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Specific Heat

  1. Mar 11, 2009 #1
    1. The problem statement, all variables and given/known data
    If 4.0 g of boiling water at 100.0°C was splashed onto a burn victim’s skin, and if it cooled to 45.0°C on the 37.0°C skin, (a) how much heat is given up by the water? (b) How much tissue mass, originally at 37.0°C, was involved in cooling the water?


    2. Relevant equations
    Q=mcΔT


    3. The attempt at a solution
    For part a)
    ΔT = 100.0°C - 45.0° = 55.0°C
    c for human tissue is 3.5kJ\kgK
    m = 4.0g = 0.004kg

    Q=(0.004kg)(3.5kJ\kgK)(55.0°C)
    Q=0.77kJ

    Is this correct, or am I supposed to convert my temperatures to Kelvin? The 3.5kJ\kg*K throws me off a bit.


    For part b)
    I used the same equation, but plugged in my answer from part a, and 37°C
    0.77kJ=m(3.5kJ\kgK)(37.0°C)
    m=0.77kJ/(3.5kJ\kgK)(37.0°C)
    m=0.005945946kg
    m=5.95g

    Have I done everything correctly here? I am reasonably sure that my answer for part a is correct, but part b I am not.
     
  2. jcsd
  3. Mar 11, 2009 #2
    The temperature, in this situation, need not be in Kelvin. Since degrees Kelvin are exactly the same size as degrees Celsius, one only needs to use Kelvin if absolute temperature is required, as in the Ideal Gas Law. All of your math appears to be correct, by the way.
     
  4. Mar 11, 2009 #3
    Great, thank you. Although...my math is correct, yes, but did I use the proper equation for part b? My math can be correct all it wants, but I'll still get no marks if I use the wrong equation ;)
     
  5. Mar 11, 2009 #4
    Yes, that is the correct equation.
     
  6. Mar 11, 2009 #5
    Awesome. Thanks!
     
  7. Mar 12, 2009 #6

    Mapes

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    Hold on, why are you combining the temperature change of the water with the heat capacity of the skin?
     
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