Crystal structure of ice. Properties of water

The three-dimensional state of liquid water is difficult to study, but much has been learned by analyzing the structure of ice crystals. Four neighboring hydrogen-bonded oxygen atoms occupy the vertices of a tetrahedron (tetra = four, hedron = plane). The average energy required to break such a bond in ice is estimated at 23 kJ/mol -1.

The ability of water molecules to form a given number of hydrogen chains, as well as the specified strength, creates an unusually high melting point. When it melts, it is held by liquid water, the structure of which is irregular. Most of the hydrogen bonds are distorted. To destroy the hydrogen-bonded crystal lattice of ice requires a large amount of energy in the form of heat.

Features of ice appearance (Ih)

Many ordinary people are wondering what kind of crystal lattice ice has. It should be noted that the density of most substances increases upon freezing, when molecular movements slow down and densely packed crystals form. The density of water also increases as it cools to its maximum at 4°C (277K). Then, when the temperature drops below this value, it expands.

This increase is due to the formation of an open hydrogen-bonded ice crystal with its lattice and lower density, in which each water molecule is tightly bound by the above element and four other values, and still moves fast enough to have more mass. As this action occurs, the liquid freezes from top to bottom. This has important biological consequences, whereby a layer of ice on a pond insulates living beings away from extreme cold. In addition, two additional properties of water are related to its hydrogen characteristics: specific heat capacity and evaporation.

Detailed description of structures

The first criterion is the amount required to raise the temperature of 1 gram of a substance by 1°C. Raising the degrees of water requires a relatively large portion of heat because each molecule is involved in numerous hydrogen bonds that must be broken for the kinetic energy to increase. By the way, the abundance of H 2 O in the cells and tissues of all large multicellular organisms means that temperature fluctuations inside the cells are minimized. This feature is critical because most biochemical reactions are rate sensitive.

Also significantly higher than many other liquids. To convert this solid into a gas requires a large amount of heat because the hydrogen bonds must be broken so that the water molecules can dislocate from each other and enter the said phase. Variable bodies are permanent dipoles and can interact with other similar compounds and those that are ionized and dissolved.

Other substances listed above can only come into contact if polarity is present. It is this compound that is involved in the structure of these elements. In addition, it can align around these particles formed from electrolytes, so that the negative oxygen atoms of the water molecules are oriented towards the cations, and the positive ions and hydrogen atoms are oriented towards the anions.

As a rule, molecular crystal lattices and atomic ones are formed. That is, if iodine is structured in such a way that I 2 is present in it, then in solid carbon dioxide, that is, in dry ice, there are CO 2 molecules at the nodes of the crystal lattice. When interacting with such substances, ice has an ionic crystal lattice. Graphite, for example, having an atomic structure based on carbon, is not able to change it, just like diamond.

What happens when a table salt crystal dissolves in water: polar molecules are attracted to the charged elements in the crystal, which leads to the formation of similar particles of sodium and chloride on its surface, as a result, these bodies dislocate from each other, and it begins to dissolve. From this we can observe that ice has a crystal lattice with ionic bonding. Each dissolved Na+ attracts the negative ends of several water molecules, while each dissolved Cl - attracts the positive ends. The shell surrounding each ion is called an escape sphere and usually contains several layers of solvent particles.

The variables or ion surrounded by elements are said to be sulfated. When water is the solvent, such particles become hydrated. Thus, any polar molecule tends to be solvation by elements of the liquid body. In dry ice, the type of crystal lattice forms atomic bonds in the aggregate state that are unchanged. Crystalline ice (frozen water) is another matter. Ionic organic compounds such as carboxylases and protonated amines must have solubility in hydroxyl and carbonyl groups. Particles contained in such structures move between molecules, and their polar systems form hydrogen bonds with this body.

Of course, the number of the latter groups in a molecule affects its solubility, which also depends on the reaction of the various structures in the element: for example, one-, two-, and three-carbon alcohols are miscible in water, but larger hydrocarbons with single hydroxyl compounds are much less dilute in liquids.

Hexagonal Ih is similar in shape to the atomic crystal lattice. For ice and all natural snow on Earth, it looks exactly like this. This is evidenced by the symmetry of the ice crystal lattice grown from water vapor (that is, snowflakes). Located in space group P 63/mm with 194; D 6h, Laue class 6/mm; similar to β-, which has a multiple of 6 helical axis (rotation around in addition to shear along it). It has a fairly open structure with low density, where the efficiency is low (~1/3) compared to simple cubic (~1/2) or face-centered cubic (~3/4) structures.

Compared to ordinary ice, the crystal lattice of dry ice, bound by CO 2 molecules, is static and changes only when atoms decay.

Description of lattices and their constituent elements

Crystals can be thought of as crystalline patterns consisting of sheets stacked on top of each other. Hydrogen bonding is ordered when in reality it is random, since protons can move between water (ice) molecules at temperatures above about 5 K. Indeed, it is likely that protons behave like a quantum fluid in a constant tunneling flow. This is enhanced by the scattering of neutrons showing their scattering density halfway between the oxygen atoms, indicating localization and coordinated motion. Here the similarity of ice with an atomic, molecular crystal lattice is observed.

The molecules have a stepped arrangement of the hydrogen chain in relation to their three neighbors in the plane. The fourth element has an eclipsed hydrogen bond arrangement. There is a slight deviation from perfect hexagonal symmetry, as much as 0.3% shorter in the direction of this chain. All molecules experience the same molecular environment. There is enough space inside each “box” to retain interstitial water particles. Although not generally considered, they have recently been effectively detected by neutron diffraction from powdered ice crystal lattice.

Change of substances

The hexagonal body has triple points with liquid and gaseous water 0.01 °C, 612 Pa, solid elements three -21.985 °C, 209.9 MPa, eleven and two -199.8 °C, 70 MPa, and -34 .7 °C, 212.9 MPa. The dielectric constant of hexagonal ice is 97.5.

The melting curve of this element is given by MPa. Equations of state are available, in addition to them some simple inequalities relating the change in physical properties with the temperature of hexagonal ice and its aqueous suspensions. Hardness varies with degrees, increasing from about or below gypsum (≤2) at 0°C, to feldspar levels (6 at -80°C, an abnormally large change in absolute hardness (>24 times).

The hexagonal crystal lattice of ice forms hexagonal plates and columns, where the top and bottom faces are the basal planes (0 0 0 1) with an enthalpy of 5.57 μJ cm -2, and the other equivalent side planes are called prism parts (1 0 -1 0) with 5.94 µJ cm -2. Secondary surfaces (1 1 -2 0) with 6.90 μJ ˣ cm -2 can be formed along the planes formed by the sides of the structures.

This structure shows an anomalous decrease in thermal conductivity with increasing pressure (like cubic and low-density amorphous ice), but differs from most crystals. This is due to a change in hydrogen bonding, which reduces the transverse speed of sound in the crystal lattice of ice and water.

There are methods that describe how to prepare large crystal samples and any desired ice surface. It is assumed that the hydrogen bond on the surface of the hexagonal body under study will be more ordered than inside the bulk system. Phase-lattice frequency-oscillating variational spectroscopy has shown that there is a structural asymmetry between the top two layers (L1 and L2) in the subsurface HO chain of the basal surface of hexagonal ice. The hydrogen bonds adopted in the upper layers of the hexagons (L1 O ··· HO L2) are stronger than those adopted in the second layer to the upper accumulation (L1 OH ··· O L2). Interactive hexagonal ice structures available.

Features of development

The minimum number of water molecules required for ice nucleation is approximately 275 ± 25, the same as for a complete icosahedral cluster of 280. Formation occurs at a factor of 10 10 at the air-water interface rather than in bulk water. The growth of ice crystals depends on different growth rates of different energies. Water must be protected from freezing during cryopreservation of biological samples, food and organs.

This is typically achieved by rapid cooling rates, the use of small samples and a cryoconservator, and increasing pressure to nucleate ice and prevent cell damage. The free energy of ice/liquid increases from ~30 mJ/m2 at atmospheric pressure to 40 mJ/m2 at 200 MPa, indicating the reason why this effect occurs.

Alternatively, they may grow more rapidly from prism surfaces (S2), on randomly disturbed surfaces of flash-frozen or disturbed lakes. The growth from the faces (1 1 -2 0) is at least the same, but turns them into the bases of a prism. Ice crystal development data have been fully explored. The relative growth rates of elements of different faces depend on the ability to form a greater degree of joint hydration. The (low) temperature of the surrounding water determines the degree of branching in the ice crystal. Particle growth is limited by the rate of diffusion at low degrees of supercooling, i.e.<2 ° C, что приводит к большему их количеству.

But it is limited by development kinetics at higher levels of lowering degrees >4°C, which leads to needle-like growth. This form is similar to the structure of dry ice (has a crystal lattice with a hexagonal structure), different characteristics of surface development and the temperature of the surrounding (supercooled) water that lies behind the flat forms of snowflakes.

The formation of ice in the atmosphere profoundly influences the formation and properties of clouds. Feldspars, found in desert dust that enters the atmosphere by the millions of tons per year, are important formatives. Computer simulations have shown that this is due to the nucleation of planes of prismatic ice crystals on high-energy surface planes.

Some other elements and lattices

Solutes (except for a very small amount of helium and hydrogen, which may enter interstices) cannot be incorporated into the Ih structure at atmospheric pressure, but are forced to the surface or an amorphous layer between the particles of the microcrystalline body. At the sites of the crystal lattice of dry ice there are some other elements: chaotropic ions, such as NH 4 + and Cl -, which are included in the freezing of the liquid more easily than other kosmotropic ones, such as Na + and SO 4 2-, so their removal is impossible, due to the fact that they form a thin film of the remaining liquid between the crystals. This can lead to electrical charging of the surface due to the dissociation of surface water balancing the remaining charges (which can also result in magnetic radiation) and a change in the pH of the residual liquid films, for example NH 4 2 SO 4 becoming more acidic and NaCl becoming more alkaline.

They are perpendicular to the faces of the ice crystal lattice, showing the attached next layer (with O-black atoms). They are characterized by a slowly growing basal surface (0 0 0 1), where only isolated water molecules are attached. A rapidly growing (1 0 -1 0) surface of a prism, where pairs of newly attached particles can bond with each other with hydrogen (one bond/two molecules of the element). The fastest growing face is (1 1 -2 0) (secondary prismatic), where chains of newly attached particles can interact with each other by hydrogen bonding. One of its chain/element molecule is a form that forms ridges that divide and encourage the transformation into two sides of a prism.

Zero point entropy

kBˣ Ln ( N

Scientists and their works in this field

Can be defined as S 0 = kBˣ Ln ( N E0), where k B is Boltzmann's constant, N E is the number of configurations at energy E, and E0 is the lowest energy. This value for the entropy of hexagonal ice at zero kelvin does not violate the third law of thermodynamics, “The entropy of an ideal crystal at absolute zero is exactly zero,” since these elements and particles are not ideal and have disordered hydrogen bonding.

In this body, hydrogen bonding is random and rapidly changing. These structures are not exactly equal in energy, but extend to a very large number of energetically close states and obey the “rules of ice.” Zero point entropy is the disorder that would remain even if the material could be cooled to absolute zero (0 K = -273.15 °C). Gives rise to experimental confusion for hexagonal ice 3.41 (±0.2) ˣ mol -1 ˣ K -1 . Theoretically, it would be possible to calculate the zero entropy of known ice crystals with much greater accuracy (neglecting defects and energy level scatter) than determining it experimentally.

Although the order of protons in bulk ice is not ordered, the surface probably prefers the order of said particles in the form of bands of dangling H atoms and O lone pairs (zero entropy with ordered hydrogen bonds). The disorder of the zero point ZPE, J ˣ mol -1 ˣ K -1 and others was found. From all of the above, it is clear and understandable what types of crystal lattices are characteristic of ice.

