Distribution of water on earth. Report: The ordinary and unusual substance water A message on the topic of water in our lives
Introduction 3
Physical properties of water. 5
Aggregate states. 7
Chemical properties of water. 9
Types of water. 9
World water reserves. eleven
Conclusion. 20
Bibliography: 21
Introduction
Water (hydrogen oxide) is a transparent liquid that is colorless (in small volumes), odorless and tasteless. Chemical formula: H2O. In the solid state it is called ice or snow, and in the gaseous state it is called water vapor. About 71% of the Earth's surface is covered with water (oceans, seas, lakes, rivers, ice at the poles).
It is a good highly polar solvent. IN natural conditions 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. Hard water - snow and ice - covers 20% of the land. Of the total amount of water on Earth, equal to 1 billion 386 million cubic kilometers, 1 billion 338 million cubic kilometers are the share of salty waters of the World Ocean, and only 35 million cubic kilometers are the share of fresh waters. The total amount of ocean water would be enough to cover the globe with a layer of more than 2.5 kilometers. For every inhabitant of the Earth there is approximately 0.33 cubic kilometers of sea water and 0.008 cubic kilometers of fresh water. But the difficulty is that the vast majority of fresh water on Earth is in a state that makes it difficult for humans to access. Almost 70% of fresh water is contained in the ice sheets of polar countries and in mountain glaciers, 30% is in aquifers underground, and only 0.006% of fresh water is contained in the beds of all rivers. Water molecules have been discovered in interstellar space. Water is part of comets, most planets in the solar system and their satellites.
Composition of water (by mass): 11.19% hydrogen and 88.81% oxygen. Pure water is transparent, odorless and tasteless. It has the greatest density at 0° C (1 g/cm3). The density of ice is less than the density of liquid water, so the ice floats to the surface. Water freezes at 0°C and boils at 100°C at a pressure of 101,325 Pa. It conducts heat poorly and conducts electricity very poorly. Water is a good solvent. The water molecule has an angular shape; hydrogen atoms form an angle of 104.5° with respect to oxygen. Therefore, a water molecule is a dipole: the part of the molecule where hydrogen is located is positively charged, and the part where oxygen is located is negatively charged. Due to the polarity of water molecules, the electrolytes in it dissociate into ions.
Liquid water, along with ordinary H20 molecules, contains associated molecules, i.e., connected into more complex aggregates (H2O)x due to the formation of hydrogen bonds. The presence of hydrogen bonds between water molecules explains the anomalies of its physical properties: maximum density at 4 ° C, high boiling point (in the series H20-H2S - H2Se) and abnormally high heat capacity. As the temperature increases, hydrogen bonds are broken, and complete rupture occurs when water turns into steam.
Water is a highly reactive substance. Under normal conditions, it reacts with many basic and acidic oxides, as well as with alkali and alkaline earth metals. Water forms numerous compounds - crystalline hydrates.
Obviously, compounds that bind water can serve as drying agents. Other drying substances include P2O5, CaO, BaO, metal Ma (they also react chemically with water), as well as silica gel. Important chemical properties of water include its ability to enter into hydrolytic decomposition reactions.
Physical properties of water.
Water has a number of unusual features:
When ice melts, its density increases (from 0.9 to 1 g/cm³). For almost all other substances, the density decreases when melted.
When heated from 0°C to 4°C (3.98°C to be exact), water contracts. Accordingly, when cooling, the density drops. Thanks to this, fish can live in freezing reservoirs: when the temperature drops below 4 °C, more cold water how the less dense one remains on the surface and freezes, while a positive temperature remains under the ice.
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.
High heat capacity of liquid water.
High viscosity.
High surface tension.
Negative electrical potential of the water surface.
All these features are associated with the presence of hydrogen bonds. Due to the large difference in electronegativity between hydrogen and oxygen atoms, the electron clouds are strongly biased towards oxygen. Due to this, and also the fact that the hydrogen ion (proton) does not have internal electronic layers and is small in size, it can penetrate into the electron shell of a negatively polarized atom of a neighboring molecule. Due to this, each oxygen atom is attracted to the hydrogen atoms of other molecules and vice versa. The proton exchange interaction between and within water molecules plays a certain role. Each water molecule can participate in a maximum of four hydrogen bonds: 2 hydrogen atoms - each in one, and an oxygen atom - in two; In this state, the molecules are in an ice crystal. When ice melts, some of the bonds break, which allows water molecules to be packed more tightly; When water is heated, bonds continue to break and its density increases, but at temperatures above 4 °C this effect becomes weaker than thermal expansion. During evaporation, all remaining bonds are broken. Breaking bonds requires a lot of energy, hence the high temperature and specific heat of melting and boiling and high heat capacity. The viscosity of water is due to the fact that hydrogen bonds prevent water molecules from moving at different speeds.
For similar reasons, water is a good solvent for polar substances. Each molecule of the solute is surrounded by water molecules, and the positively charged parts of the molecule of the solute attract oxygen atoms, and the negatively charged parts attract hydrogen atoms. Since a water molecule is small in size, many water molecules can surround each solute molecule.
This property of water is used by living beings. In a living cell and in the intercellular space, solutions of various substances in water interact. Water is necessary for the life of all single-celled and multicellular living creatures on Earth without exception.
Pure (free from impurities) water is a good insulator. Under normal conditions, water is weakly dissociated and the concentration of protons (more precisely, hydronium ions H4O+) and hydroxyl ions HO− is 0.1 µmol/l. But since water is a good solvent, certain salts are almost always dissolved in it, that is, there are positive and negative ions in water. Thanks to this, water conducts electricity. The electrical conductivity of water can be used to determine its purity.
Water has a refractive index n=1.33 in the optical range. However, it strongly absorbs infrared radiation, and therefore water vapor is the main natural greenhouse gas, responsible for more than 60% of the greenhouse effect. Due to the large dipole moment of the molecules, water also absorbs microwave radiation, which is what the operating principle of a microwave oven is based on.
Aggregate states.
According to the condition they are distinguished:
Solid - ice
Liquid - water
Gaseous - water vapor
Fig. 1 “Types of snowflakes”
At atmospheric pressure, water freezes (turns into ice) at 0°C and boils (turns into water vapor) at 100°C. As pressure decreases, the melting point of water slowly increases, and the boiling point decreases. At a pressure of 611.73 Pa (about 0.006 atm), the boiling and melting points coincide and become equal to 0.01 °C. This pressure and temperature is called the triple point of water. At lower pressures, water cannot be liquid and ice turns directly into steam. The sublimation temperature of ice drops with decreasing pressure.
