Are there many chemically pure substances in nature? What is sea water, milk, steel wire - individual substances, or do they consist of several components? In our article, we will get acquainted with the properties of solutions - the most common physico-chemical systems that have a variable composition. They may contain several components. So, milk is an organic solution containing water, drops of fat, protein molecules and mineral s alts. What is a solution and how can it be obtained? We will answer this and other questions in our article.
Use of solutions and their role in nature
Metabolism in biogeocenoses is carried out in the form of interaction of compounds dissolved in water. For example, the absorption of soil solution by plant roots, the accumulation of starch as a result of photosynthesis in plants, the digestive processes of animals and humans - all of them are reactions that occur in chemical solutions. It is impossible to imagine modern industries: space and aircraft industry, military industry, nuclear energywithout the use of alloys - solid solutions with unique technical characteristics. Several gases can also form mixtures, which we may call solutions. For example, air is a physical and chemical system that contains components such as nitrogen, oxygen, carbon dioxide, etc.
What is a solution?
By mixing together sulfate acid and water, we get its aqueous solution. Consider what it consists of. We will find the solvent - water, the solute - sulfuric acid and the products of their interaction. These include hydrogen cations, hydrosulfate - and sulfate ions. The composition of the physico-chemical system, consisting of a solvent and components, will depend not only on which substance is the solvent.
The most common and important solvent is water. The nature of the dissolved components is also of great importance. They can be roughly divided into three groups. These are practically insoluble compounds, slightly soluble and highly soluble. The last group is the most important. It includes most s alts, acids, alkalis, alcohols, monosaccharides. Poorly soluble compounds are also quite common in nature. These are gypsum, nitrogen, methane, oxygen. Practically insoluble in water will be metals, noble gases: argon, helium, etc., kerosene, oils.
How to quantify the solubility of a compound
The concentration of a saturated solution is the most important value that shows the solubility of a substance. Herexpressed as a value numerically equal to the mass of the compound in 100 g of solution. For example, a disinfectant medical product - salicylic alcohol is sold in pharmacies in the form of a 1% alcohol solution. This means that 100 g of the solution contains 1 gram of the active substance. What is the largest mass of sodium chloride that can be dissolved in 100 g of solvent at a certain temperature? You can find the answer to this question using a special table of solubility curves for solid compounds. So, at a temperature of 10 ⁰С, 38 g of table s alt can be dissolved in 100 g of water, at 80 ⁰С - 40 g of the substance. How to make a solution dilute? You need to add a certain amount of water to it. It is possible to increase the concentration of the physicochemical system by evaporating the solution, or by adding a certain portion of the dissolved compound to it.
Types of solutions
At a certain temperature, the system can be in equilibrium with the dissolved compound in the form of its precipitate. In this case, one speaks of a saturated solution. How to make a solution saturated? To do this, refer to the table of solubility of solids. For example, table s alt weighing 31 g is introduced into water at a temperature of 20 ºС and normal pressure, then it is well stirred. With additional heating and the introduction of an additional portion of s alt, its excess ensures the formation of a supersaturated solution. The cooling of the system will lead to the process of precipitation of sodium chloride crystals. Diluted solutions will be called such solutions in which the concentration of compounds in comparison with the volume of the solvent will besmall enough. For example, saline, which is part of the blood plasma and used in medicine after undergoing surgical interventions, is a 0.9% sodium chloride solution.
Mechanism of substance dissolution
Having considered the question of what a solution is, let's determine what processes underlie its formation. At the heart of the phenomenon of dissolution of substances, we see the interaction of both physical and chemical transformations. The main role in them is played by the phenomenon of the destruction of chemical bonds: covalent polar or ionic, in the molecules of the dissolved compound. The physical aspect of bond breaking is expressed in the absorption of energy. There is also an interaction of solvent particles with molecules of the solute, called solvation, in the case of aqueous solutions - hydration. It is accompanied not only by the emergence of new bonds, but also by the release of energy.
In our article, we examined the question of what a solution is, and also found out the mechanism for the formation of solutions and their significance.
