Alcohol is a liquid or gaseous substance. Gaseous substances: examples and properties

Today, the existence of more than 3 million different substances is known. And this figure is growing every year, as synthetic chemists and other scientists are constantly conducting experiments to obtain new compounds that have some useful properties.

Some substances are natural inhabitants, formed naturally. The other half are artificial and synthetic. However, in both the first and second cases, a significant part is made up of gaseous substances, examples and characteristics of which we will consider in this article.

Aggregate states of substances

Since the 17th century, it was generally accepted that all known compounds are capable of existing in three states of aggregation: solid, liquid, and gaseous substances. However, careful research in recent decades in the fields of astronomy, physics, chemistry, space biology and other sciences has proven that there is another form. This is plasma.

What is she? This is partially or completely. And it turns out that there is an overwhelming majority of such substances in the Universe. So, it is in the plasma state that the following are found:

• interstellar matter;
• cosmic matter;
• upper layers of the atmosphere;
• nebulae;
• composition of many planets;
• stars.

Therefore, today they say that there are solids, liquids, gases and plasma. By the way, every gas can be artificially transferred to this state if it is subjected to ionization, that is, forced to turn into ions.

Gaseous substances: examples

There are a lot of examples of the substances under consideration. After all, gases have been known since the 17th century, when Van Helmont, a natural scientist, first obtained carbon dioxide and began to explore its properties. By the way, he also gave the name to this group of compounds, since, in his opinion, gases are something disordered, chaotic, associated with spirits and something invisible, but tangible. This name has taken root in Russia.

It is possible to classify all gaseous substances, then it will be easier to give examples. After all, it is difficult to cover all the diversity.

According to the composition they are distinguished:

• simple,
• complex molecules.

The first group includes those that consist of identical atoms in any quantity. Example: oxygen - O 2, ozone - O 3, hydrogen - H 2, chlorine - CL 2, fluorine - F 2, nitrogen - N 2 and others.

• hydrogen sulfide - H 2 S;
• hydrogen chloride - HCL;
• methane - CH 4;
• sulfur dioxide - SO 2;
• brown gas - NO 2;
• freon - CF 2 CL 2;
• ammonia - NH 3 and others.

Classification by nature of substances

You can also classify the types of gaseous substances according to their belonging to the organic and inorganic world. That is, by the nature of the atoms that make up it. Organic gases are:

• the first five representatives (methane, ethane, propane, butane, pentane). General formula C n H 2n+2 ;
• ethylene - C 2 H 4;
• acetylene or ethylene - C 2 H 2;
• methylamine - CH 3 NH 2 and others.

Another classification that can be applied to the compounds in question is division based on the particles they contain. Not all gaseous substances are made of atoms. Examples of structures in which ions, molecules, photons, electrons, Brownian particles, and plasma are present also refer to compounds in this state of aggregation.

Properties of gases

The characteristics of substances in the state under consideration differ from those of solid or liquid compounds. The thing is that the properties of gaseous substances are special. Their particles are easily and quickly mobile, the substance as a whole is isotropic, that is, the properties are not determined by the direction of movement of the structures included in the composition.

We can identify the most important physical properties gaseous substances, which will distinguish them from all other forms of existence of matter.

1. These are connections that cannot be seen, controlled, or felt by ordinary human means. To understand the properties and identify a particular gas, they rely on four parameters that describe them all: pressure, temperature, amount of substance (mol), volume.
2. Unlike liquids, gases are capable of occupying the entire space without a trace, limited only by the size of the vessel or room.
3. All gases easily mix with each other, and these compounds do not have an interface.
4. There are lighter and heavier representatives, so under the influence of gravity and time, it is possible to see their separation.
5. Diffusion is one of the the most important properties these connections. The ability to penetrate other substances and saturate them from the inside, while performing completely disordered movements within its structure.
6. Real gases electricity cannot conduct, but if we talk about rarefied and ionized substances, then conductivity increases sharply.
7. The heat capacity and thermal conductivity of gases is low and varies among different species.
8. Viscosity increases with increasing pressure and temperature.
9. There are two options for interphase transition: evaporation - a liquid turns into vapor, sublimation - a solid substance, bypassing the liquid one, becomes gaseous.

