Physical properties of water. Properties of water in nature Scientific and technical encyclopedic dictionary

Water (hydrogen oxide) is a transparent liquid that is colorless (in small volumes), odorless and tasteless. Chemical formula: H2O. In the solid state it is called ice or snow, and in the gaseous state it is called water vapor. About 71% of the Earth's surface is covered with water (oceans, seas, lakes, rivers, ice at the poles).

It is a good highly polar solvent. Under natural conditions, it always contains dissolved substances (salts, gases). Water is key to creating and maintaining life on Earth, in chemical structure living organisms, in the formation of climate and weather.

Almost 70% of the surface of our planet is occupied by oceans and seas. Hard water - snow and ice - covers 20% of the land. Of the total amount of water on Earth, equal to 1 billion 386 million cubic kilometers, 1 billion 338 million cubic kilometers account for the salty waters of the World Ocean, and only 35 million cubic kilometers account for fresh water. The total amount of ocean water would be enough to cover the globe with a layer of more than 2.5 kilometers. For every inhabitant of the Earth there is approximately 0.33 cubic kilometers of sea water and 0.008 cubic kilometers of fresh water. But the difficulty is that the vast majority of fresh water on Earth is in a state that makes it difficult for humans to access. Almost 70% of fresh water is contained in the ice sheets of polar countries and in mountain glaciers, 30% is in aquifers underground, and only 0.006% of fresh water is contained in the beds of all rivers. Water molecules have been discovered in interstellar space. Water is part of comets and most planets solar system and their companions.

Composition of water (by mass): 11.19% hydrogen and 88.81% oxygen. Pure water is transparent, odorless and tasteless. It has the greatest density at 0° C (1 g/cm3). The density of ice is less than the density of liquid water, so the ice floats to the surface. Water freezes at 0°C and boils at 100°C at a pressure of 101,325 Pa. It conducts heat poorly and conducts electricity very poorly. Water is a good solvent. The water molecule has an angular shape; hydrogen atoms form an angle of 104.5° with respect to oxygen. Therefore, a water molecule is a dipole: the part of the molecule where hydrogen is located is positively charged, and the part where oxygen is located is negatively charged. Due to the polarity of water molecules, the electrolytes in it dissociate into ions.

Liquid water, along with ordinary H20 molecules, contains associated molecules, i.e., connected into more complex aggregates (H2O)x due to the formation of hydrogen bonds. The presence of hydrogen bonds between water molecules explains the anomalies of its physical properties: maximum density at 4°C, high temperature boiling (in the series H20-H2S - H2Se) an abnormally high heat capacity. As the temperature increases, hydrogen bonds are broken, and complete rupture occurs when water turns into steam.

Water is a highly reactive substance. At normal conditions it reacts with many basic and acidic oxides, as well as with alkali and alkaline earth metals. Water forms numerous compounds - crystalline hydrates.

Obviously, compounds that bind water can serve as drying agents. Other drying substances include P2O5, CaO, BaO, metallic Ma (they also react chemically with water), as well as silica gel. To the important chemical properties water refers to its ability to enter into hydrolytic decomposition reactions.

Physical properties of water.

Water has a number of unusual features:

1. When ice melts, its density increases (from 0.9 to 1 g/cm³). For almost all other substances, the density decreases when melted.

2. When heated from 0 °C to 4 °C (more precisely, 3.98 °C), water contracts. Accordingly, when cooling, the density drops. Thanks to this, fish can live in freezing reservoirs: when the temperature drops below 4 °C, colder water, as less dense, remains on the surface and freezes, and a positive temperature remains under the ice.

3. High temperature and specific heat of fusion (0 °C and 333.55 kJ/kg), boiling point (100 °C) and specific heat of vaporization (2250 KJ/kg), compared to hydrogen compounds with similar molecular weight.

