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Thread: Microwave oven

  1. #1 Microwave oven 
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    Microwaves in the oven heat up food by heating water. Is the heating by water molecule excitation or by exciting the atoms in the molecule?


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    Bullshit Intolerant PhDemon's Avatar
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    It is the bonds in the molecule, the polar O-H bond in water interacts with microwave radiation (leading the to water molecules being in excited rotational energy states). This increased molecular motion leads to heating.

    It is also incidentally why frozen food heats up much more slowly in the microwave, if the water molecules are fixed in ice crystals it needs a lot more energy to get them to rotate...


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  4. #3  
    exchemist
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    Quote Originally Posted by PhDemon View Post
    It is the bonds in the molecule, the polar O-H bond in water interacts with microwave radiation (leading the to water molecules being in excited rotational energy states). This increased molecular motion leads to heating.

    It is also incidentally why frozen food heats up much more slowly in the microwave, if the water molecules are fixed in ice crystals it needs a lot more energy to get them to rotate...
    Do you know what it is in some earthenware that makes the empty dish heat up in the microwave? I find certain cheapo coloured dishes get hot and the more expensive white ones don't. I presume there is something in the glaze but since they are solid one would not expect there to be O-H elements that are free to rotate.
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  5. #4  
    Bullshit Intolerant PhDemon's Avatar
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    It could be the metals in the coloured pigments, conductors will absorb microwaves and generate a current which causes heating.
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