Which change is most likely to be accompanied by an increase in entropy?

• A. Condensation of a gas to a liquid
• B. Freezing a liquid to a solid
• C. Dissolution of a solid into water
• D. Precipitation of a solid from solution

Answer: (C)

Entropy reflects how disordered a system is or how many ways its energy and matter can be arranged. When a solid dissolves in water, the orderly solid lattice breaks apart and the solute particles spread throughout the solvent, creating many more possible arrangements for both solute and solvent molecules. This increase in dispersal and microstates raises the system’s disorder, so the entropy goes up. The other changes move the system toward greater order: condensing a gas to a liquid reduces disorder, freezing a liquid to a solid locks particles into fixed positions, and precipitation forms a solid lattice from ions in solution, both of which lower entropy.