break open vs split up

break open is not a noun while split up is a noun.

Word	Noun	Adjective	Verb	Adverb
break open	No	No	Yes	No
split up	Yes	No	Yes	No

As verbs, split up is a hypernym of break open; that is, split up is a word with a broader meaning than break open:

Other hypernyms of break open include break, come apart, fall apart, separate.

break open (noun)	split up (noun)
	an increase in the number of outstanding shares of a corporation without changing the shareholders' equity

break open (verb)	split up (verb)
erupt or intensify suddenly	become separated into pieces or fragments
come open suddenly and violently, as if from internal pressure	get a divorce; formally terminate a marriage
open with force	discontinue an association or relation; go different ways
	separate into parts or portions