 2 · 0⤊ 0⤋
The foil has a big surface area and a very small volume. The heat radiates out of the surface until all the heat energy within the volume of material is dissipated. Thus a small store of heat is dissipated quickly from the foil.
I hope this is a concise explaination.
2006-06-13 17:41:26 · answer #6 · answered by monkeymanelvis 7 · 0⤊ 0⤋
it does absorb heat, but as it is so thin, it looses it very quickly, so the time taken to move your meat from the oven to the worktop and then remove the foil, it would have cooled
2006-06-13 17:33:26 · answer #7 · answered by olllly 1 · 0⤊ 0⤋
it does absorb the heat. it also gets rid of it very fast.
2006-06-13 17:34:40 · answer #8 · answered by sprcpt 6 · 0⤊ 0⤋
It has little to no density. Heat transfers quickly.
2006-06-13 17:33:52 · answer #9 · answered by flintrock86 1 · 0⤊ 0⤋
metal doesn't absorb heat, it conducts it.
2006-06-13 17:32:45 · answer #10 · answered by Anonymous · 0⤊ 0⤋