Whereas, it is likely that you remember that in all other substances, their solid phase is heavier than the liquid phase.
Accordingly, it is good that ice is lighter than water - and this is also the main property of water, thanks to which life is possible in its current form.
Well, if this property of water did not exist, we would have to develop on the basis of, for example, ammonia. It's still a pleasure 🙂
Now let's focus on the fact that water can evaporate when boiling. But this is not the main property of water - since almost any substance evaporates during boiling, and there is nothing wrong with that. The important thing is that water evaporates just in a liquid state, and even from the surface of the ice.... Why is this property more important than boiling evaporation? Here's why.
The fact that water can evaporate not only when boiling is the main property of water, since this makes it possible water cycle... Which is definitely good, since water does not accumulate in one place, but more or less evenly spreads throughout the planet. That is, roughly speaking, the Sahara Desert is not as hot and dry as it could be, because in Antarctica water evaporates from the surface of glaciers. Well, the oceans play an important role in this.
Accordingly, without the water cycle in nature, life would sit near a couple of oases, and the rest of the place would be an arid desert, where there is not a drop of moisture.
And therefore the property of water to evaporate is the main property of water.
Naturally, not only water can evaporate without boiling. Most aromatic compounds (alcohols, ethers, chloroform, etc.) do not evaporate when boiling. But water has one important plus, one more main property - water is not toxic to living organisms... Whereas alcohols and esters are toxic. By the way, in more detail about the toxicity (and how to cope with it) of ethyl alcohol, that is, vodka, in the article "Positive properties of structured vodka".
Of course, in modern conditions, water can also become toxic. But this is dealt with for water, and it is not a problem so big that it cannot be dealt with.
So, another main property of water is that it is not toxic.
Otherwise, we would, again, be different 🙂
And finally, the main property of water, which is important not only for life, but also for industry: water heats up rather slowly and cools slowly (that is, can absorb a lot of heat). This property protects people and other animals, and the Earth, from overheating. And hypothermia. That is why living organisms can survive at -50 degrees Celsius and at + 50 degrees. If we were built on the basis of another substance, we would not be able to cope with such a temperature range.
In addition, it must be borne in mind that warm and cold water have different weights- warm water is lighter, cold water is heavier. Accordingly, water stratification occurs in the ocean - both in salinity and in temperature. And in the ocean just such a life is possible, as it is now organized. Well, since we all came out of the ocean, then if it were not for this property of water, then we would also be completely different.
And, finally, the property of water to absorb heat and be on the surface in a heated state allows such things as warm currents to exist - and in particular, the Gulf Stream. Which heats the whole of Europe, and without which, in place of Europe, there would be tundra with taiga, and not vineyards.
Perhaps you can name some other basic properties of water, but the ones listed above, in my opinion, are truly fundamental, since the existence of life on the planet depends on them in the form in which life exists. I hope this information will be useful to you when you need to answer questions from curious children :)
And here is the promised presentation on the topic "Basic properties of water" for download: http://festival.1september.ru/articles/513123/
So, the main properties of water are the properties thanks to which we are all alive!
And we have the form and shape that we have 🙂
other substances in water are COMPLETELY insoluble p
Water (hydrogen oxide) is a transparent liquid that has no color (in a small volume), odor and taste. Chemical formula: H2O. In the solid state it is called ice or snow, and in the gaseous state it is called water vapor. About 71% of the Earth's surface is covered with water (oceans, seas, lakes, rivers, ice at the poles).
It is a good highly polar solvent. Under natural conditions, it always contains dissolved substances (salts, gases). Water is 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.
Almost 70% of the surface of our planet is occupied by oceans and seas. Solid water - snow and ice - covers 20% of the land. Out of the total amount of water on Earth, equal to 1 billion 386 million cubic kilometers, 1 billion 338 million cubic kilometers falls on the salt waters of the World Ocean, and only 35 million cubic kilometers falls on fresh waters. The total amount of oceanic water would be enough to cover the globe with a layer of more than 2.5 kilometers. For every inhabitant of the Earth, there are approximately 0.33 cubic kilometers of seawater and 0.008 cubic kilometers of fresh water. But the difficulty is that the overwhelming majority of fresh water on Earth is in such a state that makes it difficult for humans to access. Almost 70% of fresh water is contained in the ice sheets of the polar countries and in mountain glaciers, 30% - in aquifers underground, and in the channels of all rivers simultaneously contain only 0.006% of fresh water. Water molecules have been found in interstellar space. Water is part of comets, most of the planets in the solar system and their satellites.
Water composition (by weight): 11.19% hydrogen and 88.81% oxygen. Pure water is clear, odorless and tasteless. It has the highest density at 0 ° C (1 g / cm3). The density of ice is less than that of liquid water, so the ice floats to the surface. Water freezes at 0 ° C and boils at 100 ° C at a pressure of 101,325 Pa. It conducts heat poorly and conducts electricity very poorly. Water is a good solvent. The water molecule has an angular shape; hydrogen atoms with respect to oxygen form an angle equal to 104.5 °. Therefore, a water molecule is a dipole: the part of the molecule where the hydrogen is located is positively charged, and the part where the oxygen is located is negatively charged. Due to the polarity of water molecules, electrolytes in it dissociate into ions.
