Incongruent transition, in
chemistry
Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds made of atoms, molecules and ions: their composition, structure, proper ...
, is a mass transition between two
phases which involves a change in
chemical composition
A chemical composition specifies the identity, arrangement, and ratio of the elements making up a compound.
Chemical formulas can be used to describe the relative amounts of elements present in a compound. For example, the chemical formula for ...
. This is contrasted with congruent transition, for which the composition remains the same.
The transition may be that of
melting
Melting, or fusion, is a physical process that results in the phase transition of a substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or pressure, which in ...
,
vaporization
Vaporization (or vaporisation) of an element or compound is a phase transition from the liquid phase to vapor. There are two types of vaporization: evaporation and boiling. Evaporation is a surface phenomenon, whereas boiling is a bulk phenomenon ...
or
allotropism. The concept is also often extended to related phenomena, for example,
incongruent dissolution of a solid by a liquid solvent, which is often encountered in
geology
Geology () is a branch of natural science concerned with Earth and other Astronomical object, astronomical objects, the features or rock (geology), rocks of which it is composed, and the processes by which they change over time. Modern geology ...
.
The term "phase decomposition" is sometimes used to describe incongruent transition. However, it has to be kept in mind that incongruent transition is described by an
equilibrium.
For an example, see
incongruent melting.
References
*
{{refend
Physical chemistry