4. High heat capacity of liquid water.

5. High viscosity.

6. High surface tension.

7. Negative electrical potential of the water surface.

All these features are associated with the presence of hydrogen bonds. Due to the large difference in electronegativity between hydrogen and oxygen atoms, the electron clouds are strongly biased towards oxygen. Due to this, and also the fact that the hydrogen ion (proton) does not have internal electronic layers and is small in size, it can penetrate into the electron shell of a negatively polarized atom of a neighboring molecule. Due to this, each oxygen atom is attracted to the hydrogen atoms of other molecules and vice versa. The proton exchange interaction between and within water molecules plays a certain role. Each water molecule can participate in a maximum of four hydrogen bonds: 2 hydrogen atoms - each in one, and an oxygen atom - in two; In this state, the molecules are in an ice crystal. When ice melts, some of the bonds break, which allows water molecules to be packed more tightly; When water is heated, bonds continue to break and its density increases, but at temperatures above 4 °C this effect becomes weaker than thermal expansion. During evaporation, all remaining bonds are broken. Breaking bonds requires a lot of energy, hence the high temperature and specific heat of melting and boiling and high heat capacity. The viscosity of water is due to the fact that hydrogen bonds prevent water molecules from moving at different speeds.

For similar reasons, water is a good solvent for polar substances. Each molecule of the solute is surrounded by water molecules, and the positively charged parts of the molecule of the solute attract oxygen atoms, and the negatively charged parts attract hydrogen atoms. Since a water molecule is small in size, many water molecules can surround each solute molecule.

This property of water is used by living beings. In a living cell and in the intercellular space, solutions of various substances in water interact. Water is necessary for the life of all single-celled and multicellular living creatures on Earth without exception.

Pure (free from impurities) water is a good insulator. Under normal conditions, water is weakly dissociated and the concentration of protons (more precisely, hydronium ions H3O+) and hydroxyl ions HO− is 0.1 µmol/l. But since water is a good solvent, certain salts are almost always dissolved in it, that is, there are positive and negative ions in water. Thanks to this, water conducts electricity. The electrical conductivity of water can be used to determine its purity.

Water has a refractive index n=1.33 in the optical range. However, it strongly absorbs infrared radiation, and therefore water vapor is the main natural greenhouse gas, responsible for more than 60% of the greenhouse effect. Thanks a lot dipole moment molecules, water also absorbs microwave radiation, which is what the operating principle of a microwave oven is based on.

Aggregate states.

1. According to the condition, they are distinguished:

2. Solid - ice

3. Liquid - water

4. Gaseous - water vapor

Fig. 1 “Types of snowflakes”

At atmospheric pressure Water freezes (turns into ice) at 0°C and boils (turns into water vapor) at 100°C. As pressure decreases, the melting point of water slowly increases, and the boiling point decreases. At a pressure of 611.73 Pa (about 0.006 atm), the boiling and melting points coincide and become equal to 0.01 °C. This pressure and temperature is called the triple point of water. At lower pressures, water cannot be liquid and ice turns directly into steam. The sublimation temperature of ice drops with decreasing pressure.

As pressure increases, the boiling point of water increases, the density of water vapor at the boiling point also increases, and the density of liquid water decreases. At a temperature of 374 °C (647 K) and a pressure of 22.064 MPa (218 atm), water passes the critical point. At this point, the density and other properties of liquid and gaseous water are the same. At higher pressures there is no difference between liquid water and water vapor, hence no boiling or evaporation.

Metastable states are also possible - supersaturated steam, superheated liquid, supercooled liquid. These conditions can exist long time, however, they are unstable and upon contact with a more stable phase, a transition occurs. For example, it is not difficult to obtain a supercooled liquid by cooling pure water in a clean vessel below 0 °C, but when a crystallization center appears, liquid water quickly turns into ice.

Isotopic modifications of water.

Both oxygen and hydrogen have natural and artificial isotopes. Depending on the type of isotopes included in the molecule, the following types of water are distinguished:

1. Light water (just water).

2. Heavy water (deuterium).

3. Superheavy water (tritium).

Chemical properties of water.

Water is the most common solvent on Earth, largely determining the nature of terrestrial chemistry as a science. Most of chemistry, at its inception as a science, began precisely as the chemistry of aqueous solutions of substances. It is sometimes considered as an ampholyte - both an acid and a base at the same time (cation H+ anion OH-). In the absence of foreign substances in water, the concentration of hydroxide ions and hydrogen ions (or hydronium ions) is the same, pKa ≈ approx. 16.

Water is a light transparent liquid, colorless in small volumes and acquiring a bluish-greenish color throughout its thickness. Ice is also transparent, since its absorption coefficient of light in the visible part of the spectrum is practically zero, but this does not apply to the ultraviolet and infrared regions. On chips of large blocks of glacier and river ice it, like water, has blue and greenish shades.