In liquid water, along with ordinary H2O molecules, there are associated molecules, i.e., connected into more complex aggregates (H2O) x due to the formation of hydrogen bonds. The presence of hydrogen bonds between water molecules explains the anomalies of its physical properties: maximum density at 4 ° C, high boiling point (in the series Н20-Н2S - Н2Sе), anomalously high heat capacity. With an increase in temperature, hydrogen bonds are broken, and a complete rupture occurs when water passes into steam.
Water is a highly reactive substance. Under normal conditions, it interacts with many basic and acidic oxides, as well as with alkali and alkaline earth metals. Water forms numerous compounds - crystalline hydrates.
Obviously, water-binding compounds can serve as desiccants. Other drying substances include P205, CaO, BaO, metallic Ma (they also chemically interact with water), as well as silica gel. The important chemical properties of water include its ability to enter into hydrolytic decomposition reactions.
Physical properties of water.
Water has a number of unusual features:
1. When ice melts, its density increases (from 0.9 to 1 g / cm³). For almost all other substances, the density decreases upon melting.
2. When heated from 0 ° C to 4 ° C (more precisely, 3.98 ° C), the water is compressed. Accordingly, when it cools down, the density decreases. Thanks to this, fish can live in freezing reservoirs: when the temperature drops below 4 ° C, colder water, as less dense, remains on the surface and freezes, and a positive temperature remains under the ice.
3. High temperature and specific heat of fusion (0 ° C and 333.55 kJ / kg), boiling point (100 ° C) and specific heat of vaporization (2250 KJ / kg), compared to hydrogen compounds of similar molecular weight.
4. High heat capacity of liquid water.
5. High viscosity.
6. High surface tension.
7. Negative electric potential of the water surface.
All these features are associated with the presence of hydrogen bonds. Due to the large difference in the electronegativities of hydrogen and oxygen atoms, the electron clouds are strongly displaced towards oxygen. Because of this, as well as the fact that the hydrogen ion (proton) has no internal electronic layers and is small, it can penetrate into the electron shell of a negatively polarized atom of a neighboring molecule. Due to this, each oxygen atom is attracted to the hydrogen atoms of other molecules and vice versa. A certain role is played by the proton exchange interaction between molecules and inside water molecules. Each water molecule can participate in a maximum of four hydrogen bonds: 2 hydrogen atoms - each in one, and an oxygen atom - in two; in this state, the molecules are in the ice crystal. When the ice melts, part of the bonds breaks, which allows the water molecules to be packed more densely; when water is heated, bonds continue to break, and its density increases, but at temperatures above 4 ° C, this effect becomes weaker than thermal expansion. Evaporation breaks all remaining bonds. Breaking bonds requires a lot of energy, hence the high temperature and specific heat of melting and boiling and high heat capacity. The viscosity of water is due to the fact that hydrogen bonds prevent water molecules from moving at different speeds.
For similar reasons, water is a good solvent for polar substances. Each molecule of the dissolved substance is surrounded by water molecules, with the positively charged parts of the molecule of the dissolved substance attracting oxygen atoms, and the negatively charged ones - hydrogen atoms. Since the water molecule is small in size, many water molecules can surround each molecule of the solute.
This property of water is used by living beings. In a living cell and in the intercellular space, solutions of various substances in water interact. Water is essential for the life of all unicellular and multicellular living beings on Earth without exception.
Clean (free of impurities) water is a good insulator. Under normal conditions, water is weakly dissociated and the concentration of protons (more precisely, hydronium ions H3O +) and hydroxyl ions HO– is 0.1 μmol / L. But since water is a good solvent, certain salts are almost always dissolved in it, that is, there are positive and negative ions in the water. This allows water to conduct electricity. By the electrical conductivity of water, you can determine its purity.
Water has a refractive index of 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. Due to the large dipole moment of the molecules, water also absorbs microwave radiation, on which the principle of the microwave oven is based.
Aggregate states.
1. By state they are distinguished:
2. Solid - ice
3. Liquid - water
4. Gaseous - water vapor
Fig.1 "Types of snowflakes"
At atmospheric pressure, water freezes (turns into ice) at 0 ° C and boils (turns into water vapor) at 100 ° C. With a decrease in pressure, the melting point of water slowly rises, and the boiling point drops. At a pressure of 611.73 Pa (about 0.006 atm), the boiling point and melting point coincide and become equal to 0.01 ° C. This pressure and temperature is called the triple point of water. At lower pressures, water cannot be liquid, and ice turns directly into steam. The sublimation temperature of ice drops with decreasing pressure.
As the pressure rises, the boiling point of water rises, the density of water vapor at the boiling point also rises, and liquid water falls. At a temperature of 374 ° C (647 K) and a pressure of 22.064 MPa (218 atm), water passes the critical point. At this point, the density and other properties of liquid and gaseous water coincide. At higher pressures, there is no difference between liquid water and steam, hence there is no boiling or evaporation.
Metastable states are also possible - supersaturated vapor, 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, it is not difficult to obtain a supercooled liquid by cooling pure water in a clean vessel below 0 ° C, but when a crystallization center appears, liquid water quickly turns into ice.
Isotopic modifications of water.
