heterogeneous systems, unlike homogeneous represents a physicochemical system in which there are differing physical properties phase.That is, there are parts which are different states of aggregation and structure elements.One phase of such a system is separated from other boundary across which is a qualitative leap in the changes in the physicochemical properties of (material).These variable parameters may be the shape and structure of the crystal lattice, the density of matter, its composition, the electromagnetic field and others.
Thus, in a heterogeneous system, there is, at least, a mechanical separation of the phases.Examples of such systems are the water and steam, which are different aggregate states, oil and water, which are in the same vessel, have different compositions and others.Quite often it is impossible to distinguish between homogeneous and heterogeneous systems, because it is difficult to establish the very border of the transition between the phases.For example, in the mechanical suspensions of the border occupy colloids, and they have the smallest particles of the solute.On the one hand - this homogeneous system, because the particle size is so small that their size can be neglected.On the other hand, at least at the atomic level, but the substance they still present in this case, such a system can be regarded as a heterogeneous.
most important parameter characterizing the principle of heterogeneity are the heterogeneous equilibrium.Consider the meaning of this phenomenon on the example of aqueous solutions.They are heterogeneous equilibrium properties that are to carry the particles through the phase boundary limit, at least in two adjacent phases.We shall deal in this specification only a small range of these phenomena which are most significant in terms of its practical application.The properties of heterogeneous equilibrium are quite diverse, and therefore occur in chemical processes, and are of interest from the point of view of theoretical analysis in physical chemistry.
In practical interest are, above all, systems such as the solid - liquid phase (precipitate - a saturated solution).This system is important because in practice many chemical technologies are based on separation of one material from another.In addition, important and reverse processes where heterogeneous equilibrium play a big role.These include the transfer of the reaction of poorly soluble compounds in solutions.
Another system - solid phase - liquid solution is based on the phenomenon of ion exchange.This phenomenon is common in the chemical purification technologies aqueous solutions of different kinds of impurities, and used when necessary to separate substances from each other.In this case, there are heterogeneous equilibrium in electrolyte solutions are important because the usual methods for separating chemical compounds are ineffective.The practical implementation of such transitions is provided by ion exchange, which takes place on the surface of ion-exchange resins in the electrolytic reaction.
third common of the systems under consideration - a system of liquid - liquid phase, it is a solvent with different compositions of matter.This case is applied when two immiscible solutions contained in each other substances with different solubility characteristics, i.e., there are isolated heterogeneous equilibrium.The practical use of this phenomenon is called extraction.In the industrial production and chemical extraction process stands as the most effective method for separating substances.