As pressure increases, the boiling point of water increases, the density of water vapor at the boiling point also increases, and the density of liquid water decreases. At a temperature of 374 °C (647 K) and a pressure of 22.064 MPa (218 atm), water passes the critical point. At this point, the density and other properties of liquid and gaseous water are the same. At higher pressures there is no difference between liquid water and water vapor, hence no boiling or evaporation.
Metastable states are also possible - supersaturated steam, superheated liquid, supercooled liquid. These 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:
Light water (just water).
Heavy water (deuterium).
Superheavy water (tritium).
Chemical properties of water.
Water is the most common solvent on Earth, largely determining the nature of terrestrial chemistry as a science. Most of chemistry, at its inception as a science, began precisely as the chemistry of aqueous solutions of substances. It is sometimes considered as an ampholyte - both an acid and a base at the same time (cation H+ anion OH-). In the absence of foreign substances in water, the concentration of hydroxide ions and hydrogen ions (or hydronium ions) is the same, pKa ≈ approx. 16.
Water itself is relatively inert under normal conditions, but its highly polar molecules solvate ions and molecules and form hydrates and crystalline hydrates. Solvolysis, and in particular hydrolysis, occurs in living and nonliving 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:
Hydrogen oxide
Hydrogen hydroxide
Dihydrogen monoxide
Hydroxylic acid
English hydroxic acid
Oxidane
Dihydromonoxide
Types of water.
Water on Earth can exist in three main states - liquid, gaseous and solid, and in turn take on 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 ground. Water can dissolve many substances in itself, acquiring one or another taste. Because of the importance of water “as a source of life,” it is often divided into types.
Characteristics of waters: according to the characteristics of their origin, composition or application, they are distinguished, among other things:
Soft water and hard water - according to the content of calcium and magnesium cations
The groundwater
Melt water
Fresh water
Sea water
Brackish water
Mineral water
Rainwater
Drinking water, Tap water
Heavy water, deuterium and tritium
Distilled water and deionized water
Wastewater
Storm water or surface water
By isotopes of the molecule:
Light water (just water)
Heavy water (deuterium)
Super heavy water (tritium)
Imaginary water (usually with fairy-tale properties)
Dead water - a type of water from fairy tales
Living water - a type of water from fairy tales
Holy water is a special type of water according to religious teachings
Polywater
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 a roughly 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 found in the oceans. Approximately 2.1% of water is concentrated in polar ice and glaciers. All fresh water in lakes, rivers and groundwater is only 0.6%. The remaining 0.1% of water is composed of salt water from wells and saline waters.
The 20th century is characterized by 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, and the 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 non-waste technological processes, and a reduction in air and water pollution. Security environment is a very multifaceted problem, the solution of which is addressed, in particular, by engineers and technical workers of almost all specialties who are associated with economic activities in populated areas and industrial enterprises, which can be a source of pollution mainly in the air and water environment.
Water environment. The aquatic environment includes surface and groundwater.
Surface water is mainly concentrated in the ocean, containing 1 billion 375 million cubic kilometers - about 98% of all water on Earth. The ocean surface (water area) is 361 million square kilometers. It is approximately 2.4 times more area land territory, occupying 149 million square kilometers. The water in the ocean is salty, and most of it (more than 1 billion cubic kilometers) maintains a constant salinity of about 3.5% and a temperature of approximately 3.7oC. Noticeable differences in salinity and temperature are observed almost exclusively in the surface layer of water, 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.
Groundwater can be saline, brackish (less salinity) and fresh; existing geothermal waters have an elevated temperature (more than 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 share of it (only 0.36%) is available in places that are easily accessible for extraction. Most of the fresh water is contained in snow and freshwater icebergs found in areas mainly in the Antarctic Circle. The annual global 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 river flow in Russia, amounting to about 5,000 cubic kilometers, falls on the infertile and sparsely populated northern territories. In the absence of fresh water, salty surface or underground water is used, desalinating it or hyperfiltrating it: passing it under a high pressure difference through polymer membranes with microscopic holes that trap salt molecules. Both of these processes are very energy-intensive, so an interesting proposal is to use freshwater icebergs (or parts thereof) as a source of fresh water, which for this purpose are towed through the water to shores that do not have fresh water, where they are organized to melt. According to preliminary calculations by the developers of this proposal, obtaining fresh water will be approximately half as energy intensive as 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, and tuberculosis, are also transmitted through the air. In order to combat the spread of diseases through water, the World Health Organization (WHO) has declared the current decade the Decade of Drinking Water.
Fresh water. Fresh water 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, water volumes are indicated without cubic meters).
86% of this amount comes from the salty waters of the World Ocean and inland seas - the Caspian. Aralsky and others; the rest evaporates on land, half due to transpiration of moisture by plants. Every year, a layer of water approximately 1250 mm thick evaporates. Some of it falls again with precipitation into the ocean, and some 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 approximately 20% of this energy.
Only 2% of the hydrosphere is fresh water, but it is constantly renewed. The rate of renewal determines the resources available to humanity. 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 amounts to 8000 years. Surface waters on land renew themselves approximately 500 times faster than in the ocean. River waters are renewed even faster, in about 10-12 days. Fresh waters from rivers are of greatest practical importance to humanity.
Rivers have always been a source of fresh water. But in the modern era, they began to transport waste. Waste in the catchment area flows along river beds into the seas and oceans. Most of the used river water is returned to rivers and reservoirs in the form of wastewater. Until now, the growth of wastewater treatment plants has lagged behind the growth of water consumption. And at first glance, this is the root of evil. In reality, 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 the ratio of the absolute amount of wastewater, even purified, and the water flow of rivers is important for people.
The global water balance showed that 2,200 km of water per year is spent on all types of water use. Effluent dilution consumes almost 20% of the world's freshwater resources. Calculations for 2000, assuming that water consumption standards will decrease and treatment will cover all wastewater, showed that 30-35 thousand km of fresh water will still be required annually to dilute wastewater. This means that the world's total river flow resources will be close to exhaustion, and in many areas of the world they are already exhausted. After all, 1 km of treated wastewater “spoils” 10 km of river water, and untreated waste water spoils 3-5 times more. The amount of fresh water does not decrease, but its quality drops sharply and it becomes unsuitable for consumption.
Humanity will have to change its water use strategy. 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 reduction in the volume of water consumption and treated wastewater.
Fresh water reserves are potentially large. However, in any area of the world they can be depleted due to unsustainable water use or pollution. The number of such places is growing, covering entire geographic areas. Water needs are unmet for 20% of the world's urban and 75% of the rural population. The volume of water consumed depends on the region and 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 all water withdrawals, and in India - 1%. The most water-intensive industries are steel, chemicals, petrochemicals, pulp and paper and food processing. They consume almost 70% of all water spent in industry. On average, industry uses approximately 20% of all water consumed worldwide. The main consumer of fresh water is agriculture: 70-80% of all fresh water is used for its needs. Irrigated agriculture occupies only 15-17% of agricultural land, but produces half of all production. Almost 70% of the world's cotton crops depend on irrigation.