Both oxygen and hydrogen have natural and artificial isotopes. Depending on the type of isotopes included in the molecule, the following types of water are distinguished:
1. Light water (just water).
2. Heavy water (deuterium).
3. Super heavy water (tritium).
Chemical properties of water.
Water is the most common solvent on Earth, largely determining the nature of Earth's chemistry as a science. Most of chemistry, at its inception as a science, began precisely as the chemistry of aqueous solutions of substances. It is sometimes considered as an ampholyte - and an acid and a base at the same time (cation H + anion OH-). In the absence of foreign substances in the water, the concentration of hydroxide ions and hydrogen ions (or hydronium ions) is the same, pKa ≈ approx. 16.
Water itself is relatively inert under normal conditions, but its strongly polar molecules solvate ions and molecules, form hydrates and crystalline hydrates. Solvolysis, and in particular hydrolysis, occurs in living and inanimate nature, and is widely used in the chemical industry.
Chemical names of water.
From a formal point of view, water has several different correct chemical names:
1. Hydrogen oxide
2. Hydrogen hydroxide
3. Dihydrogen monoxide
4. Hydroxy acid
5.English hydroxic acid
6. Oxidane (eng. Oxidane)
7. Dihydromone oxide
Types of water.
Water on Earth can exist in three basic states - liquid, gaseous and solid and, in turn, acquire a variety of forms, which are often adjacent to each other. Water vapor and clouds in the sky, sea water and icebergs, mountain glaciers and mountain rivers, aquifers in the earth. Water is capable of dissolving many substances in itself, acquiring one or another taste. Because of the importance of water, “as a source of life,” it is often subdivided into types.
Characteristics of waters: according to the peculiarities of origin, composition or use, they distinguish, among other things:
1. Soft water and hard water - by the content of calcium and magnesium cations
2. Groundwater
3. Melt water
4. Fresh water
5. Sea water
6. Brackish water
7. Mineral water
8. Rainwater
9. Drinking water, tap water
10. Heavy water, deuterium and tritium
11. Distilled water and deionized water
12. Wastewater
13. Storm water or surface water
14. By isotopes of the molecule:
15. Light water (just water)
16. Heavy water (deuterium)
17. Super heavy water (tritium)
18. Fictional water (usually with fabulous properties)
19. Dead water - a kind of water from fairy tales
20. Living water - a kind of water from fairy tales
21. Holy water is a special type of water according to religious teachings
22. Watering
23. Structured water is a term used in various non-academic theories.
World water reserves.
The huge layer of salt water that covers most of the Earth is a single whole and has an approximately constant composition. The world's oceans are huge. Its volume reaches 1.35 billion cubic kilometers. It covers about 72% of the earth's surface. Almost all the water on Earth (97%) is in the world's oceans. Approximately 2.1% of water is concentrated in polar ice and glaciers. All fresh water in lakes, rivers and in the composition of groundwater is only 0.6%. The remaining 0.1% of the water is part of salt water from wells and saline waters.
The 20th century is characterized by an intensive growth of the world's population and the development of urbanization. Giant cities with a population of more than 10 million people appeared. The development of industry, transport, energy, industrialization of agriculture have led to the fact that the anthropogenic impact on the environment has become global.
Increasing the efficiency of environmental protection measures is primarily associated with the widespread introduction of resource-saving, low-waste and waste-free technological processes, and a decrease in air pollution and water pollution. Environmental protection is a very multifaceted problem, the solution of which is dealt, in particular, by engineering and technical workers of almost all specialties who are associated with economic activities in settlements and industrial enterprises, which can be a source of pollution mainly of the air and water environment.
Water environment. The aquatic environment includes surface and groundwater.
Surface waters are mainly concentrated in the ocean, containing 1 billion 375 million cubic kilometers - about 98% of all water on Earth. The surface of the ocean (water area) is 361 million square kilometers. It is about 2.4 times the land area of an area of 149 million square kilometers. The water in the ocean is salty, and most of it (over 1 billion cubic kilometers) maintains a constant salinity of about 3.5% and a temperature of about 3.7oC. Noticeable differences in salinity and temperature are observed almost exclusively in the surface water layer, as well as in the marginal and especially in the Mediterranean seas. The content of dissolved oxygen in water decreases significantly at a depth of 50-60 meters.
Ground waters are salty, brackish (less salinity) and fresh; the existing geothermal waters have an elevated temperature (over 30 ° C). For the production activities of mankind and its household needs, fresh water is required, the amount of which is only 2.7% of the total volume of water on Earth, and a very small fraction of it (only 0.36%) is available in easily accessible places for extraction. Most of the fresh water is found in snow and freshwater icebergs found in areas mainly in the Antarctic Circle. The annual world river flow of fresh water is 37.3 thousand cubic kilometers. In addition, a part of groundwater, equal to 13 thousand cubic kilometers, can be used. Unfortunately, most of the river flow in Russia, amounting to about 5,000 cubic kilometers, falls on the marginal and sparsely populated northern territories. In the absence of fresh water, salt surface or underground water is used, making it desalination or hyperfiltration: it is passed under a large pressure drop through polymer membranes with microscopic holes that trap salt molecules. Both of these processes are very energy-intensive; therefore, it is of interest to propose that freshwater icebergs (or parts of them) be used as a source of fresh water, which for this purpose are towed along the water to the shores that do not have fresh water, where they will melt. According to preliminary calculations of the developers of this proposal, the production of fresh water will be approximately half the energy consumption compared to desalination and hyperfiltration. An important circumstance inherent in the aquatic environment is that infectious diseases are mainly transmitted through it (approximately 80% of all diseases). However, some of them, such as whooping cough, chickenpox, tuberculosis, are transmitted through the air. To combat the spread of disease through the aquatic environment, the World Health Organization (WHO) has declared the current decade to be the decade of drinking water.
