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Latent heat vs specific heat

  1. May 1, 2013 #1
    1. The problem statement, all variables and given/known data
    I took a test and got it back I'm wondering if my prof. definition is correct.
    The heat required per unit mass of a substance to produce a phase change is called?

    A. specific heat B. Specific heat capacity C. latent heat

    I said it was C.
    He say's B
    Please explain. Thanks
     
  2. jcsd
  3. May 1, 2013 #2

    cepheid

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    From the terminology I'm familiar with, specific heat capacity (B) is the amount of heat required per unit mass of a substance to cause a unit of temperature change. I have heard the term "latent heat" (C) used to describe the heat required to produce a phase change e.g. latent heat of fusion, latent heat of vaporization.
     
  4. May 1, 2013 #3
    Thanks, I looked up definitions I feel something is wrong here. Anyone else know? Thanks for the reply.
     
  5. May 1, 2013 #4

    cepheid

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    Just for clarification, I'm saying that I thought the answer should be C as well, because latent heat is what pertains to phase changes, whereas specfic heat capacity is just for temperature changes of the substance at a given phase, not during a phase transition. This is AFAIK.
     
  6. May 1, 2013 #5
    Latent heat is as stated...the energy needed to produce a phase change (usually solid-liquid, liquid-vapour)
    If it expressed as 'per unit mass' then it should be called SPECIFIC latent heat. This might be the source of confusion because one of your options is specific heat capacity.
    LATENT means 'hidden' because the heat energy does not cause a change in temperature.
    SPECIFIC means per unit mass (usually per kg)
     
  7. May 1, 2013 #6
    What is AFAIK?
    I think I might challenge him on his grading of this question. I need to be sure though. Thanks for reply;s
    I feel this question is ambiguous.
     
  8. May 1, 2013 #7

    cepheid

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    It means As Far As I Know.

    Use whatever terminology is in your textbook and notes. That having been said, given my answer, and technician's, it seems pretty clear that it's a bad question. You can have specific latent heat or latent heat, and these have to do with phase transitions. Heat capacity and specific heat capacity do not.
     
  9. May 1, 2013 #8

    CWatters

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    Your professor is wrong. The answer is C.

    See wikipedia..

    A & B). Specific Heat Capacity & Specific Heat

    http://en.wikipedia.org/wiki/Heat_capacity#Extensive_and_intensive_quantities

    C). Latent Heat
    http://en.wikipedia.org/wiki/Latent_heat

    In all cases the word "specific" generally means it's "per unit mass" of the material.
     
    Last edited: May 1, 2013
  10. May 1, 2013 #9

    CWatters

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    EDIT: Now that I look again at the options I believe most people would answer c) Latent Heat however if I was being picky I would prefer d) Specific Latent Heat because the question says "per unit mass".

    Either way it's not Specific Heat or Specific Heat Capacity.
     
  11. May 1, 2013 #10
    Hey thanks for the help I will let you guy's know the outcome. Appreciated.
     
  12. May 2, 2013 #11
    I got my 2 points back thanks for the reply's.
     
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