Today we will talk about the properties of snow and ice. It is worth clarifying that ice is formed not only from water. In addition to water ice, there is ammonia and methane ice. Not long ago, scientists invented dry ice. Its properties are unique, we will consider them a little later. It is formed when carbon dioxide freezes. Dry ice got its name due to the fact that when it melts it does not leave puddles. The carbon dioxide contained in it immediately evaporates into the air from its frozen state.

Ice definition

First of all, let's take a closer look at ice, which is obtained from water. There is a regular crystal lattice inside it. Ice is a common natural mineral produced when water freezes. One molecule of this liquid binds to four nearby ones. Scientists have noticed that such an internal structure is inherent in various precious stones and even minerals. For example, diamond, tourmaline, quartz, corundum, beryl and others have this structure. The molecules are held at a distance by a crystal lattice. These properties of water and ice indicate that the density of such ice will be less than the density of the water due to which it was formed. Therefore, ice floats on the surface of the water and does not sink in it.

Millions of square kilometers of ice

Do you know how much ice there is on our planet? According to recent research by scientists, there are approximately 30 million square kilometers of frozen water on planet Earth. As you may have guessed, the bulk of this natural mineral is found on the polar ice caps. In some places the thickness of the ice cover reaches 4 km.

How to get ice

Making ice is not difficult at all. This process is not difficult and does not require any special skills. This requires low water temperature. This is the only constant condition for the ice formation process. Water will freeze when your thermometer shows a temperature below 0 degrees Celsius. The crystallization process begins in water due to low temperatures. Its molecules are built into an interesting ordered structure. This process is called the formation of a crystal lattice. It is the same in the ocean, in a puddle, and even in the freezer.

Research into the freezing process

Conducting research on the topic of water freezing, scientists came to the conclusion that the crystal lattice is built in the upper layers of water. Microscopic ice sticks begin to form on the surface. A little later they freeze together. Thanks to this, a thin film is formed on the surface of the water. Large bodies of water take much longer to freeze compared to still water. This is due to the fact that the wind ripples and ripples the surface of a lake, pond or river.

Ice pancakes

Scientists made another observation. If excitement continues at low temperatures, then the thinnest films are collected into pancakes with a diameter of about 30 cm. Then they freeze into one layer, the thickness of which is at least 10 cm. A new layer of ice freezes on top and bottom of the ice pancakes. This creates a thick and durable ice cover. Its strength depends on the type: the most transparent ice will be several times stronger white ice. Environmentalists have noticed that 5-centimeter ice can support the weight of an adult. A layer of 10 cm can withstand a passenger car, but it should be remembered that going out on the ice in autumn and spring is very dangerous.

Properties of snow and ice

Physicists and chemists have long studied the properties of ice and water. The most famous and also important property of ice for humans is its ability to easily melt even at zero temperature. But other physical properties of ice are also important for science:

• ice is transparent, so it transmits well sunlight;
• colorlessness - ice has no color, but it can be easily colored using color additives;
• hardness - ice masses perfectly retain their shape without any outer shells;
• fluidity is a particular property of ice, inherent in the mineral only in some cases;
• fragility - a piece of ice can be easily split without much effort;
• cleavage - ice breaks easily in those places where it is fused along a crystallographic line.

Ice: displacement and purity properties

Ice has a high degree of purity in its composition, since the crystal lattice does not leave free space for various foreign molecules. When water freezes, it displaces various impurities that were once dissolved in it. In the same way, you can get purified water at home.

But some substances can slow down the freezing process of water. For example, salt in sea water. Ice in the sea only forms when very low temperatures. Surprisingly, the process of freezing water every year is capable of maintaining self-purification of various impurities for many millions of years in a row.

The secrets of dry ice

The peculiarity of this ice is that it contains carbon in its composition. Such ice forms only at a temperature of -78 degrees, but it melts already at -50 degrees. Dry ice, the properties of which allow you to skip the stage of liquids, immediately produces steam when heated. Dry ice, like its counterpart water ice, has no odor.

