chemical science vs long chain

chemical science and long chain both are nouns.

Word	Noun	Adjective	Verb	Adverb
chemical science	Yes	No	No	No
long chain	Yes	No	No	No

chemical science (noun)	long chain (noun)
the science of matter; the branch of the natural sciences dealing with the composition of substances and their properties and reactions	(chemistry) a relatively long chain of atoms in a molecule