The change in entropy of a mass m of a solid substance which has a latent heat of fusion L and melts at a temperature T is
A) LT/m
B) mL ln(T)
C) mLT
D) mL/T
E) L/mT

Question

Quizplus · Accepted Answer

The change in entropy of a system during a phase change with a constant temperature is given by ΔS = Q/T where Q is the heat absorbed or released during the phase change and T is the temperature at which it occurs. In this case, the substance is melting at a temperature T, so the heat absorbed is the latent heat of fusion L. Therefore, ΔS = L/T. However, we are interested in the change in entropy of a mass m of the substance, so we need to divide by the mass: ΔS = L/(mT). This matches choice D, so the answer is D.

The Change in Entropy of a Mass M of a Solid