O. V. Mosin, I. Ignatov (Bulgaria)

annotation The importance of ice in supporting life on our planet cannot be underestimated. Ice has a great influence on the living conditions of plants and animals and on various types of human economic activity. Covering water, ice, due to its low density, plays in nature the role of a floating screen, protecting rivers and reservoirs from further freezing and preserving the life of underwater inhabitants. The use of ice for various purposes (snow retention, construction of ice crossings and isothermal warehouses, ice filling of storage facilities and mines) is the subject of a number of sections of hydrometeorological and engineering sciences, such as ice engineering, snow engineering, permafrost engineering, as well as the activities of special ice reconnaissance services and icebreaking transport and snow removal equipment. Natural ice is used for storing and cooling food products, biological and medical preparations, for which it is specially produced and prepared, and melt water prepared by melting ice is used in folk medicine to increase metabolism and remove toxins from the body. The article introduces the reader to new little-known properties and modifications of ice.

Ice is a crystalline form of water, which, according to the latest data, has fourteen structural modifications. Among them there are crystalline (natural ice) and amorphous (cubic ice) and metastable modifications, differing from each other in the mutual arrangement and physical properties of water molecules connected by hydrogen bonds that form the crystal lattice of ice. All of them, except for the familiar natural ice I h, which crystallizes in a hexagonal lattice, are formed under exotic conditions - at very low temperatures of dry ice and liquid nitrogen and high pressures of thousands of atmospheres, when the angles of hydrogen bonds in the water molecule change and crystalline systems are formed that are different from hexagonal. Such conditions resemble those in space and do not occur on Earth.

In nature, ice is represented mainly by one crystalline variety, crystallizing in a hexagonal lattice, reminiscent of the structure of diamond, where each water molecule is surrounded by the four nearest molecules, located at equal distances from it, equal to 2.76 angstroms and placed at the vertices of a regular tetrahedron. Due to the low coordination number, the structure of ice is reticular, which affects its low density, amounting to 0.931 g/cm 3 .

The most unusual property of ice is its amazing variety of external manifestations. With the same crystalline structure, it can look completely different, taking the form of transparent hailstones and icicles, flakes of fluffy snow, a dense shiny crust of ice or giant glacial masses. Ice occurs in nature in the form of continental, floating and underground ice, as well as snow and frost. It is widespread in all areas of human habitation. When collected in large quantities, snow and ice form special structures with properties that are fundamentally different from those of individual crystals or snowflakes. Natural ice is formed mainly by ice of sedimentary-metamorphic origin, formed from solid atmospheric precipitation as a result of subsequent compaction and recrystallization. A characteristic feature of natural ice is graininess and banding. The graininess is due to recrystallization processes; Each grain of glacial ice is an irregularly shaped crystal, closely adjacent to other crystals in the ice mass in such a way that the protrusions of one crystal fit tightly into the recesses of another. This type of ice is called polycrystalline. In it, each ice crystal is a layer of the thinnest leaves overlapping each other in the basal plane perpendicular to the direction of the optical axis of the crystal.

The total ice reserves on Earth are estimated to be about 30 million. km 3(Table 1). Most ice is concentrated in Antarctica, where its layer thickness reaches 4 km. There is also evidence of the presence of ice on the planets of the Solar System and in comets. Ice is so important for the climate of our planet and the habitat of living things on it that scientists have designated a special environment for ice - the cryosphere, the boundaries of which extend high into the atmosphere and deep into the earth's crust.

Table 1. Amount, distribution and lifetime of ice.

Ice crystals are unique in their shape and proportions. Any growing natural crystal, including an ice crystal, always strives to create an ideal regular crystal lattice, since this is beneficial from the point of view of the minimum of its internal energy. Any impurities, as is known, distort the shape of the crystal, therefore, when water crystallizes, water molecules are first built into the lattice, and foreign atoms and impurity molecules are forced out into the liquid. And only when the impurities have nowhere to go, the ice crystal begins to integrate them into its structure or leaves them in the form of hollow capsules with a concentrated non-freezing liquid - brine. Therefore, sea ice is fresh and even the dirtiest bodies of water are covered with transparent and clean ice. When ice melts, it displaces impurities into the brine. On a planetary scale, the phenomenon of freezing and thawing of water, along with evaporation and condensation of water, plays the role of a gigantic purification process in which water on Earth constantly purifies itself.

Table 2. Some physical properties of ice I.

Property	Meaning	Note
Heat capacity, cal/(g °C) Heat of melting, cal/g Heat of vaporization, cal/g		Decreases greatly with decreasing temperature
Thermal expansion coefficient, 1/°C	9.1 10 -5 (0 °C)	Polycrystalline ice
Thermal conductivity, cal/(cm sec °C)		Polycrystalline ice
Refractive index:		Polycrystalline ice
Specific electrical conductivity, ohm -1 cm -1		Apparent activation energy 11 kcal/mol
Surface electrical conductivity, ohm -1		Apparent activation energy 32 kcal/mol
Young's modulus of elasticity, dyn/cm2	9 10 10 (-5 °C)	Polycrystalline ice
Resistance, MN/m 2: crushing		Polycrystalline ice Polycrystalline ice Polycrystalline ice
Dynamic viscosity, poise		Polycrystalline ice
Activation energy during deformation and mechanical relaxation, kcal/mol		Increases linearly by 0.0361 kcal/(mol °C) from 0 to 273.16 K

1 cal/(g °C)=4.186 kJ/(kg K); 1 ohm -1 cm -1 =100 sim/m; 1 dyne = 10 -5 N ; 1 N = 1 kg m/s²; 1 dyne/cm=10 -7 N/m; 1 cal/(cm·sec°C)=418.68 W/(m·K); 1 poise = g/cm s = 10 -1 N sec/m 2 .

Due to the wide distribution of ice on Earth, the difference in the physical properties of ice (Table 2) from the properties of other substances plays an important role in many natural processes. Ice has many other life-sustaining properties and anomalies - anomalies in density, pressure, volume, thermal conductivity. If there were no hydrogen bonds holding water molecules together into a crystal, ice would melt at –90 °C. But this does not happen due to the presence of hydrogen bonds between water molecules. Due to its lower density than water, ice forms a floating cover on the surface of the water, protecting rivers and reservoirs from bottom freezing, since its thermal conductivity is much lower than that of water. In this case, the lowest density and volume is observed at +3.98 °C (Fig. 1). Further cooling of water to 0 0 C gradually leads not to a decrease, but to an increase in its volume by almost 10%, when the water turns into ice. This behavior of water indicates the simultaneous existence of two equilibrium phases in water - liquid and quasicrystalline, by analogy with quasicrystals, the crystal lattice of which not only has a periodic structure, but also has symmetry axes of different orders, the existence of which previously contradicted the ideas of crystallographers. This theory, first put forward by the famous Russian theoretical physicist Ya. I. Frenkel, is based on the assumption that some of the liquid molecules form a quasicrystalline structure, while the remaining molecules are gas-like, freely moving throughout the volume. The distribution of molecules in a small vicinity of any fixed water molecule has a certain ordering, somewhat reminiscent of crystalline, although more loose. For this reason, the structure of water is sometimes called quasicrystalline or crystal-like, i.e., having symmetry and order in the relative arrangement of atoms or molecules.

Rice. 1. Dependence of the specific volume of ice and water on temperature

Another property is that the speed of ice flow is directly proportional to the activation energy and inversely proportional to the absolute temperature, so that with decreasing temperature, ice approaches an absolutely solid body in its properties. On average, at temperatures close to melting, the fluidity of ice is 10 6 times higher than that of rocks. Due to its fluidity, ice does not accumulate in one place, but constantly moves in the form of glaciers. The relationship between flow velocity and stress for polycrystalline ice is hyperbolic; when approximately described by a power equation, the exponent increases as the voltage increases.

Visible light is practically not absorbed by ice, since light rays pass through the ice crystal, but it blocks ultraviolet radiation and most of the infrared radiation from the Sun. In these regions of the spectrum, ice appears completely black, since the absorption coefficient of light in these regions of the spectrum is very high. Unlike ice crystals, white light falling on snow is not absorbed, but is refracted many times in ice crystals and reflected from their faces. That's why snow looks white.

Due to the very high reflectivity of ice (0.45) and snow (up to 0.95), the area covered by them is on average about 72 million km per year. km 2 in the high and middle latitudes of both hemispheres - it receives solar heat 65% less than normal and is a powerful source of cooling the earth's surface, which largely determines the modern latitudinal climatic zonation. In summer, in the polar regions, solar radiation is greater than in the equatorial zone, however, the temperature remains low, since a significant part of the absorbed heat is spent on melting ice, which has a very high heat of melting.

Other unusual properties of ice include the generation of electromagnetic radiation by its growing crystals. It is known that most dissolved impurities in water are not transferred to the ice when it begins to grow; they are frozen out. Therefore, even on the dirtiest puddle, the ice film is clean and transparent. In this case, impurities accumulate at the boundary of solid and liquid media, in the form of two layers of electrical charges of different signs, which cause a significant difference in potentials. The charged layer of impurities moves along with the lower boundary of the young ice and emits electromagnetic waves. Thanks to this, the crystallization process can be observed in detail. Thus, a crystal growing in length in the form of a needle emits differently than one covered with lateral processes, and the radiation of growing grains differs from what occurs when crystals crack. By the shape, sequence, frequency and amplitude of the radiation pulses, one can determine at what speed the ice freezes and what kind of ice structure is formed.

But the most amazing thing about the structure of ice is that water molecules at low temperatures and high pressures inside carbon nanotubes can crystallize into a double helix shape, reminiscent of DNA molecules. This was proven by recent computer experiments by American scientists led by Xiao Cheng Zeng from the University of Nebraska (USA). In order for water to form a spiral in a simulated experiment, it was placed in nanotubes with a diameter of 1.35 to 1.90 nm under high pressure, varying from 10 to 40,000 atmospheres and a temperature of –23 °C. It was expected to see that the water in all cases forms a thin tubular structure. However, the model showed that with a nanotube diameter of 1.35 nm and an external pressure of 40,000 atmospheres, the hydrogen bonds in the ice structure were bent, which led to the formation of a spiral with a double wall - internal and external. Under these conditions, the inner wall turned out to be twisted into a quadruple helix, and the outer wall consisted of four double helices, similar to a DNA molecule (Fig. 2). This fact can serve as confirmation of the connection between the structure of the vital DNA molecule and the structure of water itself and that water served as a matrix for the synthesis of DNA molecules.

Rice. 2. A computer model of the structure of frozen water in nanotubes, reminiscent of a DNA molecule (Photo from New Scientist magazine, 2006)

Another of the most important properties of water discovered recently is that water has the ability to remember information about past influences. This was first proven by the Japanese researcher Masaru Emoto and our compatriot Stanislav Zenin, who was one of the first to propose a cluster theory of the structure of water, consisting of cyclic associates of a volumetric polyhedral structure - clusters of the general formula (H 2 O) n, where n, according to the latest data, can reach hundreds and even thousand units. It is thanks to the presence of clusters in water that water has information properties. Researchers photographed the processes of freezing water into ice microcrystals, influencing it with various electromagnetic and acoustic fields, melodies, prayer, words or thoughts. It turned out that under the influence of positive information in the form of beautiful melodies and words, the ice froze into symmetrical hexagonal crystals. Where irregular music and angry and offensive words sounded, the water, on the contrary, froze into chaotic and shapeless crystals. This is proof that water has a special structure that is sensitive to external information influences. Presumably the human brain, consisting of 85-90% water, has a strong structuring effect on water.

Emoto crystals arouse both interest and insufficiently substantiated criticism. If you look at them carefully, you can see that their structure consists of six tops. But an even more careful analysis shows that snowflakes in winter have the same structure, always symmetrical and with six tops. To what extent do crystallized structures contain information about the environment in which they were created? The structure of snowflakes can be beautiful or shapeless. This indicates that the control sample (cloud in the atmosphere) where they originate has the same influence on them as the original conditions. The initial conditions are solar activity, temperature, geophysical fields, humidity, etc. All this means that from the so-called. average ensemble, we can conclude that the structure of water droplets and then snowflakes is approximately the same. Their mass is almost the same, and they move through the atmosphere at similar speeds. In the atmosphere they continue to form their structures and increase in volume. Even if they formed in different parts of the cloud, in one group there is always a certain number of snowflakes that arose under almost the same conditions. And the answer to the question of what constitutes positive and negative information about snowflakes can be found in Emoto. In laboratory conditions, negative information (earthquake, sound vibrations unfavorable for humans, etc.) does not form crystals, but positive information, just the opposite. It is very interesting to what extent one factor can shape the same or similar structures of snowflakes. The highest density of water is observed at a temperature of 4 °C. It has been scientifically proven that the density of water decreases when hexagonal ice crystals begin to form when the temperature drops below zero. This is the result of hydrogen bonds between water molecules.

