Solutions are a homogeneous mass or mixture consisting of two or more substances, in which one substance acts as a solvent, and the other as soluble particles.
There are two theories of interpretation of the origin of solutions: chemical, the founder of which is D. I. Mendeleev, and physical, proposed by the German and Swiss physicists Ostwald and Arrhenius. According to Mendeleev's interpretation, the components of the solvent and the solute become participants in a chemical reaction with the formation of unstable compounds of these very components or particles.
The physical theory denies the chemical interaction between the molecules of the solvent and the dissolved substances, explaining the process of formation of solutions as a uniform distribution of particles (molecules, ions) of the solvent between the particles of the dissolved substance due to a physical phenomenon called diffusion.
Classification of solutions according to various criteria
Today there is no unified classification system for solutions, however, conditionally, the types of solutions can be grouped according to the most significant criteria, namely:
I) According to the state of aggregation, solid, gaseous and liquid solutions are distinguished.
II) Bysolute particle sizes: colloidal and true.
III) According to the degree of concentration of the particles of the solute in the solution: saturated, unsaturated, concentrated, diluted.
IV) According to the ability to conduct electric current: electrolytes and non-electrolytes.
V) By purpose and scope: chemical, medical, construction, special solutions, etc.
Types of solutions by state of aggregation
Classification of solutions according to the state of aggregation of the solvent is given in the broadest sense of the meaning of this term. It is customary to consider liquid substances as solutions (moreover, both a liquid and a solid element can act as a solute), but if we take into account the fact that a solution is a homogeneous system of two or more substances, then it is quite logical to recognize also solid solutions, and gaseous. Solid solutions are considered to be mixtures of, for example, several metals, better known in everyday life as alloys. Gaseous types of solutions are mixtures of several gases, an example is the air around us, which is presented as a combination of oxygen, nitrogen and carbon dioxide.
Solutions by particle size
Types of solutions by the size of dissolved particles include true (ordinary) solutions and colloidal systems. In true solutions, the solute breaks down into small molecules or atoms that are close in size to the molecules of the solvent. At the same time, the true types of solutions retain the original properties of the solvent, only slightlytransforming it under the action of the physicochemical properties of the element added to it. For example: when s alt or sugar is dissolved in water, the water remains in the same state of aggregation and the same consistency, almost the same color, only its taste changes.
Colloid solutions differ from conventional ones in that the added component does not completely decompose, retaining complex molecules and compounds, the size of which is much larger than the solvent particles, exceeding the value of 1 nanometer.
Types of solution concentration
In the same amount of solvent, you can add a different amount of dissolved element, the output will have solutions with different concentrations. We list the main ones:
- Saturated solutions are characterized by the degree of solubility of a substance, at which the dissolved component, under the influence of a constant value of temperature and pressure, no longer decomposes into atoms and molecules, and the solution reaches phase equilibrium. Saturated solutions can also be conditionally divided into concentrated ones, in which the mass fraction of the dissolved component is comparable to the solvent, and dilute ones, where the solute is several times less than the solvent.
- Unsaturated are those solutions in which the solute can still decompose into small particles.
- Supersaturated solutions are obtained when the parameters of the influencing factors (temperature, pressure) change, as a result of which the process of "crushing" of the dissolvedsubstance, it becomes more than it was under normal (usual) conditions.
Electrolytes and non-electrolytes
Some substances in solutions decompose into ions capable of conducting electric current. Such homogeneous systems are called electrolytes. This group includes acids, most s alts. And solutions that do not conduct electric current are commonly called non-electrolytes (almost all organic compounds).
Groups of solutions by purpose
Solutions are indispensable in all sectors of the national economy, the specificity of which has created such types of special solutions as medical, construction, chemical and others.
Medical solutions are a collection of drugs in the form of ointments, suspensions, mixtures, solutions for infusions and injections and other dosage forms used for medical purposes for the treatment and prevention of various diseases.
Types of chemical solutions include a huge variety of homogeneous compounds used in chemical reactions: acids, s alts. These solutions can be of organic or inorganic origin, aqueous (sea water) or anhydrous (based on benzene, acetone, etc.), liquid (vodka) or solid (brass). They have found their application in various sectors of the national economy: chemical, food, textile industry.
Types of mortars have a viscous and thick consistency, which is why they are more suitable for the name of the mixture.
Due to their ability to harden quickly, they are successfully used as a binder for masonry walls, ceilings, load-bearing structures, as well as for finishing work. They are aqueous solutions, most often three-component (solvent, cement of various markings, aggregate), where sand, clay, crushed stone, lime, gypsum and other building materials are used as a filler.
