Every substance contains impurities. A substance is considered pure if it contains almost no impurities.

Mixtures of substances are either homogeneous or heterogeneous. In a homogeneous mixture, the components cannot be detected by observation, but in an inhomogeneous mixture it is possible.

Some physical properties of a homogeneous mixture differ from those of the components.

In a heterogeneous mixture, the properties of the components are preserved.

Heterogeneous mixtures of substances are separated by settling, filtering, sometimes by the action of a magnet, and homogeneous mixtures are separated by evaporation and distillation (distillation).

Pure substances and mixtures

We live among chemicals. We inhale air, and this is a mixture of gases (nitrogen, oxygen and others), we exhale carbon dioxide. We wash ourselves with water - this is another substance, the most common on Earth. We drink milk - a mixture of water with the smallest droplets of milk fat, and not only: there is also casein milk protein, mineral salts, vitamins and even sugar, but not the one with which they drink tea, but a special milk - lactose. We eat apples, which consist of a whole range of chemicals - sugar, malic acid, and vitamins... apple, but also any other food. We not only live among chemicals, but we ourselves are made of them. Every person - his skin, muscles, blood, teeth, bones, hair are built of chemicals, like a house of bricks. Nitrogen, oxygen, sugar, vitamins are substances of natural, natural origin. Glass, rubber, steel are also substances, more precisely, materials (mixtures of substances). Both glass and rubber are of artificial origin; they did not exist in nature. Completely pure substances are not found in nature or are very rare.

Each substance always contains a certain amount of impurities. A substance that contains almost no impurities is called pure. They work with such substances in a scientific laboratory, a school chemistry room. Note that absolutely pure substances do not exist.

An individual pure substance has a certain set of characteristic properties (constant physical properties). Only pure distilled water has tmelt = 0 °С, tboil = 100 °С, and has no taste. Sea water freezes at a lower temperature, and boils at a higher temperature, its taste is bitter-salty. The water of the Black Sea freezes at a lower temperature and boils at a higher temperature than the water of the Baltic Sea. Why? The fact is that sea water contains other substances, for example, dissolved salts, i.e. it is a mixture of various substances, the composition of which varies over a wide range, but the properties of the mixture are not constant. The concept of "mixture" was defined in the 17th century. English scientist Robert Boyle: "A mixture is an integral system consisting of heterogeneous components."

Almost all natural substances, food products (except salt, sugar, and some others), many medicinal and cosmetic products, household chemicals, and building materials are mixtures.

Comparative characteristics of a mixture and a pure substance

Each substance contained in a mixture is called a component.

Classification of mixtures

There are homogeneous and heterogeneous mixtures.

Homogeneous mixtures (homogeneous)

Add a small portion of sugar to a glass of water and stir until all the sugar is dissolved. The liquid will taste sweet. Thus, the sugar did not disappear, but remained in the mixture. Ho, we will not see its crystals, even when examining a drop of liquid in a powerful microscope. The prepared mixture of sugar and water is homogeneous; the smallest particles of these substances are evenly mixed in it.

Mixtures in which components cannot be detected by observation are called homogeneous.

Most metal alloys are also homogeneous mixtures. For example, an alloy of gold and copper (used to make jewelry) lacks red copper particles and yellow gold particles.

From materials that are homogeneous mixtures of substances, many items for various purposes are made.

All mixtures of gases, including air, belong to homogeneous mixtures. There are many homogeneous mixtures of liquids.

Homogeneous mixtures are also called solutions, even if they are solid or gaseous.

Let us give examples of solutions (air in a flask, table salt + water, small change: aluminum + copper or nickel + copper).

Heterogeneous mixtures (heterogeneous)

You know that chalk does not dissolve in water. If its powder is poured into a glass of water, then chalk particles can always be found in the resulting mixture, which are visible to the naked eye or through a microscope.

Mixtures in which components can be detected by observation are called heterogeneous.

Heterogeneous mixtures include most minerals, soil, building materials, living tissues, turbid water, milk and other foods, some medicines and cosmetics.

In a heterogeneous mixture, the physical properties of the components are preserved. So, iron filings mixed with copper or aluminum do not lose their ability to be attracted to a magnet.

Some types of heterogeneous mixtures have special names: foam (for example, foam, soap suds), suspension (a mixture of water with a small amount of flour), emulsion (milk, well-shaken vegetable oil with water), aerosol (smoke, fog).

Methods for separating mixtures

In nature, substances exist in the form of mixtures. For laboratory research, industrial production, for the needs of pharmacology and medicine, pure substances are needed.

There are many methods for separating mixtures. They are chosen taking into account the type of mixture, state of aggregation and differences in the physical properties of the components.

Methods for separating mixtures

These methods are based on differences in the physical properties of the components of the mixture.

Consider methods for separating heterogeneous and homogeneous mixtures.

Blend example	Separation method
Suspension - a mixture of river sand with water	settling Separation by settling is based on different densities of the substances. Heavier sand settles to the bottom. You can also separate the emulsion: to separate oil or vegetable oil from water. In the laboratory, this can be done using a separating funnel. Oil or vegetable oil forms the top, lighter layer. As a result of settling, dew falls out of the fog, soot is deposited from smoke, cream is settled in milk.
A mixture of sand and table salt in water	Filtration The separation of heterogeneous mixtures by filtration is based on the different solubility of substances in water and on different particle sizes. Only particles of substances commensurate with them pass through the pores of the filter, while larger particles are retained on the filter. So you can separate a heterogeneous mixture of table salt and river sand. Various porous substances can be used as filters: cotton wool, coal, fired clay, pressed glass, and others. The filtering method is the basis for the operation of household appliances, such as vacuum cleaners. It is used by surgeons - gauze bandages; drillers and workers of elevators - respiratory masks. With the help of a tea strainer for filtering tea leaves, Ostap Bender - the hero of the work of Ilf and Petrov - managed to take one of the chairs from Ellochka the Cannibal ("The Twelve Chairs").
A mixture of iron powder and sulfur	Action by magnet or water Iron powder was attracted by a magnet, but sulfur powder was not. The non-wettable sulfur powder floated to the surface of the water, while the heavy wettable iron powder settled to the bottom.
A solution of salt in water is a homogeneous mixture	Evaporation or crystallization The water evaporates and salt crystals remain in the porcelain cup. When water is evaporated from lakes Elton and Baskunchak, table salt is obtained. This separation method is based on the difference in the boiling points of the solvent and the solute. If a substance, such as sugar, decomposes when heated, then the water is not completely evaporated - the solution is evaporated, and then sugar crystals are precipitated from a saturated solution. Sometimes it is required to remove impurities from solvents with a lower boiling point, for example, water from salt. In this case, the vapors of the substance must be collected and then condensed upon cooling. This method of separating a homogeneous mixture is called distillation, or distillation. In special devices - distillers, distilled water is obtained, which is used for the needs of pharmacology, laboratories, and car cooling systems. At home, you can design such a distiller. If, however, a mixture of alcohol and water is separated, then the first to be distilled off (collected in a receiving test tube) is alcohol with tboil = 78 °C, and water will remain in the test tube. Distillation is used to obtain gasoline, kerosene, gas oil from oil.