The properties of water have left their mark on the system of physical constants and units of measurement: the freezing temperature of water - the melting temperature of ice is accepted

for 0 0 C, and the boiling point of water for 100 0 C (both at atmospheric pressure of about 1013 mbar or hPa = 759.8 mm Hg). Unit of volume

in the metric system, it was chosen from the condition that one cubic meter of water at a temperature of 3.98 0 C has a mass of 1000 kg.

Each water molecule has two hydrogen atoms and two unshared electron pairs and can thus form four hydrogen bonds. The latter are carried out with the participation of a hydrogen atom located either between molecules or between atoms within a molecule:

We will perceive water as an association of molecules united by hydrogen bonds. And if liquid water contains individual associates of its molecules, then a similar arrangement of molecules is characteristic of ice,

but orderliness already extends to the entire system as a whole, which,

ultimately leading to the formation of the characteristic tetrahedral structure of ice. In other words, ice crystals are entirely built on hydrogen bonds alone. The structure of ice is figuratively called “very openwork”, because in it the molecules are packed less densely than in liquid water.

Compared to other substances, water is characterized by the highest specific heat capacity, which at a temperature of 15°C is

4190 J/(kg*K).

The thermal conductivity of water is very insignificant, but water has a very high latent heat of fusion and evaporation. In order to turn 1 kg of ice into water (latent heat of fusion), it is necessary to expend 330,000 J/kg, and when evaporating 1 kg of water (latent heat of evaporation), 2260 J are expended. These features of water are important for the heat balance of the Earth.

When water freezes, it expands by 9% relative to

to the original volume.

Of all liquids except mercury, water has the highest surface tension.

Another remarkable property of water is its ability to dissolve many substances. Those chemical compounds that can form hydrogen bonds with it are especially soluble in water. In our daily activities, we are accustomed to consider substances such as alcohol, gasoline, ether and many others to be good solvents, which really dissolve fats and many organics in general well, but, for example, salts do not dissolve in them. But the latter dissolve well in water, because... it has an extremely high dielectric constant and its molecules tend to combine with ions, converting them into hydrated ions, thereby stabilizing them in solution. Good solubility of various salts in water is very important for many natural processes.

End of work -

This topic belongs to the section:

General hydrology

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All topics in this section:

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River catchment area. Morphometric characteristics of the catchment
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Thermal balance of the river basin. Thermal and ice regime of rivers
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Hydrochemical composition of river waters
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Water balance of the lake. Water level regime in lakes
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Water is a transparent liquid, colorless (in small volumes) and odorless. Water is of key importance in the creation and maintenance of life on Earth, in the chemical structure of living organisms, in the formation of climate and weather. In the solid state it is called ice or snow, and in the gaseous state it is called water vapor. About 71% of the Earth's surface is covered with water (oceans, seas, lakes, rivers, ice at the poles).

Properties of water are a set of physical, chemical, biochemical, organoleptic, physicochemical and other properties of water.
Water - hydrogen oxide - is one of the most common and important substances. The Earth's surface occupied by water is 2.5 times larger than the land surface. There is no pure water in nature; it always contains impurities. Pure water is obtained by distillation. Distilled water is called distilled water. Composition of water (by mass): 11.19% hydrogen and 88.81% oxygen.

Pure water is transparent, odorless and tasteless. It has the greatest density at 0° C (1 g/cm3). The density of ice is less than the density of liquid water, so the ice floats to the surface. Water freezes at 0°C and boils at 100°C at a pressure of 101,325 Pa. It conducts heat poorly and conducts electricity very poorly. Water is a good solvent. The water molecule has an angular shape; hydrogen atoms form an angle of 104.5° with respect to oxygen. Therefore, a water molecule is a dipole: the part of the molecule where hydrogen is located is positively charged, and the part where oxygen is located is negatively charged. Due to the polarity of water molecules, the electrolytes in it dissociate into ions.

Liquid water, along with ordinary H20 molecules, contains associated molecules, i.e., connected into more complex aggregates (H2O)x due to the formation of hydrogen bonds. The presence of hydrogen bonds between water molecules explains the anomalies of its physical properties: maximum density at 4 ° C, high boiling point (in the series H20-H2S - H2Se) and abnormally high heat capacity. As the temperature increases, hydrogen bonds are broken, and complete rupture occurs when water turns into steam.

