Chemical composition of

water .

Water (H2O) is the most abundant compound on Earth's surface, covering 70 percent of the planet.

In nature, water is present in the states of liquid, solid and gas. It is a dynamic equilibrium between liquid and gas states at standard temperature and pressure. At room temperature, the liquid is tasteless and odorless, nearly colorless with a hint of blue. Many substances are dissolved in water and is commonly referred to as the universal solvent. Therefore, the water in nature is rarely pure and some of the properties may differ from those of the pure form of it. However, there are also many compounds which are substantially, if not completely insoluble in water. Water is the only common substance found naturally in the three common states of matter and is essential for life on Earth. Water makes up 55% to 78% of the human body.

Water is a chemical compound with the chemical formula H2O: one water molecule has two hydrogen atoms covalently bonded to one atom of oxygen. Water occurs naturally in three states of matter (solid, liquid and gas) and can take various forms on the Earth surface: water, vapor and clouds in the sky, the sea water in the oceans, the oceans, glaciers, polar glacier mountains, fresh and salt water, lakes, rivers.

The main physical and chemical properties of water are:

Water is a liquid at normal temperature and pressure. It is tasteless and odorless. Water and ice are of light blue hue, although both appear colorless in small quantities. Water in a vapor state is essentially invisible.

Water is transparent in the visible range of the electromagnetic spectrum. Thus aquatic plants can live in water because sunlight can reach them. Infrared radiation is strongly absorbed by oxygen or hydrogen bonds with OH. Since the water molecule is not linear, and the oxygen atom has a higher electronegativity than hydrogen atoms, an oxygen atom is converted to a small negative charge and the hydrogen atoms are slightly positive. As a result, water is bipolar with the electric dipole moment. Water also may be a very large number of hydrogen bonds (four) in the molecule's size. These factors lead to strong attractive forces between the water molecules, resulting in high surface tension and capillary forces. Capillarity refers to the tendency of water to pass a narrow tube against the force of gravity. This property is relied upon by all vascular plants, such as trees.

Water is a good polar solvent and is often referred to as the universal solvent. Substances which are soluble in water, for example, salts, sugars, acids, bases, and certain gases - in particular oxygen and carbon dioxide (carbonation) - are known as hydrophilic (water loving) substances, while those which are miscible with water (for example, fats and oils), are known as hydrophobic (water-fearing) substances.

All the components in the cells (proteins, DNA, and polysaccharides) are dissolved in water, the discharge structure and activity of their interaction with water. A pure water is of low electrical conductivity, but the conductivity increases with additional small amount of dissolved ionic material such as sodium chloride. A boiling point of water (and all other liquids) is dependent on the atmospheric pressure. For example, on the top of Mount Everest, water boils at a temperature of 68 ° C (154 ° F), compared to 100 ° C (212 ° F) at the sea level. Conversely, water deep in the ocean, near geothermal wells, can reach temperatures of hundreds of degrees and remain liquid.

At 4181.3 J the water has a high heat capacity, and a large amount of heat of vaporization (40.65 kJ · mol-1), both of which are the result of extensive hydrogen bonds between the molecules. These two unique properties allow water to moderate climate of the Earth by buffering temperature. Density fluctuations in liquid water is 1000 kg / m 3 (62.43 lb / ft Cu) at 4° C. The ice has a density of 917 kg / m 3 (57.25 kg / cu ft).

The maximum density of water occurs at 3.98 ° C (39.16 ° F). The best known chemical substances have become more compact, however, as the cooling water has the property of becoming less dense when cooled to form a solid ice. As the water is cooled, there are two competing effects: 1) reducing the volume and 2) increasing the total volume of liquid, as the particles orient in an organized structure of ice. Between 3.98 ° C and 0 ° C, the second effect as the effect cancels the first effect is the increase in volume as the temperature drops. Water expands to occupy 9% larger volume of the ice, which is the fact that the ice floats on liquid water as icebergs.

The water is mixed with many liquids, such as ethanol, in any proportions, forming a single homogeneous liquid. On the other hand, water and most of the oil, normally do not mix to form a thick liquid layer, at least one upper layer, and the most dense layer at the bottom. Water forms an azeotrope with many other solvents. Water can be divided by the electrolysis into hydrogen and oxygen. Water is not a fuel, it is the final product of hydrogen combustion. Elements which are more electropositive than hydrogen such as lithium, sodium, calcium, potassium and cesium hydrogen are displaced with water to form hydroxides. Being a flammable gas, hydrogen is very dangerous, flammable and explosive when put in the reaction with water.

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GROUP 2Patrycja Orman- PolandWiktoria Waniak – PolandZuzanna Pruchniak -PolandGloria Fernández Barbusano - SpainAlba García Gómez - SpainEduardo González Anelo - SpainAbraham González Guisado - SpainJanet González Rodríguez - SpainAdriana Mañero Santana - SpainPascal - Germany