A distinctive feature of vapors from true gases is that the former, under certain conditions, are capable of turning into a liquid or solid phase, while the latter are not. It should also be noted that the compounds in question are able to resist deformation and be fluid.

Such properties of gaseous substances allow them to be widely used in the most various areas science and technology, industry and national economy. In addition, specific characteristics are strictly individual for each representative. We considered only the features common to all real structures.

Compressibility

At different temperatures, as well as under the influence of pressure, gases are able to compress, increasing their concentration and reducing their occupied volume. At elevated temperatures they expand, at low temperatures they contract.

Changes also occur under pressure. The density of gaseous substances increases and, upon reaching a critical point, which is different for each representative, a transition to another state of aggregation may occur.

The main scientists who contributed to the development of the study of gases

There are many such people, because the study of gases is a labor-intensive and historically long process. Let's focus on the most famous personalities who managed to make the most significant discoveries.

1. made a discovery in 1811. It doesn’t matter what kind of gases, the main thing is that under the same conditions, one volume contains an equal amount of them in terms of the number of molecules. There is a calculated value named after the name of the scientist. It is equal to 6.03 * 10 23 molecules for 1 mole of any gas.
2. Fermi - created the theory of an ideal quantum gas.
3. Gay-Lussac, Boyle-Marriott - the names of the scientists who created the basic kinetic equations for calculations.
4. Robert Boyle.
5. John Dalton.
6. Jacques Charles and many other scientists.

Structure of gaseous substances

The most important feature in the construction of the crystal lattice of the substances under consideration is that its nodes contain either atoms or molecules that are connected to each other by weak covalent bonds. Van der Waals forces are also present when it comes to ions, electrons and other quantum systems.

Therefore, the main types of structure of gas lattices are:

• atomic;
• molecular.

The connections inside are easily broken, so these connections do not have a constant shape, but fill the entire spatial volume. This also explains the lack of electrical conductivity and poor thermal conductivity. But gases have good thermal insulation, because, thanks to diffusion, they are able to penetrate into solids and occupy free cluster spaces inside them. At the same time, air is not passed through, heat is retained. This is the basis for the combined use of gases and solids for construction purposes.

Simple substances among gases

We have already discussed above which gases belong to this category in terms of structure and structure. These are those that consist of identical atoms. Many examples can be given, because a significant part of non-metals from the entire periodic table under normal conditions exists in precisely this state of aggregation. For example:

• white phosphorus - one of this element;
• nitrogen;
• oxygen;
• fluorine;
• chlorine;
• helium;
• neon;
• argon;
• krypton;
• xenon.

The molecules of these gases can be either monatomic (noble gases) or polyatomic (ozone - O 3). The type of bond is covalent nonpolar, in most cases it is quite weak, but not in all of them. Crystal cell molecular type, which allows these substances to easily move from one state of aggregation to another. For example, iodine under normal conditions is dark purple crystals with a metallic luster. However, when heated, they sublimate into clouds of bright purple gas - I 2.

By the way, any substance, including metals, can exist in a gaseous state under certain conditions.

Complex compounds of gaseous nature

Such gases, of course, are the majority. Various combinations of atoms in molecules, united by covalent bonds and van der Waals interactions, allow the formation of hundreds of different representatives of the considered state of aggregation.

Examples of complex substances among gases can be all compounds consisting of two or more different elements. This may include:

• propane;
• butane;
• acetylene;
• ammonia;
• silane;
• phosphine;
• methane;
• carbon disulfide;
• sulphur dioxide;
• brown gas;
• freon;
• ethylene and others.

Crystal lattice of molecular type. Many of the representatives easily dissolve in water, forming the corresponding acids. Most of these compounds are an important part of chemical syntheses carried out in industry.

Methane and its homologues

Sometimes general concept“gas” refers to a natural mineral, which is a whole mixture of gaseous products of predominantly organic nature. It contains substances such as:

• methane;
• ethane;
• propane;
• butane;
• ethylene;
• acetylene;
• pentane and some others.