What is the reason for this structuring? Crystals are solids, and their constituent atoms, molecules or ions are arranged in a regular, repeating pattern in three spatial dimensions. The structure of water crystals is slightly different. According to Isaac, only 10% of the hydrogen bonds in ice are covalent, i.e. with fairly stable information. Hydrogen bonds between the oxygen of one water molecule and the hydrogen of another are most sensitive to external influences. The spectrum of water when building crystals is relatively different over time. According to the effect of discrete evaporation of a water drop proved by Antonov and Yuskeseliev and its dependence on the energy states of hydrogen bonds, we can look for an answer about the structuring of crystals. Each part of the spectrum depends on the surface tension of the water droplets. There are six peaks in the spectrum, which indicate the branches of the snowflake.

It is clear that in Emoto's experiments, the initial "control" sample affects the appearance of the crystals. This means that after exposure to a certain factor, the formation of similar crystals can be expected. It is almost impossible to obtain identical crystals. When testing the effect of the word "love" on water, Emoto does not clearly indicate whether the experiment was carried out with different samples.

Double-blind experiments are needed to test whether the Emoto technique is sufficiently differentiated. Isaac's proof that 10% of water molecules form covalent bonds after freezing shows us that water uses this information when it freezes. Emoto's achievement, even without doubly blind experiments, remains quite important regarding the information properties of water.

Natural Snowflake, Wilson Bentley, 1925

Emoto snowflake obtained from natural water

One snowflake is natural, and the other is created by Emoto, indicating that the diversity in the water spectrum is not limitless.

Earthquake, Sofia, 4.0 Richter scale, 15 November 2008,
Dr. Ignatov, 2008©, Prof. Antonov's device©

This figure indicates the difference between the control sample and those taken on other days. Water molecules break the most energetic hydrogen bonds in water, as well as two peaks in the spectrum during a natural phenomenon. The study was carried out using an Antonov device. The biophysical result shows a decrease in the vital tone of the body during an earthquake. During an earthquake, water cannot change its structure in the snowflakes in Emoto's laboratory. There is evidence of changes in the electrical conductivity of water during an earthquake.

In 1963, Tanzanian schoolboy Erasto Mpemba noticed that hot water freezes faster than cold water. This phenomenon is called the Mpemba effect. Although the unique property of water was noticed much earlier by Aristotle, Francis Bacon and Rene Descartes. The phenomenon has been proven many times over by a number of independent experiments. Water has another strange property. In my opinion, the explanation for this is the following: the differential nonequilibrium energy spectrum (DNES) of boiled water has a lower average energy of hydrogen bonds between water molecules than that of a sample taken at room temperature. This means that boiled water needs less energy to begin to structure crystals and freeze.

The key to the structure of ice and its properties lies in the structure of its crystal. Crystals of all modifications of ice are built from H 2 O water molecules connected by hydrogen bonds into three-dimensional mesh frameworks with a specific arrangement of hydrogen bonds. A water molecule can be simply imagined as a tetrahedron (a pyramid with a triangular base). In its center there is an oxygen atom, which is in a state of sp 3 hybridization, and in two vertices there is a hydrogen atom, one of the 1s electrons of which is involved in the formation of a covalent H-O bond with oxygen. The two remaining vertices are occupied by pairs of unpaired oxygen electrons, which do not participate in the formation of intramolecular bonds, so they are called lone. The spatial shape of the H 2 O molecule is explained by the mutual repulsion of hydrogen atoms and lone electron pairs of the central oxygen atom.

Hydrogen bonding is important in the chemistry of intermolecular interactions and is caused by weak electrostatic forces and donor-acceptor interactions. It occurs when the electron-deficient hydrogen atom of one water molecule interacts with the lone electron pair of the oxygen atom of a neighboring water molecule (O-H...O). A distinctive feature of the hydrogen bond is its relatively low strength; it is 5-10 times weaker than a chemical covalent bond. In terms of energy, a hydrogen bond occupies an intermediate position between a chemical bond and van der Waals interactions that hold molecules in a solid or liquid phase. Each water molecule in an ice crystal can simultaneously form four hydrogen bonds with other neighboring molecules at strictly defined angles equal to 109°47", directed towards the vertices of the tetrahedron, which do not allow the creation of a dense structure when water freezes (Fig. 3). In ice structures I, Ic, VII and VIII, this tetrahedron is regular. In ice structures II, III, V and VI, the tetrahedra are noticeably distorted. In ice structures VI, VII and VIII, two intersecting systems of hydrogen bonds can be distinguished. This invisible framework of hydrogen bonds arranges water molecules in the form of a reticulated mesh, the structure of which resembles a hexagonal honeycomb with hollow internal channels.If ice is heated, the mesh structure is destroyed: water molecules begin to fall into the voids of the mesh, leading to a denser liquid structure - this explains why water is heavier than ice.

Rice. 3. Formation of a hydrogen bond between four H2O molecules (red balls represent central oxygen atoms, white balls represent hydrogen atoms)

The specificity of hydrogen bonds and intermolecular interactions characteristic of the structure of ice is preserved in melt water, since when an ice crystal melts, only 15% of all hydrogen bonds are destroyed. Therefore, the connection between each water molecule and four neighboring molecules inherent in ice ("short-range order") is not violated, although a greater blurring of the oxygen framework lattice is observed. Hydrogen bonds can also be maintained when water boils. Only in water vapor are there no hydrogen bonds.

Ice, which forms at atmospheric pressure and melts at 0 °C, is the most common, but still not fully understood, substance. Much in its structure and properties looks unusual. At the sites of the crystal lattice of ice, the oxygen atoms of the tetrahedrons of water molecules are arranged in an orderly manner, forming regular hexagons, like a hexagonal honeycomb, and the hydrogen atoms occupy a variety of positions on the hydrogen bonds connecting the oxygen atoms (Fig. 4). Therefore, six equivalent orientations of water molecules relative to their neighbors are possible. Some of them are excluded, since the presence of two protons simultaneously on the same hydrogen bond is unlikely, but there remains sufficient uncertainty in the orientation of water molecules. This behavior of atoms is atypical, since in a solid substance all atoms obey the same law: either the atoms are arranged in an orderly manner, and then it is a crystal, or randomly, and then it is an amorphous substance. Such an unusual structure can be realized in most modifications of ice - Ih, III, V, VI and VII (and apparently in Ic) (Table 3), and in the structure of ice II, VIII and IX the water molecules are orientationally ordered. According to J. Bernal, ice is crystalline in relation to oxygen atoms and glassy in relation to hydrogen atoms.

Rice. 4. Ice structure of natural hexagonal configuration I h

In other conditions, for example in Space at high pressures and low temperatures, ice crystallizes differently, forming other crystal lattices and modifications (cubic, trigonal, tetragonal, monoclinic, etc.), each of which has its own structure and crystal lattice (Table 3 ). The structures of ice of various modifications were calculated by Russian researchers Dr. G.G. Malenkov and Ph.D. in Physics and Mathematics. E.A. Zheligovskaya from the Institute of Physical Chemistry and Electrochemistry named after. A.N. Frumkin of the Russian Academy of Sciences. Ices of the II, III and V modifications are preserved for a long time at atmospheric pressure if the temperature does not exceed -170 °C (Fig. 5). When cooled to approximately -150 °C, natural ice turns into cubic ice Ic, consisting of cubes and octahedra several nanometers in size. Ice I c sometimes appears when water freezes in capillaries, which is apparently facilitated by the interaction of water with the wall material and the repetition of its structure. If the temperature is slightly higher than -110 0 C, crystals of denser and heavier glassy amorphous ice with a density of 0.93 g/cm 3 form on the metal substrate. Both of these forms of ice can spontaneously transform into hexagonal ice, and the faster the higher the temperature.

Table 3. Some modifications of ice and their physical parameters.

Note. 1 Å = 10 -10 m

Rice. 5. Diagram of the state of crystalline ices of various modifications.

There are also high-pressure ices - II and III trigonal and tetragonal modifications, formed from hollow honeycombs formed by hexagonal corrugated elements, shifted relative to each other by one third (Fig. 6 and Fig. 7). These ices are stabilized in the presence of the noble gases helium and argon. In the structure of ice V monoclinic modification, the angles between neighboring oxygen atoms range from 86 0 to 132 °, which is very different from the bond angle in a water molecule, which is 105 ° 47 '. Ice VI of the tetragonal modification consists of two frames inserted into each other, between which there are no hydrogen bonds, resulting in the formation of a body-centered crystal lattice (Fig. 8). The structure of ice VI is based on hexamers - blocks of six water molecules. Their configuration exactly repeats the structure of a stable cluster of water, which is given by calculations. Ice VII and VIII of the cubic modification, which are low-temperature ordered forms of ice VII, have a similar structure with frames of ice I inserted into each other. With a subsequent increase in pressure, the distance between the oxygen atoms in the crystal lattice of ices VII and VIII will decrease, as a result the structure of ice X is formed, the oxygen atoms in which are arranged in a regular lattice, and the protons are ordered.

Rice. 7. Ice III configuration.

Ice XI is formed by deep cooling of ice I h with the addition of alkali below 72 K at normal pressure. Under these conditions, hydroxyl crystal defects are formed, allowing the growing ice crystal to change its structure. Ice XI has an orthorhombic crystal lattice with an ordered arrangement of protons and is formed simultaneously in many crystallization centers near the hydroxyl defects of the crystal.

Rice. 8. Ice VI configuration.

Among the ices there are also metastable forms IV and XII, whose lifetimes are seconds, and have the most beautiful structure (Fig. 9 and Fig. 10). To obtain metastable ice, it is necessary to compress ice I h to a pressure of 1.8 GPa at liquid nitrogen temperature. These ices form much more easily and are especially stable if supercooled heavy water is subjected to pressure. Another metastable modification, ice IX, is formed when ice III is supercooled and essentially represents its low-temperature form.

Rice. 9. Ice IV configuration.

Rice. 10. Ice XII configuration.

The last two modifications of ice - with a monoclinic XIII and an orthorhombic configuration XIV - were discovered by scientists from Oxford (UK) quite recently - in 2006. The assumption that there should be ice crystals with monoclinic and orthorhombic lattices was difficult to confirm: the viscosity of water at a temperature of -160 ° C is very high, and it is difficult for molecules of pure supercooled water to come together in such quantities to form a crystal nucleus. This was achieved using a catalyst - hydrochloric acid, which increased the mobility of water molecules at low temperatures. Such modifications of ice cannot form on Earth, but they can exist in Space on cooled planets and frozen satellites and comets. Thus, calculations of the density and heat flows from the surface of the satellites of Jupiter and Saturn allow us to state that Ganymede and Callisto must have an icy shell in which ices I, III, V and VI alternate. On Titan, the ices form not a crust, but a mantle, the inner layer of which consists of ice VI, other high-pressure ices and clathrate hydrates, and ice I h is located on top.

Rice. eleven. Diversity and shape of snowflakes in nature

High in the Earth's atmosphere at low temperatures, water crystallizes from tetrahedra forming hexagonal ice Ih. The center of ice crystal formation is solid dust particles, which are lifted into the upper layers of the atmosphere by the wind. Around this embryonic microcrystal of ice, needles formed by individual water molecules grow in six symmetrical directions, on which lateral processes - dendrites - grow. The temperature and humidity of the air around the snowflake are the same, so it is initially symmetrical in shape. As snowflakes form, they gradually fall into the lower layers of the atmosphere, where the temperature is higher. Here melting occurs and their ideal geometric shape is distorted, forming a variety of snowflakes (Fig. 11).

