decomposition reaction vs chemical science

decomposition reaction and chemical science both are nouns.

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

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