In industry, they are very important, because the propane-butane mixture is the household gas with which people cook, which is used as a source of energy and heat.

Many of them are used for the synthesis of alcohols, aldehydes, acids and others organic matter. Annual consumption of natural gas amounts to trillions of cubic meters, and this is quite justified.

Oxygen and carbon dioxide

What gaseous substances can be called the most widespread and known even to first-graders? The answer is obvious - oxygen and carbon dioxide. After all, they are the direct participants in the gas exchange that occurs in all living beings on the planet.

It is known that it is thanks to oxygen that life is possible, since only some species can exist without it. anaerobic bacteria. And carbon dioxide is a necessary “food” product for all plants that absorb it in order to carry out the process of photosynthesis.

From a chemical point of view, both oxygen and carbon dioxide are important substances for carrying out syntheses of compounds. The first is a strong oxidizing agent, the second is more often a reducing agent.

Halogens

This is a group of compounds in which the atoms are particles of a gaseous substance, connected in pairs to each other due to covalent non-polar bond. However, not all halogens are gases. Bromine is a liquid under ordinary conditions, and iodine is an easily sublimated solid. Fluorine and chlorine are toxic substances that are dangerous to the health of living beings, which are strong oxidizing agents and are used very widely in syntheses.

Exercise 1. Insert these adjectives instead of dots liquid, solid, gaseous .

Exercise 2. Answer the questions.

          1. What substances are found in nature?
         2. What state is the salt in?
         3. What state is bromine in?
         4. What state is nitrogen in?
         5. What state are hydrogen and oxygen in?

Exercise 3. Insert the necessary words instead of dots.

          1. There are... substances in nature.
         2. Bromine is in ... state.
         3. Salt is... a substance.
         4. Nitrogen is in ... state.
         5. Hydrogen and oxygen are... substances.
         6. They are in... condition.

Exercise 4. Listen to the text. Read it out loud.

         Chemical substances are soluble or insoluble in water. For example, sulfur (S) is insoluble in water. Iodine (I 2) is also insoluble in water. Oxygen (O 2) and nitrogen (N 2) are poorly soluble in water. These are substances that are slightly soluble in water. Some chemical substances dissolves well in water, for example, sugar.

Exercise 5. Answer the questions to the text of Exercise 4. Write down your answers in your notebook.

          1. What substances do not dissolve in water?
         2. What substances dissolve well in water?
         3. What substances do you know that are slightly soluble in water?

Exercise 6. Complete the sentences.

          1. Chemicals dissolve or….
         2. Some chemicals are good...
         3. Glucose and sucrose….
         4. Oxygen and nitrogen are bad...
         5. Sulfur and iodine….

Exercise 7. Write sentences. Use the words in brackets in the correct form.

          1. Salt dissolves in (ordinary water).
         2. Some fats dissolve in (gasoline).
         3. Silver dissolves in (nitric acid).
         4. Many metals dissolve in (sulfuric acid - H 2 SO 4).
         5. Glass does not dissolve even in ( hydrochloric acid– HCl).
         6. Oxygen and nitrogen are poorly soluble in (water).
         7. Iodine dissolves well in (alcohol or benzene).

Exercise 8. Listen to the text. Read it out loud.

         All substances have physical properties. Physical properties are color, taste and smell. For example, sugar is white in color and tastes sweet. Chlorine (Cl 2) has a yellow-green color and a strong, unpleasant odor. Sulfur (S) is yellow in color, and bromine (Br 2) is dark red. Graphite (C) is dark gray in color and copper (Cu) is light pink. NaCl salt is white in color and has a salty taste. Some salts have a bitter taste. Bromine has a pungent odor.

Exercise 9. Answer the questions to the text of Exercise 8. Write down the answers in your notebook.

          1. What physical properties do you know?
         2. What physical properties does sugar have?
         3. What physical properties does chlorine have?
         4. What color are graphite, sulfur, bromine and copper?
         5. What physical properties does sodium chloride (NaCl) have?
         6. What do some salts taste like?
         7. What does bromine smell like?

