chemical science vs decomposition reaction

chemical science and decomposition reaction both are nouns.

Word	Noun	Adjective	Verb	Adverb
chemical science	Yes	No	No	No
decomposition reaction	Yes	No	No	No

chemical science (noun)	decomposition reaction (noun)
the science of matter; the branch of the natural sciences dealing with the composition of substances and their properties and reactions	(chemistry) separation of a substance into two or more substances that may differ from each other and from the original substance