mop vs soak up

mop is a noun but soak up is not a noun.

Word	Noun	Adjective	Verb	Adverb
mop	Yes	No	Yes	No
soak up	No	No	Yes	No

As verbs, soak up is a hypernym of mop; that is, soak up is a word with a broader meaning than mop:

Other hypernyms of mop include absorb, draw, imbibe, sop up, suck, suck up, take in, take up.

mop (noun)	soak up (noun)
cleaning implement consisting of absorbent material fastened to a handle; for cleaning floors

mop (verb)	soak up (verb)
make a sad face and thrust out one's lower lip	devote (oneself) fully to
to wash or wipe with or as if with a mop	take in, also metaphorically