Water is a highly reactive substance. Under normal conditions, it reacts with many basic and acidic oxides, as well as with alkali and alkaline earth metals. Water forms numerous compounds - crystalline hydrates.
Obviously, compounds that bind water can serve as drying agents. Other drying substances include P2O5, CaO, BaO, metallic Ma (they also react chemically with water), as well as silica gel. Important chemical properties of water include its ability to enter into hydrolytic decomposition reactions.

The chemical properties of water are determined by its composition. Water consists of 88.81% oxygen, and only 11.19% hydrogen. As we mentioned above, water freezes at zero degrees Celsius, but boils at one hundred. Distilled water has a very low concentration of positively charged hydronium ions HO and H3O+ (only 0.1 µmol/l), so it can be called an excellent insulator. However, the properties of water in nature would not be realized correctly if it were not a good solvent. The water molecule is very small in size. When another substance enters water, its positive ions are attracted by the oxygen atoms that make up the water molecule, and the negative ions are attracted by the hydrogen atoms. Water seems to surround the chemical elements dissolved in it on all sides. Therefore, water almost always contains various substances, in particular, metal salts, which ensure the conduction of electric current.

The physical properties of water “gave” us such phenomena as the greenhouse effect and the microwave oven. About 60% of the greenhouse effect is created by water vapor, which perfectly absorbs infrared rays. In this case, the optical refractive index of water is n=1.33. In addition, water also absorbs microwaves due to the high dipole moment of its molecules. These properties of water in nature prompted scientists to think about the invention of the microwave oven.

The role of water in nature and human life is immeasurably great. We can say that all living things consist of water and organic substances. She is an active participant in the formation of the physical and chemical environment, climate and weather. At the same time, it also affects the economy, industry, agriculture, transport and energy.

We can live without food for several weeks, but without water - only 2-3 days. To ensure normal existence, a person must introduce into the body approximately 2 times more water by weight than nutrients. Loss of more than 10% of water by the human body can lead to death. On average, the body of plants and animals contains more than 50% water, in the body of a jellyfish it is up to 96%, in algae 95-99%, in spores and seeds from 7 to 15%. The soil contains at least 20% water, while in the human body water makes up about 65%. Different parts of the human body contain unequal amounts of water: the vitreous body of the eye consists of 99% water, the blood contains 83%, adipose tissue 29%, the skeleton 22%, and even tooth enamel 0.2%. Throughout his life, a person loses water from the body, and his bioenergetic potential decreases. In a six-week human embryo, the water content is up to 97%, in a newborn - 80%, in an adult - 60-70%, and in the body of an elderly person - only 50-60%.

Water is absolutely essential for all key human life support systems. Water and the substances it contains become a nutritional medium and supply living organisms with microelements necessary for life. It is found in the blood (79%) and facilitates the transport of thousands of essential substances and elements through the circulatory system in a dissolved state (geo chemical composition water is close to the composition of animal and human blood.).
In lymph, which carries out the exchange of substances between blood and tissues of a living organism, water makes up 98%.
Water exhibits the properties of a universal solvent more strongly than other liquids. After a certain time, it can dissolve almost any solid substance.
This comprehensive role of water is due to its unique properties.

Recently, the efforts of researchers have been focused on the accelerated study of processes occurring at the interface. It turned out that water in the boundary layers has many interesting properties that do not appear in the bulk phase. This information is extremely necessary for solving a number of important practical problems. An example would be the creation of a fundamentally new element base for microelectronics, where further miniaturization of circuits will be based on the principle of self-organization of macromolecules on a water surface. A developed surface is also characteristic of biological systems, due to the importance of surface phenomena for their functioning. Almost always, the presence of water has a significant influence on the nature of the processes occurring in the near-surface region. In turn, under the influence of the surface, the properties of the water itself radically change, and water near the boundary must be considered as a fundamentally new physical object of study. It is very likely that the study of the molecular statistical properties of water near the surface, which is essentially just beginning, will make it possible to effectively control many physical and chemical processes.

