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Joule free adiabatic expansion dT=0?

  1. Nov 23, 2012 #1
    In that experiment , the internal energy is zero , volume increase , pressure of system decrease, then temperature will constant ?

    Thanks
     
  2. jcsd
  3. Nov 24, 2012 #2
    Nope, not guaranteed. The expansion can also be adiabatic, or heat can even be loss while work is done by the gas.

    Only an isothermal expansion guarantees no change in internal energy.
     
  4. Nov 24, 2012 #3
    Then when it expand to vacuum?
    No work will be done because the external pressure is zero.
    Internal energy will not change as no heat enter, no work done
    Will the temperature change ?
     
  5. Nov 24, 2012 #4
    That depends.

    Since w = 0 and q = 0 for the experiment that Joule performed, the change in internal energy U was also 0.
    Joule measured the temperature change to also be 0.
    The conclusion was that for an ideal gas, the internal energy U is a function of temperature only.

    For a real gas, that is no longer true but varies slightly.

    Here is some reading for you.
    http://www.chem.arizona.edu/~salzmanr/480a/480ants/jadjte/jadjte.html
     
  6. Nov 24, 2012 #5
    Thank
    Then the answer for this thread is dT= 0 for ideal gas.

    When a chemical endothermic reaction is carried out, then heat from the surrounding is absorbed , that is why the container of the chemical solution feel cold.
    I wondered if I carry out the same experiment adiabatically, will the temperature of chemical solution drop?
     
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