Exercise 10. Make up sentences based on the model.

          Sample: Nitrogen is taste.   Nitrogen has no taste.   Nitrogen has no taste.   Nitrogen is a substance without taste.

         1. Sodium chloride - odor. -...
         2. Chalk – taste and smell. -...
         3. Alcohol is color. -...
         4. Water – taste, color and smell. -...
         5. Sugar is a smell. -...
         6. Graphite – taste and smell. –….

Exercise 11. Say that substances have the same properties as water.

          Sample: Water is compound, ethyl alcohol is also a complex substance.

         1. Water is a liquid, nitric acid too...
         2. Water is a transparent substance, sulfuric acid too...
         3. Water has no color, neither does diamond...
         4. Water has no odor, oxygen too... .

Exercise 12. Say that water has different qualities than ethyl alcohol.

          1. Ethyl alcohol is a light liquid, and water...
         2. Ethyl alcohol has a characteristic odor, and water...
         3. Ethyl alcohol has a low boiling point, and water...

Exercise 13. Clarify the following messages, use words characteristic, specific, sharp, violet, red-brown, colorless, tall, yellow .

          Sample: Bromine is a dark liquid. Bromine is a dark red liquid.

         1. Ethyl alcohol has an odor. 2. Iodine has a smell. 3. Iodine vapors are colored. 4. Dark iodine solution. 5. Sulfuric acid is a liquid. 6. Sulfuric acid has a boiling point. 7. Sulfur has color.

Exercise 14. Talk about the physical properties of substances, use the given words and phrases.

          1. Fluorine (F 2) – gas – light green color – pungent odor – poisonous.
         2. Chlorine (Cl 2) – gas – yellow-green color – pungent odor – poisonous.

You take a very hot shower for a long time, the bathroom mirror becomes covered in steam. You forget a pot of water on the window, and then you discover that the water has boiled away and the pan has burnt. You might think that water likes to change from gas to liquid, then from liquid to gas. But when does this happen?

In a ventilated space, water gradually evaporates at any temperature. But it boils only under certain conditions. The boiling point depends on the pressure above the liquid. Under normal conditions atmospheric pressure The boiling point will be 100 degrees. With altitude, the pressure will decrease as well as the boiling point. At the top of Mont Blanc it will be 85 degrees, and you won’t be able to make delicious tea there! But in a pressure cooker, when the whistle sounds, the water temperature is already 130 degrees, and the pressure is 4 times higher than atmospheric pressure. At this temperature, food cooks faster and the flavors don't escape with the guy because the valve is closed.

Changes in the state of aggregation of a substance with temperature changes.

Any liquid can turn into a gaseous state if it is heated enough, and any gas can turn into a liquid state if it is cooled. Therefore, butane, which is used in gas stoves and in the country, is stored in closed cylinders. It is liquid and under pressure, like a pressure cooker. And in the open air, at a temperature just below 0 degrees, methane boils and evaporates very quickly. Liquefied methane is stored in giant reservoirs called tanks. At normal atmospheric pressure, methane boils at a temperature of 160 degrees below zero. To prevent the gas from escaping during transportation, the tanks are carefully touched like thermoses.

Changes in the aggregative states of a substance with changes in pressure.

There is a dependence between the liquid and gaseous states of a substance on temperature and pressure. Since a substance is more saturated in a liquid state than in a gaseous state, you might think that if you increase the pressure, the gas will immediately turn into a liquid. But that's not true. However, if you start to compress air with a bicycle pump, you will find that it heats up. It accumulates the energy that you transfer to it by pressing on the piston. Gas can be compressed into liquid only if it is cooled at the same time. On the contrary, liquids need to receive heat in order to turn into gas. That is why evaporating alcohol or ether takes away heat from our body, creating a feeling of cold on the skin. Evaporation sea ​​water under the influence of wind it cools the water surface, and sweating cools the body.

