melting vs phase change

melting and phase change both are nouns.

Word	Noun	Adjective	Verb	Adverb
melting	Yes	Yes	No	No
phase change	Yes	No	No	No

As nouns, phase change is a hypernym of melting; that is, phase change is a word with a broader meaning than melting:

melting: the process whereby heat changes something from a solid to a liquid
phase change: a change from one state (solid or liquid or gas) to another without a change in chemical composition

Other hypernyms of melting include heating, warming, phase transition, physical change, state change.

melting (noun)	phase change (noun)
the process whereby heat changes something from a solid to a liquid	a change from one state (solid or liquid or gas) to another without a change in chemical composition

melting (adjective)	phase change (adjective)
becoming liquid