Chromatography is a special method for separating components based on their different absorption by a particular substance.

If you hang a strip of filter paper over a vessel with red ink, immersing only the end of the strip in them. The solution is absorbed by the paper and rises along it. But the border of the rise of the paint lags behind the border of the rise of the water. This is how the separation of two substances occurs: water and the coloring matter in the ink.

With the help of chromatography, the Russian botanist M. S. Tsvet was the first to isolate chlorophyll from the green parts of plants. In industry and laboratories, instead of filter paper for chromatography, starch, coal, limestone, and aluminum oxide are used. Are substances always required with the same degree of purification?

For different purposes, substances with different degrees of purification are needed. Cooking water is sufficiently settled to remove impurities and chlorine used to disinfect it. Drinking water must first be boiled. And in chemical laboratories for the preparation of solutions and experiments, in medicine, distilled water is needed, as purified as possible from the substances dissolved in it. Highly pure substances, the content of impurities in which does not exceed one millionth of a percent, are used in electronics, semiconductor, nuclear technology and other precision industries.

Lesson type. Learning new material.

Lesson goals. Educational- to study the concepts of "pure substance" and "mixture", homogeneous (homogeneous) and heterogeneous (heterogeneous) mixtures, consider ways to separate mixtures, teach students to separate mixtures into components.

Educational- develop the intellectual and cognitive skills of students: highlight essential features and properties, establish cause-and-effect relationships, classify, analyze, draw conclusions, perform experiments, observe, draw up observations in the form of tables, diagrams.

Educational- to promote the education of students in organization, accuracy during the experiment, the ability to organize mutual assistance when working in pairs, the spirit of competition when performing exercises.

Teaching methods. Methods of organizing educational and cognitive activities- verbal (heuristic conversation), visual (tables, drawings, demonstrations of experiments), practical (laboratory work, exercises).

Methods for stimulating interest in learning- cognitive games, educational discussions.

Control methods– oral control, written control, experimental control.

Equipment and reagents.On student tables- sheets of paper, spoons for substances, glass rods, glasses of water, magnets, sulfur and iron powders.

On the teacher's desk- spoons, test tubes, test tube holder, alcohol lamp, magnet, water, chemical beakers, a stand with a ring, a stand with a foot, a funnel, glass rods, filters, a porcelain cup, a separating funnel, a test tube with a vent tube, a test tube-receiver, a "glass - refrigerator "with water, filter paper tape (2x10 cm), red ink, flask, sieve, iron and sulfur powders in a mass ratio of 7: 4, river sand, table salt, vegetable oil, copper sulfate solution, semolina, buckwheat.

DURING THE CLASSES

Organizing time

Mark those absent, explain the purpose of the lesson, and introduce students to the lesson plan.

P lan n u r o k a

1. Pure substances and mixtures. Distinctive features.

2. Homogeneous and heterogeneous mixtures.

3. Methods for separating mixtures.

Conversation on the topic "Substances and their properties"

Teacher. Remember what chemistry studies.

Student. Substances, properties of substances, changes that occur with substances, i.e. transformation of substances.

Teacher. What is a substance?

Student. Matter is what the physical body is made of.

Teacher. You know that substances are simple and complex. Which substances are called simple and which are complex?

Student. Simple substances are made up of atoms of one chemical element, complex substances are made up of atoms of different chemical elements..

Teacher. What physical properties do substances have?

Student. Aggregate state, melting and boiling points, electrical and thermal conductivity, solubility in water, etc..

Explanation of new material

Pure substances and mixtures.
Distinctive features

Teacher. Only pure substances have constant physical properties. Only pure distilled water has t pl \u003d 0 ° C, t kip \u003d 100 ° C, it has no taste. Sea water freezes at a lower temperature, and boils at a higher temperature, its taste is bitter-salty. The water of the Black Sea freezes at a lower temperature and boils at a higher temperature than the water of the Baltic Sea. Why? The fact is that sea water contains other substances, for example, dissolved salts, i.e. it is a mixture of various substances, the composition of which varies over a wide range, but the properties of the mixture are not constant. The concept of "mixture" was defined in the 17th century. English scientist Robert Boyle: "A mixture is an integral system consisting of heterogeneous components."

Consider the distinctive features of a mixture and a pure substance. To do this, we will perform the following experiments.

Experience 1. Using the experiment instructions, study the essential physical properties of iron and sulfur powders, prepare a mixture of these powders and determine whether these substances retain their properties in the mixture.

Discussion with students of the results of the experiment.

Teacher. Describe the state of aggregation and color of sulfur.

Student. Sulfur is a yellow solid.

Teacher. What is the state of aggregation and color of iron in powder form?

Student. Iron is a hard gray matter.

Teacher. How do these substances relate: a) to a magnet; b) to water?

Student. Iron is attracted by a magnet, but sulfur is not; iron powder sinks in water, because. iron is heavier than water, and sulfur powder floats to the surface of the water, because it is not wetted by water.

Teacher. What can be said about the ratio of iron and sulfur in the mixture?

Student. The ratio of iron and sulfur in the mixture can be different, i.e. fickle.

Teacher. Are the properties of iron and sulfur retained in the mixture?

Student. Yes, the properties of each substance in the mixture are preserved.

Teacher. How can a mixture of sulfur and iron be separated?

Student. This can be done by physical methods: a magnet or water.

Teacher . Experience 2. Now I will show the reaction of the interaction of sulfur and iron. Your task is to carefully observe this experiment and determine whether iron and sulfur retain their properties in the iron (II) sulfide obtained as a result of the reaction and whether iron and sulfur can be separated from it by physical methods.

I thoroughly mix iron and sulfur powders in a mass ratio of 7:4:

m(Fe ) : m( S ) = A r ( Fe ) : A r ( S ) = 56: 32 = 7: 4,

I put the mixture in a test tube, heat it in the flame of an alcohol lamp, heat it up strongly in one place and stop heating when a violent exothermic reaction begins. After the test tube has cooled, I carefully break it, after wrapping it in a towel, and remove the contents. Take a close look at the resulting substance - iron(II) sulfide. Are gray iron powder and yellow sulfur powder visible in it separately?

