This is a big issue with explosion involving sand --> glass.
Alternatively:
We could make the state change happen, but put the particle in a special state in which it will move even if INERTIA_UNMOVABLE until it comes to a rest (so, for example, it turns to glass then "sticks" to things)
We could make this only be the case for state change into INERTIA_UNMOVABLE objects. I'm particularly worried about messing up water --> steam, for example.
This is a big issue with explosion involving sand --> glass.
Alternatively: