Entropy change in phase transformation

Entropy is a thermodynamic quantity which is related to uniformity of a system being measured. Entropy is central to the second law of thermodynamics. The second law of thermodynamics determines which physical processes can occur, for example it predicts that heat will flow from high temperature to low temperature. The second law of thermodynamics can be stated as: the entropy of an isolated systemalways increases, and processes which increase entropy can occur spontaneously. Since entropy increases as uniformity increases, qualitatively the second law says that uniformity increases.

The thermodynamic entropy S, often simply called the entropy in the context of thermodynamics, can provide a measure of the amount of energy in a physical system that cannot be used to do work. The term entropy was coined in 1865 by the German physicist Rudolf Clausius, from the Greek words en-, "in", and trope "a turning", in analogy with energy.