Student. No, the resulting substance has a dark gray color.

Teacher. Then I test the resulting substance with a magnet. Do iron and sulfur separate?

Student. No, the resulting substance is not magnetized.

Teacher. I put iron(II) sulfide in water. What do you observe while doing this?

Student. Iron(II) sulfide sinks in water.

Teacher. Do sulfur and iron retain their properties when incorporated into iron(II) sulfide?

Student. No, the new substance has properties that are different from the properties of the substances taken for the reaction.

Teacher. Is it possible to separate iron(II) sulfide by physical methods into simple substances?

Student. No, neither a magnet nor water can separate iron(II) sulfide into iron and sulfur.

Teacher. Is there a change in energy when a chemical is formed?

Student. Yes, for example, when iron and sulfur interact, energy is released.

Teacher. We will record the results of the discussion of experiments in the table.

Table

Comparative characteristics of a mixture and a pure substance

To consolidate this part of the lesson, do the exercise: determine where in the figure(see p. 34) a simple substance, a complex substance or a mixture is depicted.

Homogeneous and heterogeneous mixtures

Teacher. Find out if the mixtures differ in appearance from each other.

The teacher demonstrates examples of suspensions (river sand + water), emulsions (vegetable oil + water) and solutions (air in a flask, common salt + water, small change: aluminum + copper or nickel + copper).

Teacher. In suspensions, solid particles are visible, in emulsions - liquid droplets, such mixtures are called heterogeneous (heterogeneous), and in solutions the components are not distinguishable, they are homogeneous (homogeneous) mixtures. Consider the classification scheme for mixtures(scheme 1).

Scheme 1

Give examples of each type of mixture: suspensions, emulsions and solutions.

Methods for separating mixtures

Teacher. In nature, substances exist in the form of mixtures. For laboratory research, industrial production, for the needs of pharmacology and medicine, pure substances are needed.

Various methods for separating mixtures are used to purify substances (Scheme 2).

Scheme 2

These methods are based on differences in the physical properties of the components of the mixture.

Consider ways to separate heterogeneous mixtures.

How can a suspension be separated - a mixture of river sand with water, i.e., clean the water from sand?

Student. Settling and then filtering.

Teacher. Right. Separation upholding based on different densities of substances. Heavier sand settles to the bottom. You can also separate the emulsion: to separate oil or vegetable oil from water. In the laboratory, this can be done using a separating funnel. Petroleum or vegetable oil forms an upper, lighter layer. (Teacher demonstrates relevant experiments.)

As a result of settling, dew falls out of the fog, soot is deposited from smoke, cream is settled in milk.

And what is the basis for the separation of heterogeneous mixtures using filtering?

Student. On different solubility of substances in water and on different particle sizes.

Teacher. It is true that only particles of substances commensurate with them pass through the pores of the filter, while larger particles are retained on the filter. This is how you can separate a heterogeneous mixture of table salt and river sand.

The student shows experience: pours water into a mixture of sand and salt, mixes, and then passes the suspension (suspension) through the filter - a solution of salt in water passes through the filter, and large particles of sand insoluble in water remain on the filter.

Teacher. What substances can be used as filters?

Student. Various porous substances can be used as filters: cotton wool, coal, fired clay, pressed glass, and others.

Teacher. What examples of the application of filtering in human life can you give?

Student. The filtering method is the basis for the operation of household appliances, such as vacuum cleaners. It is used by surgeons - gauze bandages; drillers and workers of elevators - respiratory masks. With the help of a tea strainer for filtering tea leaves, Ostap Bender, the hero of the work of Ilf and Petrov, managed to take one of the chairs from Ellochka Ogre (“The Twelve Chairs”).

Teacher. And now, having become acquainted with these methods of separating the mixture, let's help the heroine of the Russian folk tale "Vasilisa the Beautiful".

Student. In this tale, Baba Yaga ordered Vasilisa to separate the rye from the nigella and the poppy from the ground. The heroine of the fairy tale was helped by pigeons. We can now separate the grains by filtration through a sieve if the grains are of different sizes, or by shaking with water if the particles have different densities or different wettability with water. Take as an example a mixture consisting of grains of various sizes: a mixture of semolina and buckwheat.(The student shows how semolina with smaller particle sizes passes through a sieve, and buckwheat remains on it.)

Teacher. But with a mixture of substances having different wettability with water, you have already met today. What mixture am I talking about?

Student. It is a mixture of iron and sulfur powders. We conducted a laboratory experiment with this mixture..

Teacher. Remember how you separated such a mixture.

Student. With the help of settling in water and with the help of a magnet.

Teacher. What did you observe while separating a mixture of iron and sulfur powders with water?

Student. The non-wettable sulfur powder floated to the surface of the water, while the heavy wettable iron powder settled to the bottom..

Teacher. And how was the separation of this mixture with a magnet?

Student. Iron powder was attracted by a magnet, but sulfur powder was not..

Teacher. So, we got acquainted with three methods for separating heterogeneous mixtures: settling, filtering and magnet action. Now let's look at ways to separate homogeneous (homogeneous) mixtures. Remember, after filtering off the sand, we got a solution of salt in water - a homogeneous mixture. How to isolate pure salt from a solution?

Student. Evaporation or crystallization.

The teacher demonstrates an experiment: water evaporates, and salt crystals remain in a porcelain cup.

Teacher. When water is evaporated from lakes Elton and Baskunchak, table salt is obtained. This separation method is based on the difference in the boiling points of the solvent and the solute.

If a substance, such as sugar, decomposes when heated, then the water is not completely evaporated - the solution is evaporated, and then sugar crystals are precipitated from a saturated solution.

Sometimes it is required to remove impurities from solvents with a lower boiling point, for example, water from salt. In this case, the vapors of the substance must be collected and then condensed upon cooling. This method of separating a homogeneous mixture is called distillation or distillation.

The teacher shows the distillation of a solution of copper sulfate, water evaporates when t bp = 100 °C, then the vapors are condensed in a receiving test tube cooled with water in a beaker.

Teacher. In special devices - distillers, distilled water is obtained, which is used for the needs of pharmacology, laboratories, and car cooling systems.

The student demonstrates a drawing of a “device” designed by him for distilling water.