Recently, interest in studying the properties of water at the microscopic level has increased. Thus, to understand many issues in the physics of surface phenomena, it is necessary to know the properties of water at the interface. The lack of strict ideas about the structure of water and the organization of water at the molecular level leads to the fact that when studying the properties of aqueous solutions both in the bulk phase and in capillary systems, water is often considered as a structureless medium. However, it is known that the properties of water in the boundary layers can differ markedly from those in the bulk. Therefore, considering water as a structureless liquid, we lose unique information about the properties of the boundary layers, which, as it turns out, largely determine the nature of the processes occurring in thin pores. For example, the ion selectivity of cellulose acetate membranes is explained by the special molecular organization of water in the pores, which, in particular, is reflected in the concept of “non-solvent volume”. Further development a theory that takes into account the specifics of intermolecular interactions underlying selective membrane transport will contribute to a more complete understanding of membrane desalination of solutions. This will make it possible to give informed recommendations for improving the efficiency of water desalination processes. This implies the importance and necessity of studying the properties of liquids in boundary layers, in particular near the surface of a solid body.

Water is a unique substance, the basis of all living organisms on the planet. She can acquire different shape and be in three states. What are the main physical and chemical properties of water? These are the ones that will be discussed in our article.

Water is...

Water is the most common thing on our planet inorganic compound. The physical and chemical properties of water are determined by the composition of its molecules.

Thus, the structure of a water molecule contains two hydrogen atoms (H) and one oxygen atom (O). Under normal environmental conditions, it is a tasteless, odorless and colorless liquid. Water can also exist in other states: in the form of steam or in the form of ice.

More than 70% of our planet is covered with water. Moreover, about 97% occurs in the seas and oceans, so most of it is not suitable for human consumption. You will learn further about the basic chemical properties of drinking water.

Water in nature and human life

Water is an essential component of any living organism. In particular, human body, as you know, more than 70% consists of water. Moreover, scientists suggest that it was in this environment that life on Earth originated.

Water is found (in the form of water vapor or droplets) in different layers of the atmosphere. It reaches the earth's surface from the atmosphere in the form of rain or other precipitation (snow, dew, hail, frost) through condensation processes.

Water is an object of research for a number of scientific disciplines. Among them are hydrology, hydrography, hydrogeology, limnology, glaciology, oceanology and others. All these sciences, one way or another, study the physical as well as chemical properties of water.

Water is actively used by humans in their economic activities, in particular:

• for growing crops;
• in industry (as a solvent);
• in energy (as a coolant);
• for extinguishing fires;
• in cooking;
• in pharmacy and so on.

Of course, in order to effectively use this substance in economic activities, the chemical properties of water should be studied in detail.

Types of water

As mentioned above, water in nature can be in three states: liquid (actually water), solid (ice crystals) and gaseous (steam). It can also take on any form.

There are several types of water. So, depending on the content of Ca and Na cations, water can be:

• hard;
• soft.

• fresh;
• mineral;
• salty.

In esotericism and some religions there is water:

• dead;
• alive;
• holy.

In chemistry there are also such concepts as distilled and deionized water.

Formula of water and its biological significance

Hydrogen oxide is what chemists call this substance. The formula of water is: H 2 O. It means that this compound consists of one oxygen atom and two hydrogen atoms.

The unique chemical properties of water have determined its exceptional role for the life of living organisms. It is thanks to water biological life exists on our planet.

The most unique feature of water is that it perfectly dissolves a huge number of other substances (both organic and inorganic). An important consequence of this feature is that all chemical reactions in living organisms occur quite quickly.

In addition, thanks to unique properties water, it exists in a liquid state over an extremely wide temperature range.

Physical properties of water

Thanks to unique hydrogen bonds, water, under standard environmental conditions, is in a liquid state. This explains the extremely high boiling point of water. If the molecules of the substance were not connected by these hydrogen bonds, then water would boil at +80 degrees and freeze at -100 degrees.

Water boils at +100 degrees Celsius and freezes at zero degrees. True, under certain, specific conditions, it can begin to freeze even at positive temperatures. When water freezes, it increases in volume (due to a decrease in density). By the way, this is almost the only substance in nature that has such a physical property. Besides water, the only things that expand when frozen are bismuth, antimony, germanium and gallium.

The substance is also characterized by high viscosity, as well as fairly strong surface tension. Water is an excellent solvent for polar substances. You should also know that water conducts electricity very well. This feature is explained by the fact that water almost always contains large number ions of salts dissolved in it.

Chemical properties of water (grade 8)

Water molecules have extremely high polarity. Therefore, this substance in reality consists not only of simple molecules of the type H 2 O, but also of complex aggregates (formula - (H 2 O) n).

