Water structure: new experimental data. Water structure
In a water molecule, the protagonist is an oxygen atom.
Since hydrogen atoms are noticeably repelled from each other, the angle between chemical bonds (lines connecting the nuclei of atoms) hydrogen - oxygen is not straight (90 °), but a little more - 104.5 °.
The chemical bonds in the water molecule are polar, since oxygen pulls negatively charged electrons toward itself, and hydrogen - positively charged electrons. As a result, an excess negative charge accumulates near the oxygen atom, and a positive charge for hydrogen atoms.
Therefore, the whole water molecule is a dipole, that is, a molecule with two opposite poles. The dipole structure of a water molecule largely determines its unusual properties.
The water molecule is a diamagnet.
If you connect the epicenters of positive and negative charges with straight lines, you get a three-dimensional geometric figure - a tetrahedron. This is the structure of the water molecule itself.
When the state of the water molecule changes, the length of the sides and the angle between them change in the tetrahedron.
For example, if a water molecule is in a vaporous state, then the angle formed by its sides is 104 ° 27 ". In the water state, the angle is 105 ° 03". And in a state of ice, the angle is 109.5 °.
The geometry and dimensions of the water molecule for various states
a - for the vapor state
b - for the lowest vibrational level
c - for a level close to the formation of an ice crystal, when the geometry of the water molecule corresponds to the geometry of two Egyptian triangles with an aspect ratio of 3: 4: 5
g - for the state of ice.
If we halve these angles, we get the angles:
104 ° 27 ": 2 \u003d 52 ° 13",
105 ° 03 ": 2 \u003d 52 ° 31",
106 ° 16 ": 2 \u003d 53 ° 08",
109.5 °: 2 \u003d 54 ° 32 ".
So, among the geometric patterns of the water and ice molecule there is the famous Egyptian triangle, the construction of which is based on the golden ratio - the lengths of the sides are 3: 4: 5 with an angle of 53 ° 08 ".
A water molecule takes on a golden ratio along the way when water passes into ice, and vice versa, when ice melts. Obviously, melt water is appreciated for this state, when its structure in the construction has the proportions of the golden section.
Now it becomes clear that the famous Egyptian triangle with an aspect ratio of 3: 4: 5 is "taken" from one of the states of a water molecule. The geometry of the water molecule itself is formed by two Egyptian right-angled triangles having a common leg equal to 3.
The water molecule, which is based on the golden ratio, is a physical manifestation of the Divine Nature, which is involved in creating life. That is why in earthly nature that harmony is inherent in the whole cosmos.
And therefore, the ancient Egyptians deified the numbers 3, 4, 5, and the triangle itself was considered sacred and tried to lay its properties, its harmony in any design, houses, pyramids and even in the layout of the fields. By the way, Ukrainian huts were also built using the golden ratio.
In space, a water molecule occupies a certain volume, and is covered with an electronic shell in the form of a veil. If you imagine a hypothetical model of the molecule in the plane, then it looks like butterfly wings, the X-shaped chromosome, in which the program of life of a living creature is recorded. And this is an indicative fact that water itself is an indispensable element of all living things.
If you imagine the form of a hypothetical model of a water molecule in volume, then it conveys the shape of a triangular pyramid, which has 4 faces, and each face has 3 edges. In geometry, a triangular pyramid is called a tetrahedron. Such a structure is characteristic of crystals.
Thus, the water molecule forms a strong angular structure, which it retains even when it is in a vaporous state, on the verge of transition to ice, and when it turns into ice.
If the "skeleton" of a water molecule is so stable, then its energy "pyramid" - tetrahedron also stands firm.
Such structural properties of a water molecule under various conditions are explained by strong bonds between two hydrogen atoms and one oxygen atom. This bond is about 25 times stronger than the bond between neighboring water molecules. Therefore, it is easier to separate one water molecule from another, for example, when heated, than to destroy the water molecule itself.
Due to orientation, induction, dispersion interactions (Van der Waals forces) and hydrogen bonds between hydrogen and oxygen atoms of neighboring molecules, water molecules are able to form as random associates, i.e. not having an ordered structure, and clusters are associates having a certain structure.