Fresh water. Freshwater resources exist thanks to the eternal water cycle. As a result of evaporation, a gigantic volume of water is formed, reaching 525 thousand km per year. (due to font problems, the volumes of water are indicated without cubic meters).
86% of this amount falls on the salty waters of the World Ocean and inland seas - the Caspian. Aralsky and others; the rest evaporates on land, half of which is due to the transpiration of moisture by plants. Every year a layer of water with a thickness of about 1250 mm evaporates. Part of it again falls with precipitation into the ocean, and part is carried by winds to land and here feeds rivers and lakes, glaciers and groundwater. A natural distiller is powered by the energy of the Sun and takes about 20% of this energy.
Only 2% of the hydrosphere is freshwater, but they are constantly renewed. The speed of renewal determines the resources available to mankind. Most of the fresh water - 85% - is concentrated in the ice of the polar zones and glaciers. The rate of water exchange here is less than in the ocean, and is 8000 years. Surface water on land is renewed about 500 times faster than in the ocean. Even faster, in about 10-12 days, the waters of the rivers are renewed. Fresh waters of rivers are of the greatest practical importance for mankind.
Rivers have always been a source of fresh water. But in the modern era, they began to transport waste. Waste from the catchment area flows along river beds into the seas and oceans. Most of the used river water is returned to rivers and bodies of water in the form of wastewater. Until now, the growth of wastewater treatment plants has lagged behind the growth in water consumption. And at first glance, this is the root of all evil. In fact, everything is much more serious. Even with the most advanced treatment, including biological treatment, all dissolved inorganic substances and up to 10% of organic pollutants remain in the treated wastewater. Such water can again become suitable for consumption only after repeated dilution with pure natural water. And here, for a person, the ratio of the absolute amount of wastewater, even if treated, and the water flow of rivers is important.
The world water balance showed that 2200 km of water per year are spent on all types of water use. Diluting wastewater consumes almost 20% of the world's freshwater resources. Calculations for 2000, assuming that the rates of water consumption will decrease, and treatment will cover all wastewater, have shown that 30-35 thousand km of fresh water will still be required annually to dilute wastewater. This means that the resources of the total world river flow will be close to depletion, and in many parts of the world they have already been depleted. After all, 1 km of purified waste water "spoils" 10 km of river water, and not purified water - 3-5 times more. The amount of fresh water does not decrease, but its quality drops sharply, it becomes unsuitable for consumption.
Humanity will have to change its water use strategy. The necessity forces us to isolate the anthropogenic water cycle from the natural one. In practice, this means a transition to a closed water supply, to low-water or low-waste, and then to "dry" or non-waste technology, accompanied by a sharp decrease in the volume of water and treated wastewater consumption.
Fresh water supplies are potentially large. However, in any part of the world, they can be depleted due to unsustainable water use or pollution. The number of such sites is growing, encompassing entire geographic areas. The need for water is not met by 20% of the urban and 75% of the rural population of the world. The amount of water consumed depends on the region and the standard of living and ranges from 3 to 700 liters per day per person. Industrial water consumption also depends on the economic development of the area. For example, in Canada, industry consumes 84% of the total water withdrawal, and in India - 1%. The most water-intensive industries are steel, chemical, petrochemical, pulp and paper and food. They consume almost 70% of all water used in industry. On average, in the world, industry consumes about 20% of all water consumed. The main consumer of fresh water is agriculture: 70-80% of all fresh water is consumed for its needs. Irrigated agriculture occupies only 15-17% of the agricultural land area, and gives half of all production. Almost 70% of the world's cotton crop subsists on irrigation.
The total flow of the rivers of the CIS (USSR) for the year is 4720 km. But the distribution of water resources is extremely uneven. In the most inhabited regions, where up to 80% of industrial production lives and 90% of land suitable for agriculture is located, the share of water resources is only 20%. Many parts of the country are insufficiently supplied with water. These are the south and southeast of the European part of the CIS, the Caspian lowland, the south of Western Siberia and Kazakhstan, and some other regions of Central Asia, the south of Transbaikalia, Central Yakutia. The northern regions of the CIS, the Baltic states, the mountainous regions of the Caucasus, Central Asia, the Sayan and the Far East are most provided with water.
River flow changes with climate fluctuations. Human intervention in natural processes has already affected the river flow. In agriculture, most of the water does not return to the rivers, but is spent on evaporation and the formation of plant mass, since during photosynthesis, hydrogen is converted from water molecules into organic compounds. To regulate the flow of rivers, which is not uniform throughout the year, 1,500 reservoirs have been built (they regulate up to 9% of the total flow). Human economic activity has hardly influenced the flow of rivers in the Far East, Siberia and the North of the European part of the country. However, in the most populated areas, it decreased by 8%, and in such rivers as the Terek, Don, Dniester and Ural - by 11-20%. The water runoff in the Volga, Syrdarya and Amu Darya has noticeably decreased. As a result, the inflow of water to the Sea of Azov decreased by 23%, to the Aral Sea by 33%. The Aral Sea level dropped by 12.5 m.
