Calculate the change in entropy of the universe

AI Thread Summary
The discussion revolves around calculating the change in entropy of the universe when a copper block is placed in a lake. The formulas used for the entropy change of the copper and the lake are presented, with specific temperatures converted to Kelvin. The user notes a discrepancy between their calculated answer and the expected result of 6.3 JK-1. A key realization is made regarding the use of heat capacity instead of specific heat capacity, emphasizing the importance of unit consistency in calculations. The conversation highlights common pitfalls in thermodynamic calculations and the need for careful attention to details.
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Homework Statement



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?
 
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Carry your units through the calculation and you'll see.
 
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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