True solutions are what? Properties and composition

In nature, there are practically no pure substances. Basically, they are presented in the form of mixtures that are capable of forming homogeneous or heterogeneous systems.

Features of true solutions

True solutions are a kind of disperse systems having great strength between the dispersion medium and the disperse phase.

Any chemical can produce crystals of different sizes. In any case, they will have the same internal structure: an ionic or molecular crystal lattice.

Dissolution

During the dissolution of grains of sodium chloride and sugar in the water, an ionic and molecular solution forms. Depending on the degree of fragmentation, the substance can be in the form:

• Visible macroscopic particles, the size of which is greater than 0.2 mm;
• Microscopic particles having a size smaller than 0.2 mm, they can be caught only by means of a microscope.

The true and colloidal solutions differ in the size of the particles of the solute. Invisible crystals are called colloidal particles in a microscope, and the resulting state is called a colloidal solution.

Solution phase

In many cases, true solutions are disintegrated (disperse) systems of a homogeneous form. They contain a continuous continuous phase - the dispersion medium, and crushed particles of a certain shape and size (dispersed phase). What is the difference between colloidal solutions and true systems?

The main difference is in the size of the particles. Colloidal-dispersed systems are considered heterogeneous, since it is impossible to detect the interface between the phases in a light microscope.

True solutions are the option when in the environment the substance is represented as ions or molecules. They refer to single-phase homogeneous solutions.

As a prerequisite for the formation of dispersed systems, the mutual dissolution of the dispersion medium and the dispersible substance is considered. For example, sodium chloride and sucrose are insoluble in benzene and kerosene, therefore, in such a solvent, colloidal solutions will not be formed.

Classification of disperse systems

How are disperse systems divided ? True solutions, colloidal systems differ in several parameters.

There is a subdivision of dispersed systems over the aggregate state of the medium and the dispersed phase, the formation or absence of interaction between them.

Characteristics

There are certain quantitative characteristics of the dispersity of matter. First of all, the degree of dispersion is distinguished. This quantity is the inverse of the particle size. It characterizes the number of particles that can be placed in a row at a distance of one centimeter.

In the case when all particles have the same dimensions, a monodisperse system is formed. With unequal particles of the disperse phase, a polydisperse system is formed.

With the increase in the dispersity of matter, the processes that occur in the interphase surface increase in it. For example, the specific surface area of the dispersed phase increases, physicochemical effects of the medium on the interface between the two phases increase.

Variants of disperse systems

Depending on the phase in which the solute is to be found, different variants of disperse systems are isolated.

Aerosols are disperse systems in which a dispersed medium is represented in gaseous form. Fogs are aerosols that have a liquid dispersed phase. Smoke and dust form a solid dispersed phase.

Foams are a dispersion in the liquid of a gaseous substance. Liquids in foams degenerate to films that separate gas bubbles.

Emulsions are called disperse systems, where one liquid is distributed in volume by another without dissolving in it.

Suspensions or suspensions are low-dispersion systems in which solid particles are in a liquid. Colloidal solutions or sols with an aqueous dispersed system are called hydrosols.

Depending on the presence (absence) between the particles of the disperse phase, free-dispersed or coherent dispersed systems are isolated. The first group includes lysozols, aerosols, emulsions, suspensions. In such systems, there are no contacts between the particles and the dispersed phase. They are free to move in solution under the influence of gravity.

Coupled-disperse systems arise in the case of contact of particles with a dispersed phase, as a result of which structures are formed in the form of a grid or a framework. Such colloidal systems are called gels.

The process of gelation (gelation) is the conversion of the sol to a gel based on a decrease in the stability of the initial sol. Examples of cohesive dispersed systems are suspensions, emulsions, powders, foams. They can also include the soil formed during the interaction of organic (humic) substances and soil minerals.

Capillary-disperse systems are characterized by a continuous mass of substance penetrating the capillaries and pores. They consider fabrics, different membranes, wood, cardboard, paper.

True solutions are homogeneous systems consisting of two components. They can exist in solvents different in the aggregate state. The solvent is considered to be a substance taken in excess. A component that is taken in insufficient quantities is considered to be a dissolved substance.

Features of solutions

Solid alloys are also solutions in which various metals act as dispersed media and components. From a practical point of view of particular interest are such liquid mixtures in which the liquid acts as a solvent.

Of the many inorganic solvents, water is of particular interest. Almost always, the true solution is formed when particles of a dissolved substance are mixed with water.

Among organic compounds, the following substances are excellent solvents: ethanol, methanol, benzene, carbon tetrachloride, acetone. Due to the chaotic motion of molecules or ions of the dissolved component, a partial transition to the solution takes place, the formation of a new homogeneous system.

Substances differ in their ability to form solutions. Some can mix with each other in unlimited quantities. An example is the dissolution in water of crystals of common salt.

The essence of the process of dissolution from the point of view of the molecular-kinetic theory lies in the fact that after the introduction of crystals of sodium chloride into the solvent, it dissociates into sodium cations and chlorine anions. Charged particles vibrate, collisions with particles of the solvent itself lead to the transition of ions into the solvent (binding). Gradually, other particles are connected to the process, the surface layer is destroyed, the salt crystal dissolves in water. Diffusion makes it possible to distribute particles of matter along the volume of the solvent.

Kinds of true solutions

A true solution is a system that is divided into several types. There is a classification of such systems for water and non-aqueous by the type of solvent. They are also classified according to the variant of the dissolved substance for alkalis, acids, salts.

There are different types of true solutions with respect to electric current: nonelectrolytes, electrolytes. Depending on the concentration of the solute, they can be diluted or concentrated.

The true solutions of low-molecular substances from the thermodynamic point of view are divided into real and ideal.

Such solutions can be ionic-dispersed, as well as molecular-dispersed systems.

Saturation of solutions

Supersaturated, unsaturated, saturated solutions exist, depending on how many particles pass into the solution. The solution is a liquid or solid, homogeneous system that consists of several components. In any such system, there is necessarily a solvent, as well as a dissolved substance. With the dissolution of some substances, heat is released.

Such a process confirms the theory of solutions, according to which, dissolution is regarded as a physicochemical process. There is a subdivision of the process of solubility into three groups. The first are those substances that are capable of dissolving in an amount of 10 g per 100 g of solvent, they are called well soluble.

The substances are considered to be a little soluble if less than 10 g is dissolved in 100 g of the component, the others are called insoluble.

Conclusion

Systems consisting of different in aggregate state, particle sizes, are necessary for normal human activity. The true, colloidal solutions discussed above are used for making medicines, creating food products. Having an idea of the concentration of the dissolved substance, you can independently prepare the necessary solution, for example, ethyl alcohol or acetic acid, for various purposes in everyday life. Depending on the state in which the soluble substance and solvent are in the aggregate state, the resulting systems have certain physical and chemical characteristics.