For melting, the sign is positive, as the solid gains disorder. For dissolving, it is usually positive too, unless the solute is very ordered in solution. For gas expansion into a vacuum, it is definitely positive.
But this clear theory feels distant when I am worrying about our leaking roof. The entropy of my household increases daily as monsoon approaches, with pots scattered to catch water—a messy, practical expansion the textbooks never quantify.
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