a phase change is when a substance changes from one state into another state
soiling is change_of_state. change_of_state is not change. nullification is change_of_state. termination is change_of_state. physical_state_change_event is not becoming. thaw is phase_change. phase_change is natural_process. phase_change is not natural_process. transfer is change_of_state. change_of_state is change.