With further melting, the hexagonal structure of ice is destroyed and a mixture of cyclic associates of clusters, as well as tri-, tetra-, penta-, hexamers of water (Fig. 12) and free water molecules is formed. Studying the structure of the resulting clusters is often significantly difficult, since water, according to modern data, is a mixture of various neutral clusters (H 2 O) n and their charged cluster ions [H 2 O] + n and [H 2 O] - n, which are in dynamic equilibrium between itself with a lifetime of 10 -11 -10 -12 seconds.

Rice. 12. Possible water clusters (a-h) of composition (H 2 O) n, where n = 5-20.

Clusters are able to interact with each other through outwardly protruding hydrogen bond faces, forming more complex polyhedral structures such as hexahedron, octahedron, icosahedron and dodecahedron. Thus, the structure of water is associated with the so-called Platonic solids (tetrahedron, hexahedron, octahedron, icosahedron and dodecahedron), named after the ancient Greek philosopher and geometer Plato who discovered them, the shape of which is determined by the golden ratio (Fig. 13).

Rice. 13. Platonic solids, the geometric shape of which is determined by the golden ratio.

The number of vertices (B), faces (G) and edges (P) in any spatial polyhedron is described by the relation:

B + G = P + 2

The ratio of the number of vertices (B) of a regular polyhedron to the number of edges (P) of one of its faces is equal to the ratio of the number of faces (G) of the same polyhedron to the number of edges (P) emerging from one of its vertices. For a tetrahedron this ratio is 4:3, for a hexahedron (6 faces) and octahedron (8 faces) it is 2:1, and for a dodecahedron (12 faces) and icosahedron (20 faces) it is 4:1.

The structures of polyhedral water clusters, calculated by Russian scientists, were confirmed using modern analytical methods: proton magnetic resonance spectroscopy, femtosecond laser spectroscopy, X-ray and neutron diffraction on water crystals. The discovery of water clusters and the ability of water to store information are two of the most important discoveries of the 21st millennium. This clearly proves that nature is characterized by symmetry in the form of precise geometric shapes and proportions, characteristic of ice crystals.

LITERATURE.

1. Belyanin V., Romanova E. Life, the water molecule and the golden proportion // Science and Life, 2004, Vol. 10, No. 3, p. 23-34.

2. Shumsky P.A., Fundamentals of structural ice science. - Moscow, 1955b p. 113.

3. Mosin O.V., Ignatov I. Awareness of water as a substance of life. // Consciousness and physical reality. 2011, T 16, No. 12, p. 9-22.

4. Petryanov I.V. The most extraordinary substance in the world. Moscow, Pedagogy, 1981, p. 51-53.

5 Eisenberg D, Kautsman V. Structure and properties of water. - Leningrad, Gidrometeoizdat, 1975, p. 431.

6. Kulsky L. A., Dal V. V., Lenchina L. G. Familiar and mysterious water. – Kyiv, Rodyanbsk school, 1982, p. 62-64.

7. Zatsepina G. N. Structure and properties of water. – Moscow, ed. Moscow State University, 1974, p. 125.

8. Antonchenko V. Ya., Davydov N. S., Ilyin V. V. Fundamentals of water physics - Kyiv, Naukova Dumka, 1991, p. 167.

9. Simonite T. DNA-like ice "seen" inside carbon nanotubes // New Scientist, V. 12, 2006.

10. Emoto M. Messages of water. Secret codes of ice crystals. - Sofia, 2006. p. 96.

11. Zenin S.V., Tyaglov B.V. The nature of hydrophobic interaction. The emergence of orientation fields in aqueous solutions // Journal of Physical Chemistry, 1994, T. 68, No. 3, p. 500-503.

12. Pimentel J., McClellan O. Hydrogen bonding - Moscow, Nauka, 1964, p. 84-85.

13. Bernal J., Fowler R. Structure of water and ionic solutions // Uspekhi Fizicheskikh Nauk, 1934, T. 14, No. 5, p. 587-644.

14. Khobza P., Zahradnik R. Intermolecular complexes: The role of van der Waals systems in physical chemistry and biodisciplines. – Moscow, Mir, 1989, p. 34-36.

15. Pounder E. R. Physics of Ice, trans. from English - Moscow, 1967, p. 89.

16. Komarov S. M. Ice patterns of high pressure. // Chemistry and Life, 2007, No. 2, pp. 48-51.

17. E. A. Zheligovskaya, G. G. Malenkov. Crystalline ices // Uspekhi khimii, 2006, No. 75, p. 64.

18. Fletcher N. H. The chemical physics of ice, Cambreage, 1970.

19. Nemukhin A.V. Diversity of clusters // Russian Chemical Journal, 1996, T. 40, No. 2, p. 48-56.

20. Mosin O.V., Ignatov I. The structure of water and physical reality. // Consciousness and physical reality, 2011, T. 16, No. 9, p. 16-32.

21. Ignatov I. Bioenergetic medicine. The origin of living matter, memory of water, bioresonance, biophysical fields. - GayaLibris, Sofia, 2006, p. 93.

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Water structure

Ph.D. O.V. Mosin

A water molecule is a small dipole containing positive and negative charges at its poles. Since the mass and charge of the oxygen nucleus is greater than that of the hydrogen nuclei, the electron cloud is pulled towards the oxygen nucleus. In this case, the hydrogen nuclei are exposed. Thus, the electron cloud has a non-uniform density. There is a lack of electron density near the hydrogen nuclei, and on the opposite side of the molecule, near the oxygen nucleus, there is an excess of electron density. It is this structure that determines the polarity of the water molecule. If you connect the epicenters of positive and negative charges with straight lines, you get a three-dimensional geometric figure - a regular tetrahedron.

The structure of a water molecule (picture on the right)

Due to the presence of hydrogen bonds, each water molecule forms a hydrogen bond with 4 neighboring molecules, forming an openwork mesh frame in the ice molecule. However, in the liquid state, water is a disordered liquid; These hydrogen bonds are spontaneous, short-lived, quickly break and form again. All this leads to heterogeneity in the structure of water.

Hydrogen bonds between water molecules (picture below left)

The fact that water is heterogeneous in composition was established long ago. It has long been known that ice floats on the surface of water, that is, the density of crystalline ice is less than the density of liquid.

For almost all other substances, the crystal is denser than the liquid phase. In addition, even after melting, with increasing temperature, the density of water continues to increase and reaches a maximum at 4C. Less well known is the anomaly of water compressibility: when heated from the melting point up to 40C, it decreases and then increases. The heat capacity of water also depends nonmonotonically on temperature.

In addition, at temperatures below 30C, with an increase in pressure from atmospheric to 0.2 GPa, the viscosity of water decreases, and the self-diffusion coefficient, a parameter that determines the speed of movement of water molecules relative to each other, increases.

For other liquids, the relationship is the opposite, and almost nowhere does it happen that some important parameter behaves non-monotonically, i.e. first increased, and after passing a critical value of temperature or pressure decreased. An assumption arose that in fact water is not a single liquid, but a mixture of two components that differ in properties, for example, density and viscosity, and therefore structure. Such ideas began to arise at the end of the 19th century, when a lot of data on water anomalies accumulated.

Whiting was the first to propose the idea that water consists of two components in 1884. His authorship is cited by E.F. Fritsman in the monograph “The Nature of Water. Heavy Water,” published in 1935. In 1891, V. Rengten introduced the concept of two states of water, which differ in density. After it, many works appeared in which water was considered as a mixture of associates of different compositions (hydrols).

When the structure of ice was determined in the 1920s, it turned out that water molecules in the crystalline state form a three-dimensional continuous network in which each molecule has four nearest neighbors located at the vertices of a regular tetrahedron. In 1933, J. Bernal and P. Fowler suggested that a similar network exists in liquid water. Since water is denser than ice, they believed that the molecules in it are arranged not like in ice, that is, like silicon atoms in the mineral tridymite, but like silicon atoms in a denser modification of silica, quartz. The increase in the density of water when heated from 0 to 4C was explained by the presence of the tridymite component at low temperatures. Thus, Bernal Fowler's model retained the element of two-structure, but their main achievement was the idea of ​​​​a continuous tetrahedral network. Then the famous aphorism of I. Langmuir appeared: “The ocean is one big molecule.” Excessive specification of the model did not increase the number of supporters of the unified grid theory.

It was not until 1951 that J. Pople created a continuous grid model, which was not as specific as Bernal Fowler's model. Pople imagined water as a random tetrahedral network, the bonds between the molecules in which are curved and have different lengths. Pople's model explains the compaction of water during melting by the bending of bonds. When the first definitions of the structure of ices II and IX appeared in the 60-70s, it became clear how the bending of bonds can lead to compaction of the structure. Pople's model could not explain the non-monotonic dependence of water properties on temperature and pressure as well as two-state models. Therefore, the idea of ​​two states was shared by many scientists for a long time.

But in the second half of the 20th century it was impossible to fantasize about the composition and structure of hydrols as they did at the beginning of the century. It was already known how ice and crystalline hydrates work, and they knew a lot about hydrogen bonding. In addition to continuum models (Pople's model), two groups of mixed models have emerged: cluster and clathrate. In the first group, water appeared in the form of clusters of molecules connected by hydrogen bonds, which floated in a sea of ​​molecules not involved in such bonds. The second group of models treated water as a continuous network (usually called a framework in this context) of hydrogen bonds that contained voids; they contain molecules that do not form bonds with the molecules of the framework. It was not difficult to select the properties and concentrations of two microphases of cluster models or the properties of the framework and the degree of filling of its voids of clathrate models in order to explain all the properties of water, including the famous anomalies.

Among the cluster models, the most striking was the model of G. Nemeti and H. Sheragi: The pictures they proposed, depicting clusters of bound molecules floating in a sea of ​​unbound molecules, were included in many monographs.

The first model of the clathrate type was proposed in 1946 by O.Ya. Samoilov: in water, a network of hydrogen bonds similar to hexagonal ice is preserved, the cavities of which are partially filled with monomer molecules. L. Pauling in 1959 created another option, suggesting that the basis of the structure could be a network of bonds inherent in some crystalline hydrates.

During the second half of the 60s and the beginning of the 70s, a convergence of all these views was observed. Variants of cluster models appeared in which molecules in both microphases are connected by hydrogen bonds. Proponents of clathrate models began to admit the formation of hydrogen bonds between void and framework molecules. That is, in fact, the authors of these models consider water as a continuous network of hydrogen bonds. And we are talking about how heterogeneous this grid is (for example, in density). The idea of ​​water as hydrogen-bonded clusters floating in a sea of ​​unbonded water molecules was put to an end in the early eighties, when G. Stanley applied the percolation theory, which describes the phase transitions of water, to the water model.

In 1999, the famous Russian water researcher S.V. Zenin defended his doctoral dissertation at the Institute of Medical and Biological Problems of the Russian Academy of Sciences on cluster theory, which was a significant step in the advancement of this area of ​​research, the complexity of which is enhanced by the fact that they are at the intersection of three sciences: physics, chemistry and biology. Based on data obtained by three physicochemical methods: refractometry (S.V. Zenin, B.V. Tyaglov, 1994), high-performance liquid chromatography (S.V. Zenin et al., 1998) and proton magnetic resonance (C S.V. Zenin, 1993) constructed and proved a geometric model of the main stable structural formation of water molecules (structured water), and then (S.V. Zenin, 2004) an image of these structures was obtained using a contrast-phase microscope.

Science has now proven that the peculiarities of the physical properties of water and numerous short-lived hydrogen bonds between neighboring hydrogen and oxygen atoms in a water molecule create favorable opportunities for the formation of special associated structures (clusters) that perceive, store and transmit a wide variety of information.

The structural unit of such water is a cluster consisting of clathrates, the nature of which is determined by long-range Coulomb forces. The structure of the clusters encodes information about the interactions that took place with these water molecules. In water clusters, due to the interaction between covalent and hydrogen bonds between oxygen atoms and hydrogen atoms, migration of a proton (H+) can occur via a relay mechanism, leading to delocalization of the proton within the cluster.

Water, consisting of many clusters of various types, forms a hierarchical spatial liquid crystal structure that can perceive and store huge amounts of information.

The figure (V.L. Voeikov) shows diagrams of several simple cluster structures as an example.