The limited and even scarce resources of fresh water in many countries are significantly reduced due to pollution. Pollutants are usually divided into several classes depending on their nature, chemical structure and origin.
Pollution of water bodies. Fresh water bodies are polluted mainly as a result of the discharge of wastewater from industrial enterprises and settlements into them. As a result of wastewater discharge, the physical properties of water change (temperature rises, transparency decreases, color, tastes, odors appear); floating substances appear on the surface of the reservoir, and sediment forms at the bottom; the chemical composition of water changes (the content of organic and inorganic substances increases, toxic substances appear, the oxygen content decreases, the active reaction of the environment changes, etc.); the qualitative and quantitative bacterial composition changes, pathogenic bacteria appear. Contaminated water bodies become unsuitable for drinking, and often for technical water supply; lose their fishery value, etc. The general conditions for the discharge of wastewater of any category into surface water bodies are determined by their national economic significance and the nature of water use. After the discharge of wastewater, some deterioration in the quality of water in reservoirs is allowed, but this should not noticeably affect its life and the possibility of further use of the reservoir as a source of water supply, for cultural and sports events, and fishery purposes.
Monitoring of the fulfillment of the conditions for the discharge of industrial wastewater into water bodies is carried out by sanitary-epidemiological stations and basin departments.
The water quality standards for reservoirs for domestic and drinking, cultural and domestic water use establish the quality of water for reservoirs for two types of water use: the first type includes areas of water bodies used as a source for centralized or non-centralized domestic and drinking water supply, as well as for water supply to food industry enterprises; to the second type - areas of reservoirs used for swimming, sports and recreation of the population, as well as located within the boundaries of settlements.
The assignment of reservoirs to a particular type of water use is carried out by the bodies of the State Sanitary Supervision, taking into account the prospects for the use of reservoirs.
The standards for water quality of reservoirs given in the rules refer to sections located on flowing water bodies 1 km higher than the nearest water use point, and on stagnant water bodies and reservoirs 1 km on both sides of the water use point.
Much attention is paid to the prevention and elimination of pollution of the coastal areas of the seas. The seawater quality standards, which must be ensured during the discharge of wastewater, relate to the area of water use within the designated boundaries and to sections at a distance of 300 m to the sides of these boundaries. When using the coastal areas of the seas as a receiver of industrial wastewater, the content of harmful substances in the sea should not exceed the MPCs established for the sanitary-toxicological, general sanitary and radioleptic limiting indicators of harmfulness. At the same time, the requirements for the discharge of wastewater are differentiated in relation to the nature of water use. The sea is viewed not as a source of water supply, but as a curative, health-improving, cultural and everyday factor.
Pollutants entering rivers, lakes, reservoirs and seas make significant changes in the established regime and disrupt the equilibrium state of aquatic ecological systems. As a result of the processes of transformation of substances polluting water bodies, proceeding under the influence of natural factors, in water sources there is a complete or partial restoration of their original properties. In this case, secondary products of the decay of pollution can form, which have a negative effect on the quality of water.
Self-purification of water in reservoirs is a combination of interconnected hydrodynamic, physicochemical, microbiological and hydrobiological processes leading to the restoration of the original state of a water body.
Due to the fact that the wastewater of industrial enterprises may contain specific pollution, their release into the city drainage network is limited by a number of requirements. Industrial waste water discharged into the drainage network should not: disrupt the operation of networks and structures; have a destructive effect on the material of pipes and elements of treatment facilities; contain more than 500mg / l of suspended and floating substances; contain substances that can clog networks or be deposited on the walls of pipes; contain flammable impurities and dissolved gaseous substances capable of forming explosive mixtures; contain harmful substances that prevent biological wastewater treatment or discharge into a water body; have a temperature above 40 ° C.
Industrial waste water that does not meet these requirements must be pre-treated and only then discharged into the city drainage network.
Table 1
World water reserves
| P / p No. | Name of objects | Distribution area in million cubic km | Volume, thousand cubic meters km | Share in the world stock, |
| 1 | World Ocean | 361,3 | 1338000 | 96,5 |
| 2 | The groundwater | 134,8 | 23400 | 1,7 |
| 3 | including underground: fresh water |
10530 | 0,76 | |
| 4 | Soil moisture | 82,0 | 16,5 | 0,001 |
| 5 | Glaciers and permanent snow | 16,2 | 24064 | 1,74 |
| 6 | Underground ice | 21,0 | 300 | 0,022 |
| 7 | Lake water | |||
| 8 | fresh | 1,24 | 91,0 | 0,007 |
| 9 | salty | 0,82 | 85.4 | 0,006 |
| 10 | Swamp water | 2,68 | 11,5 | 0,0008 |
| 11 | River water | 148,2 | 2,1 | 0,0002 |
| 12 | Water in the atmosphere | 510,0 | 12,9 | 0,001 |
| 13 | Water in organisms | 1,1 | 0,0001 | |
| 14 | Total water reserves | 1385984,6 | 100,0 | |
| 15 | Total fresh water supplies | 35029,2 | 2,53 |
Conclusion.