The total flow of rivers in the CIS (USSR) per year is 4,720 km. But water resources are distributed extremely unevenly. In the most populated regions, where up to 80% of industrial production resides and 90% of land suitable for agriculture is located, the share of water resources is only 20%. Many areas 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 areas Central Asia, south of Transbaikalia, Central Yakutia. The northern regions of the CIS, the Baltic states, and the mountainous regions of the Caucasus, Central Asia, Sayan Mountains and the Far East are most supplied with water.
River flows vary depending on climate fluctuations. Human intervention in natural processes has already affected 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 from water molecules is converted into organic compounds. To regulate river flow, which is not uniform throughout the year, 1,500 reservoirs were built (they regulate up to 9% of the total flow). Human economic activity has so far had almost no impact on 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 near rivers such as Terek, Don, Dniester and Ural - by 11-20%. Water flow in the Volga, Syr Darya and Amu Darya has noticeably decreased. As a result, the water inflow to the Sea of Azov decreased by 23%, and to the Aral Sea by 33%. The level of the Aral Sea dropped by 12.5 m.
Limited and even scarce freshwater supplies in many countries are being significantly reduced due to pollution. Typically, pollutants are 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 populated areas into them. As a result of wastewater discharge, the physical properties of water change (temperature increases, transparency decreases, color, tastes, and 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, and pathogenic bacteria appear. Polluted water bodies become unsuitable for drinking, and often for technical water supply; lose their fishery significance, etc. The general conditions for the release of wastewater of any category into surface water bodies are determined by their national economic significance and the nature of water use. After the release of wastewater, some deterioration in the quality of water in reservoirs is allowed, but this should not significantly affect its life and the possibility of further use of the reservoir as a source of water supply, for cultural and sports events, or for fishing purposes.
Monitoring the fulfillment of the conditions for discharging industrial wastewater into water bodies is carried out by sanitary-epidemiological stations and basin departments.
Water quality standards for water bodies for household and drinking cultural and domestic water use establish the water quality for reservoirs for two types of water use: the first type includes areas of reservoirs used as a source for centralized or non-centralized household 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 those located within the boundaries of populated areas.
The assignment of reservoirs to one or another type of water use is carried out by the State Sanitary Inspection authorities, taking into account the prospects for the use of reservoirs.
The water quality standards for reservoirs given in the rules apply to sites located on flowing reservoirs 1 km above the nearest water use point downstream, and on non-flowing reservoirs and reservoirs 1 km on both sides of the water use point.
Much attention is paid to the prevention and elimination of pollution of coastal areas of the seas. The seawater quality standards that must be ensured when discharging wastewater apply to the water use area within the designated boundaries and to sites at a distance of 300 m to the sides from these boundaries. When using coastal areas of the seas as a recipient of industrial wastewater, the content of harmful substances in the sea should not exceed the maximum permissible concentrations established by sanitary-toxicological, general sanitary and organoleptic limiting hazard indicators. At the same time, the requirements for wastewater discharge are differentiated in relation to the nature of water use. The sea is considered not as a source of water supply, but as a therapeutic, health-improving, cultural and everyday factor.
Pollutants entering rivers, lakes, reservoirs and seas make significant changes to 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, occurring under the influence of natural factors, water sources undergo a complete or partial restoration of their original properties. In this case, secondary decay products of contaminants may be formed, which have a negative impact on water quality.
Self-purification of water in reservoirs is a set 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 wastewater from industrial enterprises may contain specific contaminants, their discharge into the city drainage network is limited by a number of requirements. Industrial wastewater released into the drainage network must 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 500 mg/l of suspended and floating substances; contain substances that can clog networks or deposit on pipe walls; contain flammable impurities and dissolved gaseous substances capable of forming explosive mixtures; contain harmful substances that interfere with the biological treatment of wastewater or discharge into a body of water; have a temperature above 40 °C.
Industrial wastewater that does not meet these requirements must be pre-treated and only then discharged into the city drainage network.
Table 1
World water reserves
|
Name of objects |
Distribution area in million cubic km |
Volume, thousand cubic meters km |
Share in world reserves, |
|
|
World Ocean |
||||
|
The groundwater |
||||
|
including underground: fresh waters |
||||
|
Soil moisture |
||||
|
Glaciers and permanent snow |
||||
|
Underground ice |
||||
|
Lake water |
||||
|
Swamp water |
||||
|
River water |
||||
|
Water in the atmosphere |
||||
|
Water in organisms |
||||
|
Total water reserves |
||||
|
Total fresh water reserves |
Conclusion.
Water is one of the main resources on Earth. It is difficult to imagine what would happen to our planet if fresh water disappeared. A person needs to drink about 1.7 liters of water per day. And each of us needs about 20 times more daily for washing, cooking, and so on. The threat of fresh water disappearance 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 Doctor of Biological Sciences B.F. Sergeev began his book “Entertaining Physiology” with a chapter about water - “The Substance that Created Our Planet.”
Scientists are right: there is no substance on Earth more important for us than ordinary water, and at the same time, there is no other substance of the same type whose properties would have as many contradictions and anomalies as its properties.
Bibliography:
Korobkin V.I., Peredelsky L.V. Ecology. Textbook for universities. - Rostov/on/Don. Phoenix, 2005.
Moiseev N. N. Interaction of nature and society: global problems // Bulletin of the Russian Academy of Sciences, 2004. T. 68. No. 2.
Environmental protection. Textbook manual: In 2t / Ed. V. I. Danilov - Danilyan. – M.: Publishing house MNEPU, 2002.
Belov S.V. Environmental protection / S.V. Belov. – M. Higher School, 2006. – 319 p.
Derpgolts V.F. Water in the Universe. - L.: "Nedra", 2000.
Krestov G. A. From crystal to solution. - L.: Chemistry, 2001.
Khomchenko G.P. Chemistry for those entering universities. - M., 2003
Water as the information basis of living systems (ordinary and extraordinary water)
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Abnormal properties water
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Without water life on our planet could not exist. Water important for living organisms for two reasons. Firstly, it is a necessary component of living cells, and, secondly, for many organisms it also serves as a habitat. Only drinking water has value for humans. To obtain drinking water, they are used to purify it from harmful impurities and make it suitable for drinking and cooking. That is why a few words should be said about its chemical and physical properties.
