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Homework Help: Someone please help me specific heat capacity?

  1. Jan 17, 2010 #1
    "What is the specific heat capacity of a 50-gram piece of 100 degree C metal that will change 400 grams of 20 degrees C water to 22 degrees C?

    Could someone please explain to me how to do this problem? I have to figure it out on my own because my teacher is no help at all.

    Thanks in advance.
     
  2. jcsd
  3. Jan 17, 2010 #2

    rock.freak667

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    The heat lost by the metal is equal to the heat gained by the water.

    cwater=4.18 kJ/kgK
     
  4. Jan 17, 2010 #3
    Okay, thank you. That leads me to another question, perhaps a silly one. How do I know when to use the 4.18 value instead of 1 cal/gC for water's specific heat capacity?
     
  5. Jan 17, 2010 #4
    And... since the metal caused the water's temperature to increase by 2 degrees, does the metal's temperature decrease by 2 degrees?
     
  6. Jan 17, 2010 #5

    rock.freak667

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    it does not matter which one you use, you just need to be consistent with the units.

    For example, if you just 4.18 kJ/kgK, you need mass to be in kg and temperature to be in K.

    similarly for 1cal/gC, you need mass to be in grams (g) and temperature in C
     
  7. Jan 17, 2010 #6
    Okay. That's what I presumed; that it didn't matter as long as units were consistent. Thank you for your help, though.

    Hopefully my last question: is the change in temperature for the metal 2 degrees?
     
  8. Jan 17, 2010 #7

    rock.freak667

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    I think it should be that the metal and water would have the same final temperature.
     
  9. Jan 17, 2010 #8
    Okay. I cannot believe I didn't realize that before I asked. Haha how embarrassing... anyway, thank you very much for your help.
     
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