Do you know where dry ice is used? Due to its properties, this mineral is used to transport food and medicine over long distances. And the granules of this ice can extinguish the fire of gasoline. Also, when dry ice melts, it forms a thick fog, which is why it is used on film sets to create special effects. In addition to all of the above, you can take dry ice with you on hikes and in the forest. After all, when it melts, it repels mosquitoes, various pests and rodents.

As for the properties of snow, we can observe this amazing beauty every winter. After all, every snowflake has the shape of a hexagon - this is unchanged. But besides the hexagonal shape, snowflakes can look different. The formation of each of them is influenced by air humidity, atmospheric pressure and other natural factors.

The properties of water, snow, and ice are amazing. It is important to know a few more properties of water. For example, it is able to take the shape of the vessel into which it is poured. When water freezes, it expands and also has memory. It is able to remember the surrounding energy, and when it freezes, it “resets” the information that it has absorbed.

We looked at the natural mineral - ice: properties and its qualities. Continue to study science, it is very important and useful!

It is in a state of aggregation, which tends to have a gaseous or liquid form at room temperature. The properties of ice began to be studied hundreds of years ago. About two hundred years ago, scientists discovered that water is not a simple compound, but a complex chemical element consisting of oxygen and hydrogen. After discovery, the formula of water became H2O.

Ice structure

H 2 O consists of two hydrogen atoms and one oxygen atom. In a quiet state, hydrogen is located on the tops of the oxygen atom. Oxygen and hydrogen ions should occupy the vertices of an isosceles triangle: oxygen is located at the vertex of a right angle. This structure of water is called a dipole.

Ice consists of 11.2% hydrogen, and the rest is oxygen. The properties of ice depend on its chemical structure. Sometimes it contains gaseous or mechanical formations - impurities.

Ice occurs in nature in the form of a few crystalline species that stably retain their structure at temperatures from zero and below, but at zero and above it begins to melt.

Crystal structure

The properties of ice, snow and steam are completely different and depend on. In the solid state, H 2 O is surrounded by four molecules located at the corners of the tetrahedron. Since the coordination number is low, the ice may have an openwork structure. This is reflected in the properties of ice and its density.

Ice shapes

Ice is one of the most common substances in nature. On Earth there are the following varieties:

• river;
• lake;
• nautical;
• firn;
• glacier;
• ground.

There is ice that is directly formed by sublimation, i.e. from the vapor state. This appearance takes on a skeletal shape (we call them snowflakes) and aggregates of dendritic and skeletal growth (frost, hoarfrost).

One of the most common forms are stalactites, i.e. icicles. They grow all over the world: on the surface of the Earth, in caves. This type of ice is formed by the flow of water droplets when the temperature difference is about zero degrees in the autumn-spring period.

Formations in the form of ice strips that appear along the edges of reservoirs, at the boundary of water and air, as well as along the edge of puddles, are called ice banks.

Ice can form in porous soils in the form of fibrous veins.

Properties of Ice

A substance can be in different states. Based on this, the question arises: what property of ice is manifested in this or that state?

Scientists distinguish physical and mechanical properties. Each of them has its own characteristics.

Physical properties

The physical properties of ice include:

