The viscosity of water is about 103 pa s.01 poise at 20 C (68 f and the speed of sound in liquid water ranges between 1,400 and 1,540 meters per second (4,600 and 5,100 ft/s) depending on temperature. Sound travels long distances in water with little attenuation, especially at low frequencies (roughly.03 dB /km for 1 k hz a property that is exploited by cetaceans and humans for communication and environment sensing ( sonar ). 30 reactivity Elements which are more electropositive than hydrogen such as lithium, sodium, calcium, potassium and caesium displace hydrogen from water, forming hydroxides and releasing hydrogen. On Earth main articles: Hydrology and Water distribution write on Earth Water covers 71 of the earth's surface; the oceans contain.5 of the earth's water. The Antarctic ice sheet, which contains 61 of all fresh water on Earth, is visible at the bottom. Condensed atmospheric water can be seen as clouds, contributing to the earth's albedo. Hydrology is the study of the movement, distribution, and quality of water throughout the earth.
These properties make water more effective at moderating Earth's climate, by storing heat and transporting it between the oceans and the atmosphere. The hydrogen bonds of water are of moderate strength, around 23 kJ/mol (compared add to a covalent o-h bond at 492 kJ/mol). Of this, it is estimated that 90 of the hydrogen bond is attributable to electrostatics, while the remaining 10 reflects partial covalent character. 26 Electrical conductivity and electrolysis Pure water has a low electrical conductivity, which increases with the dissolution of a small amount of ionic material such as common salt. Liquid water can be split into the elements hydrogen and oxygen by passing an electric current through it—a process called electrolysis. The decomposition requires more energy input than the heat released by the inverse process (285.8 kJ/ mol,.9 MJ/kg). 27 Mechanical properties Liquid water can be assumed to be incompressible for most purposes: its compressibility ranges from.4.11010 Pa1 in ordinary conditions. 28 even in oceans at 4 km depth, where the pressure is 400 atm, water suffers only.8 decrease in volume.
Many inorganic substances are insoluble too, including most metal oxides, sulfides, and silicates. Because of its polarity, a molecule of water in the liquid or solid state can form up to four hydrogen bonds with neighboring molecules. These bonds are the cause of water's high surface tension 24 and capillary forces. The capillary action refers to the tendency of water to move up a narrow tube against the force of gravity. This property is relied upon by all vascular plants, such as trees. 25 The hydrogen bonds are also the reason why the melting and boiling points of water are much higher than those of other analogous compounds like hydrogen sulfide (H 2S). They also explain its exceptionally high specific heat capacity (about.2 J /g/K heat of fusion (about 333 J/g heat of vaporization (2257 J/g and thermal conductivity (between.561 and.679 W/m/K).
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Water vapour is essentially invisible thesis as a gas. Through a thickness of 10 meters (33 ft) or more, however, the intrinsic color of water (or ice) is visibly turquoise (greenish blue as its absorption spectrum has a sharp minimum at the corresponding color of light (1/227 m1 at 418 nm). The color becomes increasingly stronger and darker with increasing thickness. (Practically no sunlight reaches the parts of the oceans below 1,000 meters (3,300 ft) of depth.) Infrared and ultraviolet light, on the other hand, is strongly absorbed by water. The refraction index of liquid water (1.333 at 20 C (68 F) is much higher than that of air (1.0 similar to those of alkanes and ethanol, but lower than those of glycerol (1.473 benzene (1.501 carbon disulfide (1.627 and common types of glass (1.4.6). The refraction index of ice (1.31) is lower than that of liquid water. Polarity and hydrogen bonding see also: Chemical bonding of H2O Impact from a water drop causes an upward "rebound" jet surrounded by circular capillary waves.
Since the water molecule is not linear and the oxygen atom has a higher electronegativity than hydrogen atoms, it is a polar molecule, with an electrical dipole moment : the oxygen atom carries a slight negative charge, whereas the hydrogen atoms are slightly positive. Water is a good polar solvent, that dissolves many salts and hydrophilic organic molecules such as sugars and simple alcohols such as ethanol. Most acids dissolve in water to yield the corresponding anions. Many substances in living organisms, such as proteins, dna and polysaccharides, are dissolved in water. Water also dissolves many gases, such as oxygen and carbon dioxide —the latter giving the fizz of carbonated beverages, sparkling wines and beers. On the other hand, many organic substances (such as fats and oils and alkanes ) are hydrophobic, that is, insoluble in water.
At very low pressures (below about.006 atm water cannot exist in the liquid state and passes directly from solid to gas by sublimation —a phenomenon exploited in the freeze drying of food. At very high pressures (above 221 atm the liquid and gas states are no longer distinguishable, a state called supercritical steam. Water also differs from most liquids in that it becomes less dense as it freezes. The maximum density of water in its liquid form (at 1 atm) is 1,000 kg/m3 (62.43 lb/cu ft that occurs.98 C (39.16 F). 14 The density of ice is 917 kg/m3 (57.25 lb/cu ft). 15 16 Thus, water expands 9 in volume as it freezes, which accounts for the fact that ice floats on liquid water.
