More than 10 million organic and more than 500 thousand inorganic compounds known to chemists today.Among them are complex in structure and properties that are unique in chemical or medical applications.And there are those that are not difficult to find and are very common in everyday life.But no less important and significant.One of such substances is common salt.In life it is also called the food and chemical industry called sodium chloride or sodium chloride.In the process industry it is known mineral that it forms in nature - halite and solid rock salt or rock salt.Let us consider the state of aggregation of salt, structure, properties, production, use, and history of the introduction of mass consumption.
In some states there is salt?
What is the physical state of matter and how it happens?It depends on what kind of substance in question.Each student is older than 7 class can call the state of aggregation of salt, because it is a substance that is in every home.Today, without difficult for mode
conditions for changing the state of aggregation
- To get the salt in a liquid state by melting solid crystals of natural origin, it is necessary to use a temperature equal to 800 ° C.
- To put salt in the gaseous state, molten crystals need to bring to a boil (about 1400 ° C) and heated to complete the transition of the structural components in the ions (Na + and CL-).
- solid state salt - is its natural look in natural conditions.
Why is this range of temperatures when handling crystals?This is due to the structure of the crystal lattice.
It is a regular face-centered cubic crystals are transparent.In each corner of the cube (lattice sites) are alternating positively charged Na + ions and negatively charged ions CL-.Due to sharply differing electronegativity of atoms occurs between the electrostatic attraction is so strong that its destruction is necessary to apply stringent conditions (high temperature, mechanical action).This type of lattice is known ionic, and it is characteristic of all alkali, alkaline earth and transition metals.
Therefore, the temperature of salt (for melting and for boiling) is so high.However, you can not only obtain crystals of cubic form, but also pyramidal (eight-, twelve- and icosahedral).To do this, you simply need to adjust the temperature of the evaporation of salt solution in a certain way.In any case, the inner cavity is filled with liquid crystal, if it is a solution of salt in water.
chemical formula for sodium chloride is simple and elemental composition expressed NaCL.
physical properties of halite
physical properties of sodium chloride can be described by a few points:
- solid crystals of white, pink, blue, purple, red.Colouring depends on the presence of impurities in the extraction.Pure white crystalline substance.
- dissolves in water in the approximate ratio 100/30 (100 g of water 30 g salt).Good solubility due to the presence of water dipoles that associate themselves around the sodium ions and chlorine, causing destruction of the electrostatic attraction between them and, consequently, destruction of the crystal lattice.
- melt and boil at high temperatures (800-1400oS).
- has barely perceptible pleasant odor.
- salty taste.
chemical properties of sodium chloride
Like any soluble average salt, sodium chloride is able to interact with:
- other salts by exchange reactions (prerequisite: evolution reaction gas precipitation or formation malodissotsiiruemogo substance):NaCL + AgNO3 = NaNO3 + AgCL (white curd was).This qualitative reaction on the ion CL-.
- with metals standing in the left EHRNM Sodium: To + NaCL = KCL + Na.
- dissociate in aqueous solution to free the dipoles of water hydrated ions: NaCL (water solution) = Na + + CL-.The result is a solution of salt, which is a strong electrolyte.
- not subjected to hydrolysis, as is the salt formed with a strong acid and a strong base.
- the electrolysis (the electric current) can be expanded with the formation of free products and sodium hydroxide (caustic soda): NaCL = Na + Cl2 + NaOH.
Where naturally contains sodium chloride?
Currently salt - a substance commonly found in nature.Although it has always been, but in ancient times and the Middle Ages it was considered a very expensive product.All this from the fact that did not know the methods of extraction of salt from natural sources.But these sources in world stocks very much - halite considered almost unlimited natural resource.Where is the salt found in nature?
- Seas and oceans of salt water.
- Salt Lake.
- Salty sources.
- waters of estuaries.
Extraction of halite
Extraction and processing of salt have their technology as a mined substance often unfit for consumption because of the high content of impurities.Mined rock salt in various ways, for example:
- by underground mining;
- layers at the bottom of the salt ponds;
- evaporation or freeze salty sea or ocean water;
- evaporation of groundwater.
Either method makes it possible to obtain crystals of halite.However, for food they have just one type of treatment - grinding.After all, hardly anyone uses the house for cooking large crystal salt.In most cases, it has become a cleansed of impurities, crushed to a powder form practically.There are also types of salt iodinated, fluorinated and so on, not only for food but also technical purposes.
The use of rock salt
Areas of application and use of sodium chloride are extensive.The main ones, together with examples and results are given in the table.
|of Industry||basics of using salt||result|
|Landscape Construction||softening soil at low temperatures and the removal of water leakage||construction of irrigation canals and reservoirs|
|Medicine||similarity of the salt solution with the blood of man.Krovezamenyayuschy sodium chloride solution (0.85%), called the physiologic||recovery after extensive blood krovepoter balance, normalization of the sodium-potassium pump in the circulatory system to maintain constant composition of gastric juice|
|Chemical synthesis of practically important substanceson the basis of raw material sodium chloride||obtained: sodium bicarbonate, hydrochloric acid, sodium metal, chlorine, sodium hydroxide, glass, plastic, soap, paper and other products|
|Food||antiseptic and antibacterial salt||Canning products (meat, fish, vegetables), improved palatability of food|
|Metallurgical||Physical and chemical properties of salt||Aluminium, salt batteries, filters|
|Tanning||antiseptic and antibacterial salt||processing fur and rawhideLeather tanning|
story of everyday life in
Sol appeared on the tables in each house is not immediately.Once it was worth its weight in gold, and in the truest sense.In the XVIII century, some African nations exchanged a handful of salt on a handful of golden sand.Later in Ethiopia wedges salt were the standard currency.In ancient Rome, the military legionnaires even monthly salaries were given this substance, that eventually led to the naming of their soldiers.Children of poor African people just licked pieces of stone table salt as a delicacy.In the Netherlands it was used to punish criminals for torture.The guilty do not give salt, and a man died in a short time.
first select and consume food in this stuff, people learned in ancient times.Then it was discovered that the salt contained in plants.Therefore, they were burned, and the ashes were used as a seasoning.Later in China have learned to evaporate salt from sea water, and the development of methods of its production began to move faster.
In Russia mined salt from the lakes (the most famous salt lakes Russia so far - Elton and Baskunchak).Then the commercial importance of matter is a very rare phenomenon.We extract it only a few merchants, who then sold at exorbitant prices.Afford salt could only rich and famous people.Over time, the production and extraction of normal.Steel used different methods of extraction and processing, and today is one of the most common household substances - salt.Chemistry of this compound, properties, applications in medicine and other industries have become known around XVI-XVII centuries.
Studying in a school course
study of the structure and the state of aggregation, as well as the chemical properties of the salt begins at school, within such disciplines as chemistry (Grade 8).Salts in a school course examines in all their diversity in nature.Students gain an understanding of the chemical basis of empirical formulas, the basic physical and chemical properties.For simplicity and ease of memorizing formulas and physical properties on the flyleaf of the textbook are usually located salt, table which gives an idea of their solubility in water.There you can find information on the solubility of acids, alkalis and bases.
important characteristic of salt is their melting behavior, on which also built their prey in nature.Students easily orient in solving problems in the melting behavior of salt.The table and graphics can not only see the low-melting or refractory material, but also determine the approximate melting point and boiling point.Typically, these tables are also located in the textbooks ("Chemistry", Grade 8).Salt should be studied in the context of such sciences as biology and physics.Therefore, the set of tasks for the students is built on the integration of interdisciplinary connections.