1. Density. In physics, an inhomogeneous medium is represented by the limit of the ratio of the mass of the substance of the medium itself to the volume in which it is contained. The density of water, like other substances, is a function of temperature and pressure. Typically, calculations use a constant density of water equal to 1000 kg/m3. A more accurate density indicator is taken into account only when it is necessary to carry out very accurate calculations due to the importance of the resulting density difference result.
   When calculating the density of ice, it is taken into account what kind of water has become ice: as is known, the density of salt water is higher than distilled water.
2. Water temperature. Usually occurs at a temperature of zero degrees. Freezing processes occur intermittently with the release of heat. The reverse process (melting) occurs when the same amount of heat is absorbed that was released, but without jumps, but gradually.
   In nature, there are conditions under which water is supercooled, but it does not freeze. Some rivers retain liquid water even at a temperature of -2 degrees.
3. the amount of heat that is absorbed when a body is heated by each degree. There is a specific heat capacity, which is characterized by the amount of heat required to heat a kilogram of distilled water by one degree.
4. Compressibility. Another physical property of snow and ice is compressibility, which affects the decrease in volume under the influence of increased external pressure. The reciprocal quantity is called elasticity.
5. Ice strength.
6. Ice color. This property depends on the absorption of light and the scattering of rays, as well as the amount of impurities in the frozen water. River and lake ice without foreign impurities is visible in soft blue light. Sea ice can be completely different: blue, green, indigo, white, brown, or have a steely tint. Sometimes you can see black ice. It gets this color due to large quantity minerals and various organic impurities.

Mechanical properties of ice

The mechanical properties of ice and water are determined by their resistance to the influence of the external environment relative to a unit area. Mechanical properties depend on structure, salinity, temperature and porosity.

Ice is an elastic, viscous, plastic formation, but there are conditions under which it becomes hard and very brittle.

Sea ice and freshwater ice are different: the former is much more flexible and less durable.

When passing ships, the mechanical properties of ice must be taken into account. This is also important when using ice roads, crossings and more.

Water, snow and ice have similar properties that determine the characteristics of the substance. But at the same time, these readings are influenced by many other factors: ambient temperature, impurities in the solid, as well as the initial composition of the liquid. Ice is one of the most interesting substances on Earth.

Job 1

Snowflakes as a phenomenon of physics

The work was carried out by Daniil Kholodyakov

Goals: learn more about snowflakes from the MKT point of view

Objectives: understand the nature of the formation of snowflakes

1. Formation of snowflakes

2. Snowflake shapes

3. Crystal symmetry

4. Identical snowflakes

5. Color and light

6. Additional materials

1. Have you ever looked at a snowflake and wondered how it is formed and why it is different from other types of snow you have seen before?

Snowflakes are a special form of water ice. Snowflakes form in clouds that are made of water vapor. When the temperature is 32°F (0°C) or colder, water turns from liquid form to ice. Several factors influence the formation of snowflakes. Temperature, air currents, humidity - all this has an impact on their shape and size. Dirt and dust can mix in the water and change the weight and durability of the crystals. Dirt particles make the snowflake heavier, can make it susceptible to melting, and can cause cracks and breaks in the crystal. The formation of a snowflake is a dynamic process. A snowflake can encounter many different environmental conditions, sometimes melting, sometimes growing - the snowflake's structure is constantly changing.

2. What are the most common shapes of snowflakes?

Typically, hexagonal crystals form in high clouds; needles or flat six-sided crystals form in mid-height clouds, and a wide variety of six-sided shapes form in low clouds. Colder temperatures create snowflakes with sharper tips on the sides of the crystals and can lead to branching arrows. Snowflakes produced in warmer conditions grow more slowly, resulting in a smoother, less complex shape.

0; -3°C - Thin hexagonal plates

3; -6° C - Needles

6; -10°C - Hollow columns

10; -12°C - Sector plates (hexagons with indentations)

12; -15°C - Dendrites (lacey hexagonal shapes)

3. Why are snowflakes symmetrical?

First of all, not all snowflakes are the same from all sides. Uneven temperatures, dirt, and other factors can cause a snowflake to appear lopsided. However, it is true that many snowflakes are symmetrical and very complex in structure. This is because the shape of a snowflake reflects the internal order of the water molecules. Water molecules in solid states, such as snow and ice, form weak bonds (called hydrogen bonds) with each other. These ordered mechanisms result in the symmetrical, hexagonal shape of the snowflake. During crystallization, water molecules are subject to a maximum force of attraction, and repulsive forces are reduced to a minimum. Consequently, water molecules line up in given spaces in a specific arrangement, such as to occupy space and maintain symmetry.

