intumescency vs chemical action

intumescency and chemical action both are nouns.

Word	Noun	Adjective	Verb	Adverb
intumescency	Yes	No	No	No
chemical action	Yes	No	No	No

As nouns, chemical action is a hypernym of intumescency; that is, chemical action is a word with a broader meaning than intumescency:

intumescency: the increase in volume of certain substances when they are heated (often accompanied by release of water)
chemical action: (chemistry) any process determined by the atomic and molecular composition and structure of the substances involved

Other hypernyms of intumescency include chemical change, chemical process.

intumescency (noun)	chemical action (noun)
the increase in volume of certain substances when they are heated (often accompanied by release of water)	(chemistry) any process determined by the atomic and molecular composition and structure of the substances involved
swelling up with blood or other fluids (as with congestion)