changeover vs change over

changeover is a noun but change over is not a noun.

Word	Noun	Adjective	Verb	Adverb
changeover	Yes	No	No	No
change over	No	No	Yes	No

changeover (noun)	change over (noun)
an event that results in a transformation

changeover (verb)	change over (verb)
	make a shift in or exchange of
	change from one system to another or to a new plan or policy