4. Is it true that no two snowflakes are alike?

Yes and no. No two snowflakes will ever be identical, down to the exact number of water molecules, electron spin, hydrogen and oxygen isotopes, etc. On the other hand, two snowflakes can look the same, and any snowflake probably had its prototype at some point in history. The structure of a snowflake is constantly changing according to environmental conditions and under the influence of many factors, so it seems unlikely that two snowflakes will be identical.

5. If water and ice are transparent, why does snow look white?

The short answer is that snowflakes have so many reflective surfaces that they scatter light in all its colors, which is why snow appears white. The long answer has to do with how the human eye perceives color. Even though the light source may not be truly "white" in color (for example, sunlight, fluorescent, and incandescent lights all have a specific color), human brain compensates for the light source. Thus, even though the sunlight is yellow, and the light scattered from the snow is also yellow, the brain sees maximum snow white, because the entire picture received by the brain has a yellow tint, which is automatically subtracted.

Conclusions:

1. Snowflakes are a special form of water ice.

2. Temperature, air currents, humidity are factors affecting the shape and size of a snowflake.

3. It is the order of water molecules that determines the symmetry of a snowflake.

them in real snow crystals.

Job 2

Ice and water in nature.

The work was performed by Guseva Alina

Goal: learn something new.

Tasks:

Consider the meaning of water in nature;

Understand the properties and types of water;

Familiarize yourself with the basic properties of water ice;

Expand your knowledge regarding water in general.

Water (hydrogen oxide) - a binary inorganic compound, chemical formula H2O. A water molecule consists of two hydrogen atoms and one oxygen atom, which are connected by a covalent bond. Under normal conditions, it is a transparent liquid, colorless, odorless and tasteless. In the solid state it is called ice, snow or frost, and in the gaseous state it is called water vapor. Water can also exist in the form of liquid crystals.

About 71% of the Earth's surface is covered with water (oceans, seas, lakes, rivers, ice) - 361.13 million km2. On Earth, approximately 96.5% of water comes from the oceans (1.7% of the world's reserves are groundwater, another 1.7% in glaciers and ice caps in Antarctica and Greenland, a small portion in rivers, lakes and swamps, and 0.001% in clouds). Most of the earth's water is salty, and it is unsuitable for agriculture and drinking. The share of fresh water is about 2.5%.

Water is a good highly polar solvent. Under natural conditions, it always contains dissolved substances (salts, gases). Water is of key importance in the creation and maintenance of life on Earth, in the chemical structure of living organisms, in the formation of climate and weather. It is an essential substance for all living beings on planet Earth.

In the atmosphere of our planet, water is found in the form of small droplets, in clouds and fog, and also in the form of steam. During condensation, it is removed from the atmosphere in the form of precipitation (rain, snow, hail, dew). Water is an extremely common substance in space, however, due to the high intra-fluid pressure, water cannot exist in a liquid state in the vacuum of space, which is why it is present only in the form of steam or ice.

Types of water.

Water on Earth can exist in three main states - liquid, gaseous and solid and acquire various shapes, which can simultaneously coexist with each other: water vapor and clouds in the sky, sea water and icebergs, glaciers and rivers on the surface of the earth, aquifers in the ground. Water is often divided into types according to different principles. According to the characteristics of their origin, composition or application, they distinguish, among other things: soft and hard water - according to the content of calcium and magnesium cations. According to the isotopes of hydrogen in the molecule: light (in composition almost identical to normal), heavy (deuterium), super-heavy water (tritium). Also distinguished: fresh, rain, sea, mineral, brackish, drinking, tap, distilled, deionized, pyrogen-free, holy, structured, melt, underground, waste and surface water.

Physical properties.