Some possible structures of water clusters

Physical fields of very different nature can be carriers of information. Thus, the possibility of remote information interaction of the liquid crystalline structure of water with objects of various natures using electromagnetic, acoustic and other fields has been established. The influencing object can also be a person.

Water is a source of ultra-weak and weak alternating electromagnetic radiation. The least chaotic electromagnetic radiation is created by structured water. In this case, the induction of a corresponding electromagnetic field may occur, changing the structural and information characteristics of biological objects.

In recent years, important data have been obtained on the properties of supercooled water. Studying water at low temperatures is very interesting, since it can be supercooled more than other liquids. Crystallization of water, as a rule, begins on some inhomogeneities either on the walls of the vessel or on floating particles of solid impurities. Therefore, it is not easy to find the temperature at which supercooled water would spontaneously crystallize. But scientists managed to do this, and now the temperature of the so-called homogeneous nucleation, when the formation of ice crystals occurs simultaneously throughout the entire volume, is known for pressures up to 0.3 GPa, that is, covering the regions of existence of ice II.

From atmospheric pressure to the boundary separating ices I and II, this temperature drops from 231 to 180 K, and then increases slightly to 190 K. Below this critical temperature, liquid water is impossible in principle.

Ice structure (picture on the right)

However, there is a mystery associated with this temperature. In the mid-eighties, a new modification of amorphous ice was discovered - high-density ice, and this helped revive the idea of ​​water as a mixture of two states. Not crystalline structures, but structures of amorphous ice of different densities were considered as prototypes. This concept was formulated in the most clear form by E.G. Ponyatovsky and V.V. Sinitsin, who wrote in 1999: “Water is considered as a regular solution of two components, the local configurations in which correspond to the short-range order of modifications of amorphous ice.” Moreover, by studying short-range order in supercooled water at high pressure using neutron diffraction methods, scientists were able to find components corresponding to these structures.

A consequence of the polymorphism of amorphous ice has also led to assumptions about the separation of water into two immiscible components at temperatures below the hypothetical low-temperature critical point. Unfortunately, according to researchers, this temperature at a pressure of 0.017 GPa is 230 K below the nucleation temperature, so no one has yet been able to observe the stratification of liquid water. Thus, the revival of the two-state model raised the question of the heterogeneity of the network of hydrogen bonds in liquid water. This heterogeneity can only be understood using computer modeling.

Speaking about the crystalline structure of water, it should be noted that 14 modifications of ice are known, most of which are not found in nature, in which water molecules both retain their individuality and are connected by hydrogen bonds. On the other hand, there are many variants of the hydrogen bond network in clathrate hydrates. The energies of these networks (high-pressure ices and clathrate hydrates) are not much higher than the energies of cubic and hexagonal ices. Therefore, fragments of such structures can also appear in liquid water. It is possible to construct countless different non-periodic fragments, the molecules of which have four nearest neighbors located approximately at the vertices of the tetrahedron, but their structure does not correspond to the structures of known modifications of ice. As numerous calculations have shown, the interaction energies of molecules in such fragments will be close to each other, and there is no reason to say that any structure should prevail in liquid water.

Structural studies of water can be studied using different methods; proton magnetic resonance spectroscopy, infrared spectroscopy, X-ray diffraction, etc. For example, the diffraction of X-rays and neutrons has been studied many times. However, these experiments cannot provide detailed information about the structure. Inhomogeneities that differ in density could be seen by the scattering of X-rays and neutrons at small angles, but such inhomogeneities must be large, consisting of hundreds of water molecules. It would be possible to see them by studying the scattering of light. However, water is an exceptionally clear liquid. The only result of diffraction experiments is the radial distribution function, that is, the distance between the atoms of oxygen, hydrogen and oxygen-hydrogen. It is clear from them that there is no long-range order in the arrangement of water molecules. These functions decay much faster for water than for most other liquids. For example, the distribution of distances between oxygen atoms at temperatures close to room temperature gives only three maxima, at 2.8, 4.5 and 6.7. The first maximum corresponds to the distance to the nearest neighbors, and its value is approximately equal to the length of the hydrogen bond. The second maximum is close to the average length of a tetrahedron edge: remember that water molecules in hexagonal ice are located along the vertices of a tetrahedron described around the central molecule. And the third maximum, very weakly expressed, corresponds to the distance to third and more distant neighbors in the hydrogen network. This maximum itself is not very bright, and there is no need to talk about further peaks. There have been attempts to obtain more detailed information from these distributions. So in 1969, I.S. Andrianov and I.Z. Fisher found the distances up to the eighth neighbor, while to the fifth neighbor it turned out to be 3, and to the sixth 3.1. This makes it possible to obtain data on the distant environment of water molecules.

Another method of studying the structure - neutron diffraction on water crystals - is carried out in exactly the same way as x-ray diffraction. However, due to the fact that the neutron scattering lengths do not differ so much between different atoms, the isomorphic substitution method becomes unacceptable. In practice, one usually works with a crystal whose molecular structure has already been approximately determined by other methods. Neutron diffraction intensities are then measured for this crystal. Based on these results, a Fourier transform is performed, during which the measured neutron intensities and phases are used, calculated taking into account non-hydrogen atoms, i.e. oxygen atoms, the position of which in the structure model is known. Then, on the Fourier map obtained in this way, the hydrogen and deuterium atoms are represented with much larger weights than on the electron density map, because the contribution of these atoms to neutron scattering is very large. Using this density map, you can, for example, determine the positions of hydrogen atoms (negative density) and deuterium (positive density).

A variation of this method is possible, which consists in the fact that the crystal formed in water is kept in heavy water before measurements. In this case, neutron diffraction not only makes it possible to determine where hydrogen atoms are located, but also identifies those of them that can be exchanged for deuterium, which is especially important when studying isotope (H-D) exchange. Such information helps to confirm that the structure has been established correctly.

Other methods also make it possible to study the dynamics of water molecules. These are experiments on quasi-elastic neutron scattering, ultrafast IR spectroscopy and the study of water diffusion using NMR or labeled deuterium atoms. The NMR spectroscopy method is based on the fact that the nucleus of a hydrogen atom has a magnetic moment—spin—that interacts with magnetic fields, constant and variable. From the NMR spectrum one can judge in what environment these atoms and nuclei are located, thus obtaining information about the structure of the molecule.

As a result of experiments on quasi-elastic neutron scattering in water crystals, the most important parameter was measured - the self-diffusion coefficient at various pressures and temperatures. To judge the self-diffusion coefficient from quasielastic neutron scattering, it is necessary to make an assumption about the nature of the molecular motion. If they move in accordance with the model of Ya.I. Frenkel (a famous Russian theoretical physicist, author of the “Kinetic Theory of Liquids” - a classic book translated into many languages), also called the “jump-waiting” model, then the time of settled life (the time between jumping) of a molecule is 3.2 picoseconds. The latest methods of femtosecond laser spectroscopy have made it possible to estimate the lifetime of a broken hydrogen bond: it takes a proton 200 fs to find a partner. However, these are all average values. It is possible to study the details of the structure and nature of the movement of water molecules only with the help of computer simulation, sometimes called a numerical experiment.

This is what the structure of water looks like according to the results of computer modeling (according to Doctor of Chemical Sciences G.G. Malenkov). The general disordered structure can be divided into two types of regions (shown as dark and light balls), which differ in their structure, for example, in the volume of the Voronoi polyhedron (a), the degree of tetrahedrality of the immediate environment (b), the value of potential energy (c), and also in the presence of four hydrogen bonds in each molecule (d). However, these areas literally in a moment, after a few picoseconds, will change their location.

The simulation is carried out like this. The ice structure is taken and heated until it melts. Then, after some time for the water to forget about its crystalline origin, instantaneous microphotographs are taken.

To analyze the structure of water, three parameters are selected:
- degree of deviation of the local environment of the molecule from the vertices of a regular tetrahedron;
-potential energy of molecules;
-the volume of the so-called Voronoi polyhedron.

To construct this polyhedron, take an edge from a given molecule to the nearest one, divide it in half, and draw a plane through this point perpendicular to the edge. This gives the volume per molecule. The volume of a polyhedron is density, tetrahedrality is the degree of distortion of hydrogen bonds, energy is the degree of stability of the molecular configuration. Molecules with similar values ​​of each of these parameters tend to group together into separate clusters. Both low-density and high-density regions have different energy values, but they can also have the same energy values. Experiments have shown that areas with different structures, clusters arise spontaneously and spontaneously disintegrate. The entire structure of water is alive and constantly changing, and the time during which these changes occur is very short. The researchers monitored the movements of the molecules and found that they performed irregular vibrations with a frequency of about 0.5 ps and an amplitude of 1 angstrom. Rare slow jumps of angstroms that last for picoseconds were also observed. In general, in 30 ps a molecule can move 8-10 angstroms. The lifetime of the local environment is also short. Regions composed of molecules with similar volume values ​​of the Voronoi polyhedron can decay in 0.5 ps, or they can live for several picoseconds. But the distribution of hydrogen bond lifetimes is very large. But this time does not exceed 40 ps, ​​and the average value is several ps.

In conclusion, it should be emphasized that The theory of the cluster structure of water has many pitfalls. For example, Zenin suggests that the main structural element of water is a cluster of 57 molecules formed by the fusion of four dodecahedrons. They have common faces, and their centers form a regular tetrahedron. It has long been known that water molecules can be located at the vertices of a pentagonal dodecahedron; Such a dodecahedron is the basis of gas hydrates. Therefore, there is nothing surprising in the assumption of the existence of such structures in water, although it has already been said that no specific structure can be predominant and exist for a long time. It is therefore strange that this element is assumed to be the main one and that it contains exactly 57 molecules. From balls, for example, you can assemble the same structures, which consist of dodecahedrons adjacent to each other and contain 200 molecules. Zenin claims that the process of three-dimensional polymerization of water stops at 57 molecules. In his opinion, there should not be larger associates. However, if this were so, hexagonal ice crystals, which contain a huge number of molecules linked together by hydrogen bonds, could not precipitate from water vapor. It is not at all clear why the growth of the Zenin cluster stopped at 57 molecules. To avoid contradictions, Zenin packs clusters into more complex formations—rhombohedra—of almost a thousand molecules, and the original clusters do not form hydrogen bonds with each other. Why? How are the molecules on their surface different from those inside? According to Zenin, the pattern of hydroxyl groups on the surface of rhombohedrons provides the memory of water. Consequently, the water molecules in these large complexes are rigidly fixed, and the complexes themselves are solids. Such water will not flow, and its melting point, which is related to molecular weight, should be very high.

What properties of water does Zenin's model explain? Since the model is based on tetrahedral structures, it can be more or less consistent with X-ray and neutron diffraction data. However, it is unlikely that the model can explain the decrease in density during melting; the packing of dodecahedrons is less dense than ice. But it is most difficult to agree with a model with dynamic properties - fluidity, a large value of the self-diffusion coefficient, short correlation and dielectric relaxation times, which are measured in picoseconds.

Ph.D. O.V. Mosin

References:
G.G. Malenkov. Advances in Physical Chemistry, 2001
S.V.Zenin, B.M. Polanuer, B.V. Tyaglov. Experimental proof of the presence of water fractions. G. Homeopathic medicine and acupuncture. 1997.No.2.P.42-46.
S.V. Zenin, B.V. Tyaglov. Hydrophobic model of the structure of associates of water molecules. J. Physical Chemistry. 1994. T. 68. No. 4. P. 636-641.
S.V. Zenin Study of the structure of water using the proton magnetic resonance method. Dokl.RAN.1993.T.332.No.3.S.328-329.
S.V.Zenin, B.V.Tyaglov. The nature of hydrophobic interaction. The emergence of orientation fields in aqueous solutions. J. Physical Chemistry. 1994. T. 68. No. 3. P. 500-503.
S.V. Zenin, B.V. Tyaglov, G.B. Sergeev, Z.A. Shabarova. Study of intramolecular interactions in nucleotidamides using NMR. Materials of the 2nd All-Union Conf. By dynamic Stereochemistry. Odessa.1975.p.53.
S.V. Zenin. The structured state of water as the basis for controlling the behavior and safety of living systems. Thesis. Doctor of Biological Sciences. State Scientific Center "Institute of Medical and Biological Problems" (SSC "IMBP"). Protected 1999. 05. 27. UDC 577.32:57.089.001.66.207 p.
IN AND. Slesarev. Research progress report

Properties of water

Why is water water?

