during a phase change, even though heat is entering or leaving the system, the overall temperature of the system does not change. a good example of this is the freezing of liquid water to form ice cubes (an exothermic reaction) or the melting of an ice cube to liquid water (an endothermic reaction). if the temperature of the system does not change, what happens to the heat (energy) that is being released from (exothermic) or put into the system (endothermic)?