At all temperatures, the entropy of water molecules decrease upon freezing because water molecules are more ordered in the crystalline state than in the liquid. Entropy is a measure of the disorder or randomness of the system. The greater the randomness in a system, greater is its entropy. The randomness is greater in liquid state as compared to solid state so the entropy increases when ice melts into water. During evaporation, as the liquid state changes to a vapor state, the randomness between the particles increases, due to which the entropy of the system also increases.