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Aqeuous

Aqeuous

:This article focuses on water as it is experienced in everyday life. See water (molecule) for information on the chemical and physical properties of pure water (H₂O, hydrogen oxide). Water (from the Old English word wæter; c.f German "Wasser", from PIE
- wod-or, "water") is a tasteless, odorless, and nearly colorless (it has a slight hint of blue) substance in its pure form that is essential to all known forms of life and is known also as the most universal solvent. Water is an abundant substance on Earth. It exists in many places and forms. It appears mostly in the oceans and polar ice caps, but also as clouds, rain water, rivers, freshwater aquifers, and sea ice. On the planet, water is continuously moving through the cycle involving evaporation, precipitation, and runoff to the sea. Water fit for human consumption is called potable water. This natural resource is becoming more scarce in certain places as human population in those places increases, and its availability is a major social and economic concern.

Molecular properties

Forms of water

potable water] Water takes many different shapes on earth: water vapor and clouds in the sky, waves and icebergs in the sea, glaciers in the mountain, aquifers in the ground, to name but a few. Through evaporation, precipitation, and runoff, water is continuously flowing from one form to another, in what is called the water cycle. Because of the importance of precipitation to agriculture, and to mankind in general, different names are given to its various forms: while rain is common in most countries, other phenomena are quite surprising when seen for the first time. Hail, snow, fog or dew are examples. When appropriately lit, water drops in the air can refract sunlight to produce rainbows. Similarly, water runoffs have played major roles in human history as rivers and irrigation brought the water needed for agriculture. Rivers and seas offered opportunity for travel and commerce. Through erosion, runoffs played a major part in shaping the environment providing river valleys and deltas which provide rich soil and level ground for the establishment of population centers. Water also infiltrates the ground and goes into aquifers. This groundwater later flows back to the surface in springs, or more spectacularly in hot springs and geysers. Groundwater is also extracted artificially in wells. Because water can contain many different substances, it can taste or smell very differently. In fact, humans and other animals have developed their senses to be able to evaluate the drinkability of water: animals generally dislike the taste of salty sea water and the putrid swamps and favor the purer water of a mountain spring or aquifer.

Water in biology

From a biological standpoint, water has many distinct properties that are critical for the proliferation of life that set it apart from other substances. Water carries out this role by allowing organic compounds to react in ways that ultimately allows replication. It is a good solvent and has a high surface tension, and thus allows organic compounds and living things to be transported in it. Fresh water has its greatest density at 4°C, then becoming less dense as it freezes or heats up from this point. As a stable, polar molecule prevalent in the atmosphere, it plays an important atmospheric role as an absorber of infrared radiation, crucial in the atmospheric greenhouse effect without of which, the average surface temperature would be −18° Celsius. Water also has an unusually high specific heat, which plays many roles in regulating global and regional climate, such as the Gulf Stream climate, allowing life to survive. Water is a very good solvent, chemically not unlike ammonia, and dissolves many types of substances, such as various salts and sugar, and facilitates their chemical interaction, which aids complex metabolisms. Some substances, however, do not mix well with water, including oils and other hydrophobic substances. Cell membranes, composed of lipids and proteins, take advantage of this property to carefully control interactions between their contents and external chemicals. This is facilitated somewhat by the surface tension of water. Water drops are stable due to the high surface tension of water caused by the strong intermolecular forces called cohesive forces. This can be seen when small quantities of water are put onto a nonsoluble surface such as polythene: the water stays together as drops. On extremely clean glass the water may form a thin film because the molecular forces between glass and water molecules (adhesive forces) are stronger than the cohesive forces. This property plays a key role in plant transpiration. A simple but environmentally important and unique property of water is that its common solid form, ice, floats on the liquid. This solid phase is less dense than liquid water, due to the geometry of the strong hydrogen bonds which are formed only at lower temperatures. For almost all other substances and for all other 11 uncommon phases of water ice except ice-XI, the solid form is more dense than the liquid form. Fresh water is most dense at 4°C, and will sink by convection as it cools to that temperature, and if it becomes colder it will rise instead. This reversal will cause deep water to remain warmer than shallower freezing water, so that ice in a body of water will form first at the surface and progress downward, while the majority of the water underneath will hold a constant 4°C. This effectively insulates a lake floor from the cold. While this behavior may seem obvious, even intuitive, it should be noted that almost all other chemicals are denser as solids than they are as liquids, and freeze from the bottom up. Life on earth has evolved with and adapted itself to the important features of water. The existence of abundant liquid, vapor and solid forms of water on Earth has been an important factor in the abundant colonization of Earth's various environments by life-forms adapted to those varying and often extreme conditions. Civilizations have historically flourished around rivers and major waterways; Mesopotamia, the so-called cradle of civilization, is situated between two major rivers. Large metropolises like London, Paris, New York, and Tokyo owe their success in part to their easy accessibility via water and the resultant expansion of trade. Islands with safe water ports, like Singapore and Hong Kong, have flourished for precisely this reason. In places such as North Africa and the Middle East, where water is scarcer, access to clean drinking water was and is a major factor in human development.

