Etc.), present in the soil, is obligatory. component of all living things.
Isotopic composition. There are 9 stable isotope species of water. Their average content in fresh water is as follows (mol %): 1 H 2 16 O - 99.13; 1 H 2 18 O - 0.2; 1 N 2 17 0-0.04;
1 H 2 O 16 O-0.03; the remaining five isotopic species are present in water in negligible quantities. In addition to stable isotopic species, water contains a small amount of radioactive 3 H 2 (or T 2 O). Isotopic composition of natural water of various origins. varies. The ratio 1 H/2 H is especially variable: in fresh waters - on average 6900, in sea water -5500, in water - 5500-9000. According to physical The properties of D 2 O are noticeably different from ordinary water (see). Water containing 18 O is closer to water with 16 O.
Phys. the properties of water are abnormal. at atm. accompanied by a decrease in volume by 9%. Temperature coef. volumetric expansion and liquid water is negative at t-pax resp. below -210°C and 3.98°C. C° at almost doubles and in the range 0-100°C is almost independent of temperature (there is a minimum at 35°C). Minimum isothermal (44.9*10 -11 Pa -1), observed at 46°C, is expressed quite clearly. At low temperatures up to 30 °C, water drops with increasing temperature. High dielectric The permeability and dipole moment of water determine its good dissolving ability in relation to polar and ionic substances. Due to high C° values, water is an important climate regulator. conditions on the earth, stabilizing the t-ru on its surface. In addition, the proximity of the H-O-H angle to the tetrahedral (109° 28") determines the looseness of structures and liquid water and, as a consequence, an anomalous dependence of density on temperature. Therefore, large bodies of water do not freeze to the bottom, which makes it possible to exist in them life. 
But the density of modifications II-VI is significantly lower than what ice could have at . Only in modifications VII and VIII is a sufficiently high packing density achieved: in their structure, two regular networks built from tetrahedra (similar to those existing in cubic low-temperature Ic, isostructural) are inserted into one another; at the same time, the system of rectilinear and coordinates is preserved. the number doubles and reaches 8. The arrangement in VII and VIII is similar to the arrangement in and many others. In ordinary (Ih) and cubic (Ic), as well as in HI, V-VII, the orientation is not defined: both closest to O form with it, which can. directed to any two of the four adjacent vertices of the tetrahedron. Dielectric the permeability of these modifications is high (higher than that of liquid water). Modifications II, VIII and IX are orientationally ordered; their dielectric permeability is low (approx. 3). VIII is a placement-ordered version of VII, and IX is III. The densities of orientationally ordered modifications (VIII, IX) are close to the densities of the corresponding disordered modifications (VII, III).
Water like . Water dissolves many well. polar and dissociating into substances. Typically, pH increases with increasing temperature, but sometimes the temperature dependence is more complex. So, r-reality is plural. , and when the temperature increases, it decreases or first increases, and then passes through a maximum. The pH value of low-polar substances (including those included in) in water is low and when the temperature rises, it usually first decreases and then passes through a minimum. With increasing p-rate increases, passing through a maximum at high values. Many substances, when dissolved in water, react with it. For example, NH 3 solutions may contain NH 4 (see also). Between dissolved in water,
WATER
A water molecule consists of an oxygen atom and two hydrogen atoms attached to it at an angle of 104.5°.
The angle of 104.5° between the bonds in a water molecule determines the friability of ice and liquid water and, as a consequence, the anomalous dependence of density on temperature. This is why large bodies of water do not freeze to the bottom, which makes life possible in them.
Physical properties
WATER, ICE AND STEAM,respectively, liquid, solid and gaseous states of a chemical compound with the molecular formula H 2 O.
Due to the strong attraction between molecules, water has high melting points (0C) and boiling points (100C). A thick layer of water has a blue color, which is determined not only by its physical properties, but also by the presence of suspended particles of impurities. The water of mountain rivers is greenish due to the suspended particles of calcium carbonate it contains. Pure water is a poor conductor of electricity. The density of water is maximum at 4C; it is equal to 1 g/cm3. Ice has a lower density than liquid water and floats to its surface, which is very important for the inhabitants of reservoirs in winter.
Water has an exceptionally high heat capacity, so it heats up slowly and cools down slowly. Thanks to this, water pools regulate the temperature on our planet.
Chemical properties of water
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.
