arousal vs change of state

arousal and change of state both are nouns.

Word	Noun	Adjective	Verb	Adverb
arousal	Yes	No	No	No
change of state	Yes	No	No	No

As nouns, change of state is a hypernym of arousal; that is, change of state is a word with a broader meaning than arousal:

arousal: the act of arousing
change of state: the act of changing something into something different in essential characteristics

arousal (noun)	change of state (noun)
the act of arousing	the act of changing something into something different in essential characteristics
mutual sexual fondling prior to sexual intercourse
awakening from sleep
a state of heightened physiological activity