Water is one of the main resources on Earth. It is difficult to imagine what would become of our planet if fresh water disappeared. A person needs to drink about 1.7 liters of water per day. And about 20 times more daily is required for each of us for washing, cooking, and so on. The threat of extinction of fresh water exists. All living things suffer from water pollution, it is harmful to human health.
Water is a familiar and unusual substance. The famous Soviet scientist Academician I.V. Petryanov called his popular science book about water "The most extraordinary substance in the world." And the doctor of biological sciences BF Sergeev began his book "Entertaining physiology" with a chapter on water - "The substance that created our planet."
Scientists are right: there is no substance on Earth that is more important for us than ordinary water, and at the same time there is no other substance of the same kind, in the properties of which there would be as many contradictions and anomalies as in its properties.
Bibliographic list:
1. Korobkin V. I., Peredelskiy L. V. Ecology. Textbook for universities. - Rostov / on / Don. Phoenix, 2005.
2. Moiseev NN Interaction between nature and society: global problems // Bulletin of the Russian Academy of Sciences, 2004. V. 68. No. 2.
3. Environmental protection. Textbook. allowance: In 2t / Ed. V.I.Danilov - Danilyan. - M .: Publishing house of MNEPU, 2002.
4. Belov S. V. Environmental protection / S. V. Belov. - M. Higher School, 2006 .-- 319 p.
5. Derpgolts VF Water in the universe. - L .: "Nedra", 2000.
6. Krestov GA From crystal to solution. - L .: Chemistry, 2001.
7. Khomchenko G.P. Chemistry for university applicants. - M., 2003.
The chemical and physical properties of water are unusual. They are explained, first of all, by the small size of water molecules, their polarity and the ability to bond with each other by hydrogen bonds.
In a water molecule, one oxygen atom is covalently bonded to two hydrogen atoms. The molecule is polar: an oxygen atom carries a partial negative charge, and two hydrogen atoms carry a partially positive charge. This makes the water molecule a dipole. Therefore, when water molecules interact with each other, hydrogen bonds are established between them. They are weaker than covalent, but since each water molecule is capable of forming 4 hydrogen bonds, they significantly affect the physical properties of water. The high heat capacity, heat of fusion and heat of vaporization are explained by the fact that most of the heat absorbed by water is spent on breaking the hydrogen bonds between its molecules. Water has a high thermal conductivity. Water practically does not compress, it is transparent in the visible part of the spectrum. Finally, water is the only substance whose density is greater in the liquid state than in the solid.
The biological significance of water
Its physical and chemical properties make it a unique liquid and determine its biological significance.Water is a good solvent for ionic (polar) compounds, as well as some non-ionic ones, in the molecule of which charged (polar) groups are present. If the energy of attraction of water molecules to the molecules of any substance is greater than the energy of attraction between the molecules of the substance, then the molecules are hydrated and the substance dissolves (Fig. 256). In relation to water, there are:
hydrophilic substances- substances that are readily soluble in water;
hydrophobic substances - substances that are practically insoluble in water.
B
Fig. 254. Properties of the water molecule: 1 - cohesion of water molecules; 2 - hydration of the cation; 3 - hydration of the anion.
The high heat capacity and thermal conductivity of water prevent the emergence of "hot spots" in the body, as they contribute to an even distribution of heat in the cell.
Due to the high heat of evaporation of water, the body is cooled.
The density of ice is less than the density of water. Therefore, when water bodies freeze under the ice, there is a living space for aquatic organisms.
Due to the forces of adhesion 3 and cohesion 4, water has the property of capillarity, that is, the ability to rise through the capillaries (one of the factors that ensure the movement of water in the vessels of plants) (Fig. 254).
Water is a direct participant in many chemical reactions (gyrolytic breakdown of proteins, carbohydrates, fats, etc.).
The incompressibility of water determines the stressed state of the cell walls (turgor), and also performs a supporting function (hydrostatic skeleton, for example, in roundworms).
Minerals
Cell minerals are mainly represented by salts that dissociate into anions and cations, some in non-ionized form in micro doses (Fe, Mg, Cu, Co, Ni, etc.)For the processes of vital activity of the cell, the most important cations are Na +, Ca 2+, Mg 2+, anions HPO 4 2-, Cl -, HCO 3 -. As a rule, the concentration of ions in the cell and its environment is different. For example, in the external environment (blood plasma, seawater) K + is always less, and Na + is always more than in the cell. There are a number of mechanisms that allow the cell to maintain a certain ratio of ions in the protoplast and the external environment.
Various ions take part in many processes of the cell's life:
cations K +, Na +, Ca 2+ provide irritability of living organisms;
cations Mg 2+, Mn 2+, Zn 2+, Ca 2+, etc. are necessary for the normal functioning of many enzymes;
the formation of carbohydrates during photosynthesis is impossible without Mg 2+ (a component of chlorophyll);
the weakly alkaline reaction of the cell contents is supported by the anions of weak acids (HCO 3 -, HPO 4 -) and weak acids (H 2 CO 3);
The concentration of salts inside the cell depends on its buffering properties. Buffering is the ability of a cell to maintain a slightly alkaline reaction of its contents at a constant level. Inside the cell, buffering is provided mainly by the anions H 2 PO 4 - and HPO 4 2-. In the extracellular fluid and in the blood, the role of a buffer is played by H 2 CO 3 - and HCO 3 2-.
