Heat of Transition

Heat of Transition

(or heat of transformation), the quantity of heat that must be absorbed or given up by a substance when it undergoes an equilibrium constant-pressure and constant-temperature transition from one phase to another. Boiling, melting, crystallization, and changes from one polymorph to another are examples of first-order transitions. In second-order transitions, the heat of transition is zero.

An equilibrium phase transition at a given temperature occurs at a constant temperature known as the transition point, or transition temperature. The heat of transition is equal to the product of the transition point and the difference in the entropy of the two phases between which the transition occurs. Heats of transition may be determined per unit mass, for example, per kg, or per mole.

References in periodicals archive ?
For various values of the parameters, namely, phononfrequencies, we calculate the values of critical temperatures of Bose condensation, latent heat of transition into the condensed state, heat capacity, and heat capacity jumps at the point of transition.
At the same time transition of Bose particles from a condensate state to a supracondensate one occurs with consumption of energy which is determined by the value q (Section 4, Table 1), determining the latent heat of transition of a Bose gas which makes it a phase transition of the 1st kind.
It has been found that the heat of transition for the crystals obeys a linear relationship with logarithmic time, log [t.sub.c] (annealing time [t.sub.c]), as described by the following equation:
The relationships between the heat of transition, [DELTA][H.sub.d], and logarithmic time, log [t.sub.c], for both high and low melting peaks are illustrated in Fig.

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