According to statistics, in random water there are random associates - 60% (degraded water) and clusters - 40% (structured water).
As a result of studies conducted by Russian scientist S.V. Zenin, stable long-lived clusters of water were discovered.
Zenin found that water molecules initially form the dodecahedron. Combining, the four dodecahedrons form the main structural element of water - a cluster consisting of 57 water molecules.
In the cluster, dodecahedrons have common faces, and their centers form the regular tetrahedron. This is a three-dimensional compound of water molecules, including hexamers, which has positive and negative poles.
Hydrogen bridges allow water molecules to combine in a variety of ways. Due to this, an infinite variety of clusters is observed in water.
Clusters can interact with each other due to free hydrogen bonds, which leads to the appearance of second-order structures in the form of hexagons. They consist of 912 water molecules, which are practically not capable of interaction. The lifetime of such a structure is very long.
This structure, similar to a small sharp ice crystal of 6 rhombic faces, S.V. Zenin called “the main structural element of water.” Numerous experiments have confirmed; in water - myriads of such crystals.
These ice crystals almost do not interact with each other, therefore they do not form more complex stable structures and easily glide with faces relative to each other, creating fluidity. In this sense, water resembles a supercooled solution, which cannot crystallize in any way.
The composition of water can be determined using the decomposition reaction by electric current. Two volumes of hydrogen are formed per one volume of oxygen (the volume of gas is proportional to the amount of substance):
2H 2 O \u003d 2H 2 + O 2
Water is made up of molecules. Each molecule contains two hydrogen atoms connected by covalent bonds with one oxygen atom. The angle between the bonds is about 105 °:
O - h
H
Since oxygen is a more electronegative element (strong oxidizing agent), the total electron pair of the covalent bond shifts to the oxygen atom, a partial negative charge δ− forms on it, and a partial positive δ + on hydrogen atoms. Neighboring molecules are attracted to each other by opposite charges - this leads to a relatively high boiling point of water.
Water at room temperature is a colorless, clear liquid. The melting point is 0º C, the boiling point at atmospheric pressure is 100 ° C. Pure water does not conduct electric current.
An interesting feature of water is that it has the highest density of 1 g / cm 3 at a temperature of about 4 ° C. With a further decrease in temperature, the density of water decreases. Therefore, with the onset of winter, the upper freezing layers of water become lighter and do not sink down. Ice forms on the surface. Freezing of a reservoir to the bottom usually does not occur (moreover, ice also has a density less than water and floats on the surface).
Chemical properties:
The main pollutants of natural water include wastewater from industrial enterprises containing compounds of mercury, arsenic and other toxic elements. The drains of livestock complexes and cities may contain wastes that cause the rapid development of bacteria. Improper storage (not providing protection from atmospheric precipitation) or the use of fertilizers and pesticides washed away in water bodies is a great danger to natural water bodies. Transport, especially water, pollutes water bodies with oil products and household garbage that is thrown by unscrupulous people directly into the water.
For water protection, it is necessary to introduce closed water supply to industrial enterprises, integrated processing of raw materials and waste, construction of treatment facilities, and environmental education of the population.
* For electrolysis of water, salt solutions are used
2. Experience. Recognition of a carbonic acid salt among the three proposed salts.
A qualitative reaction to carbonates is the interaction with acids, accompanied by the rapid release of carbon dioxide:
CaCO 3 + 2HCl \u003d CaCl 2 + H 2 O + CO 2
or, in ionic form:
CO 3 2− + 2H + \u003d H 2 O + CO 2
To prove that it is carbon monoxide (IV) that is released, it is possible by passing it through a solution of lime water, which causes its turbidity:
CO 2 + Ca (OH) 2 \u003d CaCO 3 ↓ + H 2 O
To recognize the salt of carbonic acid, add a little acid to all three tubes (so that it does not spill over the edge during “boiling”). Where odorless colorless gas will be released, there is carbonate.
