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Heat of vaporization conceptual problem

  1. Mar 25, 2015 #1
    When I'm doing the Physics homework the problem for heat of vaporization uses Q=mcΔT and Q=mLv. How do I know when to use which equation through out the problem?
     
  2. jcsd
  3. Mar 25, 2015 #2

    DrClaude

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    Staff: Mentor

    The first formula is related to a change in temperature (hence the presence of ##\Delta T##), when a single phase is heated, while the second is related to the phase transition at constant temperature.
     
  4. Mar 25, 2015 #3
    So I use that one just when the temperature has changed?
     
  5. Mar 25, 2015 #4

    DrClaude

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    Problems usually ask to make calculations going from ##T_1## to ##T_2##, with a phase transition somewhere in there, ##T_1 < T_t < T_2##. You then need to calculate for instance the heat in the liquid phase from ##T_1## to ##T_t##, then the latent heat of vaporization, then heat in the gas phase from ##T_t## to ##T_2##.
     
  6. Mar 25, 2015 #5
    so use the mLv for phase changes?
     
  7. Mar 26, 2015 #6

    DrClaude

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    Staff: Mentor

    Yes.
     
  8. Mar 26, 2015 #7
    Thank you so much for your help
     
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