Teacher. If, however, a mixture of alcohol and water is separated, then the first to be distilled off (collected in a receiving test tube) is alcohol with t bp = 78 ° C, and water will remain in the test tube. Distillation is used to obtain gasoline, kerosene, gas oil from oil.

A special method of separating components, based on their different absorption by a certain substance, is chromatography.

The teacher demonstrates the experience. He hangs a strip of filter paper over a vessel of red ink, dipping only the end of the strip into it. The solution is absorbed by the paper and rises along it. But the border of the rise of the paint lags behind the border of the rise of the water. This is how the separation of two substances occurs: water and the coloring matter in the ink.

Teacher. With the help of chromatography, the Russian botanist M.S. Tsvet was the first to isolate chlorophyll from the green parts of plants. In industry and laboratories, instead of filter paper for chromatography, starch, coal, limestone, and aluminum oxide are used. Are substances always required with the same degree of purification?

Student. For different purposes, substances with different degrees of purification are needed. Cooking water is sufficiently settled to remove impurities and chlorine used to disinfect it. Drinking water must first be boiled. And in chemical laboratories for the preparation of solutions and experiments, in medicine, distilled water is needed, as purified as possible from the substances dissolved in it. Highly pure substances, the content of impurities in which does not exceed one millionth of a percent, are used in electronics, semiconductor, nuclear technology and other precision industries.

Teacher. Listen to L. Martynov's poem "Distilled Water":

Water
Favored
pour!
She is
shone
So pure
Whatever to drink
Don't wash.
And it was no accident.
She missed
Willows, tala
And the bitterness of flowering vines,
She missed seaweed
And fish oily from dragonflies.
She missed being wavy
She missed flowing everywhere.
She didn't have enough life.
Clean -
Distilled water!

To consolidate and test the assimilation of the material, students answer the following questions: questions.

1. When ore is crushed at mining and processing plants, fragments of iron tools fall into it. How can they be extracted from ore?

2. Before recycling household waste, as well as waste paper, it is necessary to get rid of iron objects. What is the easiest way to do this?

3. The vacuum cleaner sucks in air containing dust, and releases clean air. Why?

4. Water after washing cars in large garages is contaminated with engine oil. What should be done before draining it into the sewer?

5. Flour is cleaned of bran by sifting. Why do they do it?

6. How to separate tooth powder and table salt? Gasoline and water? Alcohol and water?

Literature

Alikberova L.Yu. Entertaining chemistry. M.: AST-Press, 1999; Gabrielyan O.S., Voskoboynikova N.P., Yashukova A.V. Handbook of the teacher. Chemistry. 8th grade. Moscow: Bustard, 2002; Gabrielyan O.S. Chemistry.
8th grade. Moscow: Bustard, 2000; Guzey L.S., Sorokin V.V., Surovtseva R.P. Chemistry. 8th grade. Moscow: Bustard, 1995; Ilf I.A., Petrov E.P. Twelve Chairs. M.: Enlightenment, 1987; Kuznetsova N.E., Titova I.M., Gara N.N., Zhegin A.Yu. Chemistry. Textbook for students of the 8th grade of educational institutions. M.: Ventana-Graf, 1997; Rudzitis G.E., Feldman F.G. Chemistry. Textbook for grade 8 educational institutions. Moscow: Education, 2000; Tyldsepp A.A., Kork V.A.. We are studying chemistry. Moscow: Education, 1998.

Topic: "Methods for separating mixtures" (Grade 8)

theoretical block.

The concept of "mixture" was defined in the 17th century. English scientist Robert Boyle: "A mixture is an integral system consisting of heterogeneous components."

Comparative characteristics of a mixture and a pure substance

Signs of comparison	pure substance	Mixture
	Constant	fickle
Substances	Same	Various
Physical properties	Permanent	Fickle
Energy change during formation	going on	Not happening
Separation	Through chemical reactions	Physical methods

Mixtures differ from each other in appearance.

The classification of mixtures is shown in the table:

Here are examples of suspensions (river sand + water), emulsions (vegetable oil + water) and solutions (air in a flask, salt + water, small change: aluminum + copper or nickel + copper).

Methods for separating mixtures

In nature, substances exist in the form of mixtures. For laboratory research, industrial production, for the needs of pharmacology and medicine, pure substances are needed.

Various methods of separation of mixtures are used to purify substances.

Evaporation is the separation of solids dissolved in a liquid by converting it into vapor.

Distillation- distillation, separation of substances contained in liquid mixtures according to boiling points, followed by cooling of the vapor.

In nature, water in its pure form (without salts) does not occur. Oceanic, sea, river, well and spring water are varieties of salt solutions in water. However, often people need clean water that does not contain salts (used in car engines; in chemical production to obtain various solutions and substances; in the manufacture of photographs). Such water is called distilled, and the method of obtaining it is called distillation.

Filtration is the filtering of liquids (gases) through a filter in order to purify them from solid impurities.

These methods are based on differences in the physical properties of the components of the mixture.

Consider ways to separate heterogeneous and homogeneous mixtures.

Blend example	Separation method
Suspension - a mixture of river sand with water	settling Separation upholding based on different densities of substances. Heavier sand settles to the bottom. You can also separate the emulsion: to separate oil or vegetable oil from water. In the laboratory, this can be done using a separating funnel. Oil or vegetable oil forms the top, lighter layer. As a result of settling, dew falls out of the fog, soot is deposited from smoke, cream is settled in milk. Separation of a mixture of water and vegetable oil by settling
A mixture of sand and table salt in water	Filtration What is the basis for the separation of heterogeneous mixtures using filtering? On various solubility of substances in water and on various sizes of particles. Only particles of substances commensurate with them pass through the pores of the filter, while larger particles are retained on the filter. So you can separate a heterogeneous mixture of table salt and river sand. Various porous substances can be used as filters: cotton wool, coal, fired clay, pressed glass, and others. The filtering method is the basis for the operation of household appliances, such as vacuum cleaners. It is used by surgeons - gauze bandages; drillers and workers of elevators - respiratory masks. With the help of a tea strainer for filtering tea leaves, Ostap Bender, the hero of the work of Ilf and Petrov, managed to take one of the chairs from Ellochka Ogre (“The Twelve Chairs”). Separation of a mixture of starch and water by filtration
A mixture of iron powder and sulfur	Action by magnet or water Iron powder was attracted by a magnet, but sulfur powder was not. The non-wetting sulfur powder floated to the surface of the water, while the heavy wettable iron powder settled to the bottom. Separation of a mixture of sulfur and iron using a magnet and water
A solution of salt in water is a homogeneous mixture	Evaporation or crystallization The water evaporates and salt crystals remain in the porcelain cup. When water is evaporated from lakes Elton and Baskunchak, table salt is obtained. This separation method is based on the difference in the boiling points of the solvent and the solute. If a substance, such as sugar, decomposes when heated, then the water is not completely evaporated - the solution is evaporated, and then sugar crystals are precipitated from a saturated solution. Sometimes it is required to remove impurities from solvents with a lower temperature boiling, such as water from salt. In this case, the vapors of the substance must be collected and then condensed upon cooling. This method of separating a homogeneous mixture is called distillation or distillation. In special devices - distillers, distilled water is obtained, which is used for the needs of pharmacology, laboratories, and car cooling systems. At home, you can design such a distiller: If, however, a mixture of alcohol and water is separated, then the first to be distilled off (collected in a receiving test tube) is alcohol with t bp = 78 ° C, and water will remain in the test tube. Distillation is used to obtain gasoline, kerosene, gas oil from oil. Separation of homogeneous mixtures

