state change vs natural action

state change and natural action both are nouns.

Word	Noun	Adjective	Verb	Adverb
state change	Yes	No	No	No
natural action	Yes	No	No	No

As nouns, natural action is a hypernym of state change; that is, natural action is a word with a broader meaning than state change:

state change: a change from one state (solid or liquid or gas) to another without a change in chemical composition
natural action: a process existing in or produced by nature (rather than by the intent of human beings)

Other hypernyms of state change include action, activity, natural process.

state change (noun)	natural action (noun)
a change from one state (solid or liquid or gas) to another without a change in chemical composition	a process existing in or produced by nature (rather than by the intent of human beings)