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Homework Help: Calculate the change in entropy of the universe

  1. Jul 5, 2009 #1
    1. The problem statement, all variables and given/known data

    Calculate the change in entropy of the universe as a result of the following process:

    A copper block of mass 0.4 kg and heat capacity 150 JK-1 at 1000C is placed in a lake at 100C.

    2. The attempt at a solution

    change in entropy (copper) = mc ln (T2 / T1)

    change in entropy (lake) = mc ( T1 - T2 ) / T2

    where T1 = 373 K, T2 = 283 K.

    The answer given is 6.3 JK-1. which is differ from the answer I got. May I know if i have done any careless mistake?
  2. jcsd
  3. Jul 5, 2009 #2


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    Gold Member

    Carry your units through the calculation and you'll see.
  4. Jul 5, 2009 #3
    Thanks a lot Mapes! I never realize that it is heat capacity instead of specific heat capcity (as they give us mass in the question). :)
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