Among the vast variety of substances, water with its physical and chemical properties occupies a very special, exceptional place. And this must be taken literally.

Almost all physical and chemical properties of water are exceptions in nature. It truly is the most amazing substance in the world. Water is amazing not only for the variety of isotopic forms of the molecule and not only for the hopes that are associated with it as an inexhaustible source of energy for the future. In addition, it is amazing for its very ordinary properties.

How is a water molecule built?

How one molecule of water is built is now known very precisely. It's built like this.

The relative positions of the nuclei of hydrogen and oxygen atoms and the distance between them have been well studied and measured. It turned out that the water molecule is nonlinear. Together with the electron shells of the atoms, a water molecule, if you look at it “from the side,” could be depicted like this:

that is, geometrically, the mutual arrangement of charges in a molecule can be depicted as a simple tetrahedron. All water molecules with any isotopic composition are built exactly the same.

How many water molecules are there in the ocean?

One. And this answer is not exactly a joke. Of course, anyone can, by looking at a reference book and finding out how much water there is in the World Ocean, easily calculate how many H2O molecules it contains. But such an answer will not be entirely correct. Water is a special substance. Due to their unique structure, individual molecules interact with each other. A special chemical bond arises due to the fact that each of the hydrogen atoms of one molecule attracts electrons of oxygen atoms in neighboring molecules. Due to this hydrogen bond, each water molecule becomes quite tightly bound to four other neighboring molecules, just as shown in the diagram. True, this diagram is too simplified - it is flat, otherwise it cannot be depicted in the figure. Let's imagine a slightly more accurate picture. To do this, you need to take into account that the plane in which hydrogen bonds are located (they are indicated by a dotted line) in a water molecule is directed perpendicular to the plane of location of the hydrogen atoms.

All individual H2O molecules in water turn out to be connected into a single continuous spatial network - into one giant molecule. Therefore, the assertion of some physical chemists that the entire ocean is one molecule is quite justified. But this statement should not be taken too literally. Although all water molecules in water are connected to each other by hydrogen bonds, they are at the same time in a very complex mobile equilibrium, preserving the individual properties of individual molecules and forming complex aggregates. This idea applies not only to water: a piece of diamond is also one molecule.

How is an ice molecule built?

There are no special ice molecules. The molecules of water, due to their remarkable structure, are connected to each other in a piece of ice so that each of them is connected and surrounded by four other molecules. This leads to the appearance of a very loose ice structure, in which a lot of free volume remains. The correct crystalline structure of ice is expressed in the amazing grace of snowflakes and the beauty of frosty patterns on frozen window panes.

How are water molecules built in water?

Unfortunately, this very important issue has not yet been sufficiently studied. The structure of molecules in liquid water is very complex. When ice melts, its network structure is partially preserved in the resulting water. The molecules in melt water consist of many simple molecules - aggregates that retain the properties of ice. As the temperature rises, some of them disintegrate and their sizes become smaller.

Mutual attraction leads to the fact that the average size of a complex water molecule in liquid water significantly exceeds the size of a single water molecule. This extraordinary molecular structure of water determines its extraordinary physicochemical properties.

What should the density of water be?

Isn't that a very strange question? Remember how the unit of mass was established - one gram. This is the mass of one cubic centimeter of water. This means that there can be no doubt that the density of water should only be what it is. Can there be any doubt about this? Can. Theorists have calculated that if water did not retain a loose, ice-like structure in the liquid state and its molecules were tightly packed, then the density of water would be much higher. At 25°C it would be equal not to 1.0, but to 1.8 g/cm3.

At what temperature should water boil?

This question is also, of course, strange. After all, water boils at one hundred degrees. Everyone knows this. Moreover, everyone knows that it is the boiling point of water at normal atmospheric pressure that was chosen as one of the reference points of the temperature scale, conventionally designated 100°C.

However, the question is posed differently: at what temperature should water boil? After all, the boiling temperatures of various substances are not random. They depend on the position of the elements that make up their molecules in Mendeleev’s periodic table.

If we compare chemical compounds of different elements with the same composition that belong to the same group of the periodic table, it is easy to notice that the lower the atomic number of an element, the lower its atomic weight, the lower the boiling point of its compounds. Based on its chemical composition, water can be called an oxygen hydride. H2Te, H2Se and H2S are chemical analogues of water. If you monitor their boiling points and compare how the boiling points of hydrides change in other groups of the periodic table, then you can quite accurately determine the boiling point of any hydride, just like any other compound. Mendeleev himself was able to predict the properties of chemical compounds of elements not yet discovered in this way.

If we determine the boiling point of oxygen hydride by its position in the periodic table, it turns out that water should boil at -80 ° C. Consequently, water boils approximately one hundred and eighty degrees higher , than it should boil. The boiling point of water - this is its most common property - turns out to be extraordinary and surprising.

The properties of any chemical compound depend on the nature of the elements that form it and, therefore, on their position in Mendeleev’s periodic table of chemical elements. These graphs show the dependences of the boiling and melting temperatures of hydrogen compounds of groups IV and VI of the periodic system. Water is a striking exception. Due to the very small radius of the proton, the interaction forces between its molecules are so great that it is very difficult to separate them, which is why water boils and melts at abnormally high temperatures.

Graph A. Normal dependence of the boiling point of hydrides of group IV elements on their position in the periodic table.

Graph B. Among the hydrides of group VI elements, water has anomalous properties: water should boil at minus 80 - minus 90 ° C, but it boils at plus 100 ° C.

Graph B. Normal dependence of the melting temperature of hydrides of group IV elements on their position in the periodic table.

Graph D. Among the hydrides of group VI elements, water violates the order: it should melt at minus 100 ° C, and ice icicles melt at 0 ° C.

At what temperature does water freeze?

Isn't it true that the question is no less strange than the previous ones? Well, who doesn’t know that water freezes at zero degrees? This is the second reference point of the thermometer. This is the most common property of water. But even in this case, one can ask: at what temperature should water freeze in accordance with its chemical nature? It turns out that oxygen hydride, based on its position in the periodic table, should have solidified at one hundred degrees below zero.

How many liquid states of water are there?

This question is not so easy to answer. Of course, there is also one thing - the liquid water we are all familiar with. But liquid water has such extraordinary properties that one has to wonder whether such a simple, seemingly non-provoking

no doubt the answer? Water is the only substance in the world that, after melting, first contracts and then begins to expand as the temperature rises. At approximately 4°C, water is at its highest density. This rare anomaly in the properties of water is explained by the fact that in reality liquid water is a complex solution of a completely unusual composition: it is a solution of water in water.

When ice melts, large, complex water molecules are first formed. They retain remnants of the loose crystalline structure of ice and are dissolved in ordinary low-molecular-weight water. Therefore, at first the density of water is low, but as the temperature increases, these large molecules break down and so the density of the water increases until normal thermal expansion takes over, at which point the density of the water falls again. If this is true, then several states of water are possible, but no one knows how to separate them. And it is still unknown whether this will ever be possible. This extraordinary property of water is of great importance for life. In reservoirs, before the onset of winter, the cooling water gradually drops down until the temperature of the entire reservoir reaches 4°C. With further cooling, the colder water remains on top and all mixing stops. As a result, an extraordinary situation is created: a thin layer of cold water becomes like a “warm blanket” for all the inhabitants of the underwater world. At 4°C they clearly feel quite well.

What should be easier - water or ice?

Who doesn’t know this... After all, ice floats on water. Giant icebergs float in the ocean. Lakes in winter are covered with a floating continuous layer of ice. Of course, ice is lighter than water.

But why "of course"? Is it that clear? On the contrary, the volume of all solids increases during melting, and they drown in their own melt. But ice floats in water. This property of water is an anomaly in nature, an exception, and, moreover, an absolutely remarkable exception.

The positive charges in a water molecule are associated with hydrogen atoms. The negative charges are the valence electrons of oxygen. Their relative arrangement in a water molecule can be depicted as a simple tetrahedron.

Let's try to imagine what the world would look like if water had normal properties and ice was, as any normal substance should be, denser than liquid water. In winter, denser ice freezing from above would sink into the water, continuously sinking to the bottom of the reservoir. In summer, the ice, protected by a layer of cold water, could not melt. Gradually, all lakes, ponds, rivers, streams would freeze completely, turning into giant blocks of ice. Finally, the seas would freeze, followed by the oceans. Our beautiful, blooming green world would become a continuous icy desert, covered here and there with a thin layer of melt water.

How many ices are there?

In nature on our Earth there is only one: ordinary ice. Ice is a rock with extraordinary properties. It is solid, but flows like a liquid, and there are huge rivers of ice that flow slowly down from the high mountains. Ice is changeable - it continuously disappears and forms again. Ice is unusually strong and durable - for tens of thousands of years it preserves without changes the bodies of mammoths that accidentally died in glacial cracks. In his laboratories, man managed to discover at least six more different, no less amazing ices. They cannot be found in nature. They can only exist at very high pressures. Ordinary ice is preserved up to a pressure of 208 MPa (megapascals), but at this pressure it melts at - 22 °C. If the pressure is higher than 208 MPa, dense ice appears - ice-III. It is heavier than water and sinks in it. At a lower temperature and higher pressure - up to 300 MPa - even denser ice-P is formed. Pressure above 500 MPa turns ice into ice-V. This ice can be heated to almost 0 ° C, and it will not melt, although it is under enormous pressure. At a pressure of about 2 GPa (gigapascals), ice-VI appears. This is literally hot ice - it can withstand temperatures of 80° C without melting. Ice-VII, found at 3GP pressure, can perhaps be called hot ice. This is the densest and most refractory ice known. It only melts at 190° above zero.

Ice-VII has an unusually high hardness. This ice can even cause sudden disasters. The bearings in which the shafts of powerful power plant turbines rotate develop enormous pressure. If even a little water gets into the grease, it will freeze, even though the bearing temperature is very high. The resulting ice-VII particles, which have enormous hardness, will begin to destroy the shaft and bearing and quickly cause them to fail.

Maybe there is ice in space too?

As if there is, and at the same time very strange. But scientists on Earth discovered it, although such ice cannot exist on our planet. The density of all currently known ice, even at very high pressures, only very slightly exceeds 1 g/cm3. The density of the hexagonal and cubic modifications of ice at very low pressures and temperatures, even close to absolute zero, is slightly less than unity. Their density is 0.94 g/cm3.

But it turned out that in a vacuum, at negligible pressures and at temperatures below -170 ° C, under conditions when the formation of ice occurs when it condenses from steam on a cooled solid surface, absolutely amazing ice appears. Its density is... 2.3 g/cm3. All ice known so far is crystalline, but this new ice is apparently amorphous, characterized by a random relative arrangement of individual water molecules; It does not have a specific crystal structure. For this reason, it is sometimes called glass ice. Scientists are confident that this amazing ice must arise in space conditions and play a big role in the physics of planets and comets. The discovery of such super-dense ice was unexpected for physicists.

What does it take for the ice to melt?

A lot of heat. Much more than it would take to melt the same amount of any other substance. The exceptionally high specific heat of fusion -80 cal (335 J) per gram of ice is also an anomalous property of water. When water freezes, the same amount of heat is released again.

When winter comes, ice forms, snow falls and water gives back heat, warming the ground and air. They resist the cold and soften the transition to harsh winter. Thanks to this wonderful property of water, autumn and spring exist on our planet.

How much heat is needed to heat water?

So many. More than it takes to heat an equal amount of any other substance. It takes one calorie (4.2 J) to heat a gram of water one degree. This is more than double the heat capacity of any chemical compound.

Water is a substance that is extraordinary in its most ordinary properties for us. Of course, this ability of water is very important not only when cooking dinner in the kitchen. Water is the great distributor of heat throughout the Earth. Heated by the Sun under the equator, it transfers heat in the World Ocean with giant streams of sea currents to the distant polar regions, where life is possible only thanks to this amazing feature of water.

