Compare the entropy of solids, liquids, and gases.
Solids have the lowest entropy, liquids have intermediate entropy, and gases have the highest entropy: S<sub>solid</sub> < S<sub>liquid</sub> < S<sub>gas</sub>.
How do you calculate ΔS° for a reaction?
ΔS°<sub>rxn</sub> = ΣnS°<sub>products</sub> - ΣnS°<sub>reactants</sub>, where n = stoichiometric coefficient and S° = standard molar entropy.