Step 1: Understanding Exothermic vs Endothermic Transitions. Crystallization:
Molecules go from higher-energy (amorphous) to lower-energy (ordered) state → releases energy (exothermic).
Step 2: Melting, sublimation, glass transition:
All require energy input to break molecular order or increase molecular motion → endothermic. Only crystallization is exothermic among the given options.