These properties are quite unusual and are mainly due to the small size of the molecules. water, their polarity and ability to connect with each other through hydrogen bonds. Polarity refers to the uneven distribution of charges in a molecule. In water, one end of the molecule (the "pole") carries a small positive charge and the other a negative charge. Such a molecule is called a dipole. The oxygen atom has a stronger ability to attract electrons than hydrogen atoms, so the oxygen atom in a water molecule tends to attract electrons from two hydrogen atoms. Electrons are negatively charged, causing the oxygen atom to have a slight negative charge and the hydrogen atoms to have a slight positive charge.
As a result, between water molecules A weak electrostatic interaction occurs and, since opposite charges attract, the molecules seem to “stick together.” These interactions, weaker than ordinary ionic or covalent bonds, are called hydrogen bonds. Hydrogen bonds are constantly formed, broken and re-formed in the water column. And although these are weak bonds, their combined effect determines many of the unusual physical properties of water. Considering this feature water, we can now move on to consider those of its properties that are important from biological point vision.
Hydrogen bonds between water molecules. A. Two water molecules connected by a -6+ hydrogen bond - a very small positive charge; 6~ is a very small negative charge. B. A network of water molecules held together by hydrogen bonds. Such structures are constantly formed, disintegrated and re-emerged in liquid water.Biological significance of water
Water as a solvent. Water- an excellent solvent for polar substances. These include ionic compounds, such as salts, containing charged particles (ions), and some non-ionic compounds, such as sugars, in the molecule of which there are polar (weakly charged) groups (in sugars, this is the hydroxyl group, -OH, which carries a small negative charge). When a substance dissolves in water, water molecules surround ions and polar groups, separating the ions or molecules from each other.
In solution, molecules or ions are able to move more freely, so the reactivity of the substance increases. For this reason, most chemical reactions in the cell take place V aqueous solutions . Non-polar substances, such as lipids, are repelled by water and in its presence are usually attracted to each other, in other words, non-polar substances are hydrophobic (hydrophobic - water repellent). Such hydrophobic interactions play an important role in the formation of membranes, as well as in determining the three-dimensional structure of many protein molecules, nucleic acids and other cellular components.
Inherent water properties solvent also means that water serves as a medium for the transport of various. It performs this role in the blood, in the lymphatic and excretory systems, in the digestive tract and in the phloem and xylem of plants.
PRINCIPAL ABSTRACT COMPILER
PETRUNINA
ALLA
BORISOVNA
MUNICIPAL EDUCATIONAL SCHOOL
SECONDARY SCHOOL №4
ABSTRACT
in chemistry on the topic:
“Water and its properties”
Performed :
student 11 "B" class
Petrunina Elena
PENZA 2001
Water- a substance familiar and unusual. The famous Soviet scientist Academician I.V. Petryanov called his popular scientific book about water “The Most Extraordinary Substance in the World.” And Doctor of Biological Sciences B.F. Sergeev began his book “Entertaining Physiology” with a chapter about water - “The Substance that Created Our Planet.”
Scientists are right: there is no substance on Earth more important for us than ordinary water, and at the same time, there is no other substance of the same type whose properties would have as many contradictions and anomalies as its properties.
Almost ¾ of the surface of our planet is occupied by oceans and seas. Hard water - snow and ice - covers 20% of the land. Of the total amount of water on Earth, equal to 1 billion 386 million cubic kilometers, 1 billion 338 million cubic kilometers are the share of salty waters of the World Ocean, and only 35 million cubic kilometers are the share of fresh waters. The total amount of ocean water would be enough to cover the globe with a layer of more than 2.5 kilometers. For every inhabitant of the Earth there is approximately 0.33 cubic kilometers of sea water and 0.008 cubic kilometers of fresh water. But the difficulty is that the vast majority of fresh water on Earth is in a state that makes it difficult for humans to access. Almost 70% of fresh water is contained in the ice sheets of polar countries and in mountain glaciers, 30% is in aquifers underground, and only 0.006% of fresh water is contained in the beds of all rivers.
Water molecules have been discovered in interstellar space. Water is part of comets, most planets in the solar system and their satellites.
Isotopic composition. There are nine stable isotope species of water. Their average content in fresh water is as follows: 1 H216 O – 99.73%, 1 H218 O – 0.2%,
1 H217 O – 0.04%, 1 H2 H16 O – 0.03%. The remaining five isotopic species are present in water in negligible quantities.
Molecule structure. As is known, the properties of chemical compounds depend on what elements their molecules are made of and change naturally. Water can be thought of as either hydrogen oxide or oxygen hydride. The hydrogen and oxygen atoms in the water molecule are located at the corners of an isosceles triangle with an O–H bond length of 0.957 nm; bond angle H – O – H 104o 27’.
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 |
But since both hydrogen atoms are located on the same side of the oxygen atom, the electrical charges in it are dispersed. The water molecule is polar, which is the reason for the special interaction between its different molecules. The hydrogen atoms in a water molecule, having a partial positive charge, interact with the electrons of the oxygen atoms of neighboring molecules. This chemical bond is called water. It combines water molecules into unique polymers with a spatial structure. About 1% water dimers are present in water vapor. The distance between oxygen atoms is 0.3 nm. In the liquid and solid phases, each water molecule forms four hydrogen bonds: two as a proton donor and two as a proton acceptor. The average length of these bonds is 0.28 nm, the H – O – H angle tends to 1800. The four hydrogen bonds of the water molecule are directed approximately to the vertices of a regular tetrahedron.
The structure of ice modifications is a three-dimensional grid. In modifications existing with low pressures, the so-called ice - I, the H - O - H bonds are almost straight and directed towards the vertices of a regular tetrahedron. But at high pressures, ordinary ice can be transformed into the so-called ice-II, ice-III, and so on - heavier and denser crystalline forms of this substance. The hardest, densest and most refractory so far are ice - VII and ice - VIII. Ice – VII was obtained under a pressure of 3 billion Pa, it melts at a temperature of + 1900 C. In modifications – ice – II – ice – VI – the H – O – H bonds are curved and the angles between them differ from the tetrahedral one, which causes an increase in density along compared to density regular ice. Only in the ice-VII and ice-VIII modifications is the highest packing density achieved: in their structure, two regular networks built from tetrahedra are inserted into one another, while maintaining a system of straight hydrogen bonds.
A three-dimensional network of hydrogen bonds, built from tetrahedra, also exists in liquid water throughout the entire range from the melting point to the critical temperature of + 3.980C. The increase in density during melting, as in the case of dense modifications of ice, is explained by the curvature of hydrogen bonds.
The curvature of hydrogen bonds increases with increasing temperature and pressure, which leads to an increase in density. On the other hand, when heated, the average length of hydrogen bonds becomes larger, resulting in a decrease in density. The combined effect of two facts explains the presence of a maximum density of water at a temperature of + 3.980C.