Water can be in three states of aggregation - gaseous, liquid and solid. In each of these states, the water structure is not the same. Depending on the composition of the substances in it, water acquires new properties. The solid state of water can also be of at least two types: crystalline - ice and non-crystalline - glassy, \u200b\u200bamorphous (vitrification state). With instant freezing using, for example, liquid nitrogen, molecules do not have time to build into a crystal lattice, and water acquires a solid glassy state. It is this property of water that allows freezing living organisms without damage, such as unicellular algae, moss leaves Mpіut, consisting of two layers of cells. Freezing with the formation of crystalline water leads to cell damage.
The crystalline state of water is characterized by a wide variety of forms. It has long been observed that the crystalline structures of water resemble radiolarians, fern leaves, and cysts. On this occasion, A. A. Lyubishchev suggested that the laws of crystallization are somewhat similar to the laws of the formation of living structures.
Physical properties of water. Water is the most abnormal substance, although it is taken as a standard measure of density and volume for other substances.
Density. All substances increase volume when heated, while reducing density. However, at a pressure of 0.1013 MPa (1 atm.) In water in the range from 0 to 4 0 С, the volume decreases with increasing temperature and the maximum density is observed (at this temperature 1 cm 3 of water we have a mass of 1 g). When freezing, the volume of water increases sharply by 11%, and when ice melts at 0 ° C, it also sharply decreases. With increasing pressure, the freezing temperature of water decreases every 13.17 MPa (130 atm.) By 10 ° C. Therefore, at great depths at subzero temperatures, water in the ocean does not freeze. With increasing temperature to 100 0 С, the density of liquid water decreases by 4% (at 4 ° С its density is 1).
Boiling and freezing (melting) points. At a pressure of 0.1013 MPa (1 atm.), The freezing and boiling points of water are at 0 ° C and 100 ° C, which sharply distinguishes H20 from hydrogen compounds with elements of group VI of the Mendeleev’s periodic system. In a series of Н2Те, H2Se, H2S, etc. with increasing relative molecular weight, the boiling and freezing points of these substances increase. Subject to this rule, water should have freezing points between - 90 and - 120 ° С, and boiling points - between 75 and 100 ° С. The boiling point of water increases with increasing pressure, and the freezing (melting) temperature drops (Appendix 1).
Heat of fusion. The latent heat of melting ice is very high - about 335 J / g (for iron - 25, for sulfur - 40). This property is expressed, for example, in the fact that ice at normal pressure can have a temperature from - 1 to - 7 ° C. The latent heat of vaporization of water (2.3 kJ / g) is almost 7 times higher than the latent heat of fusion.
Heat capacity. The heat capacity of water (i.e., the amount of heat required to increase the temperature by 1 ° C) is 5-30 times higher than that of other substances. Only hydrogen and ammonia have a higher heat capacity. In addition, only in liquid water and mercury does the specific heat decrease with increasing temperature from 0 to 35 ° C (then begins to increase). The specific heat capacity of water at 16 ° C is conventionally taken as a unit, serving as a standard for other substances. Since the heat capacity of sand is 5 times less than that of liquid water, with the same heat from the sun, the water in the pond heats up 5 times weaker than sand on the shore, but retains heat the same amount of time. The high heat capacity of water protects plants from a sharp increase in temperature at high air temperatures, and the high heat of vaporization is involved in thermoregulation in plants.
High melting and boiling points, high heat capacity indicate a strong attraction between neighboring molecules, as a result of which liquid water has a large internal cohesion.
Water as a solvent. The polarity of a water molecule determines its ability to dissolve substances better than other liquids. The dissolution of crystals of inorganic salts is carried out due to the hydration of their constituent ions. Organic substances are well soluble in water, with carboxylic and hydroxyl. Carbonyl and with other groups, which water forms hydrogen bonds. (adj. 1)
Water in the plant is both in free and bound state (Appendix 2). Free water is mobile, it has almost all the physicochemical properties of pure water, and penetrates well through cell membranes. There are special membrane proteins that form channels permeable to water (aquaporins) inside the membrane. Free water enters into various biochemical reactions, evaporates during transpiration, and freezes at low temperatures.
Bound water - has altered physical properties mainly as a result of interaction with non-aqueous components. Conventionally, take under bound water one that does not freeze when the temperature drops to -10 ° C.