single-phase systems consisting of two or more components. According to their state of aggregation, solutions can be solid, liquid or gaseous. So, air is a gaseous solution, a homogeneous mixture of gases; vodka- liquid solution, a mixture of several substances forming one liquid phase; sea ​​water- liquid solution, a mixture of solid (salt) and liquid (water) substances forming one liquid phase; brass- solid solution, a mixture of two solids (copper and zinc) forming one solid phase. A mixture of gasoline and water is not a solution because these liquids do not dissolve in each other, remaining as two liquid phases with an interface. The components of the solutions retain their unique properties and do not enter into chemical reactions with each other to form new compounds. Thus, when two volumes of hydrogen are mixed with one volume of oxygen, a gaseous solution is obtained. If this gas mixture is ignited, a new substance is formed- water, which in itself is not a solution. The component present in the solution in larger quantities is usually called a solvent, the remaining components- dissolved substances.

However, sometimes it is difficult to draw the line between the physical mixing of substances and their chemical interaction. For example, when mixing hydrogen chloride gas HCl with water

H2O H ions are formed 3 O+ and Cl - . They attract neighboring water molecules to themselves, forming hydrates. Thus, the starting components are HCl and H 2 O - undergo significant changes after mixing. Nevertheless, ionization and hydration (in the general case, solvation) are considered as physical processes that occur during the formation of solutions.

One of the most important types of mixtures that represent a homogeneous phase are colloidal solutions: gels, sols, emulsions and aerosols. Particle size in colloidal solutions is 1-1000 nm, in true solutions

~ 0.1 nm (on the order of molecular size).Basic Concepts. Two substances that dissolve in each other in any proportions to form true solutions are called completely mutually soluble. Such substances are all gases, many liquids (for example, ethyl alcohol- water, glycerin - water, benzene - gasoline), some solids (for example, silver - gold). To obtain solid solutions, you must first melt the starting substances, then mix them and allow them to solidify. When they are completely mutually soluble, one solid phase is formed; if the solubility is partial, then small crystals of one of the original components are retained in the resulting solid.

If two components form one phase when mixed only in certain proportions, and in other cases two phases appear, then they are called partially mutually soluble. These are, for example, water and benzene: true solutions are obtained from them only by adding a small amount of water to a large volume of benzene or a small amount of benzene to a large volume of water. If you mix equal amounts of water and benzene, a two-phase liquid system is formed. Its lower layer is water with a small amount of benzene, and the upper

- benzene with a small amount of water. There are also known substances that do not dissolve in one another at all, for example, water and mercury. If two substances are only partially mutually soluble, then at a given temperature and pressure there is a limit to the amount of one substance that can form a true solution with the other under equilibrium conditions. A solution with a maximum concentration of solute is called saturated. You can also prepare a so-called supersaturated solution, in which the concentration of the dissolved substance is even greater than in a saturated one. However, supersaturated solutions are unstable, and with the slightest change in conditions, for example, with stirring, the ingress of dust particles, or the addition of crystals of a solute, the excess solute precipitates.

Any liquid begins to boil at the temperature at which its saturated vapor pressure reaches the external pressure. For example, water under a pressure of 101.3 kPa boils at 100

° C because at this temperature the water vapor pressure is exactly 101.3 kPa. If you dissolve some non-volatile substance in water, its vapor pressure will decrease. To bring the vapor pressure of the resulting solution to 101.3 kPa, you need to heat the solution above 100° C. It follows that the boiling point of the solution is always higher than the boiling point of the pure solvent. The decrease in the freezing point of solutions is explained in a similar way.Raoult's law. In 1887, the French physicist F. Raoult, studying solutions of various non-volatile liquids and solids, established a law relating the decrease in vapor pressure over dilute solutions of non-electrolytes with concentration: the relative decrease in the saturated vapor pressure of the solvent above the solution is equal to the mole fraction of the dissolved substance. Raoult's law states that the increase in boiling point or decrease in freezing point of a dilute solution compared to a pure solvent is proportional to the molar concentration (or mole fraction) of the solute and can be used to determine its molecular weight.

