Melting

As is known, the melting of direct override of a substance from the solid to the liquid aggregate state. If this process for pure substances at constant pressure, the present case melting temperature is uniquely determined. Melting temperature and pressure are referred to as the melting point. During the transition, the temperature remains constant, all the heat supplied is invested as a fusion to the change of state. Thus for example a water / ice mixture at atmospheric pressure at a temperature of 0 ° C. The opposite of melting is the solidification.

For mixtures, the melting process is more complicated because as more degrees of freedom are added, the composition of the solid and liquid phase. The melting process takes place not at a constant temperature but in a temperature range, the melting range. One exception is the pure substance behaving like a eutectic mixture. The behavior of a mixture during the melting process can be represented by a melting diagram. The liquid phase of a substance or mixture of substances is referred to as a melt.

For some substances, the transition from the solid to the liquid state via intermediate phases so-called mesophase takes place. Liquid crystals form smectic and nematic phases between the solid and liquid state. First the long-range order is given in the crystal, with a short-range order remains. In the opposite case is first dissolved in plastic crystals, the short-range order, with a long-range order is maintained. An example is the adamantane are called, where the high-symmetry ( " spherical " ) molecules in the plastic state have appropriate degrees of rotational freedom, the space in the crystal lattice but is preserved.

Supercooled melt

Under a supercooled liquid is meant a liquid which is located below its melting temperature and hence in a physical state that does not corresponds to their equilibrium state. This effect is also referred to simply as hypothermia and used in some latent heat storage.

Supercooled melt can go at the glass transition temperature in the amorphous state. This behavior specially the properties of organic polymers.