A special method for separating components, based on their different absorption by a certain substance, is chromatography.

With the help of chromatography, the Russian botanist M. S. Tsvet was the first to isolate chlorophyll from the green parts of plants. In industry and laboratories, instead of filter paper for chromatography, starch, coal, limestone, and aluminum oxide are used. Are substances always required with the same degree of purification?

For different purposes, substances with different degrees of purification are needed. Cooking water is sufficiently settled to remove impurities and chlorine used to disinfect it. Drinking water must first be boiled. And in chemical laboratories for the preparation of solutions and experiments, in medicine, distilled water is needed, as purified as possible from the substances dissolved in it. Highly pure substances, the content of impurities in which does not exceed one millionth of a percent, are used in electronics, semiconductor, nuclear technology and other precision industries.

Methods for expressing the composition of mixtures.

Mass fraction of the component in the mixture- the ratio of the mass of the component to the mass of the entire mixture. Usually the mass fraction is expressed in %, but not necessarily.

ω ["omega"] = m component / m mixture

Mole fraction of a component in a mixture- the ratio of the number of moles (amount of substance) of the component to the total number of moles of all substances in the mixture. For example, if the mixture includes substances A, B and C, then:

χ [“chi”] component A \u003d n component A / (n (A) + n (B) + n (C))

Molar ratio of components. Sometimes in tasks for a mixture, the molar ratio of its components is indicated. For example:

n component A: n component B = 2: 3

Volume fraction of the component in the mixture (only for gases)- the ratio of the volume of substance A to the total volume of the entire gas mixture.

φ ["phi"] = V component / V mixture

Practice block.

Consider three examples of problems in which mixtures of metals react with hydrochloric acid:

Example 1When a mixture of copper and iron weighing 20 g was exposed to an excess of hydrochloric acid, 5.6 liters of gas (n.o.) were released. Determine the mass fractions of metals in the mixture.

In the first example, copper does not react with hydrochloric acid, that is, hydrogen is released when the acid reacts with iron. Thus, knowing the volume of hydrogen, we can immediately find the amount and mass of iron. And, accordingly, the mass fractions of substances in the mixture.

Example 1 solution.

Finding the amount of hydrogen:
n \u003d V / V m \u003d 5.6 / 22.4 \u003d 0.25 mol.

According to the reaction equation:

The amount of iron is also 0.25 mol. You can find its mass:
m Fe \u003d 0.25 56 \u003d 14 g.

Answer: 70% iron, 30% copper.

Example 2Under the action of an excess of hydrochloric acid on a mixture of aluminum and iron weighing 11 g, 8.96 liters of gas (n.o.) were released. Determine the mass fractions of metals in the mixture.

In the second example, the reaction is both metal. Here, hydrogen is already released from the acid in both reactions. Therefore, direct calculation cannot be used here. In such cases, it is convenient to solve using a very simple system of equations, taking for x - the number of moles of one of the metals, and for y - the amount of substance of the second.

Example 2 solution.

Finding the amount of hydrogen:
n \u003d V / V m \u003d 8.96 / 22.4 \u003d 0.4 mol.

Let the amount of aluminum be x mol, and iron y mol. Then we can express in terms of x and y the amount of hydrogen released:

1. 	2HCl \u003d FeCl 2 +

We know the total amount of hydrogen: 0.4 mol. Means,
1.5x + y = 0.4 (this is the first equation in the system).

For a mixture of metals, you need to express masses through quantities of substances.
m = Mn
So the mass of aluminum
m Al = 27x,
mass of iron
m Fe = 56y,
and the mass of the whole mixture
27x + 56y = 11 (this is the second equation in the system).

So we have a system of two equations:

2. It is much more convenient to solve such systems by the subtraction method, multiplying the first equation by 18:
   27x + 18y = 7.2
   and subtracting the first equation from the second:

   (56 - 18)y \u003d 11 - 7.2
   y \u003d 3.8 / 38 \u003d 0.1 mol (Fe)
   x = 0.2 mol (Al)

m Fe = n M = 0.1 56 = 5.6 g
m Al = 0.2 27 = 5.4 g
ω Fe = m Fe / m mixture = 5.6 / 11 = 0.50909 (50.91%),

respectively,
ω Al \u003d 100% - 50.91% \u003d 49.09%

Answer: 50.91% iron, 49.09% aluminum.

Example 316 g of a mixture of zinc, aluminum and copper was treated with an excess of hydrochloric acid solution. In this case, 5.6 l of gas (n.o.) was released and 5 g of the substance did not dissolve. Determine the mass fractions of metals in the mixture.

In the third example, two metals react, but the third metal (copper) does not react. Therefore, the remainder of 5 g is the mass of copper. The quantities of the remaining two metals - zinc and aluminum (note that their total mass is 16 - 5 = 11 g) can be found using a system of equations, as in example No. 2.

Answer to Example 3: 56.25% zinc, 12.5% ​​aluminum, 31.25% copper.

Example 4A mixture of iron, aluminum and copper was treated with an excess of cold concentrated sulfuric acid. At the same time, part of the mixture dissolved, and 5.6 liters of gas (n.o.) were released. The remaining mixture was treated with an excess of sodium hydroxide solution. 3.36 liters of gas evolved and 3 g of undissolved residue remained. Determine the mass and composition of the initial mixture of metals.

In this example, remember that cold concentrated sulfuric acid does not react with iron and aluminum (passivation), but reacts with copper. In this case, sulfur oxide (IV) is released.
With alkali reacts only aluminum- amphoteric metal (in addition to aluminum, zinc and tin also dissolve in alkalis, and beryllium can still be dissolved in hot concentrated alkali).

