To characterize a sufficiently large number of both chemical and physical processes and systems, the category "phase" is used.
In the simplest sense, the category "phase"called an independent, part of a certain system, which is characterized by a relative homogeneity of structure and composition. The phase, as a rule, is quite autonomous and is separated from the other phases of the system by a certain boundary-the interphase section.
From the point of view of chemical systems, to whichthere is also a homogeneous system, the phase can be a substance in any aggregate state: gas, solid, liquid, as well as their mixtures and solutions. A common property is also that any non-miscible part of the gas, liquid or any of the solids constitute a separate phase. For example, if we consider as a sample a system that includes ice that melts and water, then in this system we can distinguish two phases - water and ice. The fact is that although they have one composition, they differ in the structure of matter, and therefore they represent autonomous phases. In the same way, we can give examples of the existence of substances in which we can fix the presence of only one phase. These include air, water solution of potassium permanganate, hydrochloric acid. In these compounds there are no visible interphase sections, and at each point of the system its composition is homogeneous.
At the same time, indicated at the very beginning of the articleThe definition of the concept is not sufficient and exhaustive. It includes the requirements of homogeneity and identity of the composition, but this approach is appropriate only for equilibrium systems. In the same case, when the system is in a state of chemical reaction, the phase may also be inhomogeneous. And the volumes of the homogeneous phase will be incommensurable with the dimensions of the elements making up this phase.
The category "phase" serves as a criterion forclassification of physical and chemical systems. In terms of their number, all systems are divided into such types as a homogeneous system and a heterogeneous system. Accordingly, it is possible to formulate a definition of these categories. A heterogeneous system is one in which the number of phases is not equal to one. And, accordingly, a homogeneous system is a system in which only one phase is released.
The phases themselves are also classified into types. The continuous phase is one in which a hit from one point to another occurs without crossing the interphase section. It is the presence of this and only such phase characterized by a homogeneous system.
In contrast, a heterogeneous system is created as a continuous phase, as well as dispersed, that is, fragmented into a number of individual components.
Examples of homogeneous systems are true solutions, because the particles that make up them are a mixture that exists at the atomic level.
The most significant physical meaning of thisThe concept characterizes such a category as the equilibrium constant of a homogeneous system. This constant, in turn, characterizes another important property of homogeneous systems - equilibrium. Reactions that occur within a single phase are called homogeneous, which means that all the elements participating in it are in the same aggregate state. Equilibrium in the course of such reactions characterizes such a concept as equilibrium in a homogeneous system. This means that the course of such reactions takes place up to an established concentration level at which both the direct and reverse reaction flow is possible. This state is also called the state of chemical equilibrium and it, by and large, acts as an indicator, in which the reaction flow ceases as such.
The equilibrium constant makes it possible to determine the ability of the complete course of a chemical reaction under certain conditions. It is a universal value and refers to any system.