Water under normal conditions maintains a liquid state, while similar hydrogen compounds are gases (H2S, CH4, HF). Due to the large difference in electronegativity between hydrogen and oxygen atoms, the electron clouds are strongly biased towards oxygen. For this reason, a water molecule has a large dipole moment(D = 1.84, second only to hydrocyanic acid). At the temperature of transition to the solid state, water molecules are ordered, during this process the volumes of voids between the molecules increase and the overall density of water decreases, which explains the reason lower density of water in the ice phase. During evaporation, on the contrary, all bonds are broken. Breaking bonds requires a lot of energy, which is why water the most high specific heat capacity among other liquids and solids. In order to heat one liter of water by one degree, 4.1868 kJ of energy is required. Due to this property, water is often used as a coolant. In addition to its high specific heat capacity, water also has high specific heat values melting(at 0 °C - 333.55 kJ/kg) and vaporization(2250 kJ/kg).

Water also has high surface tension among liquids, second only to mercury. The relatively high viscosity of water is due to the fact that hydrogen bonds prevent water molecules from moving at different speeds. Water is good solvent of polar substances. Each molecule of the solute is surrounded by water molecules, and the positively charged parts of the molecule of the solute attract oxygen atoms, and the negatively charged parts attract hydrogen atoms. Since a water molecule is small in size, many water molecules can surround each solute molecule. Water has negative electrical potential of the surface.

Clean water - good insulator. Because water is good solvent, some salts are almost always dissolved in it, that is, there are positive and negative ions in the water. Thanks to this, water conducts electricity. The electrical conductivity of water can be used to determine its purity.

Water has refractive index n=1.33 in the optical range. However, it strongly absorbs infrared radiation, and therefore water vapor is the main natural greenhouse gas, responsible for more than 60% of the greenhouse effect.

Ice - water in a solid state of aggregation. Ice is sometimes called certain substances in a solid state of aggregation, which tend to have a liquid or gaseous form at room temperature; specifically dry ice, ammonia ice or methane ice.

Basic properties of water ice.

Currently, three amorphous varieties and 15 crystalline modifications of ice are known. The openwork crystal structure of such ice leads to the fact that its density (equal to 916.7 kg/m at 0 °C) is lower than the density of water (999.8 kg/m) at the same temperature. Therefore, water, turning into ice, increases its volume by about 9%. Ice, being lighter than liquid water, forms on the surface of reservoirs, which prevents further freezing of the water.

High specific heat of fusion ice, equal to 330 kJ/kg, is an important factor in the circulation of heat on Earth. So, to melt 1 kg of ice or snow, you need the same amount of heat as it takes to heat a liter of water by 80 °C. Ice is found in nature in the form of ice itself (continental, floating, underground), as well as in the form of snow, frost, etc. Under the influence of its own weight, ice acquires plastic properties and fluidity. Natural ice is usually much purer than water, since when water crystallizes, water molecules are the first to form into the lattice.

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

As pressure increases, the density of water vapor at the boiling point also increases, and that of liquid water decreases. At a temperature of 374 °C (647 K) and a pressure of 22.064 MPa (218 atm), water passes critical point. At this point, the density and other properties of liquid and gaseous water are the same. At higher pressure and/or temperature, the difference between liquid water and water vapor disappears. This physical state called " supercritical fluid».

Water may be in metastable states- supersaturated steam, superheated liquid, supercooled liquid. These states can exist for a long time, but they are unstable and upon contact with a more stable phase, a transition occurs. For example, you can get a supercooled liquid by cooling clean water in a clean vessel below 0 °C, but when a crystallization center appears, liquid water quickly turns into ice.

Facts.

On average, the body of plants and animals contains more than 50% water.

The Earth's mantle contains 10-12 times more water than the amount of water in the World Ocean.

If all the glaciers melted, the water level in the earth's oceans would rise by 64 m and about 1/8 of the land surface would be flooded with water.

Sometimes water freezes at positive temperatures.

