Reklama

The latent heat of melting

The study of the processes of melting and solidifying showed, the change in the internal energy of the matter in these processes is directly proportional to its mass m. Since the energy change in such cases, Express the number the heat of fusion QPL, have

QPL= λm (12.1)

The heat of fusion QPLalso depends on the kind of substances and external conditions. This dependence is expressed by the coefficient of proportionality λ. The value of λ, characterizing the dependence of the change in the internal energy of a substance at its melting or solidification from such substances and the external environment, is called the specific heat of fusion. Specific heat of fusion of a substance is measured by the amount of heat, needed to melt a unit mass of the substance, taken at melting point:

λ = QPL/m (12.1and)

We define the unit of heat of fusion of λ in SI: λ=1 j/1 kg = 1 J/kg.

The SI unit of λ take the specific heat of fusion, in which to melt the mass in 1 kg at a constant temperature takes 1 J. of energy.

The specific heat of fusion determined experimentally and in the calculations taken from tables.

Reklama