Physical properties waters are anomalous, which is explained by the above data on the interaction between water molecules.
Water is the only substance on Earth that exists in nature in all three states of aggregation - liquid, solid and gaseous.
Melting of ice at atmospheric pressure is accompanied by a decrease in volume by 9%. The density of liquid water at temperatures close to zero is greater than that of ice. At 00C, 1 gram of ice occupies a volume of 1.0905 cubic centimeters, and 1 gram of liquid water occupies a volume of 1.0001 cubic centimeters. And ice floats, which is why bodies of water usually do not freeze through, but are only covered with ice.
The temperature coefficient of volumetric expansion of ice and liquid water is negative at temperatures below - 2100C and + 3.980C, respectively.
The heat capacity during melting almost doubles and in the range from 00C to 1000C is almost independent of temperature.
Water has unusually high melting and boiling points compared to other hydrogen compounds of elements main subgroup Group VI of the periodic table.
hydrogen telluride hydrogen selenide hydrogen sulfide water
N 2 Those N 2 S e N 2 S H2 O
t melting - 510С - 640С - 820С 00С
_____________________________________________________
boiling point - 40C - 420C - 610C 1000C
_____________________________________________________
Additional energy must be supplied to loosen and then destroy hydrogen bonds. And this energy is very significant. This is why the heat capacity of water is so high. Thanks to this feature, water shapes the climate of the planet. Geophysicists claim that the Earth would have cooled long ago and turned into a lifeless piece of stone if it were not for water. When it heats up, it absorbs heat, and when it cools down, it releases it. Earth's water both absorbs and returns a lot of heat, and thereby “evens out” the climate. The formation of the climate of the continents is especially noticeably influenced by sea currents, forming closed circulation rings in each ocean. Most shining example– the influence of the Gulf Stream, a powerful system of warm currents coming from the Florida Peninsula to North America to Spitsbergen and Novaya Zemlya. Thanks to the Gulf Stream, the average January temperature on the coast of Northern Norway, above the Arctic Circle, is the same as in the steppe part of Crimea - about 00C, i.e. increased by 15 - 200C. And in Yakutia at the same latitude, but far from the Gulf Stream - minus 400C. And those water molecules that are scattered in the atmosphere - in clouds and in the form of vapors - protect the Earth from cosmic cold. Water vapor creates a powerful “greenhouse effect”, which traps up to 60% of the thermal radiation of our planet and prevents it from cooling. According to M.I. Budyko’s calculations, if the water vapor content in the atmosphere was halved, the average temperature of the Earth’s surface would drop by more than 50C (from 14.3 to 90C). The mitigation of the earth's climate, in particular the equalization of air temperature in the transition seasons - spring and autumn, is noticeably influenced by the huge values of the latent heat of melting and evaporation of water.
But this is not the only reason why we consider water a vital substance. The fact is that the human body is almost 63–68% water. Almost all biochemical reactions in every living cell are reactions in aqueous solutions. With water, toxic wastes are removed from our body; Water secreted by sweat glands and evaporating from the surface of the skin regulates our body temperature. Representatives of the animal and flora contain the same abundance of water in their bodies. Some mosses and lichens contain the least amount of water, only 5–7% of their weight. Most of the world's inhabitants and plants consist of more than half water. For example, mammals contain 60 – 68%; fish – 70%; algae – 90 – 98% water.
Most of the processes occur in solutions (mostly aqueous). technological processes at chemical industry enterprises, in production medicines and food products.
It is no coincidence that hydrometallurgy - the extraction of metals from ores and concentrates using solutions of various reagents - has become an important industry.
Water is an important source of energy resources. As is known, all hydroelectric power stations in the world, from small to large, convert the mechanical energy of the water flow into electrical energy exclusively with the help of water turbines with electric generators connected to them. At nuclear power plants, a nuclear reactor heats water, water steam rotates a turbine with a generator and produces electricity.
Water, despite all its anomole properties, is the standard for measuring temperature, mass (weight), amount of heat, and terrain altitude.
Swedish physicist Anders Celsius, a member of the Stockholm Academy of Sciences, created a centigrade thermometer scale in 1742, which is now used almost everywhere. The boiling point of water is designated 100, and the melting point of ice is 0.
During the development of the metric system, established by decree of the French revolutionary government in 1793 to replace various ancient measures, water was used to create the basic measure of mass (weight) - kilogram and gram: 1 gram, as is known, is the weight of 1 cubic centimeter (milliliter) pure water at the temperature of its highest density - 40C. Therefore, 1 kilogram is the weight of 1 liter (1000 cubic centimeters) or 1 cubic decimeter of water: and 1 ton (1000 kilograms) is the weight of 1 cubic meter of water.
Water is also used to measure the amount of heat. One calorie is the amount of heat required to heat 1 gram of water from 14.5 to 15.50C.
All heights and depths on the globe are measured from sea level.
In 1932, the Americans G. Urey and E. Osborne discovered that even the purest water that can be obtained in the laboratory contains a small amount of some substance, apparently expressed by the same chemical formula H2 O, but having a molecular weight of 20 instead of the weight of 18 inherent in ordinary water. Yuri called this substance heavy water. The large weight of heavy water is explained by the fact that its molecules consist of hydrogen atoms with double the atomic weight compared to ordinary hydrogen atoms. The double weight of these atoms, in turn, is due to the fact that their nuclei contain, in addition to the single proton that makes up the nucleus of ordinary hydrogen, one more neutron. The heavy isotope of hydrogen is called deuterium.
(D or 2 H), and ordinary hydrogen began to be called protium. Heavy water, deuterium oxide, is expressed by the formula D2 O.
Soon, a third, superheavy isotope of hydrogen with one proton and two neutrons in the nucleus was discovered, which was named tritium (T or 3H). When combined with oxygen, tritium forms superheavy water T2O with a molecular weight of 22.
Natural waters contain on average about 0.016% heavy water. Heavy water looks similar to ordinary water, but in many ways physical properties different from her. The boiling point of heavy water is 101.40C, the freezing point is + 3.80C. Heavy water is 11% heavier than ordinary water. The specific gravity of heavy water at a temperature of 250C is 1.1. It dissolves various salts worse (by 5–15%). In heavy water, the rate of occurrence of some chemical reactions is different than in ordinary water.
And physiologically, heavy water affects living matter differently: unlike ordinary water Having life-giving power, heavy water is completely inert. Plant seeds, if watered with heavy water, do not germinate; tadpoles, microbes, worms, fish cannot exist in heavy water; If animals are given only heavy water to drink, they will die of thirst. Heavy water is dead water.
