The state of aggregation of salt. Salt, chemistry

Today, more than 10 million organic and more than 500 thousand inorganic compounds are known to chemists. Among them are complex in structure and properties, which are used only for chemical or medical purposes. And there are those that are not at all complicated in structure and very common in everyday life. But from this no less important and significant. One of these substances is table salt. In everyday life, it is also called food, and in the chemical industry it is called sodium chloride or sodium chloride. In the technological industry, it is called the mineral that it forms in nature - halite, as well as rock salt or hard rock salt. Let us consider in more detail the state of aggregation of salt, structure, properties, production, use and history of introduction into mass consumption.

In what conditions does table salt exist?

What is the state of aggregation of substances and how does it happen? It depends on the substance in question. Each student older than 7th grade can name the state of aggregation of salt, because this is the substance that is found in every home. Today, without it, it is difficult for a modern person to imagine his life. In addition, the aggregate state of sodium chloride is quite obvious to the naked eye - finely or coarsely dispersed crystals of the correct cubic form. However, dissolving the salt in water, we will get it already in another state of aggregation - liquid. We get the same thing if we simply melt the crystals at high temperature. The only condition that is not characteristic of salt is gaseous. But under certain conditions, you can get it.

Conditions for changing the state of aggregation

1. To obtain salt in a liquid state by melting solid crystals of natural origin, it is necessary to apply a temperature equal to 800 ^about C.
2. To transfer the salt to a gaseous state, the molten crystals must be brought to a boil (about 1400 ° C) and boiled until the structural components completely transfer into ions (Na ⁺ and CL ^- ).
3. The solid state of aggregation of salt is its natural appearance in natural conditions.

Why does such a temperature spread occur during manipulations with crystals? This is explained by the structure of the crystal lattice.

Crystal cell

It represents regular face-centered cubic transparent crystals. In each corner of the cube (nodes of the crystal lattice) there are alternating positively charged Na ⁺ ions and negatively charged CL ^- ions. Due to the sharply differing electronegativity of these atoms, so strong electrostatic attraction arises between them that in order to destroy it, it is necessary to apply harsh conditions (high temperature, mechanical stress). This type of crystal lattice is called ionic, and it is characteristic of all salts of alkali, alkaline earth and transition metals.

That is why the temperature of salt (both for melting and boiling) is so high. However, it is possible to obtain crystals not only of a cubic shape, but also of a pyramidal (eight-, twelve- and twenty-sided). To do this, you just need to adjust the evaporation temperature of the salt solution in a certain way. In any case, the internal cavity of the crystals remains filled with liquid, when it comes to a solution of salt in water.

The chemical formula of sodium chloride is simple and is expressed by the elemental composition of NaCL.

Physical properties of halite

The physical properties of sodium chloride can be described in several ways:

• Solid crystals of white, pink, blue, violet, red. The color depends on the presence of impurities during production. The pure substance is crystal white.
• It is soluble in water in a ratio of approximately 100/30 (30 g of salt in 100 g of water). Good solubility is explained by the presence of water dipoles, which associate sodium and chlorine ions around themselves, causing the destruction of electrostatic attraction between them and, as a result, the destruction of the crystal lattice.
• It melts and boils at high temperatures (800-1400 ).
• Has a subtle pleasant smell.
• Salty to the taste.

Chemical properties of sodium chloride

Like any soluble middle salt, sodium chloride is able to interact with:

• Other salts in the exchange reaction (prerequisite: gas evolution, precipitation or formation of a slightly dissociable substance): NaCL + AgNO ₃ = NaNO ₃ + AgCL (white curd cake). This is a qualitative response to the CL ^- ion ^.
• With metals standing in the ECM to the left of sodium: K + NaCL = KCL + Na.
• In an aqueous solution, it dissociates into free ions hydrated by dipoles of water: NaCL _(aqueous solution ₎ = Na ⁺ + CL ^- . The result is a solution of sodium chloride, which is a strong electrolyte.
• It is not hydrolyzed, as it is a salt formed by a strong acid and a strong base.
• During electrolysis (electric current) decomposes with the formation of free products and caustic soda (caustic): NaCL = Na + Cl ₂ + NaOH.

Where does sodium chloride naturally occur?

Currently, salt is a substance often found in nature. And although it always has been, but in ancient times and the Middle Ages it was considered a very expensive product. All this from the fact that they did not know how to extract salt from natural sources. And there are a lot of such sources in world reserves - halite is considered to be an almost unlimited natural resource. Where is salt found in nature?

1. Seas and oceans with salt water.
2. Salt lakes.
3. Salty springs.
4. The groundwater.
5. Water estuaries.

Halite mining

The extraction and processing of salt has its own technology, since simply extracted material is most often unsuitable for use due to the high content of impurities. Mining halite in different ways, for example:

• by underground work;
• from strata at the bottom of salt bodies of water;
• by evaporation or freezing of salty sea or ocean water;
• evaporation of groundwater.

Any of the methods makes it possible to obtain halite crystals. However, for eating, they must undergo another type of processing - grinding. After all, hardly anyone uses a large crystal of table salt at home in cooking. Most often, it is purchased in an already purified form of impurities, crushed almost into a powder form. There are also types of salt iodized, fluorinated, and so on, not only for food, but also for technical purposes.

The use of rock salt

Scopes and use of sodium chloride are very extensive. The main ones along with examples and results are shown in the table.

History of appearance in everyday life

Salt appeared on the tables in every house far from immediately. Once it was valued at its weight in gold, and in the most literal sense. As early as the 18th century, some African peoples exchanged a handful of salt for a handful of golden sand. A little later in Ethiopia, salt whetstones were the standard currency. In ancient Rome, military legionnaires were even given a monthly salary with this substance, which eventually led to their calling soldiers. Children of poor African nations simply licked stone chunks of salt as a treat. In Holland, it was used to punish criminals, for torture. The guilty party was not given salt at all, and the man died in a short time.

For the first time, people have learned to isolate and consume this substance in antiquity. Then it was discovered that salt is contained in plants. Therefore, they were burned, and ash was used as seasoning. Later in China, they learned to evaporate salt from sea water, and the process of developing methods for its production began to move faster.

In Russia, salt was mined from lakes (the most famous salt lakes in Russia so far are Elton and Baskunchak). Then the commercial value of the substance was a very rare occurrence. It was mined by only a few merchants who then sold at exorbitant prices. Only rich and famous people could allow themselves to have salt. Over time, production and production improved. Various methods of extraction and processing began to be used, and today one of the most common household substances is salt. The chemistry of this compound, its properties, and its use in medicine and other industries have been known since about the 16th-17th centuries.

Studying in a school course

The study of the structure and state of aggregation, as well as the chemical properties of table salt, begins with the school bench, in the framework of such a discipline as chemistry (Grade 8). Salts in the school course are studied in all their diversity in nature. Pupils get an idea of ​​the chemical base, empirical formulas, basic physical and chemical properties. For simplicity and convenience of memorizing formulas and physical properties , salts are usually placed on the bookend of the textbook, a table of which gives an idea of ​​their solubility in water. There you can find information on the solubility of acids, alkalis and bases.

An important characteristic of salts is their fusibility, on the basis of which their production in nature is also built. Students can easily navigate when solving problems on the fusibility of salt. The table and graphical images allow not only to see whether the substance is fusible or refractory, but also to determine the approximate melting and boiling points. Typically, such tables are also located in textbooks (Chemistry, Grade 8). Salts must be studied in the context of sciences such as biology and physics. Therefore, many tasks for students are built specifically on the integration of intersubject communications.