chemical science vs chemical reaction

chemical science and chemical reaction both are nouns.

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

chemical science (noun)	chemical reaction (noun)
the science of matter; the branch of the natural sciences dealing with the composition of substances and their properties and reactions	(chemistry) a process in which one or more substances are changed into others