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How does a thermos keep something hot and cold at the same time?

3 Answers

  • 2 months ago

    A thermos (or hydroflask or cooler or similar) all attempt to slow the transfer of energy (heat) to or from the contents (basically, energy will always transfer from hot to cold until the two things are at the same temperature). The type of energy here is conductive, which means it needs particles to be moving around to transfer energy. A very cheap thermos (like in a sponge box lunch set) just has air in between two layers of plastic. That will work slightly but not that well. In you house, "insulation" in used, but the main point of the insulation is to prevent the air in the walls from moving, this greatly reduces thermal conductivity.

    In a well made thermos, as much air as possible is removed from between the two layers. If there are very few air particles, there is very little that can transfer energy so it can keep the insides cold or hot. Also, the use shiny mirror surface which can also reduce the slight be of radiative energy transfer typically from hot things.

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  • Barry
    Lv 4
    2 months ago

    It doesn't do it at the same time. But the insulation and construction delays the passage of heat either into (cool) or out of (hot) the contents.

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  • Mog
    Lv 7
    2 months ago

    Because the inside layer of the container is insulated from the outside layer with a pocket of vacuum sealed air in between the two layers. 

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