There is another type of water that differs in physical properties from ordinary water - this is magnetized water. Such water is obtained using magnets mounted in the pipeline through which the water flows. Magnetized water changes its physical and chemical properties: the rate of chemical reactions in it increases, the crystallization of dissolved substances accelerates, the aggregation of solid particles of impurities increases and their precipitation with the formation of large flakes (coagulation). Magnetization is successfully used at waterworks when the water taken in is highly turbid. It also allows for the rapid sedimentation of contaminated industrial wastewater.
From chemical properties water, the ability of its molecules to dissociate (decay) into ions and the ability of water to dissolve substances of different chemical nature are especially important.
The role of water as the main and universal solvent is determined primarily by the polarity of its molecules and, as a consequence, by its extremely high dielectric constant. Opposite electric charges, and in particular ions, are attracted to each other in water 80 times weaker than they would be attracted in air. The forces of mutual attraction between molecules or atoms of a body immersed in water are also weaker than in air. In this case, it is easier for thermal movement to break up the molecules. This is why dissolution occurs, including of many sparingly soluble substances: a drop wears away a stone.
Only a small fraction of molecules (one in 500,000,000) undergo electrolytic dissociation according to the following scheme:
H2 + 1/2 O2 H2 O -242 kJ/mol for steam
286 kJ/mol for liquid water
At low temperatures in the absence of catalysts it occurs extremely slowly, but the reaction rate increases sharply with increasing temperature, and at 5500C it occurs explosively. As pressure decreases and temperature increases, the equilibrium shifts to the left.
Under the influence of ultraviolet radiation, water photodissociates into H+ and OH- ions.
Ionizing radiation causes radiolysis of water with the formation of H2; H2 O2 and free radicals: H*; HE*; ABOUT* .
Water is a reactive compound.
Water is oxidized by atomic oxygen:
H2 O + C CO + H2
At elevated temperatures in the presence of a catalyst, water reacts with CO; CH4 and other hydrocarbons, for example:
6H2 O + 3P 2HPO3 + 5H2
Water reacts with many metals to form H2 and the corresponding hydroxide. With alkali and alkaline earth metals (except Mg), this reaction occurs already at room temperature. Less active metals decompose water at elevated temperatures, for example, Mg and Zn - above 1000C; Fe – above 6000С:
2Fe + 3H2 O Fe2 O 3 + 3H2
When many oxides react with water, they form acids or bases.
Water can serve as a catalyst, for example, alkali metals and hydrogen react with CI2 only in the presence of traces of water.
Sometimes water is a catalytic poison, for example, for an iron catalyst in the synthesis of NH3.
The ability of water molecules to form three-dimensional networks of hydrogen bonds allows it to form gas hydrates with inert gases, hydrocarbons, CO2, CI2, (CH2)2 O, CHCI3 and many other substances.
Until about the end of the 19th century, water was considered a free, inexhaustible gift of nature. It was only lacking in sparsely populated desert areas. In the 20th century, the view of water changed dramatically. As a result of the rapid growth of the world's population and the rapid development of industry, the problem of supplying humanity with clean fresh water has become almost the number one global problem. Currently, people use about 3,000 billion cubic meters of water annually, and this figure is continuously growing rapidly. In many densely populated industrial areas, clean water is no longer available.
The lack of fresh water on the globe can be compensated for in various ways: by desalinating sea water, and also replacing fresh water with it, where technically possible; purify wastewater to such an extent that it can be safely discharged into reservoirs and watercourses without fear of contamination, and reused; Use fresh water sparingly, creating a less water-intensive production technology, replacing, where possible, high-quality fresh water with lower-quality water, etc.
WATER IS ONE OF THE MAIN RICH TASTS OF HUMANITY ON THE EARTH.
BIBLIOGRAPHY:
1. Chemical encyclopedia. Volume 1. Editor I.L. Knunyants. Moscow, 1988.
2. Encyclopedic dictionary of a young chemist. Compiled by
V.A. Kritsman, V.V. Stanzo. Moscow, “Pedagogy”, 1982.
“Gidrometeoizdat”, 1980.
4. The most extraordinary substance in the world. Author
I.V. Petryanov. Moscow, “Pedagogy”, 1975.
P L A N.
I. Introduction.
Statements by famous scientists about water.
II .Main part.
1.Distribution of water on planet Earth, in space
space.
2. Isotopic composition of water.
3.Structure of the water molecule.
4. Physical properties of water, their anomalies.
a).Aggregative states of water.
b).The density of water in solid and liquid states.
c).Heat capacity of water.
d). Melting and boiling points of water compared to
other hydrogen compounds of elements
main subgroup YI group of the periodic table.
5. The influence of water on the formation of climate on the planet
6.Water as the main component of plant and
animal organisms.
7.Use of water in industry, production
electricity.
8.Use water as a standard.
a).To measure temperature.
b).To measure mass (weight).
c).To measure the amount of heat.
d).To measure the height of the terrain.
9.Heavy water, its properties.
10. Magnetized water, its properties.
11. Chemical properties of water.
a).Formation of water from oxygen and hydrogen.
b).Dissociation of water into ions.
c).Photodissociation of water.
d).Radiolysis of water.
d).Oxidation of water with atomic oxygen.
f).The interaction of water with non-metals, halogens,
hydrocarbons.
g).Interaction of water with metals.
h).Interaction of water with oxides.
i).Water as a catalyst and inhibitor of chemicals
III .Conclusion.
Water is one of the main resources of humanity on Earth.
Introduction……………………………………………………………………………….3
Main part
1. Properties of water………………………………………………………5
2. Structure of a water molecule…………………………………………….10
Conclusion…………………………………………………………………………………12
Bibliography……………………………………………………………13
Appendix…………………………………………………………………………………14
Introduction
Water is one of the most common substances in nature (the hydrosphere occupies 71% of the Earth's surface). Water plays a vital role in geology and the history of the planet. Without water, living organisms cannot exist. The fact is that the human body is almost 63% - 68% water. Almost all biochemical reactions in every living cell are reactions in aqueous solutions. Most technological processes take place in solutions (mainly aqueous) at chemical industry enterprises, in the production of medicines and food products. And in metallurgy, water is extremely important, and not only for cooling. It is no coincidence that hydrometallurgy - the extraction of metals from ores and concentrates using solutions of various reagents - has become an important industry.
Water is an ordinary 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 “Entertaining Physiology,” written by Doctor of Biological Sciences B.F. Sergeev, begins with a chapter about water - “The Substance that Created Our Planet.”
Scientists are absolutely 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 whose properties would have as many contradictions and anomalies as its properties.
