Question

A student suspected that an unknown was undergoing a chemical change at its melting point.
Suggest a simple method for testing this hypothesis.

Answer 1

How about melting a small amount of the sample, letting it cool and recrystallize, then subject the "new" material to a melting point. If different it is a new material. If it has the same, then take a mixed melting point. A different material will make the mixed melting point lower.