Contractions function almost identically to the full two-word phrase. But they are only appropriate in some places in a sentence. It's one of the weird quirks of this language we've.
@bmreiniger Not as deep-dive as here:
https://lingthusiasm.com/post/662535562508517376/lingthusiasm-episode-60-thats-the-kind-of
It's a complicated question that doesn't seem to admit to any simple rules, no matter how much the enthusiastic amateurs might sound definitive.
@ColinTheMathmo
https://english.stackexchange.com/q/8
(Question number 8!)