Bound water in plants happens:
1) Osmotically linked
2) Colloidal bound
3) Capillary bound
Osmotically-bound water - bound to ions or low molecular weight substances. Water hydrates dissolved substances - ions, molecules. Water electrostatically binds and forms a monomolecular layer of primary hydration. Vacuolar juice contains sugars, organic acids and their salts, inorganic cations and anions. These substances retain water osmotically.
Colloidal-bound water - includes water that is inside the colloidal system and water that is on the surface of the colloids and between them, as well as immobilized water. Immobilization is a mechanical capture of water during conformational changes of macromolecules or their complexes, while water is enclosed in a confined space of the macromolecule. A significant amount of colloidal-bound water is located on the surface of the fibrils of the cell wall, as well as in the cytoplasmic biocolloids and the matrix of cell membrane structures.
Water that hydrates colloidal particles (primarily proteins) is called colloidal bound, and dissolved substances (mineral salts, sugars, organic acids, etc.) are called osmotically bound. Some researchers believe that all the water in the cell is more or less connected. Physiologists conventionally understand by bound water that which does not freeze when the temperature drops to -10 ° C. It is important to note that any binding of water molecules (the addition of dissolved substances, hydrophobic interactions, etc.) reduces their energy. This is what underlies the reduction in the water potential of the cell compared to pure water.
The water content in various organs of plants varies widely. It varies depending on environmental conditions, age and type of plants. So, the water content in lettuce is 93-95%, corn - 75-77%. The amount of water varies in different organs of plants: in the leaves of sunflower water contains 80-83%, in the stems - 87-89%, in the roots - 73-75%. A water content of 6–11% is characteristic mainly of air-dried seeds, in which vital processes are inhibited. Water is contained in living cells, in the dead elements of xylem and in intercellular spaces. In the intercellular spaces, water is in a vaporous state. The main evaporative organs of the plant are leaves. In this regard, it is natural that the greatest amount of water fills the intercellular spaces of the leaves. In a liquid state, water is in various parts of the cell: the cell membrane, vacuoles, and protoplasm. Vacuoles are the most water-rich part of the cell, where its content reaches 98%. With the greatest water content, the water content in the protoplasm is 95%. The lowest water content is characteristic of cell membranes. Quantifying the water content in cell membranes is difficult; apparently, it ranges from 30 to 50%.
The forms of water in different parts of the plant cell are also different. In vacuolar cell juice, water is predominant, retained by relatively low molecular weight compounds (osmotically bound) and free water. In the membrane of a plant cell, water is bound mainly by high-polymer compounds (cellulose, hemicellulose, pectin substances), i.e., colloid-bound water. In the cytoplasm itself there is free water, colloid- and osmotic-associated. Water located at a distance of 1 nm from the surface of the protein molecule is firmly bound and does not have the correct hexagonal structure (colloidal bound water). In addition, in the protoplasm there is a certain amount of ions, and, therefore, part of the water is osmotically connected.
The physiological significance of free and bound water is different. Most researchers believe that the intensity of physiological processes, including growth rates, depends primarily on the free water content. There is a direct correlation between the content of bound water and the resistance of plants to adverse environmental conditions. These physiological correlations are not always observed.
Candidate of Chemical Sciences Alexander Smirnov, Professor of MIREA.
Mysterious power given to water
To be the juice of life on Earth.
Leonardo da Vinci
Fig. 1. The structure of water at a temperature of 20 aboutC, horizontal size - 400 microns. White spots are emulsions.
Fig. 2. The structure of aqueous solutions at 20 aboutC: A — distilled water; B - degassed mineral water of Borjomi; B - alcohol tincture of 70%.
Fig. 3. Emulsions in bidistilled water at temperatures of 4 aboutC (A), 20 aboutS (B), 80 aboutC (B). Image sizes 1.5 × 1.5 mm.
Fig. 4. Change in the amplitude of acoustic emission signals and water temperature during ice melting.
Fig. 5. Relative temperature change when heating water.
Details for the curious. Scheme of experience. In a short time, 0.5 grams of water flowed out of the cup with a positive electrode (anode) through the "bridge".
The “floating water bridge” is about 3 centimeters long.
