Water is a transparent liquid that has no color (in a small volume) and no smell.
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.
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).
The properties of water are a set of physical, chemical, biochemical, organoleptic, physico chemical and other properties of water.
Water hydrogen oxide — is one of the most common and important substances.
The surface of the Earth occupied by water is 2.5 times larger than the surface of the land.
There is no pure water in nature — it always contains impurities.
Pure water is obtained by distillation.
Distilled water is called distilled water.
Water composition (by weight): 11.19 % hydrogen and 88.81 % oxygen.
Pure water is transparent, has no smell and taste.
It has the highest density at 0° C (1 g / cm^3).
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 The hydrogen atoms form an angle equal to 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 the water molecules, the electrolytes in it dissociate into ions.
In liquid water, along with ordinary H20 molecules, there are associated molecules, i.e., combined 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: the maximum density at 4° C, high boiling point (in the series H20 H2S H2Se), abnormally high heat capacity [4.18 kJ/(g * K)].
With an increase in temperature, the hydrogen bonds are broken, and a complete break occurs when water passes into steam.
Water is a very reactive substance.
Under normal conditions, it interacts with many basic and acidic oxides, as well as with alkaline and alkaline earth metals.
Water forms numerous compounds crystal hydrates.
Obviously, the compounds that bind water can serve as desiccants.
From other drying substances, you can specify P205, CaO, VaO, metal Ma (they also chemically interact with water), as well as silica gel.
The important chemical properties of water include its ability to enter into hydrolytic decomposition reactions.
Water containing heavy hydrogen is called heavy water (denoted by the formula D2O).
Chemical reactions with heavy water are much slower than with ordinary water.
Therefore, it accumulates in the electrolyzer during prolonged electrolysis of ordinary water.
The chemical properties of water are determined by its composition.
Water consists of 88.81% oxygen, and only 11.19% hydrogen.
As we mentioned above, water freezes at zero degrees Celsius, but it boils at a hundred.
Distilled water has a very low concentration of positively charged hydroxonium NO and H3O+ ions (only 0.1 mmol/L), so it can be called an excellent insulator.
However, the properties of water in nature would not be realized correctly if it was not a good solvent.
The water molecule is very small in size.
When another substance enters the water, its positive ions are attracted by the oxygen atoms that make up the water molecule, and the negative ones are attracted by hydrogen atoms.
Water seems to surround the chemical elements dissolved in it from all sides.
Therefore, water almost always contains various substances, in particular, metal salts that ensure the conduct of an electric current.
The physical properties of water "gave" us such phenomena as the greenhouse effect and the microwave oven.
About 60% of the greenhouse effect is created by water vapor, which perfectly absorbs infrared rays.
At the same time, the optical refractive index of water is n=1.33.
In addition, water also absorbs microwaves, due to the high dipole moment of its molecules.
These properties of water in nature prompted scientists to think about the invention of a microwave oven.
The role of water in nature and human life is immeasurably great.
We can say that all living things consist of water and organic substances.
It is an active participant in the formation of the physical and chemical environment, climate and weather.
At the same time, it also affects the economy, industry, agriculture, transport and energy.
water
Water.
Photo: Graham Dean
We can live without food for several weeks, and without water only 2-3 days.
To ensure a normal existence, a person must inject water into the body about 2 times more by weight than nutrients.
The loss of more than 10% of water by the human body can lead to death.
On average, the body of plants and animals contains more than 50% of water, in the body of jellyfish it is up to 96%, in algae 95-99%, in spores and seeds from 7 to 15%.
The soil contains at least 20% of water, while in the human body water is about 65%.
Different parts of the human body contain different amounts of water: the vitreous body of the eye consists of 99% water, its blood contains 83, in adipose tissue 29, in the skeleton 22 and even in tooth enamel 0.2%.
Throughout his life, a person loses water from the body, and his bioenergetic potential decreases.
In a six week old human embryo, the water content is up to 97%, in a newborn 80%, in an adult 60-70%, and in an elderly person - only 50-60%.
Water is absolutely necessary for all key human life support systems.
Water and the substances contained in it become a food medium and supply living organisms with the microelements necessary for life.
It is contained in the blood (79%) and contributes to the transfer of thousands of necessary substances and elements through the circulatory system in a dissolved state (the geochemical composition of water is close to the composition of animal and human blood.).
In the lymph, which carries out the exchange of substances between blood and tissues of a living organism, water is 98%.
Water is stronger than other liquids and exhibits the properties of a universal solvent.
After a certain time, it can dissolve almost any solid substance.
Such a comprehensive role of water is due to its unique properties.
Recently, the efforts of researchers have been focused on the accelerated study of processes occurring at the interface of phases.
It turned out that the water in the boundary layers has many interesting properties that do not manifest themselves in the bulk phase.
This information is extremely necessary for solving a number of important practical problems.
An example is the creation of a fundamentally new element base of microelectronics, where further .the miniaturization of the schemes will be based on the principle of self organization of macromolecules on the water surface.
The developed surface is also characteristic of biological systems, which is due to the importance of surface phenomena for their functioning.
Almost always, the presence of water has a significant influence on the nature of processes occurring in the near surface region.
In turn, under the influence of the surface, the properties of the water itself change dramatically, and the water at the border must be considered as a fundamentally new physical object of research.
It is very likely that the study of the molecular statistical properties of water near the surface, which, in fact, is just beginning, will make it possible to effectively control many physical and chemical processes.
Recently, there has been an increased interest in studying the properties of water at the microscopic level.
So, to understand many questions of the physics of surface phenomena, it is necessary to know the properties of water at the phase interface.
The lack of strict ideas about the structure of water, about the organization of water at the molecular level leads to the fact that when studying the properties of aqueous solutions both in the bulk phase and in capillary systems, water is often considered as a structureless medium.
However, it is known that the properties of water in the boundary layers can differ markedly from the bulk ones.
Therefore, considering water as a structureless liquid, we lose unique information about the properties of the boundary layers, which, as it turns out, largely determine the nature of the processes occurring in thin pores.
For example, the ionic selectivity of cellulose acetate membranes is explained by the special molecular organization of water in the pores, which, in particular, is reflected in the concept of "non dissolving volume".
Further development of the theory, which takes into account the specifics of intermolecular interactions underlying selective membrane transport, will contribute to a more complete understanding of membrane desalination of solutions.
This will allow us to give reasonable recommendations for improving the efficiency of technological processes of water desalination.
This implies the importance and necessity of studying the properties of a liquid in boundary layers, in particular near the surface of a solid.
