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Water is a diamagnetic material. [59] Though interaction is weak, with superconducting magnets it can attain a notable interaction. [59] Phase transitions Water moves perpetually through each of these regions in the water cycle consisting of the following transfer processes:
Because Earth's environment is relatively close to water's triple point, water exists on Earth as a solid, liquid, and gas. [22] 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 that is not fit for drinking but is not harmful to humans when used for swimming or bathing is called by various names other than potable or drinking water, and is sometimes called safe water, or "safe for bathing". Chlorine is a skin and mucous membrane irritant that is used to make water safe for bathing or drinking. Its use is highly technical and is usually monitored by government regulations (typically 1 part per million (ppm) for drinking water, and 1–2 ppm of chlorine not yet reacted with impurities for bathing water). Water for bathing may be maintained in satisfactory microbiological condition using chemical disinfectants such as chlorine or ozone or by the use of ultraviolet light. However, oxygen is more electronegative than most other elements, so the oxygen atom retains a negative charge while the hydrogen atoms are positively charged. Along with the bent structure, this gives the molecule an electrical dipole moment and it is classified as a polar molecule. [93] Water ( H 2 O) 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. [45] [46] This allows it to be the " solvent of life": [47] indeed, water as found in nature almost always includes various dissolved substances, and special steps are required to obtain chemically pure water. Water is the only common substance to exist as a solid, liquid, and gas in normal terrestrial conditions. [48] States The three common states of matterIn a water molecule, the hydrogen atoms form a 104.5° angle with the oxygen atom. The hydrogen atoms are close to two corners of a tetrahedron centered on the oxygen. At the other two corners are lone pairs of valence electrons that do not participate in the bonding. In a perfect tetrahedron, the atoms would form a 109.5° angle, but the repulsion between the lone pairs is greater than the repulsion between the hydrogen atoms. [90] [91] The O–H bond length is about 0.096nm. [92] Many organic substances (such as fats and oils and alkanes) are hydrophobic, that is, insoluble in water. Many inorganic substances are insoluble too, including most metal oxides, sulfides, and silicates. Water runoff often collects over watersheds flowing into rivers. Through erosion, runoff shapes the environment creating river valleys and deltas which provide rich soil and level ground for the establishment of population centers. A flood occurs when an area of land, usually low-lying, is covered with water which occurs when a river overflows its banks or a storm surge happens. On the other hand, drought is an extended period of months or years when a region notes a deficiency in its water supply. This occurs when a region receives consistently below average precipitation either due to its topography or due to its location in terms of latitude. The refractive 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 to 1.6). The refraction index of ice (1.31) is lower than that of liquid water.
Water fit for human consumption is called drinking water or potable water. Water that is not potable may be made potable by filtration or distillation, or by a range of other methods. More than 660 million people do not have access to safe drinking water. [108] [109] Water reclamation is the process of converting wastewater (most commonly sewage, also called municipal wastewater) into water that can be reused for other purposes. There are 2.3 billion people who reside in nations with water scarcities, which means that each individual receives less than 1,700 cubic metres (60,000cuft) of water annually. 380billion cubic metres (13 × 10
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The collective mass of water found on, under, and over the surface of a planet is called the hydrosphere. Earth's approximate water volume (the total water supply of the world) is 1.386billion cubic kilometres (333million cubic miles). [24] Water is a good polar solvent, dissolving many salts and hydrophilic organic molecules such as sugars and simple alcohols such as ethanol. Water also dissolves many gases, such as oxygen and carbon dioxide—the latter giving the fizz of carbonated beverages, sparkling wines and beers. In addition, many substances in living organisms, such as proteins, DNA and polysaccharides, are dissolved in water. The interactions between water and the subunits of these biomacromolecules shape protein folding, DNA base pairing, and other phenomena crucial to life ( hydrophobic effect).
The water cycle (known scientifically as the hydrologic cycle) is the continuous exchange of water within the hydrosphere, between the atmosphere, soil water, surface water, groundwater, and plants.In a lake or ocean, water at 4°C (39°F) sinks to the bottom, and ice forms on the surface, floating on the liquid water. This ice insulates the water below, preventing it from freezing solid. Without this protection, most aquatic organisms residing in lakes would perish during the winter. [58] Magnetism Water is fundamental to both photosynthesis and respiration. Photosynthetic cells use the sun's energy to split off water's hydrogen from oxygen. [106] In the presence of sunlight, hydrogen is combined with CO In nature, the color may also be modified from blue to green due to the presence of suspended solids or algae.
The viscosity of water is about 10 −3 Pa· s or 0.01 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 5,100ft/s) depending on temperature. Sound travels long distances in water with little attenuation, especially at low frequencies (roughly 0.03 dB/km for 1 k Hz), a property that is exploited by cetaceans and humans for communication and environment sensing ( sonar). [100] Reactivity Aquatic plants, algae, and other photosynthetic organisms can live in water up to hundreds of meters deep, because sunlight can reach them. In industry, near-infrared spectroscopy is used with aqueous solutions as the greater intensity of the lower overtones of water means that glass cuvettes with short path-length may be employed. To observe the fundamental stretching absorption spectrum of water or of an aqueous solution in the region around 3,500cm −1 (2.85μm) [89] a path length of about 25μm is needed. Also, the cuvette must be both transparent around 3500cm −1 and insoluble in water; calcium fluoride is one material that is in common use for the cuvette windows with aqueous solutions.Liquid water can be assumed to be incompressible for most purposes: its compressibility ranges from 4.4 to 5.1 ×10 −10Pa −1 in ordinary conditions. [98] Even in oceans at 4km depth, where the pressure is 400 atm, water suffers only a 1.8% decrease in volume. [99] that is, a proton) donor, can be neutralized by a base, a proton acceptor such as a hydroxide ion ( OH − At sea level, the boiling point of water is 100°C (212°F). As atmospheric pressure decreases with altitude, the boiling point decreases by 1°C every 274meters. High-altitude cooking takes longer than sea-level cooking. For example, at 1,524 metres (5,000ft), cooking time must be increased by a fourth to achieve the desired result. [67] (Conversely, a pressure cooker can be used to decrease cooking times by raising the boiling temperature. [68]) One factor in estimating when water appeared on Earth is that water is continually being lost to space. H 2O molecules in the atmosphere are broken up by photolysis, and the resulting free hydrogen atoms can sometimes escape Earth's gravitational pull (see: Atmospheric escape). When the Earth was younger and less massive, water would have been lost to space more easily. Lighter elements like hydrogen and helium are expected to leak from the atmosphere continually, but isotopic ratios of heavier noble gases in the modern atmosphere suggest that even the heavier elements in the early atmosphere were subject to significant losses. [29] In particular, xenon is useful for calculations of water loss over time. Not only is it a noble gas (and therefore is not removed from the atmosphere through chemical reactions with other elements), but comparisons between the abundances of its nine stable isotopes in the modern atmosphere reveal that the Earth lost at least one ocean of water early in its history, between the Hadean and Archean eons. [30] [ clarification needed]
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