An electrified glass rod distorts the shape of the "bridge" and breaks it into trickles.
This may look like emulsions, forming a filamentary structure of the "bridge".
It is customary to consider water both as a practically neutral solvent in which biochemical reactions take place, and as a substance that carries various substances throughout the body of living organisms. At the same time, water is an indispensable participant in all physicochemical processes and, due to its great importance, the most studied substance. The study of the properties of water has repeatedly led to unexpected results. It would seem, what surprises may the simple reaction of hydrogen oxidation 2H 2 + O 2 → 2H 2 O be fraught with? But the work of academician N. N. Semenov showed that this reaction is branched, chain. This was more than seventy years ago, and they still did not know about the chain reaction of uranium fission. The water in a glass, river or lake is not just huge quantities of individual molecules, but their associations, supramolecular structures - clusters. To describe the structure of water, a number of models have been proposed that more or less correctly explain only some of its properties, and in relation to others contradict the experiment.
in theory, clusters are usually calculated only for a few hundred molecules or for layers near the interface. However, a number of experimental facts indicate that giant structures of molecular scale can exist in water (works by Corresponding Member of the Russian Academy of Sciences E. E. Fesenko).
In carefully purified doubly distilled water and some solutions, we were able to detect by acoustic emission and using laser interferometry visualize structural formations consisting of five fractions from 1 to 100 microns in size. The experiments made it possible to establish that each solution has its own structure unique to it (Fig. 1, 2).
Supramolecular complexes are formed by hundreds of thousands of water molecules grouped around hydrogen and hydroxyl ions in the form of ion pairs. For these supramolecular complexes, we offer the name "emulsions" to emphasize their similarity with the particles forming the emulsion. The complexes consist of separate fractions from 1 to 100 microns in size, and fractions having sizes of 30, 70 and 100 microns are much larger than the others.
The content of individual fractions of emulsions depends on the concentration of hydrogen ions, temperature, concentration of the solution and the history of the sample (Fig. 3). In double-distilled water at 4 ° C, the complexes are densely packed and form a texture resembling parquet. As you know, water at this temperature has a maximum density. With an increase in temperature to 20 ° C, significant changes occur in the structure of water: the number of free emulsions becomes the largest. With further heating, they gradually collapse, their number decreases, and this process basically ends at 75 ° C, when the speed of sound in water reaches a maximum.
Due to the long-range effects of electrostatic forces, emulsions in water form a rather stable superlattice, which, however, is sensitive to electromagnetic, acoustic, thermal and other external influences.
The detected supramolecular complexes consistently include all previously obtained information about the organization of water in nanoscale volumes and allow one to explain many experimental facts that did not have a coherent, logical justification. These include, for example, the formation of a “floating water bridge”, described in a number of works.
The essence of the experiment is that if two small chemical beakers with water are placed next to each other and platinum electrodes are lowered under them at a constant voltage of 15-30 kV, a water bridge with a diameter of 3 mm and a length of up to 25 mm is formed between the vessels. The bridge soars for a long time, has a layered structure, and water transfers from the anode to the cathode along it. This phenomenon and all its properties are a consequence of the presence of emulsions in water, which, apparently, have a dipole moment. One more property of the phenomenon can be predicted: at a water temperature above 75 ° C a “bridge” will not arise.
The anomalous properties of melt water are also easily explained. As noted in the literature, many of the properties of melt water — density, viscosity, electrical conductivity, refractive index, dissolving power, and others — differ from equilibrium parameters. Reducing these effects to the removal of deuterium from water as a result of a phase transition (melting point of “heavy ice” D 2 O 3.82 ° C) is not feasible, since the concentration of deuterium is extremely low - one atom of deuterium per 5-7 thousand hydrogen atoms.
A study of ice melting by acoustic emission made it possible for the first time to establish that, after complete melting of ice, melt water in a metastable state becomes a source of acoustic impulses, which serves as experimental confirmation of the formation of supramolecular complexes in water (Fig. 4).
Experiments show that melt water can remain in an active metastable state for almost 17 hours (after melting the ice, its microcrystals are preserved only for a split second and do not determine the properties of melt water at all). This mysterious phenomenon is explained by the fact that the destruction of the hexagonal crystal lattice of ice dramatically changes the structure of the substance. Ice crystals are destroyed faster than being converted to a stable equilibrium state the water formed from it.
