heat up vs scald

heat up is not a noun while scald is a noun.

Word	Noun	Adjective	Verb	Adverb
heat up	No	No	Yes	No
scald	Yes	No	Yes	No

As verbs, scald is a hyponym of heat up; that is, scald is a word with a more specific, narrower meaning than heat up:

Other hyponyms of heat up include crisp, crispen, toast, soak, calcine, preheat, overheat, scorch, sear, bake, broil, reheat.

heat up (noun)	scald (noun)
	the act of burning with steam or hot water
	a burn cause by hot liquid or steam

heat up (verb)	scald (verb)
make hot or hotter	burn with a hot liquid or steam
gain heat or get hot	heat to the boiling point
make more intense	treat with boiling water
	subject to harsh criticism