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海や水をテーマにしたプレイリストです。 視聴してみてください！ Water Article Talk Read View source View history Page semi-protected From Wikipedia, the free encyclopedia "H2O" redirects here. For H20, see H20 (disambiguation). For other uses, see H₂O (disambiguation) and Water (disambiguation). Water The water molecule has this basic geometric structure Ball-and-stick model of a water molecule Space filling model of a water molecule Names IUPAC name Water Systematic IUPAC name Oxidane Identifiers CAS Number 7732-18-5 ECHA InfoCard 100.028.902 Edit this at Wikidata PubChem CID 962 CompTox Dashboard (EPA) DTXSID6026296 Edit this at Wikidata Properties Chemical formula H2O Molar mass 18.015 g·mol−1 Appearance Nearly colourless liquid or nearly colourless solid (blue if we look through thick layers of water) or colourless gas Density Liquid: 0.9998396 g/mL at 0 °C 0.9970474 g/mL at 25 °C 0.961893 g/mL at 95 °C Solid: 0.9167 g/ml at 0 °C Melting point 0.00 °C (32.00 °F; 273.15 K) Boiling point 99.98 °C (211.96 °F; 373.13 K) Supplementary data page Water (data page) Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references A globule of liquid water, and the concave depression and rebound in water caused by something dropping through the water surface A block of solid water (ice) Clouds in Earth's atmosphere condense from gaseous water vapor. Water is an inorganic compound with the chemical formula H2O. It is a transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a solvent[1]). It is vital for all known forms of life, despite not providing food, energy or organic micronutrients. Its chemical formula, H2O, indicates that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. The hydrogen atoms are attached to the oxygen atom at an angle of 104.45°.[2] "Water" is also the name of the liquid state of H2O at standard temperature and pressure. A number of natural states of water exist. It forms precipitation in the form of rain and aerosols in the form of fog. Clouds consist of suspended droplets of water and ice, its solid state. When finely divided, crystalline ice may precipitate in the form of snow. The gaseous state of water is steam or water vapor. Water covers about 71% of the Earth's surface, with seas and oceans making up most of the water volume on earth (about 96.5%).[3] 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%).[4][5] Water moves continually through the water cycle of evaporation, transpiration (evapotranspiration), condensation, precipitation, and runoff, usually reaching the sea. Water plays an important role in the world economy. Approximately 70% of the freshwater used by humans goes to agriculture.[6] 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.[7] Much of the long-distance trade of commodities (such as oil, natural gas, and manufactured products) is transported by boats through seas, rivers, lakes, and canals. Large quantities of water, ice, and steam are used for cooling and heating, in industry and homes. Water is an excellent solvent for a wide variety of substances both mineral and organic; as such it is widely used in industrial processes, and in cooking and washing. Water, ice and snow are also central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, surfing, sport fishing, diving, ice skating and skiing. Etymology The word water comes from Old English wæter, from Proto-Germanic *watar (source also of Old Saxon watar, Old Frisian wetir, Dutch water, Old High German wazzar, German Wasser, vatn, Gothic 𐍅𐌰𐍄𐍉 (wato), from Proto-Indo-European *wod-or, suffixed form of root *wed- ("water"; "wet").[8] Also cognate, through the Indo-European root, with Greek ύδωρ (ýdor, from Ancient Greek ὕδωρ, hýdōr, whence English "hydro-"), Russian вода́ (vodá), Irish uisce, and Albanian ujë. History Main articles: Origin of water on Earth § History of water on Earth, and Properties of water § History Properties Main article: Properties of water See also: Water (data page) and Water model A water molecule consists of two hydrogen atoms and one oxygen atom Water (H2O) is a polar inorganic compound. At room temperature it is a tasteless and odorless liquid, nearly colorless with a hint of blue. This simplest hydrogen chalcogenide is by far the most studied chemical compound and is described as the "universal solvent" for its ability to dissolve many substances.[9][10] This allows it to be the "solvent of life":[11] indeed, water