Answer
Phase transition is a transition between the phases like solid, gas and liquid of any matter.
Like phase transition between gas and liquid:
Work Step by Step
Ice (solid) ---- melting --- > water (liquid)
Water (liquid )----freezing point -- > ice (solid)
Transition liquid and gas
Water (liquid )-----boiling -- > vapor (gas)
vapor (gas) ---- condensation -- > water (liquid)
Transition in between solid and vapor:
Solid < ----sublimation ----> gas
Gas solid