Phosphate Buffer System:
Low pH High pH
NRO 4 2- + H + ← ――――――― → H 2 PO 4 -
Hydrogen phosphate - ion Dihydrogen phosphate - ion
Bicarbonate Buffer System:
Low pH High pH
HCO 3 - + H + ← ――――――― → H 2 CO 3
Bicarbonate - ion Carbonic acid
Some inorganic substances are contained in the cell not only in a dissolved state, but also in a solid state. For example, Ca and P are contained in bone tissue, in shells of mollusks in the form of double carbonic and phosphate salts.
Date: 2009-01-30
Water- one of the most unique substances on Earth. Despite the rapid development of modern science, scientists have not yet fully studied the nature of this seemingly simple substance! Because of its external simplicity, people on Earth have long considered water to be a simple indivisible substance. And only thanks to the English scientist G. Cavendish in 1766 people learned that water is not a simple chemical element, but a combination of hydrogen and oxygen. Later this was proved by A. Lavoisier (France) in 1783.
Behind the simple formula H 2 O, it turns out that a mysterious substance is hidden, which until now many leading minds of science cannot unravel. Water- a chemical compound consisting of 11.11% hydrogen and 88.89% (by weight) oxygen. Chemically pure water is a colorless liquid, odorless and tasteless.
Water possesses a number of the most unique and animal properties, which we will now consider.
Water is the only liquid on Earth for which the dependence of the specific heat capacity on temperature has a minimum. This minimum is realized at a temperature of +35 0 C. At the same time, the normal temperature of the human body, which consists of two-thirds (and even more so at a young age) of water, is in the temperature range of 36-38 0 C.
Specific heat of water is 4180 J / (kg · 0 С) at 0 0 С.
Heat capacity of water abnormally high. To heat a certain amount of it by one degree, you need to spend more energy than heating other liquids.
This results in the unique ability of water to retain heat. The overwhelming majority of other substances do not possess this property. This exceptional feature of water contributes to the fact that a person's normal body temperature is maintained at the same level both on a hot day and on a cool night.
From the above, it follows that water plays a major role in the processes of regulation of human heat exchange and allows him to maintain a comfortable state with a minimum of energy costs.
Due to the significant values of heat capacity and latent heat of water transformation, its huge volumes on the Earth's surface are heat accumulators. The same properties of water determine its use in industry as a heat carrier. Thermal characteristics of water are one of the most important factors in the stability of the biosphere.
The next uniqueness of water is its density. The density of most liquids, crystals and gases - decreases with heating and increases with cooling, up to the process of crystallization or condensation. Density of water when cooled from 100 to 3.98 0 С increases, as in the vast majority of liquids. But, having reached its maximum value at a temperature of 3.98 0 С, the density begins to decrease with further cooling of the water. In other words, the maximum density of water is observed at a temperature of 3.98 ° C, and not at a freezing point of 0 ° C.
Freezing of water is accompanied by an abrupt decrease in density by 9%, while for most other substances the crystallization process is accompanied by an increase in density. In this regard, ice occupies a larger volume than liquid water and stays on its surface.
This unusual behavior of the density of water is extremely important for the maintenance of life on Earth. Covering the water from above, ice plays in nature the role of a kind of floating blanket that protects rivers and reservoirs from further freezing and preserves life for the underwater world. If the density of water increased during freezing, the ice would be heavier than water and begin to sink, which would lead to the death of all living things in rivers, lakes and oceans, which would freeze completely, turning into blocks of ice, and the Earth would become an icy desert, which is inevitable would lead to the death of all living things.
Of all liquids, water has the highest surface tension.
Surface tension coefficientσ, H / m of some liquids at a temperature of 20 0 С are given below in the table
Water is the strongest universal solvent. Given enough time, it can dissolve almost any solid. It is because of the unique dissolving ability of water that no one has yet managed to obtain chemically pure water - it always contains the dissolved material of the vessel.
Since a person consists of 65% (in old age) and 75% (in childhood) water, naturally it is absolutely necessary for all key human life support systems. It is contained in human blood (79%) and promotes the transport of thousands of substances necessary for life through the circulatory system in a dissolved state. Water is contained in lymph (96%), which carries nutrients from the intestines to the tissues of a living organism.
Indeed, looking at the properties of water, we can conclude that any of the properties of water is unique. Only water - the only substance on the planet can be in three states - liquid, solid and gaseous. So water plays an important role in the energy-information exchange between man and nature. According to a number of scientists, it has a memory and can both heal and destroy.
A source: Kurganov A.M., Fedorov N.F. Hydraulic calculations of water supply and sewerage systems: Handbook. 1986 year
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DEFINITION
Water- hydrogen oxide is a binary compound of inorganic nature.
Formula - H 2 O. Molar mass - 18 g / mol. It can exist in three states of aggregation - liquid (water), solid (ice) and gaseous (water vapor).
