Chem test soon can someone explain why then represent a chemical reaction or why they dont 1)4P(s) = 5 O2(g)?

If bonds between atoms are destroyed and bonds of another kind are formed, it's a chemical process (e.g. when P reacts with O2 to form P2O5 or iron reacts with oxygen to form rust (iron oxydes)). Other processes: evaporation, sublimation, melting etc are physical, so melting point etc are physical properties