Chemically, water is very active; it reacts with many other substances, even at ordinary temperatures. When interacting with oxides of alkali and alkaline earth metals, it forms bases.

Water is also capable of dissolving a wide range of chemicals- salts, acids, bases, some gases. For this property it is often called a universal solvent. All substances, depending on whether they dissolve in water or not, are usually divided into two groups:

• hydrophilic (dissolves well in water) - salts, acids, oxygen, carbon dioxide etc.;
• hydrophobic (poorly soluble in water) - fats and oils.

Water also enters into chemical reactions with some metals (for example, sodium), and also takes part in the process of photosynthesis in plants.

In conclusion...

Water is the most common inorganic substance on our planet. It is found almost everywhere: on the earth’s surface and in its interior, in the mantle and rocks, in the high layers of the atmosphere and even in space.

The chemical properties of water are determined by its chemical composition. It belongs to the group chemically active substances. Water interacts with many substances

Introduction

There are four known habitats: land-air (atmosphere), water (hydrosphere), soil (edaphic) and living organisms. These guidelines relate to hydrosphere pollution.

These guidelines are intended for students technical universities all specialties. State educational standards provide for the study of the course “Ecology” and issues related to environmental protection by students of all specialties. Mastering the discipline takes one semester - a lecture and practical course of 34 classroom hours. Guidelines will allow students to most effectively study issues related to hydrosphere pollution, as well as issues of protection of water bodies.

Environmental education and solving environmental issues should permeate the process of developing a specialist of any profile. The main thing is that all specialists graduating from higher education, along with thorough legal and practical knowledge, receive a high moral charge and the ability to solve environmental problems in relation to their professional field.

The intensive development of industry, transport, and overpopulation of a number of regions of the planet have led to significant pollution of the hydrosphere. According to WHO (World Health Organization), about 80% of all infectious diseases in the world are associated with unsatisfactory quality of drinking water and violations of sanitary and hygienic water supply standards. Pollution of the surface of reservoirs with films of oil, fats, and lubricants interferes with gas exchange between water and the atmosphere, which reduces the oxygen saturation of water and has a negative effect on the state of phytoplankton and is the cause of mass death of fish and birds.

According to the UN, up to 1 million types of products are produced in the world, of which 100 thousand are chemical compounds, including 15 thousand - potential toxicants. According to expert estimates, up to 80% of all chemical compounds entering the external environment sooner or later end up in water sources.

It is estimated that more than 420 km 3 of wastewater is discharged annually in the world, which can make about 7 thousand km 3 of clean water unusable.

1. Properties of water

Water reserves on Earth are enormous; they form the hydrosphere - one of the powerful spheres of our planet. The hydrosphere, lithosphere, atmosphere and biosphere are interconnected, penetrate one another and are in constant, close interaction. All spheres contain water. Water resources are made up of static (secular) reserves and renewable resources. The hydrosphere unites the World Ocean, seas, rivers and lakes, swamps, ponds, reservoirs, polar and mountain glaciers, groundwater, soil moisture and atmospheric vapor.

Water is a chemical compound of hydrogen and oxygen (H 2 O) - an odorless, tasteless, colorless liquid (bluish in thick layers); density 1 g/cm 3 at a temperature of 3.98 ° C. At 0 °C water turns into ice, at 100 °C into steam. The molecular weight of water is 18.0153. According to V.I. Vernadsky, the chemical composition of water can be represented by the formula H 2 n O n with a value of n equal to 1-6. Not all water molecules are the same: along with ordinary molecules with a mass of 18, there are molecules with a molecular mass of 19, 20, 21 and even 22. Water is a unique substance in its physical and chemical properties. The polarity of water molecules and the presence of “hydrogen” bonds between them determine its unique properties. The density of water is greatest at a temperature of 3.98 °C; further cooling leads to its transition to ice and is accompanied by a decrease in density. A decrease in volume instead of an expansion occurs when ice melts. The volatility of water is low. Water has an abnormally high heat of fusion and specific heat; when ice melts, the heat capacity more than doubles. The heat capacity of water decreases with increasing temperature to 27 °C, and then begins to increase again. The viscosity of water (at temperatures from 0 to 30 °C) decreases with increasing pressure.

2. Distribution and state of water

Water is the most common substance on Earth. It is in three phases: gaseous (water vapor), liquid and solid. There are atmospheric, surface and underground water.