Astronomical position of Earth and impact on its water

Mesopotamia The coexistence of the solid, liquid, and gaseous phases of water on Earth is vital to the origin, evolution, and continued existence of life on Earth. However, if the Earth's location in the solar system were even marginally closer or further from the Sun (ie, a million miles or so), the conditions which allow the three forms to be present simultaneously would be far less likely to exist. Earth's mass allows gravity to hold an atmosphere. Water vapor and carbon dioxide in the atmosphere provides a greenhouse effect which helps maintain a relatively steady surface temperature. If Earth were less massive, a thinner atmosphere would cause temperature extremes preventing the accumulation of water except in polar ice caps (as on Mars). According to the solar nebula model of the solar system's formation, Earth's mass may be largely due to its distance from the Sun. The distance between Earth and the Sun and the combination of solar radiation received and the greenhouse effect of the atmosphere ensures that its surface is neither too cold nor too hot for liquid water. If Earth were more distant, most water would be frozen. If Earth were nearer to the Sun, its higher surface temperature would limit the formation of ice caps, or cause water to exist only as vapor. In the former case, the low albedo of oceans would cause Earth to absorb more solar energy. In the second case, a runaway greenhouse effect and inhospitable conditions similar to Venus would result. It has been proposed that life itself may maintain the conditions that have allowed its continued existence. The surface temperature of Earth has been relatively constant through geologic time despite varying solar flux, indicating that a dynamic process governs Earth's temperature via a combination of greenhouse gases and surface or atmospheric albedo. This proposal is known as the Gaia hypothesis.

Human uses of water

Gaia hypothesis All known forms of life depend on water. Water is a vital part of many metabolic processes within the body. Significant quantities of water are used during the digestion of food. (Note however that some bacteria and plant seeds can enter a cryptobiotic state for an indefinite period when dehydrated, and come back to life when returned to a wet environment) About 72% of the fat free mass of the human body is made of water. To function properly the body requires between one and seven litres of water per day to avoid dehydration, the precise amount depending on the level of activity, temperature, humidity, and other factors. It is not clear how much water intake is needed by healthy people. However, for those who do not have kidney problems, it is rather difficult to drink too much water, but (especially in warm humid weather and while exercising) dangerous to drink too little. People do often drink far more water than necessary while exercising, however, putting them at risk of water intoxication, which is frequently fatal. The "fact" that a person should consume eight glasses of water per day cannot be traced back to a scientific source. However, leading dieticians and nutritionists will tell you that this is the RDI (Recommended Daily Intake) of water. [http://ajpregu.physiology.org/cgi/content/full/283/5/R993]. The latest dietary reference intake report by the National Research Council recommended 2.7 liters of water total (including food sources) for women and 3.7 liters for men[http://www.iom.edu/report.asp?id=18495]. Water is lost from the body in urine and feces, through sweating, and by exhalation of water vapor in the breath. Humans require water that does not contain too much salt or other impurities. Common impurities include chemicals and/or harmful bacteria, such as crypto sporidium. Some solutes are acceptable and even desirable for perceived taste enhancement and to provide needed electrolytes.

Water as a precious resource

:See water resources for information about fresh water supplies. fresh water Because of the growth of world population and other factors, the availability of drinking water per capita is shrinking. The issue of water shortage can be solved through more production, better distribution and less waste of it. For this reason, water is a strategic resource for many countries. Many battles and wars, such as the Six-Day War in the Middle East, have been fought to gain access to it. Experts predict more trouble ahead because of the world's growing population, increasing contamination through pollution, and global warming. UNESCO's World Water Development Report (WWDR, 2003) from its World Water Assessment Program indicates that, in the next 20 years, the quantity of water available to everyone is predicted to decrease by 30%. 40% of the world's inhabitants currently have insufficient fresh water for minimal hygiene. More than 2.2 million people died in 2000 from diseases related to the consumption of contaminated water or drought. In 2004, the UK charity WaterAid reported that a child dies every 15 seconds due to easily preventable water-related diseases. Some have predicted that clean water will become the "next oil", making Canada, with this resource in abundance, possibly the richest country in the world.

