to-do vs upheaval

to-do and upheaval both are nouns.

Word	Noun	Adjective	Verb	Adverb
to-do	Yes	No	No	No
upheaval	Yes	No	No	No

As nouns, upheaval is a hyponym of to-do; that is, upheaval is a word with a more specific, narrower meaning than to-do:

to-do (noun)	upheaval (noun)
a disorderly outburst or tumult	disturbance usually in protest
	(geology) a rise of land to a higher elevation (as in the process of mountain building)
	a state of violent disturbance and disorder (as in politics or social conditions generally)
	a violent disturbance