Under the influence of electric current, water decomposes into hydrogen and oxygen:
2H2O electricity= 2 H 2 + O 2
Video "Electrolysis of water"
- Magnesium reacts with hot water to form an insoluble base:
Mg + 2H 2 O = Mg(OH) 2 + H 2
- Beryllium with water forms an amphoteric oxide: Be + H 2 O = BeO + H 2
1. Active metals are:
Li, Na, K, Rb, Cs, Fr– 1 group “A”
Ca, Sr, Ba, Ra– 2nd group “A”
2. Metal activity series
3. Alkali is a water-soluble base, a complex substance which includes an active metal and a hydroxyl group OH ( I).
4. Medium activity metals in the voltage range range from MgbeforePb(aluminum in special position)
Video "Interaction of sodium with water"
Remember!!!
Aluminum reacts with water like active metals to form a base:
2Al + 6H 2 O = 2Al( OH) 3 + 3H 2
Using the sample, write down the interaction reaction equations:
WITHO2 + H2O =
SO 3 + H 2 O =
Cl 2 O 7 + H 2 O =
P 2 O 5 + H 2 O (hot) =
N 2 O 5 + H 2 O =
Remember! Only oxides of active metals react with water. Oxides of metals of intermediate activity and metals coming after hydrogen in the activity series do not dissolve in water, for example, CuO + H 2 O = reaction is not possible.
Video "Interaction of metal oxides with water"
Li + H 2 O =
Cu + H2O =
ZnO + H2O =
Al + H 2 O =
Ba + H 2 O =
K 2 O + H 2 O =
Mg + H2O =
N 2 O 5 + H 2 O =
Structural formula
True, empirical, or gross formula: H2O
Chemical composition of water
Molecular weight: 18.015
Water (hydrogen oxide) is a binary inorganic compound with the chemical formula H2O. A water molecule consists of two hydrogen atoms and one oxygen atom, which are connected by a covalent bond. Under normal conditions, it is a transparent liquid, colorless (in small volumes), odor and taste. In the solid state it is called ice (ice crystals can form snow or frost), and in the gaseous state it is called water vapor. Water can also exist in the form of liquid crystals (on hydrophilic surfaces). It makes up approximately 0.05% of the Earth's mass.
It is a good highly polar solvent. Under natural conditions, it always contains dissolved substances (salts, gases).
Water under normal conditions is in a liquid state, while similar hydrogen compounds of other elements are gases (H 2 S, CH 4, HF). The hydrogen atoms are attached to the oxygen atom, forming an angle of 104.45° (104°27′). Due to the large difference in electronegativity between hydrogen and oxygen atoms, the electron clouds are strongly biased towards oxygen. For this reason, the water molecule has a large dipole moment (p = 1.84 D, second only to hydrocyanic acid). Each water molecule forms up to four hydrogen bonds - two of them are formed by an oxygen atom and two by hydrogen atoms. The number of hydrogen bonds and their branched structure determine the high boiling point of water and its specific heat of vaporization. If there were no hydrogen bonds, water, based on the place of oxygen in the periodic table and the boiling points of hydrides of oxygen-like elements (sulfur, selenium, tellurium), would boil at −80 °C and freeze at −100 °C.
When transitioning to a solid state, water molecules are ordered, while the volumes of voids between the molecules increase, and the overall density of water decreases, which explains the lower density (larger volume) of water in the ice phase. During evaporation, on the contrary, all hydrogen bonds are broken. Breaking bonds requires a lot of energy, which is why water has the highest specific heat of any liquid or solid. In order to heat one liter of water by one degree, 4.1868 kJ of energy is required. Due to this property, water is often used as a coolant. In addition to its high specific heat capacity, water also has high specific heats of fusion (333.55 kJ/kg at 0 °C) and vaporization (2250 kJ/kg).
Of the hydrogen oxides, the most common on Earth is water. Empirical formula – H2O. Molecular weight – 18. Structure of a water molecule(structural formula):
Water molecules have a triangular formula: hydrogen atoms form an angle of 104.3% with an oxygen atom. Near the oxygen atom, a negatively charged field is formed, since the highest electron density is concentrated on the oxygen atom, and near the hydrogen atoms a positively charged field is formed - a water molecule - a dipole. Due to polarity, water molecules associate by forming hydrogen bonds. The latter determine all the physical properties of water.
Physical properties: water is a colorless liquid, tasteless and odorless, density – 1 g/cm3; freezing temperature – 0 °C (ice), boiling point – 100 °C (steam). At 100 °C and normal pressure, hydrogen bonds are broken and water turns into a gaseous state - steam. Water has poor thermal and electrical conductivity, but good solubility.
