Freezing Point FREEZING POINT, temperature at which a liquid congeals into the solid state at a given pressure (see PRESSURE; TEMPERATURE). The freezing point of a pure (unmixed) liquid is essentially the same as the melting point of the same substance in its solid form and may be regarded as the temperature at which the solid and liquid states of the substance are in equilibrium. If heat is applied to a mixture of liquid and solid substance at its freezing point, the temperature of the substance remains constant until it has become completely liquefied, because the heat is absorbed not in warming the substance but in providing the latent heat of fusion. Simi