The uniqueness of the ice-water phase transition lies in the fact that in melt water the concentration of hydrogen ions H + and hydroxyl OH - for a short time remains nonequilibrium, as it was in ice, that is, a thousand times less than in ordinary water. After some time, the concentration of H + and OH - ions in water assumes its equilibrium value. Since hydrogen and hydroxyl ions play a decisive role in the formation of supramolecular water complexes (emulsions), water remains in a metastable state for some time. The reaction of its dissociation H 2 O → H + + OH - requires a significant expenditure of energy and proceeds very slowly. The rate constant of this reaction is only 2.5 ∙ 10 –5 s –1 at 20 о С. Therefore, the time of returning melt water to the equilibrium state should theoretically be 10-17 hours, which is observed in practice. Studies of the dynamics of changes in the concentration of hydrogen ions in melt water over time confirm this. The unusual properties of meltwater are the cause of talk about the "memory" of water. But by the “memory" of water should be understood the dependence of its properties on the background and nothing more. It is possible in different ways - freezing, heating, boiling, sonication, exposure to various fields, etc. - to transfer water to a metastable state, but it will be unstable, not retaining its properties for long. Optically, we found in melt water the presence of only one fraction of supramolecular formations with sizes of 1-3 microns. It is possible that a lower viscosity and a rarer spatial network of emulsions in melt water increase the dissolving power and diffusion rate.
The reality of the existence of emulsions is confirmed by the classical method of thermal analysis (Fig. 5). The graph shows distinct peaks, indicating structural changes in the water. The most significant ones correspond to 36 ° C, the temperature of minimum heat capacity, 63 ° C, the temperature of minimum compressibility, and a peak at 75 ° C, the temperature of the maximum speed of sound in water, is especially characteristic. They can be interpreted as a kind of phase transitions associated with the destruction of emulsions. This allows us to conclude: liquid water is a very peculiar dispersed system, including at least five structural formations with various properties. Each structure exists in a specific temperature range characteristic of it. Exceeding the temperature above the threshold level critical for a given structure leads to its decay.
Literature
Zatsepina G. L. Physical properties and structure of water. - M .: Publishing house of Moscow University. - 1998 .-- 185 s.
Kuznetsov D. M., Gaponov V. L., Smirnov A. N. On the possibility of studying the kinetics of phase transitions in a liquid medium by acoustic emission // Engineering Physics, 2008, No. 1, p. 16-20.
Kuznetsov D.M., Smirnov A.N., Syroeshkin A.V. Acoustic emission during phase transformations in an aqueous medium // Russian Chemical Journal - M .: Ros. Chem. about them. D. I. Mendeleev, 2008, v. 52, No. 1, p. 114-121.
Smirnov A.N. Water structure: new experimental data. // Science and technology in industry, 2010, No. 4, p. 41-45.
Smirnov A.N. Acoustic emission during a chemical reaction and physicochemical processes // Russian Chemical Journal. - M .: Ros. Chem. about them. D.I. Mendeleev, 2001, v. 45, p. 29-34.
Smirnov A.N., Syroeshkin A.V. Supranadmolecular complexes of water // Russian Chemical Journal. - M .: Ros. Chem. about them. D.I. Mendeleev, 2004, v. 48, No. 2, p. 125-135.
Details for the curious
How does the "bridge" arise
The formation of the “water bridge” is described in the work of the Dutch physicist Elmar Fuchs and his colleagues.
Platinum electrodes are immersed in two small adjacent containers with water and a constant voltage of 15-20 kV is applied to them. In the photographs it is clearly seen that at first in the anode cup, and then in the cathode, on the surface of the water there are elevations that merge, forming a water bridge of circular cross section with a diameter of 2-4 mm between the containers. After this, the glasses can be moved one from another by 20-25 mm. The jumper has been around for quite some time, forming a “soaring water bridge”. Along the "bridge" flows water. The ends of the "bridge" are oppositely charged, so the water in the tanks acquires different pH values: 9 and 4. The "bridge" consists of thin streams; when you bring a charged glass rod to it, it splits into several sleeves. The high experimental technique made it possible to detect the movement of spherical formations on the surface of the “water bridge”.