Almost ⅔ of the surface of our planet is occupied by oceans and seas. Hard water - snow and ice - covers 20% of the land. The climate of the planet depends on water. Geophysicists claim that the Earth would have cooled long ago and turned into a lifeless piece of stone if it were not for water. It has a very high heat capacity. When heated, it absorbs heat; cooling down, he gives it away. Earth's water both absorbs and returns a lot of heat and thereby “evens out” the climate. And what protects the Earth from cosmic cold are those water molecules that are scattered in the atmosphere - in clouds and in the form of vapor...
Properties of water
The properties of water, thanks to which life arose, have been most fully studied. These properties made it possible for living nature to exist in the temperature range that is characteristic of the Earth as a cosmic body.
What are these properties?
Density of water.
One of the most important properties water - its density. Fresh water has its maximum density at 4 °C. At this temperature, one kilogram of water occupies a minimum volume (Fig. 1). When the temperature drops from 4 °C to 0, the density decreases, i.e., water with a temperature of 4 °C is at the bottom, and colder water rises to the top, where it freezes, turning into ice.
The density of ordinary ice - the solid crystalline phase of water - is less than the density of water, so the ice floats on the surface, protecting the water from further cooling. It acts as an ice “coat” that protects the freshwater body from complete freezing. In this way, conditions are created for the inhabitants of reservoirs to live at low temperatures.
Seawater has a significant amount of salts dissolved in it, and it behaves completely differently when cooled. Its freezing point depends on the salt content, but on average it is 1.9°C. The maximum density of such water is at a temperature of -3.5°C. Sea water turns into ice before reaching its maximum density. Therefore, vertical mixing of seawater occurs when it is cooled from above-zero temperatures to freezing temperatures. Thanks to this circulation, the lower horizons of the ocean are enriched with oxygen, and water rich in oxygen enters the upper layers from the lower ones. nutrients. It should be noted that both sea and fresh ice are lighter than water and float on its surface, protecting deep layers of water in the seas and oceans from direct contact with cold air masses and thereby contributing to the conservation of heat. At the same time, various modifications of ice were obtained artificially at high pressure. Some of them are heavier than water, others melt and therefore freeze at high temperatures. This is the so-called “hot ice”. Therefore, we are all lucky not only with the presence of water on Earth and solar radiation, but also with the value of atmospheric pressure. Otherwise, the entire Earth could be bound by an ice shell.
Thermodynamic constants of water.
Water has special, anomalous properties. First of all, this concerns such thermodynamic constants as the heat capacity of water, the heat of vaporization, and the latent heat of melting of ice. The anomalous nature of these quantities determines the majority of physicochemical and biological processes on Earth.
The specific heat capacity of water is 4.1868 kJ/(kg-K), which is almost twice the specific heat capacity of substances such as ethyl alcohol (2.847), vegetable oil(2.091), paraffin (2.911) and many others. This means that when heated by the same number of degrees, water can absorb almost twice as much heat as the listed liquids. But even when cooling, water gives off more heat than other liquids. Therefore, when the waters of the World Ocean warm up under the influence sun rays and their cooling in the absence of solar radiation energy, heat capacity acts as a property that ensures minimal fluctuations in water temperature day and night, summer and winter.
The heat of vaporization of water has an abnormally high value. This value is more than twice the heat of vaporization of ethanol, sulfuric acid, aniline, acetone and other substances. Therefore, even in the hottest time, water evaporates extremely slowly, which contributes to its preservation and, consequently, the preservation of life on Earth.
The high value of the latent heat of fusion of ice also ensures the stability of the temperature regime on the planet.
One of interesting properties water is that its lowest heat capacity occurs at a temperature of 37 °C, which means that at this temperature minimal energy costs are required to change it. This is probably why the body temperature of warm-blooded creatures is close to this value.
Water has abnormally high values of other constants. Substances formed by the combination of hydrogen with oxygen, sulfur, selenium, and tellurium, which are in the same row of the periodic table, are called hydrides. Oxygen hydride is called water. The unusual properties of oxygen hydride, compared to the properties of other hydrides, is that, unlike them, water under normal conditions (at normal pressure and temperature from 0 to 100 ° C) is in a liquid state, and not in a gaseous state. If water did not have anomalous boiling and freezing temperatures, then these processes would occur at significantly lower negative temperatures, and liquid water would be present on colder planets. And therefore, there would be no life on Earth.
The force of surface tension of water.
There are other special properties of water that allow us to call it a truly amazing compound. We are talking about the surface tension of a liquid. The forces of interaction between the molecules that make up water attract them to each other, and breaking this bond is not so easy. Most people know the school experience when a needle, carefully placed in a saucer of water, floats to the surface. Many have seen an interesting trick when a significant number of coins are dropped into a full glass of water and the water, without overflowing, rises in a small dome. Finally, there is a well-known biblical legend about how Christ walked on water. All these phenomena and legends are associated with the high surface tension of water. Thanks to surface tension, water rises through capillary channels in the soil to the surface of the Earth and enters the tissues and cells of plants and living organisms. Of all the known liquids, only mercury has a higher surface tension than water.
Very famous interesting feature water associated with the propagation of sound waves in it. The speed of sound propagation in water is abnormally high, it exceeds the speed of sound propagation in air by almost 6 times.
Properties of pure water.
Pure water is a clear, colorless and odorless liquid. At a pressure of 1 atm, water freezes at a temperature of 0 and boils at 100 °C. When the pressure is doubled, water boils at a temperature of 120 °C, and when the pressure is halved, it boils at 81 °C. However, as pressure decreases, the melting point of ice (or the freezing point of water) increases. At low pressures, water can only exist in the form of ice or steam, and at high temperatures - only in the form of steam. There are also critical values for water pressure and temperature. At pressures above 22.1 atm. and temperatures above 374.4°C, the difference between liquid and steam disappears; water exists in a gaseous state.
Amazing values of atmospheric pressure and temperature have developed on Earth, since it is at these values that water is present on the planet in liquid form, ensuring the development of all existing forms of life. At these parameters, oxygen is dissolved in water, which is necessary for the life of aquatic organisms, as well as for the processes of self-purification of water. For many millennia, the presence of the atmosphere, hydrosphere and solar radiation created a slight temperature difference in summer and winter, day and night, providing conditions for the existence of life.
The ability of water to dissolve.
However, the most amazing feature of water is its ability to dissolve other substances. The ability of substances to dissolve depends on their dielectric constant. The higher it is, the more capable the substance is of dissolving others. So, for water this value is 9 times higher than for air or vacuum. Therefore, fresh or clean waters are practically never found in nature. There is always something dissolved in earth's water. These can be gases, molecules or ions of chemical elements. It is believed that all elements of the table of the periodic table of elements can be dissolved in the waters of the World Ocean; at least, more than 80 of them have been discovered today.