A solution whose behavior obeys Raoult's law is called ideal. Solutions of nonpolar gases and liquids (the molecules of which do not change orientation in an electric field) are closest to ideal. In this case, the heat of solution is zero, and the properties of solutions can be directly predicted by knowing the properties of the original components and the proportions in which they are mixed. For real solutions such a prediction cannot be made. When real solutions are formed, heat is usually released or absorbed. Processes with heat release are called exothermic, and processes with absorption are called endothermic.

Those characteristics of a solution that depend mainly on its concentration (the number of molecules of the solute per unit volume or mass of the solvent), and not on the nature of the solute, are called

colligative . For example, the boiling point of pure water at normal atmospheric pressure is 100° C, and the boiling point of a solution containing 1 mole of dissolved (non-dissociating) substance in 1000 g of water is already 100.52° C regardless of the nature of this substance. If the substance dissociates, forming ions, then the boiling point increases in proportion to the increase in the total number of particles of the solute, which, due to dissociation, exceeds the number of molecules of the substance added to the solution. Other important colligative quantities are the freezing point of a solution, osmotic pressure and partial pressure of solvent vapor.Solution concentration is a quantity that reflects the proportions between the solute and the solvent. Qualitative concepts such as “dilute” and “concentrated” only indicate that a solution contains little or a lot of solute. To quantify the concentration of solutions, percentages (mass or volume) are often used, and in scientific literature- number of moles or chemical equivalents (cm . EQUIVALENT MASS)solute per unit mass or volume of solvent or solution. To avoid confusion, the concentration units should always be specified accurately. Consider the following example. A solution consisting of 90 g of water (its volume is 90 ml, since the density of water is 1 g/ml) and 10 g of ethyl alcohol (its volume is 12.6 ml, since the density of alcohol is 0.794 g/ml) has a mass of 100 g , but the volume of this solution is 101.6 ml (and it would be equal to 102.6 ml if, when mixing water and alcohol, their volumes simply added up). The percentage concentration of a solution can be calculated in different ways: or

or

The units of concentration used in the scientific literature are based on concepts such as mole and equivalent, since all chemical calculations and equations of chemical reactions must be based on the fact that substances react with each other in certain proportions. For example, 1 eq. NaCl equal to 58.5 g reacts with 1 eq. AgNO 3 equal to 170 g. It is clear that solutions containing 1 eq. These substances have completely different percentage concentrations.Molarity (M or mol/l) - the number of moles of dissolved substances contained in 1 liter of solution.Molality (m) - the number of moles of solute contained in 1000 g of solvent.Normality (n.) - the number of chemical equivalents of a dissolved substance contained in 1 liter of solution.Mole fraction (dimensionless quantity) - number of moles of this component, divided by the total number of moles of solute and solvent. (Mole percent - mole fraction multiplied by 100.)

The most common unit is molarity, but there are some ambiguities to consider when calculating it. For example, to obtain a 1M solution of a given substance, an exact weighed portion of it equal to mol. is dissolved in a known small amount of water. mass in grams, and bring the volume of the solution to 1 liter. The amount of water required to prepare this solution may vary slightly depending on temperature and pressure. Therefore, two one-molar solutions prepared under different conditions do not actually have exactly the same concentrations. Molality is calculated based on a certain mass of solvent (1000 g), which does not depend on temperature and pressure. In laboratory practice, it is much more convenient to measure certain volumes of liquids (for this there are burettes, pipettes, and volumetric flasks) than to weigh them, therefore, in the scientific literature, concentrations are often expressed in moles, and molality is usually used only for particularly precise measurements.

Normality is used to simplify calculations. As we have already said, substances interact with each other in quantities corresponding to their equivalents. By preparing solutions of different substances of the same normality and taking equal volumes, we can be sure that they contain the same number of equivalents.

In cases where it is difficult (or unnecessary) to distinguish between solvent and solute, concentration is measured in mole fractions. Mole fractions, like molality, do not depend on temperature and pressure.

Knowing the densities of the solute and solution, one can convert one concentration to another: molarity to molality, mole fraction and vice versa. For dilute solutions of a given solute and solvent, these three quantities are proportional to each other.