Example 4 solution.

Only copper reacts with concentrated sulfuric acid, the number of moles of gas:
n SO2 \u003d V / Vm \u003d 5.6 / 22.4 \u003d 0.25 mol

	2H 2 SO 4 (conc.) = CuSO 4 +

1. (do not forget that such reactions must be equalized using an electronic balance)

   Since the molar ratio of copper and sulfur dioxide is 1:1, then copper is also 0.25 mol. You can find the mass of copper:
   m Cu \u003d n M \u003d 0.25 64 \u003d 16 g.

   Aluminum reacts with an alkali solution, and an aluminum hydroxocomplex and hydrogen are formed:
   2Al + 2NaOH + 6H 2 O = 2Na + 3H 2

   Al 0 − 3e = Al 3+
   2H + + 2e = H 2

2. Number of moles of hydrogen:
   n H3 \u003d 3.36 / 22.4 \u003d 0.15 mol,
   the molar ratio of aluminum and hydrogen is 2:3 and, therefore,
   nAl \u003d 0.15 / 1.5 \u003d 0.1 mol.
   Aluminum weight:
   m Al \u003d n M \u003d 0.1 27 \u003d 2.7 g

   The remainder is iron, weighing 3 g. You can find the mass of the mixture:
   m mixture \u003d 16 + 2.7 + 3 \u003d 21.7 g.

   Mass fractions of metals:

ω Cu \u003d m Cu / m mixture \u003d 16 / 21.7 \u003d 0.7373 (73.73%)
ω Al = 2.7 / 21.7 = 0.1244 (12.44%)
ω Fe = 13.83%

Answer: 73.73% copper, 12.44% aluminum, 13.83% iron.

Example 521.1 g of a mixture of zinc and aluminum was dissolved in 565 ml of a nitric acid solution containing 20 wt. % HNO 3 and having a density of 1.115 g/ml. The volume of the released gas, which is a simple substance and the only product of the reduction of nitric acid, was 2.912 l (n.o.). Determine the composition of the resulting solution in mass percent. (RCTU)

The text of this problem clearly indicates the product of nitrogen reduction - "simple substance". Since nitric acid does not produce hydrogen with metals, it is nitrogen. Both metals dissolved in acid.
The problem asks not the composition of the initial mixture of metals, but the composition of the solution obtained after the reactions. This makes the task more difficult.

Example 5 solution.

Determine the amount of gas substance:
n N2 \u003d V / Vm \u003d 2.912 / 22.4 \u003d 0.13 mol.

We determine the mass of the nitric acid solution, the mass and amount of the dissolved HNO3 substance:

m solution \u003d ρ V \u003d 1.115 565 \u003d 630.3 g
m HNO3 \u003d ω m solution \u003d 0.2 630.3 \u003d 126.06 g
n HNO3 \u003d m / M \u003d 126.06 / 63 \u003d 2 mol

Please note that since the metals have completely dissolved, it means - just enough acid(these metals do not react with water). Accordingly, it will be necessary to check Is there too much acid?, and how much of it remains after the reaction in the resulting solution.

We compose the reaction equations ( do not forget about the electronic balance) and, for convenience of calculations, we take for 5x - the amount of zinc, and for 10y - the amount of aluminum. Then, in accordance with the coefficients in the equations, nitrogen in the first reaction will be x mol, and in the second - 3y mol:

	12HNO 3 \u003d 5Zn (NO 3) 2 +

Zn 0 − 2e = Zn 2+
2N+5+10e=N2

	36HNO 3 \u003d 10Al (NO 3) 3 +

It is convenient to solve this system by multiplying the first equation by 90 and subtracting the first equation from the second.

x \u003d 0.04, which means n Zn \u003d 0.04 5 \u003d 0.2 mol
y \u003d 0.03, which means that n Al \u003d 0.03 10 \u003d 0.3 mol

Let's check the mass of the mixture:
0.2 65 + 0.3 27 \u003d 21.1 g.

Now let's move on to the composition of the solution. It will be convenient to rewrite the reactions again and write down over the reactions the amounts of all reacted and formed substances (except water):

The next question is: did nitric acid remain in the solution and how much is left?
According to the reaction equations, the amount of acid that reacted:
n HNO3 \u003d 0.48 + 1.08 \u003d 1.56 mol,
those. the acid was in excess and you can calculate its remainder in solution:
n HNO3 rest. \u003d 2 - 1.56 \u003d 0.44 mol.

So in final solution contains:

zinc nitrate in the amount of 0.2 mol:
m Zn(NO3)2 = n M = 0.2 189 = 37.8 g
aluminum nitrate in the amount of 0.3 mol:
m Al(NO3)3 = n M = 0.3 213 = 63.9 g
an excess of nitric acid in an amount of 0.44 mol:
m HNO3 rest. = n M = 0.44 63 = 27.72 g

What is the mass of the final solution?
Recall that the mass of the final solution consists of those components that we mixed (solutions and substances) minus those reaction products that left the solution (precipitates and gases):

Then for our task:

m new solution \u003d mass of acid solution + mass of metal alloy - mass of nitrogen
m N2 = n M = 28 (0.03 + 0.09) = 3.36 g
m new solution \u003d 630.3 + 21.1 - 3.36 \u003d 648.04 g

ωZn (NO 3) 2 \u003d m in-va / m solution \u003d 37.8 / 648.04 \u003d 0.0583
ωAl (NO 3) 3 \u003d m in-va / m solution \u003d 63.9 / 648.04 \u003d 0.0986
ω HNO3 rest. \u003d m in-va / m solution \u003d 27.72 / 648.04 \u003d 0.0428

Answer: 5.83% zinc nitrate, 9.86% aluminum nitrate, 4.28% nitric acid.

Example 6When processing 17.4 g of a mixture of copper, iron and aluminum with an excess of concentrated nitric acid, 4.48 liters of gas (n.o.) were released, and when this mixture was exposed to the same mass of excess hydrochloric acid, 8.96 l of gas (n.o.). u.). Determine the composition of the initial mixture. (RCTU)

When solving this problem, we must remember, firstly, that concentrated nitric acid with an inactive metal (copper) gives NO 2, and iron and aluminum do not react with it. Hydrochloric acid, on the other hand, does not react with copper.

Answer for example 6: 36.8% copper, 32.2% iron, 31% aluminum.

Explanatory note

Pure substances and mixtures. Ways separation mixtures. To form an understanding of pure substances and mixtures. Ways purification substances: ... substances to various classes organic compounds. Characterize: basic classes organic compounds...