Regulating water distribution

Drinking water is often collected at springs or extracted from artificial borings in the ground, or wells. Building more wells in adequate places is thus a possible way to produce more water assuming the aquifers can supply an adequate flow. Other water sources are the rainwater and river or lake water. This surface water, however, must be purified for human consumption. This may involve removal of undissolved substances, dissolved substances and harmful microbes. Popular methods are filtering with sand which only removes undissolved material while chlorination and boiling kill harmful microbes. Distillation does all three functions. More advanced techniques exist, such as reverse osmosis. Desalination of abundant ocean or seawater is a more expensive solution used in coastal arid climates. The distribution of drinking water is done through municipal water systems or as bottled water. Governments in many countries have programs to distribute water to the needy at no charge. Others argue that the market mechanism and free enterprise are best to manage this rare resource, and to finance the boring of wells or the construction of dams and reservoirs. Reducing waste, that is using drinking water only for human consumption, is another option. In some cities, such as Hong Kong, sea water is extensively used for flushing toilets citywide in order to conserve fresh water resources. Polluting water may be the biggest single misuse of water; to the extent that a pollutant limits other uses of the water, it becomes a waste of the resource, regardless of benefits to the pollutor. Pharmaceuticals consumed by humans often end up in the waterways and can have detrimental effects on aquatic life if they bioaccumulate and if they are not biodegradable.

The impact of water on human culture

Water is considered a purifier in most religions, including Christianity, Islam, Judaism, and Shinto. For instance, baptism in Christian churches is done with water. In addition, a ritual bath in pure water is performed for the dead in many religions including Judaism and Islam. In Islam, the daily Salah can only be done after ablution (Wodoo), that is, washing parts of the body in clean water. In Shinto, water is used in almost all rituals to cleanse a person or an area. Water is often believed to have spiritual powers. In Celtic mythology, Sulis is the local goddess of thermal springs; in Hinduism, the Ganga is also personified as a goddess. Alternatively, gods can be patrons of particular springs, river or lakes: for example in Greek and Roman mythology, Peneus was a river god, one of the three thousand Oceanids. The Greek philosopher Empedocles held that water is one of the four classical elements along with fire, earth and air, and was regarded as the ylem, or basic stuff of the universe. Water was considered cold and moist. In the theory of the four bodily humours, water was associated with phlegm. Water was also one of the Five Elements in traditional Chinese philosophy, along with earth, fire, wood, and metal. A common misconception about water is that it is a powerful conductor of electricity. Any electrical properties observable in water are due to the ions of mineral salts and carbon dioxide dissolved in it. Water does self-ionize (two water molecules become one hydroxide anion and one hydronium cation), but only at a very slight, almost immeasurable level. Pure water can also be electrolized into oxygen and hydrogen gases but without any dissolved ions, this is a very slow process and thus very little current is conducted. Many bottled water companies exploit another common misconception, advertising both purity and taste, even though pure water is tasteless.

External links

- [http://www.lsbu.ac.uk/water/phase.html Phase diagrams of water]
- [http://www.publicforuminstitute.org/issues/oceans/index.htm Oceans and Water Issues Page]
- [http://www.greenfacts.org/water-disinfectants/index.htm Scientific Facts on Water disinfectants] A faithful summary by GreenFacts of a leading scientific consensus report on Drinking Water Disinfectants published by the International Programme on Chemical Safety of the WHO.
- [http://www.hkc22.com/residentialwater.html Residential water problems and markets] Study paper from Helmut Kaiser Consultancy
- [http://www.hkc22.com/watermarketsworldwide.html Water markets worldwide] Study paper from Helmut Kaiser Consultancy
- [http://www.worldwaterforum.org/ World Water Forum]
- [http://www.unesco.org/water/wwap/ World Water Assessment Program]
- [http://unesdoc.unesco.org/images/0012/001295/129556e.pdf United Nations' World Water Development Report]
- [http://www.gemswater.org/ United Nations GEMS/Water Programme]
- [http://www.lsbu.ac.uk/water/ Water Structure and Behaviour]
- [http://www.wateraid.org/ WaterAid]
- [http://www.sahra.arizona.edu/newswatch/ SAHRA—Global Water Newswatch]
- [http://www.siwi.org/ Stockholm International Water Institute] (SIWI)
- [http://www.c-win.org/ California Water Impact Network (C-WIN)]
- [http://news.bbc.co.uk/2/hi/science/nature/3752590.stm BBC: The water debate]
- [http://www.geocities.com/tapvsbottled/ Tap Water Vs Bottled Water] - Interesting site providing facts about tap and bottled water.
- [http://www.emagazine.com/september-october_2003/0903feat1.html E the Environmental Magazine piece on bottled water] (Oct 2003).
- [http://www.iapws.org/ International Association for the Properties of Water and Steam]
- [http://ga.water.usgs.gov/edu/watercycle.html US Geological Survey: Comprehensive discussion of the water cycle, in many languages]
- [http://www.dartmouth.edu/~etrnsfer/water.htm Why is water blue?]
- [http://www.water.org.uk/home/resources-and-links/water-for-health/ask-about/adults Water requirements in adults]
- [http://www.hkc22.com/environmentaltechnology.html/ Climate change raises markets for environmental technology, drinking water and clean energies]