Under certain conditions (inside nanotubes), water molecules form a new state in which they retain the ability to flow even at temperatures close to absolute zero.

Water reflects 5% of the sun's rays, while snow reflects about 85%. Only 2% of sunlight penetrates under the ocean ice.

The blue color of clear ocean water is due to the selective absorption and scattering of light in the water.

Using drops of water from taps, you can create a voltage of up to 10 kilovolts, an experiment called the “Kelvin Dropper”.

Water is one of the few substances in nature that expands when transitioning from liquid to solid.

Conclusions:

Water retains a liquid state of aggregation, has a large dipole moment, high specific heat capacity, vaporization value, high surface tension, negative electrical potential of the surface, and is a good insulator and solvent.

Literature

1. Water // Encyclopedic Dictionary of Brockhaus and Efron: In 86 volumes (82 volumes and 4 additional ones). - St. Petersburg, 1890-1907.

2. Losev K. S. Water. - L.: Gidrometeoizdat, 1989. - 272 p.

3. Hydrobionts in self-purification of waters and biogenic migration of elements. - M.: MAX-Press. 2008. 200 p. Foreword by Corresponding Member. RAS V.V. Malakhova. (Series: Science. Education. Innovation. Issue 9). ISBN 978-5-317-02625-7.

4. On some issues of maintaining water quality and its self-purification // Water Resources. 2005. v. 32. no. 3. pp. 337-347.

5. Andreev V. G. The influence of proton exchange interaction on the structure of the water molecule and the strength of the hydrogen bond. Materials of the V International Conference “Current Problems of Science in Russia”. - Kuznetsk 2008, vol. 3 pp. 58-62.

Scientists analyzing data from the Red Planet say there is every reason to believe that Phoenix unearthed what it was flying for - water ice under a thin layer of soil. The proof is the sublimation of bright material that was exposed when the top layer of soil was removed.

The last days on Mars were not easy for the American probe. Researchers began analyzing soil samples. Moreover, they had to overcome a number of difficulties. We talked about a partially jammed stove door. But that was just the beginning.

When the samples were finally poured into the gap, it turned out that the soil of Mars was somehow stuck together. Large grains cling to each other, and none of them wants to get into the oven. The fact is that the stove opening is covered with a protective mesh with holes one millimeter each. The researchers hoped to heat (in order to analyze the resulting gases) just such small grains of sand.

Later, a way was invented to “re-strain” the soil. The robot's ladle was made to vibrate over an open stove, so that the smallest particles of Martian rock were gradually poured into the stove. Similarly, sand samples were brought to the microscope.

By the way, scientists explain the clumping of soil by the presence of very small particles filling the gaps between larger granules, possibly together with a certain component that plays the role of cement.

A sample of Martian sand under a microscope. The scale bar is one millimeter (photo NASA/JPL-Caltech/University of Arizona).

A sample taken under a microscope revealed about a thousand individual particles, many of which were ten times smaller than the diameter of a human hair.

Researchers say they saw at least four different minerals here. For example, there are large black glassy particles and small red ones.

Experts believe that this set reflects the history of the soil - it appears that the original particles of volcanic origin were reduced in size through weathering to grains with a higher concentration of iron.

Now regarding the ice. Scientists began to have “suspicions” back in early June. But heating the first sample in the oven did not reveal any signs of water vapor.

But Mars researchers received evidence of the presence of ice thanks to photographs of the Dodo-Goldilocks trench dug by the robot earlier (or rather, at first they were two adjacent trenches, which were later combined into one, hence the double name). The few light clumps of soil present at the beginning have disappeared in later frames.

“It has to be ice,” said mission scientist Peter Smith of the University of Arizona, Tucson. “These lumps almost completely disappeared within a few days, which is perfect proof that it is ice.” Previously, the idea was expressed that bright materials are salt. But the salt cannot evaporate.”

