Energy must be transferred, by heating, to a substance for these changes of state to happen. During these changes the particlesgain energy. This is used to overcome forces of attraction between particles.
Evaporation can take place below the boiling point of a substance. This is why damp clothes dry when they are hung from a washing line. Boiling happens at the boiling point, when the rate of evaporation is much faster.
Energy must be transferred from a substance to the environment for condensing and freezing to happen. During these changes of state the particles loseenergy as forces of attraction form between them.