References

- OA Jones, JN Lester and N Voulvoulis, Pharmaceuticals: a threat to drinking water? TRENDS in Biotechnology 23(4): 163, 2005
- Category:Beverages Category:Hydrology Category:Materials Category:Natural resources Category:Nutrition zh-min-nan:Chúi als:Wasser ko:물 ja:水 ms:Air simple:Water th:น้ำ

Water (molecule)

Water has the chemical formula H₂O, meaning that one molecule of water is composed of two hydrogen atoms and one oxygen atom. It is in dynamic equilibrium between the liquid and solid states at standard temperature and pressure. At room temperature, it is a nearly colorless, tasteless, and odorless liquid. It is often referred to in the sciences as the universal solvent and the only pure substance found naturally in all three states of matter.

Forms of water

:See the :Category:Forms of water Water may take many forms. The solid state of water is commonly known as ice (while many other forms exist, see amorphous solid water; the gaseous state is known as water vapor (or steam), and the common liquid phase is generally taken as simply water. Water may take many forms, and is the base molecule of aqueous solutions. Above a certain critical temperature and pressure (647 K and 22.064 MPa), water molecules assume a supercritical condition, in which liquid-like clusters float within a vapor-like phase. Heavy water is water in which the hydrogen atoms are replaced by its heavier isotope, deuterium. It is chemically almost identical to normal water. Heavy water is used in the nuclear industry to slow down neutrons.

A common substance

Water in the Universe

Water has been found in interstellar clouds within our galaxy, the Milky Way. It is believed that water exists in abundance in other galaxies too, because its components, hydrogen and oxygen, are among the most abundant elements in the universe. Interstellar clouds eventually condense into solar nebulae and solar systems, such as ours. The initial water can then be found in comets, planets, and their satellites. In our solar system, water, in liquid or ice form, has been found :
- on the Moon,
- on the planets Mercury, Mars, Neptune, and Pluto,
- on satellites of planets, such as Triton and Europa.

Water on Earth

The water cycle (known scientifically as the hydrologic cycle) refers to the continuous exchange of water within the hydrosphere, between the atmosphere, soil water, surface water, groundwater, and plants. Earth's approximate water volume (the total water supply of the world) is 1,360,000,000 km³ (326,000,000 mi³). Of this volume:
- 1,320,000,000 km³ (316,900,000 mi³ or 97.2%) is in the oceans
- 25,000,000 km³ (6,000,000 mi³ or 1.8%) is in glaciers and icecaps
- 13,000,000 km³ (3,000,000 mi³ or 0.9%) is groundwater.
- 250,000 km³ (60,000 mi³ or 0.02%) is fresh water in lakes, inland seas, and rivers.
- 13,000 km³ (3,100 mi³ or 0.001%) is atmospheric water vapor at any given time. Liquid water is found in bodies of water, such as an ocean, sea, lake, river, stream, canal, or pond. The majority of water on Earth is sea water. Water is also present in the atmosphere in both liquid and vapor phases. It also exists as groundwater in aquifers. Although water normally boils at about 100℃, in deep sea vents the pressurised superheated water reaches a natural temperature of 400℃, whereas at the top of Mount Everest, the low pressure allows water to boil at a mere 70℃.

Water in industry

Water is also used in many industrial processes and machines, such as the steam turbine and heat exchanger, in addition to its use as a chemical solvent. Discharge of untreated water from industrial uses is pollution. Pollution includes discharged solutes (chemical pollution) and discharged coolant water (thermal pollution). Industry requires pure water for many applications and utilizes a variety of purification techniques both in water supply and discharge.