Above: Dodo-Goldilocks trench filmed June 13th. The width of this notch is 22 and the length is 35 centimeters. The greatest depth (the area at the bottom of the frame) reaches 8 centimeters. Below: footage taken as early as June 15 and 18 (the 20th and 24th sol of the mission). The light areas become smaller, and in the lower left corner of the trench several grains of light material disappear (photos by NASA/JPL-Caltech/University of Arizona/Texas A&M University).

Also, while digging a series of trenches around the apparatus, the robot’s hand encountered hard soil under a relatively thin layer of soft soil. Moreover, at approximately the same depth in all trenches.

Ice- mineral with chemical formula H 2 O, represents water in a crystalline state.
Chemical composition of ice: H - 11.2%, O - 88.8%. Sometimes it contains gaseous and solid mechanical impurities.
In nature, ice is represented mainly by one of several crystalline modifications, stable in the temperature range from 0 to 80°C, with a melting point of 0°C. There are 10 known crystalline modifications of ice and amorphous ice. The most studied is ice of the 1st modification - the only modification found in nature. Ice is found in nature in the form of ice itself (continental, floating, underground, etc.), as well as in the form of snow, frost, etc.

See also:

STRUCTURE

The crystal structure of ice is similar to the structure: each H 2 0 molecule is surrounded by the four molecules closest to it, located at equal distances from it, equal to 2.76Α and located at the vertices of a regular tetrahedron. Due to the low coordination number, the ice structure is openwork, which affects its density (0.917). Ice has a hexagonal spatial lattice and is formed by freezing water at 0°C and atmospheric pressure. The lattice of all crystalline modifications of ice has a tetrahedral structure. Parameters of an ice unit cell (at t 0°C): a=0.45446 nm, c=0.73670 nm (c is double the distance between adjacent main planes). When the temperature drops, they change very little. H 2 0 molecules in the ice lattice are connected to each other by hydrogen bonds. The mobility of hydrogen atoms in the ice lattice is much higher than the mobility of oxygen atoms, due to which the molecules change their neighbors. In the presence of significant vibrational and rotational movements of molecules in the ice lattice, translational jumps of molecules from the site of their spatial connection occur, disrupting further order and forming dislocations. This explains the manifestation of specific rheological properties in ice, which characterize the relationship between irreversible deformations (flow) of ice and the stresses that caused them (plasticity, viscosity, yield stress, creep, etc.). Due to these circumstances, glaciers flow similarly to highly viscous liquids, and thus natural ice actively participate in the water cycle on Earth. Ice crystals are relatively large in size (transverse size from fractions of a millimeter to several tens of centimeters). They are characterized by anisotropy of the viscosity coefficient, the value of which can vary by several orders of magnitude. Crystals are capable of reorientation under the influence of loads, which affects their metamorphization and the flow rate of glaciers.

PROPERTIES

Ice is colorless. In large clusters it takes on a bluish tint. Glass shine. Transparent. It has no cleavage. Hardness 1.5. Fragile. Optically positive, refractive index very low (n = 1.310, nm = 1.309). There are 14 known modifications of ice in nature. True, everything except the familiar ice, which crystallizes in the hexagonal system and is designated as ice I, is formed under exotic conditions - at very low temperatures (about -110150 0C) and high pressures, when the angles of hydrogen bonds in a water molecule change and systems other than hexagonal are formed. Such conditions resemble those in space and do not occur on Earth. For example, at temperatures below –110 °C, water vapor precipitates on a metal plate in the form of octahedra and cubes several nanometers in size - this is the so-called cubic ice. If the temperature is slightly above –110 °C and the vapor concentration is very low, a layer of extremely dense amorphous ice forms on the plate.

