chemical reaction vs chemical science

chemical reaction and chemical science both are nouns.

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

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