Chemical properties of water
Water is the most common solvent. There is an equilibrium in a solution of water, therefore water is called ampholyte:
H 2 O ↔ H + + OH - ↔ H 3 O + + OH -.
Under the action of an electric current, water decomposes into hydrogen and oxygen:
H 2 O = H 2 + O 2.
At room temperature, water dissolves active metals with the formation of alkalis, while hydrogen also evolves:
2H 2 O + 2Na = 2NaOH + H 2.
Water is capable of interacting with fluorine and interhalogen compounds, and in the second case, the reaction proceeds at low temperatures:
2H 2 O + 2F 2 = 4HF + O 2.
3H 2 O + IF 5 = 5HF + HIO 3.
Salts formed by a weak base and a weak acid undergo hydrolysis when dissolved in water:
Al 2 S 3 + 6H 2 O = 2Al (OH) 3 ↓ + 3H 2 S.
Water is able to dissolve some substances, metals and non-metals when heated:
4H 2 O + 3Fe = Fe 3 O 4 + 4H 2;
H 2 O + C ↔ CO + H 2.
Water, in the presence of sulfuric acid, enters into interaction (hydration) reactions with unsaturated hydrocarbons - alkenes with the formation of saturated monohydric alcohols:
CH 2 = CH 2 + H 2 O → CH 3 -CH 2 -OH.
Physical properties of water
Water is a clear liquid (n.o.). The dipole moment is 1.84 D (due to the strong difference in the electronegativities of oxygen and hydrogen). Water has the highest specific heat value among all substances in the liquid and solid state of aggregation. Specific heat of fusion of water - 333.25 kJ / kg (0 С), vaporization - 2250 kJ / kg. Water is capable of dissolving polar substances. Water has a high surface tension and a negative electrical surface potential.
Receiving water
Water is obtained through a neutralization reaction, i. E. reactions of interaction between acids and alkalis:
H 2 SO 4 + 2KOH = K 2 SO 4 + H 2 O;
HNO 3 + NH 4 OH = NH 4 NO 3 + H 2 O;
2CH 3 COOH + Ba (OH) 2 = (CH 3 COO) 2 Ba + H 2 O.
One of the ways to obtain water is the reduction of metals with hydrogen from their oxides:
CuO + H 2 = Cu + H 2 O.
Examples of problem solving
EXAMPLE 1
| Exercise | How much water should you take to prepare a 5% solution from a 20% acetic acid solution? |
| Solution | According to the determination of the mass fraction of a substance, a 20% solution of acetic acid is 80 ml of a solvent (water) of 20 g of acid, and a 5% solution of acetic acid is 95 ml of a solvent (water) of 5 g of acid. Let's make the proportion: x = 20 × 95/5 = 380. Those. the new solution (5%) contains 380 ml of solvent. It is known that the original solution contained 80 ml of solvent. Therefore, to get a 5% solution of acetic acid from a 20% solution, you need to add: 380-80 = 300 ml of water. |
| Answer | Needs 300 ml of water. |
EXAMPLE 2
| Exercise | The combustion of organic matter weighing 4.8 g produced 3.36 liters of carbon dioxide (NU) and 5.4 g of water. The density of organic matter in terms of hydrogen is 16. Determine the formula of organic matter. |
| Solution | Molar masses of carbon dioxide and water, calculated using the table of chemical elements by D.I. Mendeleev - 44 and 18 g / mol, respectively. Let's calculate the amount of the substance of the reaction products: n (CO 2) = V (CO 2) / V m; n (H 2 O) = m (H 2 O) / M (H 2 O); n (CO 2) = 3.36 / 22.4 = 0.15 mol; n (H 2 O) = 5.4 / 18 = 0.3 mol. Considering that in the composition of the CO 2 molecule there is one carbon atom, and in the composition of the H 2 O molecule there are 2 hydrogen atoms, the amount of substance and the masses of these atoms will be equal: n (C) = 0.15 mol; n (H) = 2 × 0.3 mol; m (C) = n (C) x M (C) = 0.15 x 12 = 1.8 g; m (H) = n (H) × M (H) = 0.3 × 1 = 0.3 g. Determine if there is oxygen in the composition of organic matter: m (O) = m (C x H y O z) - m (C) - m (H) = 4.8 - 0.6 - 1.8 = 2.4 g. The amount of substance of oxygen atoms: n (O) = 2.4 / 16 = 0.15 mol. Then, n (C): n (H): n (O) = 0.15: 0.6: 0.15. Divide by the smallest value, we get n (C): n (H): n (O) = 1: 4: 1. Therefore, the formula of organic matter is CH 4 O. The molar mass of organic matter calculated using the table of chemical elements of D.I. Mendeleev - 32 g / mol. The molar mass of organic matter, calculated using the value of its density for hydrogen: M (C x H y O z) = M (H 2) × D (H 2) = 2 × 16 = 32 g / mol. If the formulas of organic matter derived from combustion products and using density for hydrogen are different, then the ratio of molar masses will be greater than 1. Let's check this: M (C x H y O z) / M (CH 4 O) = 1. Therefore, the formula for organic matter is CH 4 O. |
| Answer | The formula for organic matter is CH 4 O. |