First maybe catch all the possible states (is it seven or nine now - try Wikipedia bose einstein condensates, solids, liquids, gasses, plasmas etc)
Then consider substances that lie across states - like glass as a extremely slow moving liquid with no fixed melting point or crystaline structure or glass as a solid. I'd class it as a liquid barely, but many folk would say its definitionally unclear.
Or if you want to get really tricky realise that baryonic matter and energy are equivalent, so play with quantum uncertainity