Water is the most common compound in living systems. But the water content varies widely: from 10% (tooth enamel), 20% (bone tissue), to 85% (human brain), in dry seeds 10-12%, in jellyfish 95-98%, i.e. . the whole organism is essentially composed of water. The loss of 20% of the water leads to cell death or suspended animation.
The properties of water are unique, i.e. no other compound possesses them. This is due to the structure of its molecules: one oxygen atom is connected by a strong covalent bond with two hydrogen atoms, i.e. H 2 O is a very simple compound. Hydrogen atoms are attached to oxygen at an angle of 104.5 0.
Fig. 1. The structure of the water molecule.
Features of the physical properties of water are associated with the structure of its molecule and the features of intermolecular interactions. The distribution of electron density in a water molecule is such (Fig. 1, b, c) that 4 poles of charges are created: 2 positive ones connected with hydrogen atoms and 2 negative ones connected with electron clouds of electrons of the oxygen atom. The indicated 4 poles of charges are located at the vertices of the tetrahedron (Fig. 1d). Due to this, the water molecule is dipole, and the four poles of charges allow each molecule to form four hydrogen bonds with neighboring (same) molecules. As a result, clusters are formed (with instant freezing, they look like beautiful snowflakes, Fig. 2.).
Fig. 2. The formation of a water cluster.
Clusters form working "Water structure". Hydrogen bonds are weak, 15-20 times weaker than covalent bonds. Therefore, some bonds are easily broken, others arise. As a result, the molecules are very mobile. Any external changes (temperature, pressure, etc.) change this working structure. Thus, water has a high sensitivity and memory.
Water molecules can attach to molecules that carry an electronic charge, resulting in the formation of hydrates. If the force of attraction between water molecules is less than the attraction of water to the molecules of a substance, the substance dissolves.
Properties and functions of water.
1. Connects in a single system all living and non-living nature on the planet. Water is mobile, changeable, but not the chemical composition of molecules, but the structure of the cluster is changing.
2. Water is a universal solvent. Due to its polarity, it has no equal in this: more substances are dissolved in water than in any other liquids. Substances in the cell come and go only in dissolved form.
3. With respect to water, substances in the cell are divided into 2 groups:
a) hydrophobic (fobos - fear, horror): insoluble in water (fats, polysaccharides, etc.)
b) hydrophilic (fileon - I love): soluble in water (mineral salts, acids, monosaccharides, etc.)
Due to this property of water (due to hydrophobic interactions) in the cell are collected:
1) biological membranes,
2) proteins and DNA take the form of a spiral.
4. High heat capacity is characteristic of water (that is, a lot of energy is required to raise the temperature of the water and break the hydrogen bonds). So, the boiling point of water is 100 0 С, and that of alcohol is 70 0 С.
5. High thermal conductivity. Due to this property, thermal equilibrium is maintained in the cell and in the body.
6. Water itself as a chemical compound is involved in many chemical reactions. For example, hydrolysis reactions occur due to the addition of water.
7. It is a source of O 2 and H + during photosynthesis (photolysis of water).
8. Water is the main medium for the transport of substances in the cell (diffusion) and the body (blood and lymph currents, interstitial fluid containing nutrients, O 2 and CO 2, hormones, substances that turn genes on and off). This is a transport function.
9. Provides cell volume and elasticity: turgor and osmotic pressure, maintains the shape of cells and organisms (the hydroskeleton in round and annelid worms).
10. Medium for fertilization.
11. The environment for the life of aquatic organisms.
12. Environment for the development of animal embryos (in the amnion).
13. Participates in the formation of lubricating fluids in the joints, pleural cavity, pericardial sac.
14. Forms mucus, ensuring the movement of substances through the intestines, a moist environment on the mucous membranes (sneezing, coughing).
15. Participates in the formation of secrets (saliva, tears, bile, sperm and salt in the body).
16. Water is the limiting factor of life on our planet. Wherever there is water, there is life where there is no water - there is no life.