Physics and chemistry of water

Density of water and ice

For most substances, the solid form of the substance is more dense than the liquid form; thus, a block of pure solid substance will sink in a tub of pure liquid substance. But, by contrast, a block of common ice will float in a tub of water because solid water is less dense than liquid water. This is an extremely important characteristic property of water. At room temperature, liquid water becomes denser with lowering temperature, just like other substances. But at 4°C, just above freezing, water reaches its maximum density, and as water cools further toward its freezing point, the liquid water, under standard conditions, expands to become less dense. The physical reason for this is related to the crystal structure of ordinary ice, known as hexagonal ice Ih. Water, gallium, bismuth, acetic acid, antimony and silicon are some of the few materials which expand when they freeze; most other materials contract. It should be noted however, that all forms of ice are not less dense than liquid water. For example HDA and VHDA are both more dense than liquid phase pure water. Thus, the reason that the common form of ice is less dense than water is a bit non-intuitive, and relies heavily on the unusual properties inherent to the hydrogen bond. Generally, water expands when it freezes because of its molecular structure, in tandem with the unusual elasticity of the hydrogen bond and the particular lowest energy hexagonal crystal confirmation that it adopts under standard conditions. That is, when water cools, it tries to stack in a crystalline lattice configuration that stretches the rotational and vibrational components of the bond, so that the effect is that each molecule of water is pushed further from each of its neighboring molecules. This effectively reduces the density ρ of water when ice is formed under standard conditions. The importance of this property cannot be overemphasized for its role on the ecosystem of earth. For example, if water was more dense when frozen, lakes and oceans in a polar environment would eventually freeze solid (from top to bottom). This would happen because frozen ice would settle on the lake and riverbeds, and the necessary warming phenomenon (see below) could not occur in summer, as the warm surface layer would be less dense than the solid frozen layer below. It is a significant feature of nature that this does not occur naturally in the environment, but under synthetic laboratory conditions where HDA and VHDA form, specialized forms of ice are more dense, and do sink to the bottom in liquid water. Nevertheless, the unusual expansion of freezing water (in ordinary natural settings in relevant biological systems), due to the hydrogen bond, from 4 °C above freezing to the freezing point offers an important advantage for freshwater life in winter. Water chilled at the surface becomes denser and sinks, forming convection currents that cool the whole water body, but when the temperature of the lake water reaches 4 °C, water on the surface, as it chills further, becomes less dense, and stays as a surface layer which eventually freezes and forms ice. Since downward convection of colder water is blocked by the density change, any large body of fresh water frozen in winter will have the coldest water near the surface, away from the riverbed or lakebed.

Density of saltwater and ice

The situation in salt water is somewhat different. Ice still floats to keep the oceans from freezing solid (see following paragraph). However, the salt content of oceans both lowers the colligative freezing point by about 2 °C and lowers the temperature of the density maximum of water to be about at the freezing point. Hence, in ocean water, because of the salt content, the downward convection of colder water is not blocked by an expansion of water as it becomes colder near the freezing point; thus the oceans' cold water near the freezing point continues to sink. For this reason, any creature attempting to survive at the bottom of such cold water as the Arctic Ocean generally lives in water that is 4 °C colder than the temperature at the bottom of frozen-over fresh water lakes and rivers in winter. As the surface of salt water begins to freeze (at -1.9 °C for normal salinity seawater, 35‰) the ice that forms is essentially salt free with a density approximately that of freshwater ice. This ice floats on the surface and the salt that is "frozen out" adds to the salinity and density of the seawater just below it. This more dense saltwater sinks by convection and the replacing seawater is subject to the same process. This provides essentially freshwater ice at -1.9 °C on the surface. The increased density of the seawater beneath the forming ice sinks towards the bottom, thus the deep ocean waters should have a minimum temperature of -1.9 °C also.

Triple point

The temperature and pressure at which solid, liquid, and gaseous water coexist in equilibrium is called the triple point of water. This point is used to define the units of temperature (the kelvin and, indirectly, the degree Celsius and even the degree Fahrenheit). The triple point is at a temperature of 273.16 K (0.01 °C) by convention, and at a pressure of 611.2 Pa. This pressure is quite low, about 150 times lower than the normal sea level barometric pressure of 101,300 Pa. The atmospheric surface pressure on planet Mars is remarkably close to the triple point pressure.

Mpemba effect

The Mpemba effect is the surprising phenomenon whereby hot water can, under certain conditions, freeze faster than cold water, even though it must pass the lower temperature on the way to freezing. However, this can be explained with evaporation, convection, supercooling, and the insulating effect of frost.

Surface tension

Water drops are stable thanks to the high surface tension of water. This can be seen when small quantities of water are put onto a nonsoluble surface such as glass: the water stays together as drops. This property is important for life. For example, when water is carried through xylem up stems in plants the strong intermolecular attractions hold the water column together. Strong cohesive properties hold the water column together, and strong adhesive properties stick the water to the xylem, and prevent tension rupture caused by transpiration pull. Other liquids with lower surface tension would have a higher tendency to "rip", forming vacuum or air pockets and rendering the xylem water transport inoperative.