Solubility of a given substance is its ability to form solutions with other substances. Quantitatively, the solubility of a gas, liquid or solid is measured by the concentration of its saturated solution at a given temperature. This is an important characteristic of a substance, helping to understand its nature, as well as influence the course of reactions in which this substance is involved.Gases. In the absence of chemical interaction, gases mix with each other in any proportions, and in this case there is no point in talking about saturation. However, when a gas dissolves in a liquid, there is a certain limiting concentration, depending on pressure and temperature. The solubility of gases in some liquids correlates with their ability to liquefy. The most easily liquefied gases, such as NH 3, HCl, SO 2 , more soluble than difficult to liquefy gases, such as O 2 , H 2 and He. If there is a chemical interaction between the solvent and the gas (for example, between water and NH 3 or HCl) solubility increases. The solubility of a given gas varies with the nature of the solvent, but the order in which the gases are arranged according to increasing solubility remains approximately the same for different solvents.

The dissolution process obeys Le Chatelier's principle (1884): if a system in equilibrium is subject to any influence, then as a result of the processes occurring in it, the equilibrium will shift in such a direction that the effect will decrease. The dissolution of gases in liquids is usually accompanied by the release of heat. At the same time, in accordance with Le Chatelier's principle, the solubility of gases decreases. This decrease is more noticeable the higher the solubility of gases: such gases also have

greater heat of solution. The “soft” taste of boiled or distilled water is explained by the absence of air in it, since its solubility at high temperatures is very low.

As pressure increases, the solubility of gases increases. According to Henry's law (1803), the mass of a gas that can dissolve in a given volume of liquid at a constant temperature is proportional to its pressure. This property is used to make carbonated drinks. Carbon dioxide is dissolved in liquid at a pressure of 3-4 atm; under these conditions, 3-4 times more gas (by mass) can dissolve in a given volume than at 1 atm. When a container with such a liquid is opened, the pressure in it drops, and part of the dissolved gas is released in the form of bubbles. A similar effect is observed when opening a bottle of champagne or reaching the surface of groundwater saturated with carbon dioxide at great depths.

When a mixture of gases is dissolved in one liquid, the solubility of each of them remains the same as in the absence of other components at the same pressure as in the case of the mixture (Dalton's law).

Liquids. The mutual solubility of two liquids is determined by how similar the structure of their molecules is (“like dissolves in like”). Non-polar liquids, such as hydrocarbons, are characterized by weak intermolecular interactions, so molecules of one liquid easily penetrate between the molecules of another, i.e. the liquids mix well. In contrast, polar and non-polar liquids, such as water and hydrocarbons, do not mix well with each other. Each water molecule must first escape from the environment of other similar molecules that strongly attract it to itself, and penetrate between the hydrocarbon molecules that weakly attract it. Conversely, hydrocarbon molecules, in order to dissolve in water, must squeeze between water molecules, overcoming their strong mutual attraction, and this requires energy. As the temperature rises kinetic energy molecules increases, intermolecular interactions weaken and the solubility of water and hydrocarbons increases. With a significant increase in temperature, their complete mutual solubility can be achieved. This temperature is called the upper critical solution temperature (UCST).

In some cases, the mutual solubility of two partially miscible liquids increases with decreasing temperature. This effect occurs when heat is generated during mixing, usually as a result chemical reaction. With a significant decrease in temperature, but not below the freezing point, the lower critical solution temperature (LCST) can be reached. It can be assumed that all systems that have LCTE also have HCTE (the reverse is not necessary). However, in most cases, one of the mixing liquids boils at a temperature below the HTST. The nicotine-water system has an LCTR of 61

° C, and VCTR is 208° C. In the range 61-208° C, these liquids have limited solubility, and outside this range they have complete mutual solubility.Solids. All solids exhibit limited solubility in liquids. Their saturated solutions at a given temperature have a certain composition, which depends on the nature of the solute and solvent. Thus, the solubility of sodium chloride in water is several million times higher than the solubility of naphthalene in water, and when they are dissolved in benzene, the opposite picture is observed. This example illustrates general rule, according to which a solid substance readily dissolves in a liquid that has similar chemical and physical properties, but does not dissolve in a liquid with opposite properties.

