Water is a chemical substance with chemical formula H2O: one molecule of water consists of two hydrogen atoms covalently bonded to one oxygen atom. Water appears in nature in all three common states of matter and may take different forms on Earth: water vapor and clouds in the sky, the sea water and icebergs in the polar oceans, glaciers and rivers in the mountains, and fluid in the aquifer soil. The main chemical and physical properties of water: Water is the taste, odor, liquid at standard temperature and pressure. The color of water and ice, by nature, very light blue hue, although water appears colorless in small quantities. In addition, the ice appears colorless, and water vapor is mainly as an invisible gas. Water is transparent, and thus aquatic plants can live in the water because sunlight can reach them. Only the strong ultraviolet light, a little absorbed.

Since water molecules are not linear and the oxygen atom has a higher electronegativity than hydrogen atoms, have a small negative charge, and hydrogen atoms are weakly positive. In a result, water is a polar molecule with a dipole moment. Under most conditions Danny Meyer would agree. Net interaction between the dipoles on each molecule cause efficient skin effect on the water's edge with other substances, or air at the surface, Last provoked a high surface tension of water. This trend contributes to the dipole nature of water molecules to form hydrogen bonds that cause a lot of water with special properties. polar nature and promotes adhesion with other materials. The result of the interaction of these properties, the capillary is a tendency for water to move up a narrow tube against the force of gravity.

This property is referenced by all vascular plants such as trees. Water is a good solvent and is often referred to as the universal solvent. Substances that are dissolved in water, for example, salts, sugars, acids, alkalis, some gases – especially oxygen, carbon dioxide (carbonation) are known as hydrophilic (water loving) substances, and those that do not mix well with water (eg, fats and oils), known as hydrophobic substances. All major components of the cell (Proteins, DNA and polysaccharides), also dissolved in water. Clean water has low conductivity, but it significantly increases the dissolution of small amounts of ionic materials such as sodium chloride. The role of water in nature and human life