Electrical properties

Pure water is actually a good insulator (poor conductor), meaning that it does not conduct electricity well. Because water is such a good solvent, however, it almost always has some solute dissolved in it, most frequently a salt. If water has even a tiny amount of such impurities, then it can conduct electricity much better, because impurities such as salt separate into free ions in aqueous solution by which an electric current can flow. Water can be split into its constituent elements, hydrogen and oxygen, by passing a current through it. This process is called electrolysis. Water molecules naturally dissociate into H⁺ and OH^- ions, which are pulled toward the cathode and anode, respectively. At the cathode, two H⁺ ions pick up electrons and form H₂ gas. At the anode, four OH^- ions combine and release O₂ gas, molecular water, and four electrons. The gases produced bubble to the surface, where they can be collected. It is known that the theoretical maximum electrical resistivity for water is approximately 182 kilohm-meters (or 18.2 MΩ·cm) at 25 degrees Celsius. This figure agrees well with what is typically seen on reverse osmosis, ultrafiltered and deionized ultrapure water systems used for instance, in semiconductor manufacturing plants. A salt or acid contaminant level exceeding that of even 100 parts per trillion (ppt) in ultrapure water will begin to noticeably lower its resistivity level by up to several kilohm-meters (a change of several hundred nanosiemens per meter of conductance).

Dipolar nature of water

An important feature of water is its polar nature. The water molecule forms an angle, with hydrogen atoms at the tips and oxygen at the vertex. Since oxygen has a higher electronegativity than hydrogen, the side of the molecule with the oxygen atom has a partial negative charge. A molecule with such a charge difference is called a dipole. The charge differences cause water molecules to be attracted to each other (the relatively positive areas being attracted to the relatively negative areas) and to other polar molecules. This attraction is known as hydrogen bonding, and explains many of the properties of water. Although hydrogen bonding is a relatively weak attraction compared to the covalent bonds within the water molecule itself, it is responsible for a number of water's physical properties. One such property is its relatively high melting and boiling point temperatures; more heat energy is required to break the hydrogen bonds between molecules. The similar compound hydrogen sulfide (H₂S), which has much weaker hydrogen bonding, is a gas at room temperature even though it has twice the molecular weight of water. The extra bonding between water molecules also gives liquid water a large specific heat capacity. This high heat capacity makes water a good heat storage medium. Hydrogen bonding also gives water its unusual behavior when freezing. When cooled to near freezing point, the presence of hydrogen bonds means that the molecules, as they rearrange to minimize their energy, form the hexagonal crystal structure of ice that is actually of lower density: hence the solid form, ice, will float in water. In other words, water expands as it freezes, whereas virtually all other materials shrink on solidification. An interesting consequence of the solid having a lower density than the liquid is that ice will melt if sufficient pressure is applied. With increasing pressure the melting point temperature drops and when the melting point temperature is lower than the ambient temperature the ice begins to melt. A significant increase of pressure is required to lower the melting point temperature by very much - the pressure exerted by an ice skater on the ice would only reduce the melting point by something like 0.09 °C.

Water as a solvent

Water is also a good solvent due to its polarity. When an ionic or polar compound enters water, it is surrounded by water molecules. The relatively small size of water molecules typically allows many water molecules to surround one molecule of solute. The partially negative dipole ends of the water are attracted to positively charged components of the solute, and vice versa for the positive dipole ends. In general, ionic and polar substances such as acids, alcohols, and salts are relatively soluble in water, and nonpolar substances such as fats and oils are not. Nonpolar molecules stay together in water because it is energetically more favorable for the water molecules to hydrogen bond to each other than to engage in van der Waals interactions with nonpolar molecules. An example of an ionic solute is table salt; the sodium chloride, NaCl, separates into Na⁺ cations and Cl^- anions, each being surrounded by water molecules. The ions are then easily transported away from their crystalline lattice into solution. An example of a nonionic solute is table sugar. The water dipoles make hydrogen bonds with the polar regions of the sugar molecule (OH groups) and allow it to be carried away into solution. The solvent properties of water are vital in biology, because many biochemical reactions take place only within aqueous solutions (e.g., reactions in the cytoplasm and blood).

Amphoteric nature of water

Chemically, water is amphoteric -- i.e., it is able to act as either an acid or a base. Occasionally the term hydroxic acid is used when water acts as an acid in a chemical reaction. At a pH of 7 (neutral), the concentration of hydroxide ions (OH^-) is equal to that of the hydronium (H₃O⁺) or hydrogen (H⁺) ions. If the equilibrium is disturbed, the solution becomes acidic (higher concentration of hydronium ions) or basic (higher concentration of hydroxide ions). Water can act as either an acid or a base in reactions. According to the Brønsted-Lowry system, an acid is defined as a species which donates a proton (an H⁺ ion) in a reaction, and a base as one which receives a proton. When reacting with a stronger acid, water acts as a base; when reacting with a weaker acid, it acts as an acid. For instance, it receives an H⁺ ion from HCl in the equilibrium: :HCl + H₂O ↔ H₃O⁺ + Cl^- Here water is acting as a base, by receiving an H⁺ ion. An acid donates an H⁺ ion, and water can also do this, such as in the reaction with ammonia, NH₃: :NH₃ + H₂O ↔ NH₄⁺ + OH^-

Acidity in nature

In theory, pure water has a pH of 7. In practice, pure water is very difficult to produce. Water left exposed to air for any length of time will rapidly dissolve carbon dioxide, forming a dilute solution of carbonic acid, with a limiting pH of about 5.7. As cloud droplets form in the atmosphere and as raindrops fall through the air minor amounts of CO₂ are absorbed and thus most rain is slightly acidic. If high amounts of nitrogen and sulfur oxides are present in the air, they too will dissolve into the cloud and rain drops producing more serious acid rain problems.