Salts are usually easily soluble in water and less so in other polar solvents, such as alcohol and liquid ammonia. However, the solubility of salts also varies significantly: for example, ammonium nitrate is millions of times more soluble in water than silver chloride.

The dissolution of solids in liquids is usually accompanied by the absorption of heat, and according to Le Chatelier's principle, their solubility should increase with heating. This effect can be used to purify substances by recrystallization. To do this, they are dissolved at high temperature until a saturated solution is obtained, then the solution is cooled and after the dissolved substance precipitates, it is filtered. There are substances (for example, calcium hydroxide, sulfate and acetate), the solubility of which in water decreases with increasing temperature.

Solids, like liquids, can also completely dissolve in each other, forming a homogeneous mixture - a true solid solution, similar to a liquid solution. Partially soluble substances in each other form two equilibrium conjugate solid solutions, the compositions of which change with temperature.

Distribution coefficient. If a solution of a substance is added to an equilibrium system of two immiscible or partially miscible liquids, then it is distributed between the liquids in a certain proportion, independent of the total amount of the substance, in the absence of chemical interactions in the system. This rule is called the distribution law, and the ratio of the concentrations of a dissolved substance in liquids is called the distribution coefficient. The distribution coefficient is approximately equal to the ratio of the solubilities of a given substance in two liquids, i.e. the substance is distributed between liquids according to its solubility. This property is used to extract a given substance from its solution in one solvent using another solvent. Another example of its application is the process of extracting silver from ores, in which it is often included along with lead. To do this, zinc is added to the molten ore, which does not mix with lead. Silver is distributed between molten lead and zinc, mainly in the upper layer of the latter. This layer is collected and the silver is separated by zinc distillation.Solubility product (ETC ). Between excess (precipitate) solid matter M x B y and its saturated solution establishes a dynamic equilibrium described by the equationThe equilibrium constant of this reaction isand is called the solubility product. It is constant at a given temperature and pressure and is the value on the basis of which the solubility of the precipitate is calculated and changed. If a compound is added to the solution that dissociates into ions of the same name as the ions of a slightly soluble salt, then, in accordance with the expression for PR, the solubility of the salt decreases. When adding a compound that reacts with one of the ions, it, on the contrary, will increase.On some properties of solutions of ionic compounds see also ELECTROLYTES. LITERATURE Shakhparonov M.I. Introduction to molecular theory solutions . M., 1956
Remy I. Well inorganic chemistry , vol. 1-2. M., 1963, 1966

I remember how the definition of the state of aggregation of a substance was explained to us back in primary school. The teacher brought good example about the tin soldier and then everything became clear to everyone. Below I will try to refresh my memories.

Determine the state of matter

Well, everything is simple here: if you pick up a substance, you can touch it, and when you press it, it retains its volume and shape - this is solid state. In a liquid state, a substance does not retain its shape, but retains its volume. For example, there is water in a glass, this moment it is shaped like a glass. And if you pour it into a cup, it will take the shape of a cup, but the amount of water itself will not change. This means that a substance in a liquid state can change shape, but not volume. In the gaseous state, neither the shape nor the volume of the substance is preserved, but it tries to fill all the available space.

And in relation to the table, it is worth mentioning that sugar and salt may seem like liquid substances, but in fact they are free-flowing substances, their entire volume consists of small solid crystals.

States of matter: liquid, solid, gaseous

All substances in the world are in a certain state: solid, liquid or gas. And any substance can change from one state to another. Surprisingly, even tin soldier may be liquid. But for this it is necessary to create certain conditions, namely, place it in a very, very heated room, where the tin will melt and turn into liquid metal.

But it’s easiest to consider states of aggregation using water as an example.

• If liquid water is frozen, it turns into ice - this is its solid state.
• If liquid water is heated strongly, it will begin to evaporate - this is its gaseous state.
• And if you heat ice, it will begin to melt and turn back into water - this is called the liquid state.

The process of condensation is especially worth highlighting: if you concentrate and cool evaporated water, the gaseous state will turn into a solid - this is called condensation, and this is how snow is formed in the atmosphere.