Fishing in salt and fresh water bodies has been, and continues to be, a major source of food for many parts of the world, providing 6.5% of global protein. Approximately 70% of the freshwater used by humans goes to agriculture. Water plays an important role in the world economy. Water moves continually through the water cycle of evaporation, transpiration ( evapotranspiration), condensation, precipitation, and runoff, usually reaching the sea. Small portions of water occur as groundwater (1.7%), in the glaciers and the ice caps of Antarctica and Greenland (1.7%), and in the air as vapor, clouds (consisting of ice and liquid water suspended in air), and precipitation (0.001%). Water covers about 71% of the Earth's surface, with seas and oceans making up most of the water volume (about 96.5%). The gaseous state of water is steam or water vapor. When finely divided, crystalline ice may precipitate in the form of snow. Clouds consist of suspended droplets of water and ice, its solid state. It forms precipitation in the form of rain and aerosols in the form of fog. "Water" is also the name of the liquid state of H 2O at standard temperature and pressure.īecause Earth's environment is relatively close to water's triple point, water exists on Earth as a solid, liquid, and gas. The hydrogen atoms are attached to the oxygen atom at an angle of 104.45°. Its chemical formula, H 2O, indicates that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. It is vital for all known forms of life, despite not providing food energy, or organic micronutrients. It is a transparent, tasteless, odorless, and nearly colorless chemical substance, and it is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a solvent ). Water is an inorganic compound with the chemical formula H 2O. Clouds in Earth's atmosphere condense from gaseous water vapor.
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