Chemical properties: water dissociates slightly:
In the presence of water, hydrolysis of salts occurs - their decomposition by water with the formation of a weak electrolyte:
Interacts with many basic oxides and metals:
With acid oxides:
Receipt: water is formed by the combustion of hydrogen in oxygen: 2H2 + O2 = 2H2O
This reaction occurs instantly at 700 °C. A mixture of two volumes of hydrogen and one volume of oxygen is called explosive mixture. Pure water is obtained by distillation - distilled water.
Finding in nature: water makes up 2/3 of the Earth's surface. Natural water is never pure, because a huge amount of salts are dissolved in it. Water is part of many crystalline hydrates: Na2СО3 ? 10H2O; CuSO4? 5H2O; MgSO4? 7H2O. Heavy water D2O differs from the usual one formed by hydrogen - protium - by the presence in it of a second isotope of hydrogen - D(deuterium), Ar of which is 2, therefore, the molecular weight of heavy water is 20. Density D2O = 1.1050 g/cm3; boiling point – 101.4 °C, freezing point – 3.8 °C. Chemically less active. Used as a neutron moderator in nuclear reactors. It is unsuitable for life processes because it changes the rate of biochemical reactions. Ordinary water contains some heavy water.
Water is the basis of life on our planet. However, what do we know about her? This substance with a simple chemical formula can be studied endlessly. Throughout the centuries-old history of human existence, water has occupied a dominant place. That is why, rushing into the vastness of the Universe, scientists are trying to find sources of water on other planets that would become evidence of biological life. Unfortunately, such attempts are still futile. Despite numerous studies and discoveries, we have not proven the existence of other civilizations that may be many times superior to us in their development.
Water is the basis of our existence
Rarely do any of us ask the question: “What is water?” But without it, human life is simply impossible. Science says that a six-month human embryo consists of 97% water, at birth its amount decreases to 92%, the body
a teenager contains 80% of this substance, in adulthood these figures are 70%, and in old age - only 60%. There is a certain pattern in this that allows us to come into this world young and full of strength and leave it, having lived to a ripe old age. You can adhere to all kinds of diets, completely give up meat, bread and dairy products, but it is impossible to exclude water from your diet. With severe thirst, the volume of water in the body decreases by 5-8%, while the person experiences hallucinations, swallowing function is impaired, vision and hearing are impaired, and fainting occurs. A more serious lack of fluid can cost health and even life. The importance of water for humans is so great that we can no longer imagine our life without this multifunctional substance. And many of us take its presence for granted, forgetting to take care of this life-giving and healing source. Water is a universal solvent for all nutrients and minerals, as well as amino acids and vitamins. It is able to regulate our body temperature, remove waste products and various toxic components from the body. It is with the help of water that our muscles perform their main function - contractility. It is not for nothing that the diet of athletes always contains an increased amount of liquid. What is water in our everyday life? This is one of the basic and irreplaceable food products. Every morning we start with a cup of aromatic coffee or freshly brewed tea, which are simply impossible to prepare without water, like most of your favorite dishes. Scientists have proven that to maintain health, a person should consume up to 2.5 liters of fluid per day - this will ensure good health, activate mental activity and give strength.
Where does water come from?
Our planet contains about 1500 million km 3 of water, of which only 10% is fresh water. Many sources are located under the earth's crust at different depths - this allows them to be divided into underground and
In the bowels of the earth, such pools take the form of peculiar vessels that are surrounded by solid rocks and contain water under high pressure. Reservoirs located at a depth of several meters are widely used as the basis for wells. However, such water is constantly in contact with the top loose layer of soil, which makes it contaminated and not always suitable for economic needs. The glaciers of Antarctica, located in Greenland, are huge sources of fresh water. In addition, precipitation, which is formed due to evaporation from natural sources, plays a major role in our lives. How much fresh water do we get from the World Ocean every year using various physical and chemical methods? It should be noted that most often people use water from lakes and rivers for their needs. Baikal alone is worth it! After all, this is the cleanest and largest natural reservoir located in the vastness of Russia. Such tanks have no value and are a real wonder of the world. More than 6000 km 3 of water is found in living organisms, including plants. In this way, natural water resources are distributed throughout our planet. A person constantly exchanges liquid with nature: through sweat, urine and the release of droplets of liquid with breathing. However, few people ask the question: “What will happen if such mutual exchange stops?” In this case, dehydration will occur - the process We will begin to feel weak, our heart rate will increase, shortness of breath and dizziness will appear. As a result, damage to the nervous and cardiovascular systems can occur, which will lead to the death of our body.
If you look at the Earth from space, you will be amazed at how unreasonably this celestial body was named. The most suitable name for it is Water. It’s not for nothing that astronauts compared the planet to a blue ball, since ultramarine is capable of suppressing all the colors that are inherent in the earth’s surface.
