state change vs melting

state change and melting both are nouns.

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

As nouns, melting is a hyponym of state change; that is, melting is a word with a more specific, narrower meaning than state change:

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

Other hyponyms of state change include freeze, freezing, liquefaction, melt, thaw, thawing, evaporation, vapor, vaporisation, vaporization, vapour.

state change (noun)	melting (noun)
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

state change (adjective)	melting (adjective)
	becoming liquid