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B Heat conduction in a solid

  1. Feb 11, 2019 #1
    It is easy to understand heat conduction in a gas as the nucleus of atoms may collide with transfer of kinetic energy. But the space within a solid is vastly empty space and the nucleus of the atoms cannot collide. So if the surface of a solid is in contact with a hot gas, how is kinetic energy transferred across the solid body.
     
  2. jcsd
  3. Feb 11, 2019 #2

    BvU

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    Imagine the atoms as fixed in position by springs: bump one and others move too.

    [edit] re
    atomic collisions are not nuclear collisions: there is a negatively charged shroud of electrons around an atom nucleus; the shroud is huge in size compared to the nucleus
     
    Last edited: Feb 11, 2019
  4. Feb 11, 2019 #3

    sophiecentaur

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    Clearly it's not that easy. Over simplified models can give one a feeling of familiarity with Science but can that be called 'understanding'?
     
  5. Feb 11, 2019 #4

    A.T.

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    That would be more like a nuclear reaction, rather than heat conduction.
     
  6. Feb 11, 2019 #5
    We don't always go into fine details here; after all we don't have any absolute physics theory. Collision of gas particle are like between billiard balls; in gas, the +ve nucleus would "collide".

    I do suspect there are forces holding atoms in the lattice of solids - your spring model. Accepted. So is there a name for the forces holding the atoms of solids together? Van der Wall forces?

    We know such transfer of heat - kinetic energy - is through "collisions" in gases. In solid, it would the transfer of kinetic energy through the forces holding the lattice structure. A simple classical model too is helpful; if quantum treatment is better, then we use it.
     
  7. Feb 11, 2019 #6

    DrClaude

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    Chemical bonds.

    Given that you have an interatomic potential, why would it matter if the atoms are freely moving (as in a gas) or moving about an equilibrium position in a crystal lattice?

    Note that in metals, the conduction electrons form a Fermi gas which is a very important contributor to heat conduction and the reason why metals are so good at conducting heat.
     
  8. Feb 11, 2019 #7

    BvU

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    No.
     
  9. Feb 11, 2019 #8

    DrClaude

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    In a sense, it is correct. The majority contribution to the repulsive part of the interatomic potential is nuclear/nuclear interaction.
     
  10. Feb 11, 2019 #9
    Geiger–Marsden experiments where alpha particles are reflected directly by thin gold foil. It is "electrical collision" of +ve nucleus and +ve charged ions.
     
  11. Feb 11, 2019 #10

    DrClaude

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    There is a difference between ions colliding with atoms and neutral atoms colliding.
     
  12. Feb 11, 2019 #11

    BvU

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    The nuclei don't come anywhere near another in atomic collisions. The perception of billiard balls in this context is absurd and misleading.
     
  13. Feb 11, 2019 #12
    When an object rests on a table, there is reaction that prevents "merging" of the object to the matter of the table. I only vaguely know it is the electrical force that prevents the the object and the table to merge.
     
  14. Feb 11, 2019 #13

    DrClaude

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    This is getting off topic.

    Do you an answer to
    or do you get why solid can conduct heat?
     
  15. Feb 11, 2019 #14
    My physics background is not yet at a level where I can say I fully understand; one cannot fully understand without a proper background of the physics involved - say interatomic potentials. But I vaguely remember the rudimentary explanations of the kinetic theory of gas where the gas particles collide with the vessel wall. I can't see why this is not somehow related to collision of billiard balls and the electrical forces that separates solid bodies and cause the balls to bounce off each other.
     
  16. Feb 11, 2019 #15

    ZapperZ

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    This is why the field of solid state physics is different than the field of atomic physics. As Phil Anderson has said "More Is Different"!

    The fact that it is a solid means that there are strong bonds that hold the atoms and molecules in place. So there is already strong coupling between the atoms that make up the solid. It means that when one part of the solid is agitated (as in the supply of heat), then it is possible (but not always) that this agitation can be transferred.

    Metals are good conductors of heat due to two reasons (naive picture): (i) they are usually crystalline solids, so the transfer of the vibrational energy is not "haphazard", unlike amorphous or polycrystaline solids; (ii) the conduction electrons are not only very mobile, and thus, can transfer the heat energy easily, but they also have a rather low specific heat capacity, meaning that they heat up very quickly and easily, and give up heat the same way when they reach cooler regions of the metal.

    In solids, vibrational energy (something that is not available in isolated atoms) plays a huge role in their properties. This is what you are missing in your scenario, because you are focusing on free particles that can only transfer energy via collision.

    Zz.
     
  17. Feb 11, 2019 #16
    I think this is what I am missing. The answers are in reading more physics as you say - solid state physics,etc.

    Thanks to all. I have some things clarified.
     
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