The ocean is the mother of all living organisms, and many scientists insist that the first life could have originated in the aquatic environment. In a relatively small and closed reservoir, certain organic substances could accumulate, which got there with the help of inflowing waters. Such compounds were then concentrated on the inner surface of the layered mineral, which could act as a catalyst for reactions. Subsequently, a new unknown life arose, which people had yet to study. Today, water in nature is considered the most common substance, since more than 70% of the total area of the earth's surface is occupied by natural bodies of water and only about 30% is land. Water is so multifunctional that people have learned to use it in almost all areas of their lives. We all love to bask in the warm sand near the sea and are looking forward to the long-awaited vacation so that we can return to the gentle embrace of playful and gentle sea waves.
Natural water classes
Water happens:
Fresh - 2.5%;
Salty - 97.5%;
In the form of brines.
Considering that approximately 75% of water is frozen on the polar caps and glaciers, about 24% of groundwater is underground, and 0.5% of moisture is dispersed in the soil, it turns out that the cheapest and most accessible source of water for us is lakes , rivers and other land bodies of water. It's scary to think that they only make up about 0.01% of the world's water reserves. Therefore, to the question “what is water?” You can safely answer - this is the most precious treasure of our planet.
Features of water
The chemical formula of water is quite simple - it is a combination of an oxygen atom with two. It would seem that it could be simpler, but there is no substance more mysterious. Water is the only substance that can exist in nature in three states of aggregation: gaseous, solid and liquid, depending on pressure and temperature. This liquid is of great importance for the emergence and maintenance of life processes on Earth, as well as for the formation of climate and relief.
Water is the most mobile substance after air. She is constantly moving, traveling over very long distances. When exposed to solar heat, it occurs from the surface of plants, soil, rivers, reservoirs and seas. This produces water vapor, which collects in clouds and is carried by the wind, after which it falls over various continents in the form of snow or rain. It should be noted that water is capable of giving off heat without a noticeable decrease in its temperature, thereby regulating the climate. The molecular formula of water indicates that this substance has a simple structure, but it is still considered little studied, since there are still many unexplored oddities of this substance, which may contribute to the maintenance of life on Earth.
Physical properties of water
Water, or a chemical substance, appears as a colorless liquid that has neither odor nor taste. Under normal conditions, H2O (water) remains in a liquid aggregate state, while similar hydrogen compounds are gases. All this can be explained by the special characteristics of the atoms that make up the molecules and the presence of bonds between them.
A drop of water consists of molecules that are attracted by opposite poles, thereby forming polar bonds that cannot be broken without effort. Each molecule contains a hydrogen ion, which is so small that it can penetrate the shell of the negative oxygen atom located in the neighboring molecule. As a result, a hydrogen bond is formed. The diagram of water shows that each molecule has a strong bond with four neighboring molecules, two of which are formed by oxygen atoms, and the other two by hydrogen atoms. In addition, water has a high level of this property; it is second only to mercury. The relative viscosity of H2O is determined by the fact that hydrogen compounds do not allow molecules to move at different speeds. For the same reasons, water is considered an excellent solvent, since each molecule of the solute is immediately surrounded by water molecules, and in large quantities. In this case, positively charged molecular regions of a polar substance attract oxygen atoms, and negatively charged ones attract hydrogen atoms.
What does water react with?
These are the following substances:
Active metals (calcium, potassium, sodium, barium and much more);
Halogens (chlorine, fluorine) and interhalogen compounds;
Anhydrides of inorganic and carboxylic acids;
Active organometallic compounds;
Carbides, nitrides, phosphides, silicides, hydrides of active metals;
Silanes, boranes;
Carbon suboxide;
Noble gas fluorides.
What happens when heated?
Water reacts:
With magnesium, iron;
With methane, coal;
With alkyl halides.
What happens in the presence of a catalyst?
Water reacts:
With alkenes;
With acetylene;
With nitriles;
With amides;
With esters of carboxylic acids.
Density of water
The formula for the density of water resembles a parabola with a specific vertex at a temperature of 3.98 degrees. With such indicators, the density of this chemical is 1000 kg/m3. In a reservoir, the density of water is influenced by factors such as temperature, salinity, the presence of salts and the pressure of the upper layers. Science has proven that the higher the temperature, the greater the volume of the substance and the lower its density. Water has the same property, but in the range from 0 o C to 4 o C it does not hold, since with increasing temperature the volume begins to decrease. If there are no dissolved gases in the water, it can be cooled to a temperature of -70 o C without turning into ice. In the same way, you can bring this substance to a temperature of 150 o C and it will not boil. Despite the fact that the formula of water is very simple, its properties have made people worship this powerful element for many millennia.
