|MadSci Network: Physics|
Hi Calvin, Thanks for this interesting question. The reason why the foil feels cool is not its specific heat capacity (which is heat energy stored per volume per degree). It also is not caused by its heat conductivity (which is heat energy transported per area per degree temperature difference). It is the ratio between volume and surface area! I will explain this a bit more: Heat energy is stored in the volume of the material (given by its specific heat capacity). Heat energy is transported out of the material through its surface (given by the heat conductivity). A thin foil has a low volume and thus stores only little heat energy. Yet it has a big surface area and thus cools down very fast. Another way to visualise this is by comparing the thickness of the foil with the thichness of you outer skin (where you don't have nerve receptors and thus won't feel any heat): The skin is thicker. Thus by the time the heat from the foil has moved all through your skin, the foil is already much colder, and you won't feel much heat! It's a different story if you touch a hot stone (from the same oven), which has a much higher volume-to-surface-ratio (and is thicker than your skin): It cools down slower and will burn your finger. I hope this helps to understand the problem. Keep up your inquisitive spirit - I am looking forward to more such questions! Greetings, Frank
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