chemical science vs break down

chemical science is a noun but break down is not a noun.

Word	Noun	Adjective	Verb	Adverb
chemical science	Yes	No	No	No
break down	No	No	Yes	No

chemical science (noun)	break down (noun)
the science of matter; the branch of the natural sciences dealing with the composition of substances and their properties and reactions

chemical science (verb)	break down (verb)
	collapse due to fatigue, an illness, or a sudden attack
	stop operating or functioning
	separate (substances) into constituent elements or parts
	make a mathematical, chemical, or grammatical analysis of; break down into components or essential features
	make ineffective
	cause to fall or collapse
	lose control of one's emotions
	fall apart