Problem A solid substance that has a latent heat of fusion L f melts at a temper

Question

Problem A solid substance that has a latent heat of fusion Lf melts at a temperature Tm. Calculate the change in entropy when a mass m of this substance is melted. Strategy Let us assume that the melting process occurs so slowly that it can be considered a reversible process; we can reverse the process by extracting energy very slowly to freeze the liquid into the solid form. In this case, the temperature can be regarded as constant and equal to Tm.
Solution Making use of Equation 18.10 and that the latent heat of fusion Q = mLf, (Eq. 17.5), we find the following. Note that we are able to remove Tm from the integral because the process is isothermal.

Explanation / Answer

melting is a phase change process so temperature of ice will not change,

change in entropy = change in Q/T

now Q = m*L L = latent heat of fusion of water = 334 KJ/kg

= 1.6*334000

= 534400 J

change in entropy = 534400/273

= 1957.51 J/K

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