Order from 2013 No. Work program on the subject "Chemistry" Grade 8 (basic level 2 hours)

Working programm

Assessing students' knowledge of the possibility and ways separation mixtures substances; the formation of relevant experimental skills ... classification and chemical properties of basic substances classes inorganic compounds, the formation of ideas about ...

Document

... mixtures, ways separation mixtures. Tasks: Give the concept of pure substances and mixtures; Consider classification mixtures; Introduce students to ways separation mixtures... student and raises before class a card with the formula of an inorganic substance ...

12 16 ..

2.6. Processes for the separation of heterogeneous mixtures in food production

2.6.1. Classification of inhomogeneous systems and methods for their separation I

Heterogeneous systems are mixtures of at least two components that are in different phase states and separated by clear boundaries. In such systems, two phases of matter can be distinguished: a continuously distributed continuum of a phase called dispersion environment, and fragmented particles of various sizes and shapes located in it - dispersed phase. The particles of the dispersed phase have clear boundaries separating them from the dispersion medium. Inhomogeneous systems are also called heterogeneous or dispersed.The disperse medium of inhomogeneous systems can be in three states of aggregation. The dispersed phase can also be in these states. Theoretically, the existence of 9 inhomogeneous systems is possible. However, according to this classification, an inhomogeneous gas-gas (G-G) system does not exist, since the mixture of gases is a homogeneous system. In the above classification of heterogeneous systems, it is also necessary to distinguish systems with solid phases T-L, T-G, T-T, which are not subject to separation and therefore cannot be considered heterogeneous.

Thus, dusts, fumes, mists, suspensions, emulsions and foams should be classified as heterogeneous systems.

Dust- an inhomogeneous system consisting of a gas and solid particles distributed in it with a size of 5 - 50 microns. It is formed mainly during crushing and transportation of solid materials.

Smoke- an inhomogeneous system consisting of a gas and solid particles distributed in it with a size of 0.3 - 5 microns. It is formed during the combustion of substances.

Fog- an inhomogeneous system consisting of a gas and liquid droplets 0.3 - 3 μm in size distributed in it, formed as a result of condensation.

Dusts, fumes, mists bear the common name aerosols.

Suspension- an inhomogeneous system consisting of a liquid and solid particles suspended in it. Depending on the size of the particles, suspensions are distinguished: rough with particles larger than 100 microns, thin with particles larger than 0.1 - 100 microns and colloidal solutions containing particles smaller than 0.1 µm.

Emulsion- an inhomogeneous system consisting of a liquid and drops of another liquid distributed in it, which does not dissolve in the first one. The size of the particles of the dispersed phase varies within a fairly wide range.

Foam- an inhomogeneous system consisting of a liquid and gas bubbles distributed in it.

When the concentration of the dispersed phase changes, an inhomogeneous system can change its structure. This is accompanied by the so-called inversion phases. With inversion, the dispersion medium becomes a dispersed phase and vice versa. Thus, with an increase in the concentration of the solid phase in suspensions, a moment may come when the solid phase forms a continuous continuum (continuous medium) in which limited volumes of the liquid dispersed phase are distributed. In this case, it can be argued about the transition of the suspension into a plastic mass of class T-Zh.

Similar changes occur with foam if the liquid content in it increases; it passes into a supersaturated carbonated liquid, in which the dispersed phase of gas bubbles can be distinguished. Such a system is not sufficiently stable, although it can remain in this state for a relatively long time.

With an increase in the concentration of the solid dispersed phase, dust passes into a bulk product with specific properties, i.e. both solid and liquid media. Such a system has some elasticity and plasticity (the ability to maintain its shape under relatively small loads), but takes the form of a container into which it is filled; when poured onto a plane, it forms a cone with an angle of repose.

To separate inhomogeneous systems, methods and equipment are used that are distinguished by a wide variety of physical phenomena. The choice of the optimal equipment is determined by the choice of a sign according to which the dispersion medium and the dispersed phase differ significantly in their properties and according to which they should be separated. Such features are: density, strength, magnetic and electronic properties, etc. It is by the use of one or more of these features that the methods of separating these systems differ.

A sign consisting in the difference in densities that make up an inhomogeneous system is used in the following separation methods: deposition due to gravity, settling centrifugation (separation) and cyclone process.

In conservative force fields (gravity, centrifugal forces, inertial forces), the particles of the dispersed phase acquire acceleration, which, according to Newton's second law, is proportional to the acting force and inversely proportional to the particle mass. In solution, the particles begin to move in the dispersion medium in the direction of the acting force vector. Their velocities eventually stabilize at a level corresponding to the balance of the driving force and the resistance forces of the medium. With a given speed, all "heavy" and denser than the dispersion medium particles settle on the hard surfaces of the equipment.

The sign, consisting in the difference in the magnetic properties that make up an inhomogeneous system, is used to isolate particles of metallomagnetic inclusions from a dispersion medium. In this case, under the action of magnetic forces, metal-magnetic particles are accelerated in the direction of their action, while the environment remains stationary. Due to this, phase separation occurs in space.

A sign based on the difference in electrical properties that make up an inhomogeneous system is used in electrostatic precipitators. Under the action of a high electrical voltage, the particles of the dispersed phase can be ionized and move in space to the filter electrodes.

The feature, which consists in the retention of particles of the dispersed phase on solid partitions, is used in processes filtering(due to pressure difference and centrifugal filtration).

A sign associated with the association of dispersed particles into larger complexes is used in the separation of dusty gas systems wet way.

It is also possible to combine methods for separating heterogeneous systems.

2.6.2. Material balances of separation processes

Consider an inhomogeneous system, for example, a suspension to be separated and consisting of a substance (continuous phase) and particles of the substance (dispersed phase) distributed in it.

Let's designate: - weights of the initial mix, the clarified liquid and the received deposit; - the content of the substance in the initial mixture, clarified liquid and sediment (mass fractions).

In the absence of losses in the separation process, the material balance equations have the form:

by total amount of substances

by dispersed phase (substance)

The joint solution of the equations makes it possible to determine the amount of clarified liquid and the amount of sediment obtained at a given content of the substance in the sediment and clarified liquid.

In our article, we will consider what pure substances and mixtures are, methods for separating mixtures. Each of us uses them in everyday life. Do pure substances occur in nature at all? And how to distinguish them from mixtures?