Hydrogen bonding in water

Water molecule can form a maximum of four hydrogen bonds because it can accept two and donate two hydrogens. Other molecules like hydrogen fluoride, ammonia, methanol form hydrogen bonds but they do not show anomalous behaviour of thermodynamic, kinetic or structural properties like those observed in water. The answer to the apparent difference between water and other hydrogen bonding liquids lies in the fact that apart from water none of the hydrogen bonding molecules can form four hydrogen bonds either due to an inability to donate/accept hydrogens or due to steric effects in bulky residues. In water local tetrahedral order due to the four hydrogen bonds gives rise to an open structure and a 3-dimensional bonding network, which exists in contrast to the closely packed structures of simple liquids. There is a great similarity between water and silica in their anomalous behaviour, even though one (water) is a liquid which has a hydrogen bonding network while the other (silica) has a covalent network with a very high melting point. One reason that water is well suited, and chosen, by life-forms, is that it exhibits its unique properties over a temperature regime that suits diverse biological processes, including hydration. It is believed that hydrogen bond in water is largely due to electrostatic forces and some amount of covalency. The partial covalent nature of hydrogen bond predicted by Linus Pauling in 1930s is yet be to proven unambiguously by experiments and theoretical calculations.

Quantum properties of Molecular Water

Although the molecular formula of water is generally considered to be a stable result in molecular thermodynamics, recent work, started in 1995 [http://physics.about.com/gi/dynamic/offsite.htm?site=http://www.aip.org/enews/physnews/2003/split/648%2D1.html] has shown that at certain scales, water may act more like H_3/2O than H₂O at the subatomic quantum level. This result could have significant ramifications at the level of, for example, the hydrogen bond in biological, chemical and physical systems. The experiment shows that when neutrons and protons collide with water, they scatter in a way that indicates that they only are affected by a ratio of 1.5:1 of hydrogen to oxygen respectively. However, the time-scale of this response is only seen at the level of attoseconds, and so is only relevant in highly resolved kinetic and dynamical systems. For more references see [http://prola.aps.org/abstract/PRL/v79/i15/p2839_1] and [http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRLTAO000091000005057403000001&idtype=cvips&gifs=yes].

History

In 1742, Anders Celsius defined the Celsius temperature scale with the freezing point of water at 100 degrees and the boiling point at standard atmospheric pressure at 0 degrees. The scale was reversed in 1744. The first decomposition of water into hydrogen and oxygen, by electrolysis, was done in 1800 by William Nicholson, an English chemist. Gilbert Newton Lewis isolated the first sample of pure heavy water in 1933. Polywater was a hypothetical polymerized form of water that was the subject of much scientific controversy during the late 1960s. The consensus now is that it does not exist.

Systematic nomenclature and humor

Chemists sometimes jokingly refer to water as dihydrogen monoxide or DHMO, an overly pedantic systematic covalent name of this molecule, especially in parodies of chemical research that call for this "lethal chemical" to be banned. In 2004, the town of Aliso Viejo, California nearly banned foam cups after learning that DHMO was used in their production (see [http://slashdot.org/articles/04/03/16/1419252.shtml?tid=133&tid=186]). In reality, a more realistic systematic name would be hydrogen oxide, since the "di-" and "mon-" prefixes are superfluous. Hydrogen sulfide, H₂S, is never referred to as "dihydrogen monosulfide", and hydrogen peroxide, H₂O₂, is never called "dihydrogen dioxide". Some overzealous MSDSs for water list the following: Caution: May cause drowning! The systematic acid name of water is hydroxic acid or hydroxilic acid. Likewise, the systematic alkali name of water is hydrogen hydroxide – both acid and alkali names exist for water because it is able to react both as an acid or an alkali, depending on the strength of the acid or alkali it is reacted with (it is amphoteric). None of these names are used widely outside of DHMO sites.

External links

- [http://www.lsbu.ac.uk/water/ Water Structure and Behaviour]
- [http://www.dhmo.org/ A spoof site on the "dangers" of dihydrogen monoxide]
- [http://www.siwi.org/ Stockholm International Water Institute] (SIWI)
- [http://www.btinternet.com/~martin.chaplin/explan.html Explanation of the anomalous properties of water]
- [http://www.compchemwiki.org/index.php?title=Water Computational Chemistry Wiki] Category:Forms of water Category:Solvents Category:Hydrogen compounds Category:Oxygen compounds Category:Hydrides Category:Oxides Category:Hydroxides

German language

German (German: ), is a member of the western group of Germanic languages and is one of the world's major languages. It is the language with the most native speakers in the European Union. Spoken by more than 130 million people in 38 countries of the world, German is—like English—a pluricentric language with three main centers of usage: Germany, Austria and Switzerland.