Health Benefits of Water
All tissues of the human body are made of water: muscles, bones, lungs, heart,
kidneys, liver, skin and adipose tissue. The vitreous body of the eye contains the most fluid, namely 99%, and the least amount, approximately 0.2%, contains tooth enamel. The brain is also rich in water content, since without this substance we will not be able to think and form information. Any biochemical reactions occurring in the body can only proceed optimally with a sufficient supply of water, otherwise end products of metabolism will accumulate in tissues and cells, which will lead to the development of many serious diseases. To avoid this, it is necessary to maintain proper water consumption.
The role of water in the body
Water helps:
Transportation of nutrients, microelements and oxygen to various organs and tissues;
Removal of waste, toxins and salts;
Normalization of heat transfer;
Regulation of hematopoiesis and blood pressure;
Lubricates joints and muscles.
Symptoms of dehydration
When dehydration occurs, the following phenomena occur:
Drowsiness, weakness;
Dry mouth, shortness of breath;
Fever, headache;
Violation of logical thinking, fainting;
Muscle spasms;
Hallucinations;
Dulling of vision and hearing;
Formation of cholesterol plaques, deterioration of blood flow;
Joint pain.
Possible diseases due to dehydration and water intake
The following diseases may develop:
Heartburn, gastritis, constipation;
Formation of gallstones;
Obesity.
It is recommended to drink up to 2.5 liters of fluid daily, including that contained in liquid food. If a person smokes, eats meat, drinks alcohol and coffee, he should increase his daily water intake, since these tendencies contribute to increased dehydration. After a good night's rest, all vital processes in our body gain strength, which is why you should support your body and create an additional water reserve for it. During the day, when we have a peak in activity, it is better to take liquid in small portions so as not to overload the internal systems and organs. In the evening, you should remove all restrictions and drink as much as you want, of course, if there are no health problems.
Should you drink your food?
The daily amount of water should be distributed evenly; it is especially useful to drink a little liquid before meals in order to normalize metabolic and cleansing processes, as well as lower blood concentration and cholesterol levels. Doctors do not recommend drinking food with food, since in this case the gastric juice is diluted and the process of digesting food slows down. Lack of water in the body can lead to stress, causing hunger signals to be sent to the brain even though the person has recently eaten. As a result, he will eat again instead of replenishing his fluid reserves. At this point, excess nutrients will begin to be stored as fat, which in the future can negatively affect your overall condition. Drinking enough water daily can suppress hunger and reduce the amount of foods you consume, especially fatty foods. It should be noted that juices and tea cannot fully replace clean water, since they contain active substances that can disrupt the chemical composition of our body. Carbonated drinks, which contain harmful chemical compounds, can cause additional dehydration.
1. In the body of animals and plants, the average amount of water is more than 50%.
2. The earth's mantle contains 10 times more water than the World Ocean.
3. The average depth of the World Ocean is 3.6 km, it covers up to 71% of the entire surface of the Earth and contains about 97.6% of free water reserves.
4. In the absence of bulges and depressions on Earth, the surface of the water would rise above the land by 3 kilometers.
5. If all the glaciers melted, the water level would rise by 64 m, as a result of which 1/8 of the land would be flooded.
6. has an average salinity of 35%, which allows it to freeze at a temperature of -1.91 o C.
7. In some cases, water may freeze at above-zero temperatures.
8. Inside the nanotubes, the formula of water changes, its molecules take on a new state, which allows the liquid to spread even at zero temperature.
9. Water can reflect up to 5% of the sun's rays, and snow - more than 85%, but only 2% of daylight can penetrate under the ice.
10. Pure ocean water is blue, which is due to its selective absorption and dispersion.
11. Using water drops that drip from a tap, you can reproduce a voltage of about 10 kilovolts.
12. Water is one of the few natural substances that can expand when changing from liquid to solid.
13. and water can burn in combination with fluorine; such mixtures become explosive in high concentrations.
Finally
What is water? This is a diverse, albeit simplest compound, which is the main building material of our planet. No living organism can live without water. She is a source of energy, a carrier of information and a real storehouse of health. Even our distant ancestors believed in the miraculous power of water and used its healing qualities in the treatment of many ailments. The task of our generation is to preserve this beautiful element in its pristine state. There is a lot we can do to make our descendants feel relatively safe. By conserving water, we will save life on our wonderful and warm planet. People, save water! It cannot be replaced even by all the treasures of the world. Water is a reflection of the state of our planet, its heart and life-giving force.