Structure of a water molecule
These two elements - hydrogen and oxygen - are antagonists. One of them dominates in Space, the other on Earth. One (hydrogen) seeks to give away a single electron from its electron shell, and the other (oxygen) seeks to gain two electrons from other chemical elements.
Analyzing the composition of a water molecule, we can say that two hydrogen atoms and one oxygen atom “found each other” in it. Thus, in the composition of water, the chemical formula of which is written as H2 0, nine different stable types of water can theoretically be present (the number of permutations from 5 to 3). However, 99.97% of all water in the hydrosphere is represented by ordinary water of the type 1 H216 0. The share of heavy water 2 H216 0 is less than 0.02%.
Modern science Several models are known that can be used to resolve many anomalous properties of water. It is believed that some properties are determined by the number of associations of molecules of monomers (H2 O)1, dimers (H2 O)2 and trimers (H2 O)3, which are predominantly present in water at different temperatures.
Thus, at a temperature of about 0, there are mainly trimers in water, at a temperature of about 4 ° C - dimers, and in the gaseous state, water contains mainly monomers. Sometimes these associations are called trihydrols.
Some scientists propose to consider water as a set of associations of molecules, including from one to eight molecules in each association. Others believe that the structure of water is a spatial “lace” formed by various “shimmering clusters” (Fig. 2). Still others propose to study the properties of water, taking into account the structural features of its molecule, which, in turn, are determined by the characteristics of the elements that make up the water molecule. According to modern ideas, a water molecule is like a small magnet.
Why are there dissolved substances in water?
Danish scientist N. Bjerrum in 1951 proposed a model of a water molecule with a point distribution of charges. In accordance with modern concepts, a water molecule is a tetrahedron (or pyramid, (Fig. 3), in the middle of which is the center of the molecule, and in the corners are electric charges.
Two positive charges correspond to two hydrogen atoms, each of which “provided” its electrons to the oxygen atom, and two negative charges corresponding to “unpaired” electrons of oxygen. Thus, a water molecule is a dipole, one of its poles has a positive charge and the other has a negative charge. The poles of the dipole are separated by some distance, therefore, in an electrostatic field, the water dipole unfolds along the lines of electric field strength. If the electrostatic field is formed by a negatively charged ion, then the water dipole turns its positive pole towards this ion, and vice versa. The properties of water as a solvent are largely determined by the polarized structure of its molecule. The high polarity of molecules is the reason for the activity of water during chemical interactions, during the dissolution of salts, acids and bases in it, i.e. during the formation of electrolytes. Water is capable of dissolving many substances, creating with them homogeneous physical and chemical systems of variable composition. Salts dissolved in natural waters are in an ionic state, that is, they are subjected to electrolytic dissociation.
Conclusion
During course work The properties and structure of the water molecule were considered. Water is an ordinary substance at first glance, but if you look at it in more detail, you can find out a lot of interesting and unusual things. Firstly, water is the source of life on Earth; if there were no water, life would not have arisen. Secondly, the properties that water has are not possessed by any other substance. Water can be in three states of aggregation, at a certain temperature. Water can also take in and give off heat, and evaporate more slowly than other substances. Moreover, sound waves can travel in water and at very high speeds. But the most amazing property of water is its ability to dissolve other substances.
As for the structure of water, it is also unique in its own way. Water consists of two hydrogen atoms and one oxygen atom, we can say that these atoms simply found each other. But scientists still cannot unravel all the structural features of this amazing substance, and much remains a mystery to us all.
This is what a seemingly ordinary substance looks like. But no one thought about it when they encounter water every day, that this is such an unlikely and very unusual substance that contains many unsolved mysteries. But we can’t fully understand them; this is the whole unusualness and peculiarity of water, without which we would never have been born.
Bibliography
1. Akhmetov N.S., Inorganic chemistry. M., 2001
2. Glinka N.L., General chemistry. St. Petersburg, 2003
3. Knunyants I. L., Chemical Encyclopedia. Volume 1. M., 2002.
4. Petryanov I.V., The most extraordinary substance in the world. M., 2005
5. Khomchenko G.P., Chemistry for those entering universities. M., 2002
Application
Russian State Hydrometeorological University
Department of Oceanology
Discipline "Chemistry"
Abstract on the topic: "Properties of water"
Completed Art. gr. O-136
Gusev M.V.
Saint Petersburg
I. Introduction................................................... ........................................................ .............3
II. Main part................................................ ........................................................ .3
Physical properties. ........................................................ .................................4
Heavy (deuterium) water.................................................... .............................5
Magnetized water. ........................................................ ....................................7
Chemical properties of water......................................................... ...............................7
Bibliography: ............................................... ..............................................10
I. Introduction
Almost ¾ of the surface of our planet is occupied by oceans and seas, and about 20% of the land is covered with snow and ice. Of the total amount of water on Earth, equal to 1 billion 386 million cubic kilometers, 1 billion 338 million cubic kilometers are the share of salty waters of the World Ocean, and only 35 million cubic kilometers are the share of fresh waters. Almost 70% of fresh water is contained in the ice sheets of polar countries and in mountain glaciers, 30% is in aquifers underground, and only 0.006% of fresh water is contained in the beds of all rivers.
Water is the only substance on Earth that exists in nature in all three states of aggregation - liquid, solid and gaseous.
Water molecules have been discovered in interstellar space. Water is part of comets, most planets in the solar system and their satellites.
There are nine stable isotope species of water. Their average content in fresh water is as follows:
1 N 2 16 O – 99.73%, 1 N 2 18 O – 0.2%, 1 N 2 17 O – 0.04%, 1 H 2 N 16 O – 0.03%.
The remaining five isotopic species are present in water in negligible quantities.
II. Main part
Molecule structure.
As is known, the properties of chemical compounds depend on what elements their molecules are made of and change naturally. Water can be thought of as either hydrogen oxide or oxygen hydride. The hydrogen and oxygen atoms in the water molecule are located at the corners of an isosceles triangle with an O–H bond length of 0.958 nm; bond angle H – O – H 104 o 27’(104.45 o).
But since both hydrogen atoms are located on the same side of the oxygen atom, the electrical charges in it are dispersed. The water molecule is polar, which is the reason for the special interaction between its different molecules. The hydrogen atoms in a water molecule, having a partial positive charge, interact with the electrons of the oxygen atoms of neighboring molecules (hydrogen bond). It combines water molecules into unique polymers with a spatial structure. In the liquid and solid phases, each water molecule forms four hydrogen bonds: two as a proton donor and two as a proton acceptor. The average length of these bonds is 0.28 nm, the H – O – H angle tends to 180 o. The four hydrogen bonds of the water molecule are directed approximately to the vertices of a regular tetrahedron.
