1. The problem statement, all variables and given/known data Consider a closed, adiabatic system consisting of a mixture of liquid and solid substance Z at equilibrium at its melting point. Z (solid) <---------> Z (liquid) Which of the following statements is true regarding the system? A) The entropy of the system is at a maximum B) The entropy of the system is at a minimum C) The entropy of the system will increase over time. D) The entropy of the system is zero E) the entropy of pure substances does not change if at a constant temperature. 2. Relevant equations none 3. The attempt at a solution I put down my answer as being E. The entropy change for a reversible process is zero according to the second law of thermodynamics, so because my temperature is the same while melting, this answer choice makes sense. However, my review book gave me A as being the correct explanation and then did not bother to explain this at all to me why the entropy of the system is at a maximum. Could anyone please explain why this is the case and share their thoughts with me? Thanks!