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Thermodynamics question about density

  1. Dec 25, 2014 #1
    If an object is twice as dense as another object of the same volume, would the more dense object be able to contain roughly twice as much heat energy, given that the temperature was the same in each?
     
  2. jcsd
  3. Dec 25, 2014 #2

    Matterwave

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    Roughly yes.
     
  4. Dec 25, 2014 #3
    Doesn't it also depend on the heat capacities of the materials?

    Chet
     
  5. Dec 25, 2014 #4

    Matterwave

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    I think the OP is actually simply asking about the heat capacities. His question is basically "if I double the density, keeping the volume constant, do I double the heat capacity?". If I recall correctly, this should be true for an ideal gas. I'm not sure if it's still true for a non-ideal gas, which is why I said "roughly".
     
  6. Dec 25, 2014 #5
    When he said "object", I naturally assumed he was talking about solids.
     
  7. Dec 25, 2014 #6

    Matterwave

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    Ah, in that case, I'm not sure. I would think the inter-molecular forces would affect the heat capacity greatly. I'm an astrophysicist, so everything is an ideal gas to me... :D
     
  8. Dec 25, 2014 #7

    Bystander

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    Please compare heat capacities of He and Xe.
     
  9. Dec 25, 2014 #8

    Matterwave

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    Ah you are right, I was thinking of doubling the density being doubling the number of atoms not doubling the mass of the atoms. @Jay Lakoda : neglect my first answer, it has too many assumptions in it to be useful.
     
  10. Dec 27, 2014 #9
    Thanks for the replies. By "object" I just meant a clump of molecules in any arangement. Not necessarily a solid or a gas. I'm looking at it this way: molecules are bouncing around in object #1. The average speed of the molecules is its temperature, which is the same as object #2. But object #2 is twice as dense. The heavier molecules of object #2 are moving at the same speed as object #1, but they have twice the momentum which is thermal energy. Of course there are lots of variables that slight alter things, but that's why I used the term "roughly."

    But I'm asking the question because I want to confirm that my understanding is correct.

    And more practical speaking, what I want to know is how much money would the fuel cost to produce 4,000 cubic feet of foam glass (which has a much smaller density than solid glass.)
     
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