MORPHOLOGY

Ice is a very common mineral in nature. There are several types of ice in the earth's crust: river, lake, sea, ground, firn and glacier. More often it forms aggregate clusters of fine-crystalline grains. Crystalline ice formations are also known that arise by sublimation, that is, directly from the vapor state. In these cases, the ice appears as skeletal crystals (snowflakes) and aggregates of skeletal and dendritic growth (cave ice, hoarfrost, hoarfrost, and patterns on glass). Large well-cut crystals are found, but very rarely. N. N. Stulov described ice crystals in the northeastern part of Russia, found at a depth of 55-60 m from the surface, having an isometric and columnar appearance, and the length of the largest crystal was 60 cm, and the diameter of its base was 15 cm. From simple forms on ice crystals, only the faces of the hexagonal prism (1120), hexagonal bipyramid (1121) and pinacoid (0001) were identified.
Ice stalactites, colloquially called “icicles,” are familiar to everyone. With temperature differences of about 0° in the autumn-winter seasons, they grow everywhere on the surface of the Earth with the slow freezing (crystallization) of flowing and dripping water. They are also common in ice caves.
Ice banks are strips of ice cover made of ice that crystallizes at the water-air boundary along the edges of reservoirs and bordering the edges of puddles, the banks of rivers, lakes, ponds, reservoirs, etc. with the rest of the water space not freezing. When they completely grow together, a continuous ice cover is formed on the surface of the reservoir.
Ice also forms parallel columnar aggregates in the form of fibrous veins in porous soils, and ice antholites on their surface.

ORIGIN

Ice forms mainly in water basins when the air temperature drops. At the same time, an ice porridge composed of ice needles appears on the surface of the water. From below, long ice crystals grow on it, whose sixth-order symmetry axes are located perpendicular to the surface of the crust. The relationships between ice crystals under different formation conditions are shown in Fig. Ice is common wherever there is moisture and where the temperature drops below 0° C. In some areas, ground ice thaws only to a shallow depth, below which permafrost begins. These are the so-called permafrost areas; in areas of permafrost distribution in the upper layers of the earth's crust, there are so-called underground ice, among which modern and fossil underground ice are distinguished. At least 10% of the Earth's total land area is covered by glaciers; the monolithic ice rock that composes them is called glacial ice. Glacial ice is formed primarily from the accumulation of snow as a result of its compaction and transformation. The ice sheet covers about 75% of Greenland and almost all of Antarctica; the largest thickness of glaciers (4330 m) is located near the Byrd station (Antarctica). In central Greenland the ice thickness reaches 3200 m.
Ice deposits are well known. In areas with cold, long winters and short summer, as well as in high mountainous regions, ice caves with stalactites and stalagmites are formed, among which the most interesting are Kungurskaya in the Perm region of the Urals, as well as the Dobshine cave in Slovakia.
When sea water freezes, sea ice is formed. Characteristic properties sea ​​ice are salinity and porosity, which determine the range of its density from 0.85 to 0.94 g/cm 3 . Because of such low density, ice floes rise above the surface of the water by 1/7-1/10 of their thickness. Sea ice begins to melt at temperatures above -2.3°C; it is more elastic and more difficult to break into pieces than freshwater ice.

APPLICATION

In the late 1980s, Argonne Laboratory developed a technology for making ice slurry that can flow freely through pipes of various diameters without collecting in ice build-ups, sticking together, or clogging cooling systems. The salty water suspension consisted of many very small round-shaped ice crystals. Thanks to this, the mobility of water is maintained and, at the same time, from the point of view of thermal engineering, it represents ice, which is 5-7 times more effective than simple cold water in building cooling systems. In addition, such mixtures are promising for medicine. Experiments on animals have shown that microcrystals of the ice mixture pass perfectly into fairly small blood vessels and do not damage cells. “Icy Blood” extends the time during which the victim can be saved. Let's say, in case of cardiac arrest, this time lengthens, according to conservative estimates, from 10-15 to 30-45 minutes.
The use of ice as a structural material is widespread in the polar regions for the construction of dwellings - igloos. Ice is part of the Pikerit material proposed by D. Pike, from which it was proposed to make the world's largest aircraft carrier.

Ice - H 2 O

CLASSIFICATION