Why is the water in the sea salty?

This is perhaps one of the most important consequences of one of the most amazing properties of water. In its molecule, the centers of positive and negative charges are strongly displaced relative to each other. Therefore, water has an exceptionally high, anomalous value of dielectric constant. For water, e = 80, and for air and vacuum, e = 1. This means that any two opposite charges in water are mutually attracted to each other with a force 80 times less than in air. After all, according to Coulomb's law:

But still, intermolecular bonds in all bodies, which determine the strength of the body, are caused by the interaction between the positive charges of atomic nuclei and negative electrons. On the surface of a body immersed in water, the forces acting between molecules or atoms are weakened under the influence of water by almost a hundred times. If the remaining bond strength between molecules becomes insufficient to withstand the effects of thermal motion, molecules or atoms of the body begin to break away from its surface and pass into water. The body begins to dissolve, breaking up either into individual molecules, like sugar in a glass of tea, or into charged particles - ions, like table salt.

It is thanks to its abnormally high dielectric constant that water is one of the most powerful solvents. It is even capable of dissolving any rock on the earth's surface. Slowly and inevitably, it destroys even granites, leaching easily soluble components from them.

Streams, rivers and rivers carry impurities dissolved in water into the ocean. The water from the ocean evaporates and returns to the earth again to continue its eternal work again and again. And dissolved salts remain in the seas and oceans.

Do not think that water dissolves and carries into the sea only what is easily soluble, and that sea water contains only ordinary salt that stands on the dinner table. No, sea water contains almost all the elements that exist in nature. It contains magnesium, calcium, sulfur, bromine, iodine, and fluorine. Iron, copper, nickel, tin, uranium, cobalt, even silver and gold were found in it in smaller quantities. Chemists found over sixty elements in sea water. Probably all the others will be found as well. Most of the salt in sea water is table salt. That's why the water in the sea is salty.

Is it possible to run on the surface of water?

Can. To see this, look at the surface of any pond or lake in summer. A lot of living and fast people not only walk on water, but also run. If we consider that the support area of ​​​​the legs of these insects is very small, then it is not difficult to understand that, despite their low weight, the surface of the water can withstand significant pressure without breaking through.

Can water flow upward?

Yes maybe. This happens all the time and everywhere. The water itself rises up in the soil, wetting the entire thickness of the earth from the groundwater level. The water itself rises up through the capillary vessels of the tree and helps the plant deliver dissolved nutrients to great heights - from the roots deeply hidden in the ground to the leaves and fruits. The water itself moves upward in the pores of the blotting paper when you have to dry a blot, or in the fabric of a towel when you wipe your face. In very thin tubes - in capillaries - water can rise to a height of several meters.

What explains this?

Another remarkable feature of water is its exceptionally high surface tension. Water molecules on its surface experience the forces of intermolecular attraction only on one side, and in water this interaction is anomalously strong. Therefore, every molecule on its surface is drawn into the liquid. As a result, a force arises that tightens the surface of the liquid. In water it is especially strong: its surface tension is 72 mN/m (millinewtons per meter).

Can water remember?

This question sounds, admittedly, very unusual, but it is quite serious and very important. It concerns a large physico-chemical problem, which in its most important part has not yet been investigated. This question has just been posed in science, but it has not yet found an answer to it.

The question is: does the previous history of water affect its physical and chemical properties and is it possible, by studying the properties of water, to find out what happened to it earlier - to make the water itself “remember” and tell us about it. Yes, perhaps, as surprising as it may seem. The easiest way to understand this is with a simple, but very interesting and extraordinary example - the memory of ice.

Ice is water after all. When water evaporates, the isotopic composition of water and steam changes. Light water evaporates, although to an insignificant extent, faster than heavy water.

When natural water evaporates, the composition changes in the isotopic content of not only deuterium, but also heavy oxygen. These changes in the isotopic composition of steam have been very well studied, and their dependence on temperature has also been well studied.

Recently, scientists performed a remarkable experiment. In the Arctic, in the thickness of a huge glacier in northern Greenland, a borehole was sunk and a giant ice core almost one and a half kilometers long was drilled and extracted. The annual layers of growing ice were clearly visible on it. Along the entire length of the core, these layers were subjected to isotopic analysis, and based on the relative content of heavy isotopes of hydrogen and oxygen - deuterium and 18O - the formation temperatures of annual ice layers in each core section were determined. The date of formation of the annual layer was determined by direct counting. In this way, the climate situation on Earth was restored for a millennium. Water managed to remember and record all this in the deep layers of the Greenland glacier.

As a result of isotopic analyzes of ice layers, scientists constructed a climate change curve on Earth. It turned out that our average temperature is subject to secular fluctuations. It was very cold in the 15th century, at the end of the 17th century. and at the beginning of the 19th century. The hottest years were 1550 and 1930.

Then what is the mystery of the “memory” of water?

The fact is that in recent years, science has gradually accumulated many amazing and completely incomprehensible facts. Some of them are firmly established, others require quantitative reliable confirmation, and all of them are still waiting to be explained.

For example, no one yet knows what happens to water flowing through a strong magnetic field. Theoretical physicists are absolutely sure that nothing can and will not happen to it, reinforcing their conviction with completely reliable theoretical calculations, from which it follows that after the cessation of the magnetic field, the water should instantly return to its previous state and remain as it was . And experience shows that it changes and becomes different.

Is there a big difference? Judge for yourself. From ordinary water in a steam boiler, dissolved salts, released, are deposited in a dense and hard, like a stone, layer on the walls of the boiler pipes, and from magnetized water (as it is now called in technology) they fall out in the form of a loose sediment suspended in the water. It seems like the difference is small. But it depends on the point of view. According to workers at thermal power plants, this difference is extremely significant, since magnetized water ensures normal and uninterrupted operation of giant power plants: the walls of steam boiler pipes do not become overgrown, heat transfer is higher, and electricity generation is higher. Magnetic water treatment has long been installed at many thermal stations, but neither engineers nor scientists know how and why it works. In addition, it has been observed experimentally that after magnetic treatment of water, the processes of crystallization, dissolution, adsorption are accelerated in it, and wetting changes... however, in all cases the effects are small and difficult to reproduce.

The effect of a magnetic field on water (necessarily fast-flowing) lasts for small fractions of a second, but the water “remembers” this for tens of hours. Why is unknown. In this matter, practice is far ahead of science. After all, it is further unknown what exactly magnetic treatment affects - water or the impurities contained in it. There is no such thing as pure water.

The “memory” of water is not limited to the preservation of the effects of magnetic influence. In science, many facts and observations exist and are gradually accumulating, showing that water seems to “remember” that it was previously frozen.

Melt water, recently formed by melting a piece of ice, also seems to be different from the water from which this piece of ice was formed. In melt water, seeds germinate faster and better, sprouts develop faster; further, chickens that receive melt water seem to grow and develop faster. In addition to the amazing properties of melt water, established by biologists, purely physical and chemical differences are also known, for example, melt water differs in viscosity and dielectric constant. The viscosity of melt water takes on its usual value for water only 3-6 days after melting. Why this is so (if it is so), no one else knows.

Most researchers call this area of ​​phenomena the “structural memory” of water, believing that all these strange manifestations of the influence of the previous history of water on its properties are explained by changes in the fine structure of its molecular state. Maybe this is so, but... to name it does not mean to explain it. There is still an important problem in science: why and how water “remembers” what happened to it.

Where did water come from on Earth?

Streams of cosmic rays - streams of particles with enormous energy - are forever permeating the Universe in all directions. Most of them contain protons - the nuclei of hydrogen atoms. In its movement in space, our planet is continuously subjected to “proton bombardment.” Penetrating the upper layers of the earth's atmosphere, protons capture electrons, turn into hydrogen atoms and immediately react with oxygen to form water. Calculations show that every year almost one and a half tons of such “cosmic” water is born in the stratosphere. At high altitudes at low temperatures, the elasticity of water vapor is very small and water molecules, gradually accumulating, condense on cosmic dust particles, forming mysterious noctilucent clouds. Scientists suggest that they consist of tiny ice crystals that arose from such “cosmic” water. Calculations showed that the water that appeared on Earth in this way throughout its history would be just enough to give birth to all the oceans of our planet. So, water came to Earth from space? But...

Geochemists do not consider water a heavenly guest. They are convinced that she is of earthly origin. The rocks that make up the earth's mantle, which lies between the central core of the Earth and the earth's crust, melted in places under the influence of the accumulating heat of radioactive decay of isotopes. Of these, volatile components were released: nitrogen, chlorine, carbon and sulfur compounds, and most of all water vapor was released.

How much could all volcanoes emit during eruptions during the entire existence of our planet?

Scientists have calculated this too. It turned out that such erupted “geological” water would also be just enough to fill all the oceans.

In the central parts of our planet, forming its core, there is probably no water. It is unlikely that it could exist there. Some scientists believe that further, even if oxygen and hydrogen are present there, then they must, together with other elements, form new to science, unknown metal-like forms of compounds that have a high density and are stable at the enormous pressures and temperatures that reign in the center of the globe .

Other researchers are confident that the core of the globe consists of iron. What actually is not so far from us, under our feet, at depths exceeding 3 thousand km, no one yet knows, but there is probably no water there.

Most of the water in the Earth's interior is found in its mantle - layers located under the earth's crust and extending to a depth of approximately 3 thousand km. Geologists believe that at least 13 billion cubic meters are concentrated in the mantle. km of water.

The topmost layer of the earth's shell - the earth's crust - contains approximately 1.5 billion cubic meters. km of water. Almost all the water in these layers is in a bound state - it is part of rocks and minerals, forming hydrates. You cannot bathe in this water and you cannot drink it.

The hydrosphere, the water shell of the globe, is formed by approximately another 1.5 billion cubic meters. km of water. Almost all of this amount is contained in the World Ocean. It occupies about 70% of the entire earth's surface, its area is over 360 million square meters. km. From space, our planet does not look like a globe at all, but rather like a water balloon.

The average depth of the Ocean is about 4 km. If we compare this “bottomless depth” with the size of the globe itself, the average diameter of which is equal to km, then, on the contrary, we will have to admit that we live on a wet planet, it is only slightly moistened with water, and even then not over the entire surface. The water in the oceans and seas is salty - you cannot drink it.

There is very little water on land: only about 90 million cubic meters. km. Of these, more than 60 million cubic meters. km is underground, almost all of it is salt water. About 25 million cubic meters. km of solid water lies in mountainous and glacial regions, in the Arctic, Greenland, and Antarctica. These water reserves on the globe are protected.

All lakes, swamps, man-made reservoirs and soil contain another 500 thousand cubic meters. km of water.

Water is also present in the atmosphere. There is always a lot of water vapor in the air, even in the most arid deserts, where there is not a drop of water and it never rains. In addition, clouds are always floating across the sky, clouds are gathering, it is snowing, it is raining, and fog is spreading over the ground. All these reserves of water in the atmosphere have been accurately calculated: all of them taken together amount to only 14 thousand cubic meters. km.

And here we can move on to the second category. Under the word "ice" We are accustomed to understanding the solid phase state of water. But besides it, other substances are also subject to freezing. Thus, ice can be distinguished by the chemical composition of the original substance, for example, carbon dioxide, ammonia, methane ice and others.

Thirdly, there are crystal lattices (modifications) of water ice, the formation of which is determined by a thermodynamic factor. That's what we'll talk about a little in this post.

In the article Ice, we looked at how the structure of water undergoes a restructuring with a change in its state of aggregation, and touched upon the crystalline structure of ordinary ice. Thanks to the internal structure of the water molecule itself and the hydrogen bonds connecting all molecules into an ordered system, a hexagonal (hexagonal) crystal lattice of ice is formed. The molecules closest to each other (one central and four corner) are arranged in the shape of a trihedral pyramid, or tetrahedron, which underlies the hexagonal crystal modification ( Fig.1).

By the way, the distance between the smallest particles of matter is measured in nanometers (nm) or angstroms (named after the 19th century Swedish physicist Anders Jonas Ångström; denoted by the symbol Å). 1 Å = 0.1 nm = 10−10 m.