Pure substances and mixtures: ways to separate mixtures

Pure substances are substances that contain particles of only a certain type. Scientists believe that they practically do not exist in nature, since all of them, albeit in negligible proportions, contain impurities. Absolutely all substances are also soluble in water. Even if, for example, a silver ring is immersed in this liquid, the ions of this metal will go into solution.

A sign of pure substances is the constancy of composition and physical properties. In the process of their formation, a change in the amount of energy occurs. Moreover, it can both increase and decrease. A pure substance can be separated into its individual components only by a chemical reaction. For example, only distilled water has a typical boiling and freezing point for this substance, the absence of taste and smell. And its oxygen and hydrogen can be decomposed only by electrolysis.

And how do they differ from pure substances in their totality? Chemistry will help us answer this question. Methods for separating mixtures are physical, since they do not lead to a change in the chemical composition of substances. Unlike pure substances, mixtures have variable composition and properties, and they can be separated by physical methods.

What is a mixture

A mixture is a collection of individual substances. An example is sea water. Unlike distilled, it has a bitter or salty taste, boils at a higher temperature, and freezes at a lower temperature. Methods for separating mixtures of substances are physical. So, pure salt can be obtained from sea water by evaporation and subsequent crystallization.

Types of mixtures

If you add sugar to water, after a while its particles will dissolve and become invisible. As a result, they cannot be distinguished with the naked eye. Such mixtures are called homogeneous or homogeneous. Air, gasoline, broth, perfume, sweet and salt water, and an alloy of copper and aluminum are also examples of these. As you can see, they can be in different states of aggregation, but liquids are most common. They are also called solutions.

In heterogeneous, or heterogeneous mixtures, particles of individual substances can be distinguished. Iron and wood filings, sand and table salt are typical examples. Heterogeneous mixtures are also called suspensions. Among them, suspensions and emulsions are distinguished. The former consists of a liquid and a solid. So, an emulsion is a mixture of water and sand. An emulsion is a combination of two liquids with different densities.

There are heterogeneous mixtures with special names. So, an example of foam is foam, and aerosols include fog, smoke, deodorants, air fresheners, antistatic agents.

Methods for separating mixtures

Of course, many mixtures have more valuable properties than individual individual substances that make up their composition. But even in everyday life there are situations when they need to be separated. And in industry, entire industries are based on this process. For example, from oil as a result of its processing, gasoline, gas oil, kerosene, fuel oil, solar oil and machine oil, rocket fuel, acetylene and benzene are obtained. Agree, it is more profitable to use these products than mindlessly burning oil.

Now let's see if there is such a thing as chemical methods for separating mixtures. Suppose we need to obtain pure substances from an aqueous solution of salt. To do this, the mixture must be heated. As a result, the water will turn into steam, and the salt will crystallize. But at the same time, there will be no transformation of one substance into another. This means that the basis of this process are physical phenomena.

Methods for separating mixtures depend on the state of aggregation, the ability to dissolve, the difference in boiling point, the density and composition of its components. Let's consider each of them in more detail with specific examples.

Filtration

This separation method is suitable for mixtures containing a liquid and an insoluble solid. For example, water and river sand. This mixture must be passed through a filter. As a result, clean water will freely pass through it, and the sand will remain.

settling

Some methods of separating mixtures are based on the action of gravity. In this way, suspensions and emulsions can be decomposed. If vegetable oil gets into the water, the mixture must first be shaken. Then leave it for a while. As a result, the water will be at the bottom of the vessel, and the oil will cover it in the form of a film.

In laboratory conditions, they are used for settling. As a result of its work, a denser liquid is drained into a vessel, and a light one remains.

Settling is characterized by a low speed of the process. It takes a certain amount of time for the precipitate to form. In industrial conditions, this method is carried out in special structures called sedimentation tanks.

Magnet action

If the mixture contains metal, then it can be separated using a magnet. For example, to separate iron and But do all metals have such properties? Not at all. For this method, only mixtures containing ferromagnets are suitable. In addition to iron, these include nickel, cobalt, gadolinium, terbium, dysprosium, holmium, and erbium.

Distillation

This name, translated from Latin, means "draining drops." Distillation is a method of separating mixtures based on the difference in boiling points of substances. Thus, even at home, alcohol and water can be separated. The first substance begins to evaporate already at a temperature of 78 degrees Celsius. Touching the cold surface, the alcohol vapor condenses, turning into a liquid state.

In industry, oil refining products, aromatic substances, and pure metals are obtained in this way.

Evaporation and crystallization

These separation methods are suitable for liquid solutions. The substances that make up their composition differ in their boiling point. Thus, it is possible to obtain crystals of salt or sugar from the water in which they are dissolved. To do this, the solutions are heated and evaporated to a saturated state. In this case, the crystals are deposited. If it is necessary to obtain pure water, then the solution is brought to a boil, followed by condensation of the vapors on a colder surface.

Methods for separating gas mixtures

Gaseous mixtures are separated by laboratory and industrial methods, since this process requires special equipment. The raw material of natural origin is air, coke, generator, associated and natural gas, which is a combination of hydrocarbons.

The physical methods for separating mixtures in the gaseous state are as follows:

• Condensation is the process of gradual cooling of a mixture, during which the condensation of its constituents occurs. In this case, first of all, high-boiling substances, which are collected in separators, pass into the liquid state. In this way, hydrogen is obtained from and also ammonia is separated from the unreacted part of the mixture.
• Sorption is the absorption of some substances by others. This process has opposite components, between which equilibrium is established during the reaction. The forward and reverse processes require different conditions. In the first case, it is a combination of high pressure and low temperature. This process is called sorption. Otherwise, the opposite conditions are used: low pressure at high temperature.
• Membrane separation is a method in which the property of semi-permeable partitions is used to selectively pass molecules of various substances.
• Reflux - the process of condensation of high-boiling parts of mixtures as a result of their cooling. In this case, the temperature of the transition to the liquid state of the individual components should differ significantly.

Chromatography

The name of this method can be translated as "I write with color." Imagine that ink is added to the water. If you lower the end of the filter paper into such a mixture, it will begin to be absorbed. In this case, water will be absorbed faster than ink, which is associated with a different degree of sorption of these substances. Chromatography is not only a method for separating mixtures, but also a method for studying such properties of substances as diffusion and solubility.

So, we got acquainted with such concepts as "pure substances" and "mixtures". The first are elements or compounds consisting only of particles of a certain type. Their examples are salt, sugar, distilled water. Mixtures are a collection of individual substances. A number of methods are used to separate them. The way they are separated depends on the physical properties of its constituents. The main ones are settling, evaporation, crystallization, filtration, distillation, magnetization and chromatography.