thawing vs phase change

thawing and phase change both are nouns.

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

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

thawing: 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 thawing include heating, warming, phase transition, physical change, state change.

thawing (noun)	phase change (noun)
warm weather following a freeze; snow and ice melt	a change from one state (solid or liquid or gas) to another without a change in chemical composition
the process whereby heat changes something from a solid to a liquid