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Water is one of the most important chemical compounds. Information on its physical and chemical properties, abundance in astronomy, earth science, and biology will be considered. Connections to personal studies, anthropology, culture, institutions, and sociology will also be considered. |
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History. Specific details from prehistory and antiquity are lacking. Water was considered one of the elements in classical and medieval times. Its composition and chemistry have only been elucidated in modern times. Details of its future uses are uncertain.
Biology. Water is highly significant to biology. Many types of organisms live in a water environment, and those that do not must consume it in some form. It is essential in the physiology of all living organisms. Cells are largely composed of water, and it forms the principal medium for molecular biology.
Earth Science. Water has an important role in geological history, and a non-uniform distribution in physical geography. Its evaporation and condensation are important parts of the weather cycle. Ice crystals and water droplets are the principal components of clouds and water vapor is found in variable amounts in the atmosphere. It is the principal component of the hydrosphere. Water is important in geological processes and as a component of many minerals.
Astronomical significance. Water is probably the most abundant compound in the universe, though its distribution is uneven. In the solar system, it is found in the form of ice.
Gases, including hydrogen, nitrogen, and oxygen dissolve in water. Carbon does not dissolve appreciably in water. The hydrocarbons are generally not highly soluble in water.
Water does not react appreciably with hydrogen or oxygen, since it is formed by the combination of those elements. It does react with carbon, especially at high temperatures. It does not react appreciably with nitrogen.
Pure water is a poor conductor elctrical conductor, however, its electrical conductivity can be altered significantly by dissolving otner susbatnces in it.
Water has a triple point, where ice, liquid water, and water vapor are in equilibrium at 273.16 K (0.01 °C) [by convention], at a pressure of 611.73 Pa.
Water has a melting/freezing point at standard atmospherinc pressure of 273.15 K, 0 °C, 32 °F at standard atmospheric pressure 101.325 kPa. Under these conditions, water has an enthalpy of fusion of 6.009 kJ/ mol
Water has a boiling/condensation point of 373.15 K, 100 °C, 122 °F at standard atmospheric pressure 101.325 kPa. water has an enthalpy of vaporization of 40.65 kJ/ mol
Gas: steam, water vapor. As with other gases, this has a density which depends on the pressure and temperature.
Liquid: water (liquid water) This has a density of 0.9998 g/cm3 at the freezing point, and a maximum of 1.000 g/cm at a temperature of 4 °C. It decreases somewhat with temperature, reaching 0.958 at the normal boiling point.
Solid: Ice (water ice) This has a density of 0.917 g/cm3 and is one of the few solids which is less dense than the liquid form.
Formula: H2O
Molar mass 18.01528 g/mol