Biologists have been able to keep isolated chloroplasts or mitochondria for a few hours or days. can these structures be
considered alive?

Isolated chloroplasts or mitochondria cannot be considered alive, because although they can survive while isolated for a few hours or days and they resemble that of an independent cell (which are alive), they don't metabolise energy, and they don't have cells.

b. read the phase at the intersection of any given temperature and pressure.