text: how is the freezing point specifically determined from a cooling curve?   the freezing point of a pure substance can be derived from a cooling curve plotting the temperature versus time.  as energy is taken out of a liquid, its temperature falls.  when the temperature reaches the freezing point of the substance, energy is taken out, but the temperature remains constant.  at this point, the cooling curve levels out this is quite evident when looking at the graph.  this leveling off effect is seen because in order for the substance to free, additional energy must be removed from the liquid, this is called the latent heat of fusion.  after the substance is frozen, the temperature of the solid can continue to drop. {this same effect can also be seen as something melt, boils, condenses, or sublimes}