The details of the exact chemical nature of liquid water are not well understood; some theories suggest that water's unusual behaviour is as a result of it having 2 liquid states. Taste and odor Pure water is usually described as tasteless and odorless, although humans have specific sensors that can feel the presence of water in their mouths, 20 and frogs are known to be able to smell. 21 However, water from ordinary sources (including bottled mineral water) usually has many dissolved substances, that may give it varying tastes and odors. Humans and other animals have developed senses that enable them to evaluate the potability of water by avoiding water that is too salty or putrid. 22 Color and appearance The apparent color of natural bodies of water (and swimming pools) is often determined more by dissolved and suspended solids, or by reflection of the sky, than by water itself. Light in the visible electromagnetic spectrum can traverse a couple meters of pure water (or ice) without significant absorption, so that it looks transparent and colorless. 23 Thus aquatic plants, algae, and other photosynthetic organisms can live in water up to hundreds of meters deep, because sunlight can reach them.
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13 States Liquid water, showing droplets and air bubbles caused by the drops Water is a liquid at the temperatures and pressures that are most adequate for life. Specifically, at a standard pressure of 1 atm, water is a liquid between 0 and 100 C (32 and 212 F). Increasing the pressure slightly lowers the melting point, which is about 5 C (23 F) at 600 atm and 22 C (8 F) at 2100 atm. This effect is relevant, for example, to ice skating, to the buried lakes of Antarctica, and to the movement of glaciers. (At pressures higher than 2100 atm the melting point rapidly increases again, and ice takes several exotic forms that do not exist at lower pressures.) Increasing the pressure has a more dramatic effect on the boiling point, that is about 374 C (705 F) at 220 atm. This effect is important in, improve among other things, deep-sea hydrothermal vents and geysers, pressure cooking, and steam engine design. At the top of mount everest, where the atmospheric pressure is about.34 atm, water boils at 68 C (154 F).
Water is an excellent solvent for a wide variety of chemical substances; as such it is widely used in industrial processes, and in cooking and washing. Water is also central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, surfing, sport fishing, and diving. Contents 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 Old Norse "vatn gothic "wato from Proto-Indoeuropean wod-or suffixed form of root wed-" water "wet. Chemical and physical properties main article: Properties of water see also: Water (data page) and Water model Water ( H 2 O ) is a polar pdf inorganic compound that is at room temperature 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. 10 11 This allows it to be the " solvent of life". 12 It is the only common substance to exist as a solid, liquid, and gas in normal terrestrial conditions.
the last decades in almost every part of the world, but approximately one billion people still lack access to safe water and over.5 billion lack access to adequate sanitation. 5 However, some observers have estimated that by 2025 more than half of the world population will be facing water-based vulnerability. 6 A report, issued in november 2009, suggests that by 2030, in some developing regions of the world, water demand will exceed supply. 7 Water plays an important role in the world economy. Approximately 70 of the freshwater used by humans goes to agriculture. 8 Fishing in salt and fresh water bodies is a major source of food for many parts of the world. Much of long-distance trade of commodities (such as oil and 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.
It also occurs in nature as snow, glaciers, ice packs and icebergs, clouds, fog, dew, aquifers, and atmospheric humidity. Water covers 71 of the earth's surface. 1 It is vital for all known forms of life. On Earth,.5 of the planet's crust water is found in seas and oceans,.7 in groundwater,.7 in glaciers and the ice caps of Antarctica and Greenland, a small fraction in other large water bodies, and.001 in the air as vapor, clouds (formed. 2 3 Only.5 of this water is freshwater, and.8 of that water is in ice (excepting ice in clouds) and groundwater. Less than.3 of all freshwater twist is in rivers, lakes, and the atmosphere, and an even smaller amount of the earth's freshwater (0.003) is contained within biological bodies and manufactured products. 2 A greater quantity of water is found in the earth's interior. 4 Water on Earth moves continually through the water cycle of evaporation and transpiration ( evapotranspiration condensation, precipitation, and runoff, usually reaching the sea. Evaporation and transpiration contribute to the precipitation over land.
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Chemical compound, this article is about general aspects of water. For a detailed discussion of its physical and chemical properties, see. For other uses, see, water (disambiguation). Water in two writing states: liquid (including the clouds, which are examples of aerosols and solid ( ice ). Water is a transparent, tasteless, odorless, and nearly colorless chemical substance that is the main constituent of Earth's streams, lakes, and oceans, and the fluids of most living organisms. Its chemical formula is, h2o, meaning that each of its molecules contains one oxygen and two hydrogen atoms that are connected by covalent bonds. Strictly speaking, water refers to the liquid state of a substance that prevails at standard ambient temperature and pressure ; but it often refers also to its solid state ( ice ) or its gaseous state ( steam or water vapor ).