In the atmosphere, water is found in a vapor state in the air shell surrounding the Earth, in a droplet-liquid state - in clouds, fogs and in the form of rain, and solid - in the form of snow, hail and ice crystals of high clouds.

In liquid form, water is found in the hydrosphere: water in oceans, seas, lakes, rivers, swamps, ponds and reservoirs. In the solid state, water in the form of ice and snow is found at the poles of the planet, on mountain peaks, and in winter it covers large areas of reservoirs. There is capillary, gravitational, and crystallization water.

The total area of ​​oceans and seas is 2.5 times larger than the land area, and the volume of water on Earth is 1.5-109 km 3 . More than 95% of the water is salty. Water reserves and their ratio are shown in Table 1. The World Ocean covers an area of ​​361 million km 2, which is 70.8% of the Earth's surface. With an average ocean depth of 3800 m, the total volume of water reaches 1370 million km 3. When calculating groundwater resources, it is believed that the Earth's mantle contains 0.5% of water, the total volume of which is approximately 13-15 billion km 3 of water. The possible influx of deep water into the earth's crust and onto the surface of the planet averages 1 km 3 per year. With an average absolute age of the Earth of 3.5 billion years, the volume of surface water should be about 3.3 billion km 3 (Makarenko, 1966). Volume of free water in the earth's crust (groundwater) V.I. Vernadsky estimated at 60 million km 3.

Table 1 - Total world water reserves

Russia is washed by the waters of 12 seas belonging to three oceans. On the territory of Russia there are over 2.5 million large and small rivers, more than 2 million lakes. Russia's water resources are composed of static (secular) and renewable ones. The former are considered relatively constant over a long period of time; renewable water resources are estimated by the volume of annual river flow. River flow is formed by melting snow and rainfall; swamps and groundwater serve as sources of river nutrition. The total water resources of Russia are shown in Table 2.

In the socio-economic development of the country, river flow from surface fresh waters has priority importance. In terms of river flow volume, Russia ranks second after Brazil. Rivers are the basis of the water fund. Almost 65% of large Russian cities (Moscow, St. Petersburg, Nizhny Novgorod, Yekaterinburg, Perm and others) use surface water, mainly river water, for drinking and technical needs.

Table 2 - Total water resources of Russia

Over 120 thousand rivers with a length of more than 10 km and a total length of over 2.3 million km flow through the territory of Russia. About 90% of Russia's annual river flow falls on the basins of the Arctic and Pacific oceans, and only 8% on the basins of the Caspian and Azov seas. However, it is in the basins of these seas that more than 80% of the Russian population lives, and the bulk of the economic infrastructure is concentrated.

There are more than 2 million in Russia. fresh and salt lakes. Among them is the deepest freshwater lake, Lake Baikal, and the largest closed brackish body of water, the Caspian Sea. The main part of lake fresh water resources is concentrated in lakes: Baikal (23 thousand km 3, or 20% of the world and 90% of national reserves), Ladoga (903 km 3), Onega (285 km 3), Chudsko-Pskovskoye (35.2 km 3). The largest reservoirs in Russia contain about 450 km 3 of fresh water.

Glaciers are a significant accumulator of water, they are concentrated mainly in the polar regions: in Antarctica, on the Arctic islands, including the Russian sector of the Arctic, and in mountainous areas.

Groundwater together with the surface waters of rivers, lakes and ponds, they form the basis of Russia’s water fund and serve for drinking purposes. Natural fresh groundwater resources amount to 787.5 km 3 /year, projected suitable for use - over 300 km 3 /year. Mineral and medicinal underground waters are used in 450 deposits by sanatorium-resort and health-improving institutions, as well as bottling plants for medicinal mineral waters. Potential Resources mineral waters are estimated at 800 thousand m 3 /day. Thermal power (thermal, steam-water mixture with a temperature from 40 to 200 ° WITH ) Groundwater is used for heat supply and generation of electrical energy. Their significant resources (more than 7081.5 million m 3 /day) are concentrated in the North Caucasus and the Far East. Industrial groundwater resources amount to more than 4 million m 3 /day (hydromineral raw materials). They are a source of iodine, bromine and a number of other rare elements and metals. Large deposits of industrial groundwater are located in the Krasnodar region, the Urals and Western Siberia.