a phase change is when a substance changes from one state of matter into another state of matter
vaporization is not phase_change. change_of_state is not change. soiling is change_of_state. phase is not state_of_matter. vaporization is phase_change. phase_change is not natural_process. phase_change is natural_process. phase is state_of_matter. change_of_state is change. liquefaction is phase_change.