This hexagonal structure of ordinary ice extends to its entire volume. You can clearly see this with the naked eye: during snowfall in winter, catch a snowflake on your sleeve or glove and take a closer look at its shape - it is six-rayed or hexagonal. This is typical for every snowflake, but not a single snowflake ever repeats another (more about this in our article). And even large ice crystals with their external shape correspond to the internal molecular structure ( Fig.2).

We have already said that the transition of a substance, in particular water, from one state to another occurs under certain conditions. Normal ice forms at temperatures of 0°C and below and at a pressure of 1 atmosphere (normal value). Consequently, for the appearance of other modifications of ice, a change in these values ​​is required, and in most cases the presence of low temperatures and high pressure, at which the angle of hydrogen bonds changes and the entire crystal lattice is reconstructed.

Each modification of ice belongs to a specific system - a group of crystals in which the unit cells have the same symmetry and coordinate system (XYZ axes). In total, seven syngonies are distinguished. The characteristics of each of them are presented on illustrations 3-4. And just below is an image of the main forms of crystals ( Fig.5)

All modifications of ice that differ from ordinary ice were obtained in laboratory conditions. The first polymorphic structures of ice became known at the beginning of the 20th century through the efforts of scientists Gustav Heinrich Tammann And Percy Williams Bridgman. Bridgman's diagram of modifications was periodically supplemented. New modifications were identified from those obtained earlier. The latest changes to the diagram were made in our time. So far, sixteen crystalline types of ice have been obtained. Each type has its own name and is designated by a Roman numeral.

We will not delve deeply into the physical characteristics of each molecular type of water ice, so as not to bore you, dear readers, with scientific details; we will note only the main parameters.

Ordinary ice is called ice Ih (the prefix “h” means hexagonal system). On illustrations 7 its crystal structure is presented, consisting of hexagonal bonds (hexamers), which differ in shape - one in the form sun lounger(English) chair-form), another in the form rooks (boat-form). These hexamers form a three-dimensional section - two "chaise lounges" are horizontal at the top and bottom, and three "boats" occupy a vertical position.

The spatial diagram shows the order in the arrangement of hydrogen bonds of ice Ih, but in reality the connections are built randomly. However, scientists do not rule out that hydrogen bonds on the surface of hexagonal ice are more ordered than inside the structure.

The unit cell of hexagonal ice (i.e., the minimum volume of a crystal, the repeated reproduction of which in three dimensions forms the entire crystal lattice as a whole) includes 4 water molecules. The cell dimensions are 4.51 Å on both sides a,b And 7.35 Å on the c side (the c side or axis in the diagrams has a vertical direction). The angles between the sides, as seen from illustration 4: α=β = 90°, γ = 120°. The distance between neighboring molecules is 2.76 Å.

Hexagonal ice crystals form hexagonal plates and columns; the top and bottom faces in them are the base planes, and the six identical side faces are called prismatic ( Fig.10).

The minimum number of water molecules required for its crystallization to begin is about 275 (±25). To a large extent, ice formation occurs on the surface of the water mass bordering the air, rather than inside it. Coarse ice crystals Ih form slowly in the direction of the c-axis, for example, in stagnant water they grow vertically downward from the crystalline plates, or in conditions where growth to the side is difficult. Fine-grained ice, formed in turbulent water or when it freezes quickly, has accelerated growth directed from the prismatic faces. The temperature of the surrounding water determines the degree of branching of the ice crystal lattice.

Particles of substances dissolved in water, with the exception of helium and hydrogen atoms, whose dimensions allow them to fit into the cavities of the structure, are excluded from the crystal lattice at normal atmospheric pressure, being forced out onto the surface of the crystal or, as in the case of the amorphous variety (more on this later in the article) forming layers between microcrystals. Consecutive cycles of freezing and thawing water can be used to purify it from impurities, for example, gases (degassing).

Along with ice Ih there is also ice Ic (cubic system), however, in nature, the formation of this type of ice is occasionally possible only in the upper layers of the atmosphere. Artificial ice Ic obtained by instantly freezing water, for which steam is condensed on a cooled 80 to minus 110°С metal surface at normal atmospheric pressure. As a result of the experiment, crystals of cubic shape or in the form of octahedrons fall out onto the surface. It will not be possible to create cubic ice of the first modification from ordinary hexagonal ice by lowering its temperature, but the transition from cubic to hexagonal is possible by heating the ice Ic higher minus 80°C.

In the molecular structure of ice Ic the hydrogen bond angle is the same as that of ordinary ice Ih – 109.5°. And here is a hexagonal ring formed by molecules in an ice lattice Ic present only in the form of a chaise lounge.

The density of ice Ic is 0.92 g/cm³ at a pressure of 1 atm. The unit cell in a cubic crystal has 8 molecules and dimensions: a=b=c = 6.35 Å, and its angles α=β=γ = 90°.

On a note. Dear readers, in this article we will repeatedly encounter temperature and pressure indicators for one or another type of ice. And if temperature values ​​expressed in degrees Celsius are clear to everyone, then the perception of pressure values ​​may be difficult for some. In physics, various units are used to measure it, but in our article we will denote it in atmospheres (atm), rounding the values. Normal atmospheric pressure is 1 atm, which is equal to 760 mmHg, or just over 1 bar, or 0.1 MPa (megapascal).

As you understand, in particular, from the example with ice Ic, the existence of crystalline modifications of ice is possible under conditions of thermodynamic equilibrium, i.e. when the balance of temperature and pressure that determines the presence of any crystalline type of ice is disturbed, this type disappears, transforming into another modification. The range of these thermodynamic values ​​varies; it is different for each species. Let us consider other types of ice, not strictly in nomenclature order, but in connection with these structural transitions.

Ice II belongs to the trigonal system. It can be formed from the hexagonal type at a pressure of about 3,000 atm and a temperature of about minus 75°C, or from another modification ( ice V), by sharply reducing pressure at a temperature of minus 35°C. Existence II type of ice is possible in conditions of minus 170°C and pressure from 1 to 50,000 atm (or 5 gigapascals (GPa)). According to scientists, ice of this modification can probably be part of the icy satellites of the distant planets of the solar system. Normal atmospheric pressure and temperatures above minus 113°C create conditions for this type of ice to transform into ordinary hexagonal ice.

On illustrations 13 ice crystal lattice shown II. A characteristic feature of the structure is visible - a kind of hollow hexagonal channels formed by molecular bonds. The unit cell (the area highlighted in the illustration with a diamond) consists of two ligaments that are shifted relative to each other, so to speak, “in height.” As a result, a rhombohedral lattice system is formed. Cell dimensions a=b=c = 7.78 Å; α=β=γ = 113.1°. There are 12 molecules in a cell. The bond angle between molecules (O–O–O) varies from 80 to 120°.

When heating modification II, you can get ice III, and vice versa, ice cooling III turns it into ice II. Also ice III is formed when the water temperature is gradually lowered to minus 23°C, increasing the pressure to 3,000 atm.
As can be seen in the phase diagram ( ill. 6), thermodynamic conditions for a stable state of ice III, as well as another modification - ice V, are small.

Ice III And V have four triple points with surrounding modifications (thermodynamic values ​​at which the existence of different states of matter is possible). However, the ice II, III And V modifications can exist under conditions of normal atmospheric pressure and temperature of minus 170°C, and heating them to minus 150°C leads to the formation of ice Ic.

Compared to other high pressure modifications currently known, ice III has the lowest density - at a pressure of 3,500 atm. it is equal to 1.16 g/cm³.
Ice III is a tetragonal variety of crystallized water, but the ice lattice structure itself III has violations. If each molecule is usually surrounded by 4 neighboring ones, then in this case this indicator will have a value of 3.2, and in addition there may be 2 or 3 more molecules nearby that do not have hydrogen bonds.
In spatial arrangement, molecules form right-handed helices.
Dimensions of a unit cell with 12 molecules at minus 23°C and about 2800 atm: a=b = 6.66, c = 6.93 Å; α=β=γ = 90°. The hydrogen bond angle ranges from 87 to 141°.

On illustrations 15 a spatial diagram of the molecular structure of ice is conventionally presented III. Molecules (blue dots) located closer to the viewer are shown larger, and hydrogen bonds (red lines) are correspondingly thicker.

And now, as they say, hot on our heels, let’s immediately “jump over” those coming after the ice III in nomenclature order, crystalline modifications, and let’s say a few words about ice IX.
This type of ice is essentially modified ice III, subjected to rapid deep cooling from minus 65 to minus 108 ° C to avoid transforming it into ice II. Ice IX remains stable at temperatures below 133°C and pressures from 2,000 to 4,000 atm. Its density and structure are identical III mind, but unlike ice III in the ice structure IX there is order in the arrangement of protons.
Heating Ice IX does not return it to the original III modifications, but turns into ice II. Cell dimensions: a=b = 6.69, c = 6.71 Å at a temperature of minus 108°C and 2800 atm.

By the way, science fiction writer Kurt Vonnegut's 1963 novel Cat's Cradle is centered around a substance called ice-nine, which is described as a man-made material that poses a great danger to life because water crystallizes on contact with it, turning into ice-nine. The entry of even a small amount of this substance into natural waters facing the world's oceans threatens to freeze all the water on the planet, which in turn means the death of all living things. In the end, that's what happens.

Ice IV is a metastable (weakly stable) trigonal formation of a crystal lattice. Its existence is possible in the phase space of ice III, V And VI modifications. Get some ice IV can be made from high-density amorphous ice by slowly heating it, starting from minus 130°C at a constant pressure of 8,000 atm.
The size of the rhombohedral unit cell is 7.60 Å, angles α=β=γ = 70.1°. The cell includes 16 molecules; hydrogen bonds between molecules are asymmetric. At a pressure of 1 atm and a temperature of minus 163°C, the density of ice IV is 1.27 g/cm³. O–O–O bond angle: 88–128°.

Likewise IV the type of ice that forms ice XII– by heating a high-density amorphous modification (more on this below) from minus 196 to minus 90°C at the same pressure of 8,000 atm, but at a higher speed.
Ice XII also metastable in the phase region V And VI crystalline types. It is a type of tetragonal system.
The unit cell contains 12 molecules, which, due to hydrogen bonds with angles of 84–135°, are located in the crystal lattice, forming a double right-handed helix. The cell has dimensions: a=b = 8.27, c = 4.02 Å; angles α=β=γ = 90º. The density of ice XII is 1.30 g/cm³ at normal atmospheric pressure and a temperature of minus 146°C. Hydrogen bond angles: 67–132°.

Of the currently discovered modifications of water ice, ice has the most complex crystal structure V. 28 molecules make up its unit cell; hydrogen bonds span gaps in other molecular compounds, and some molecules form bonds only with certain compounds. The angle of hydrogen bonds between neighboring molecules varies greatly - from 86 to 132°, therefore in the crystal lattice of ice V there is strong tension and a huge supply of energy.
Cell parameters under conditions of normal atmospheric pressure and temperature minus 175°C: a= 9.22, b= 7.54, c= 10.35 Å; α=β = 90°, γ = 109.2°.
Ice V is a monoclinic variety formed by cooling water to minus 20°C at a pressure of about 5,000 atm. The density of the crystal lattice, taking into account a pressure of 3,500 atm, is 1.24 g/cm³.
Spatial diagram of the ice crystal lattice V type shown in illustrations 18. The region of the unit cell of the crystal is highlighted with a gray outline.

Ordered arrangement of protons in the structure of ice V makes it another variety called ice XIII. This monoclinic modification can be obtained by cooling water below minus 143°C with the addition of hydrochloric acid (HCl) to facilitate the phase transition, creating a pressure of 5,000 atm. Reversible transition from XIII type k V type is possible in the temperature range from minus 193°C to minus 153°C.
Dimensions of the unit cell of ice XIII slightly different from V modifications: a= 9.24, b= 7.47, c= 10.30 Å; α=β = 90°, γ= 109.7° (at 1 atm, minus 193°С). The number of molecules in the cell is the same - 28. The angle of hydrogen bonds: 82–135°.

In the next part of our article we will continue our review of modifications of water ice.

See you on the pages of our blog!

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