Geographic distribution

German is spoken primarily in Germany, Austria, Liechtenstein, in two-thirds of Switzerland, in two-thirds of the South Tyrol province of Italy (in German, Südtirol), in the small East Cantons of Belgium, and in some border villages of the South Jutland County (in German, Nordschleswig, in Danish, Sønderjylland) of Denmark. In Luxembourg (in German, Luxemburg), as well as in the French régions of Alsace (in German, Elsass) and parts of Lorraine (in German, Lothringen), the native populations speak several German dialects, and some people also master standard German (especially in Luxembourg), although in Alsace and Lorraine French has for the most part replaced the local German dialects in the last 40 years. Some German speaking communities still survive in parts of Romania, the Czech Republic, Hungary, and above all Russia, Kazakhstan and Poland, although massive relocations to Germany in the late 1940s and 1990s have depopulated most of these communities. Outside of Europe and the former Soviet Union, the largest German speaking communities are to be found in the USA and in Brazil where millions of Germans migrated in the last 200 years; but the great majority of their descendants no longer speak German. Additionally, German speaking communities are to be found in the former German colony of Namibia, as well as in the other countries of German emigration such as Canada, Argentina, Paraguay, Chile, Peru, Venezuela (where Alemán Coloneiro developed), Thailand, and Australia. See also Plautdietsch. In the USA, the largest concentration of German speakers are in Pennsylvania (Amish, Hutterites and some Mennonites speak Pennsylvania German and Hutterite German), Texas (Texas German), North Dakota, South Dakota, Montana, Wisconsin and Indiana also speak dialects of German. In Brazil the largest concentrations of German speakers are in Rio Grande do Sul, where Riograndenser Hunsrückisch was developed, Santa Catarina, Paraná, and Espírito Santo). Generally, German immigrant communities in the USA have lost their mother tongue more quickly than those who moved to South America, possibly due to the fact that for Germans English is easier to learn than Portuguese or Spanish. German is the main language of about 100 million people in Europe (as of 2004), or 13.3% of all Europeans, being the most spoken language in Europe excluding Russia, above French (66.5 million speakers in Europe in 2004) and English (64.2 million speakers in Europe in 2004). German is the third most taught foreign language worldwide, also in the USA (after Spanish and French); it is the second most known foreign language in the EU (after English; see [http://europa.eu.int/comm/public_opinion/archives/ebs/ebs_237.en.pdf]) It is one of the official languages of the European Union.

History

As a consequence of the colonisation patterns the Völkerwanderung, the routes for trade and communication (chiefly the rivers), and of physical isolation (high mountains and deep forests) very different regional dialects developed. These dialects, sometimes mutually unintelligible, were used across the Holy Roman Empire. As Germany was divided into many different states, the only force working for a unification or standardisation of German during a period of several hundred years was the general preference of writers trying to write in a way that could be understood in the largest possible area. When Martin Luther translated the Bible (the New Testament in 1521 and the Old Testament in 1534) he based his translation mainly on this already developed language, which was the most widely understood language at this time. This language was based on Eastern Upper and Eastern Central German dialects and preserved much of the grammatical system of Middle High German (unlike the spoken German dialects in Central and Upper Germany that already at that time began to lose the genitive case and the preterit tense). In the beginning, copies of the Bible had a long list for each region, which translated words unknown in the region into the regional dialect. Roman Catholics rejected Luther's translation in the beginning and tried to create their own Catholic standard (Gemeines Deutsch) — which, however, only differed from 'Protestant German' in some minor details. It took until the middle of the 18th century to create a standard that was widely accepted, thus ending the period of Early New High German. German used to be the language of commerce and government in the Habsburg Empire, which encompassed a large area of Central and Eastern Europe. Until the mid-19th century it was essentially the language of townspeople throughout most of the Empire. It indicated that the speaker was a merchant, an urbanite, not their nationality. Some cities, such as Prague (German: Prag) and Budapest (Buda, German: Ofen), were gradually Germanized in the years after their incorporation into the Habsburg domain. Others, such as Bratislava (German: Pressburg), were originally settled during the Habsburg period and were primarily German at that time. A few cities such as Milan (German: Mailand) remained primarily non-German. However, most cities were primarily German during this time, such as Prague, Budapest, Bratislava, Zagreb (German: Agram), and Ljubljana (German: Laibach), though they were surrounded by territory that spoke other languages. Until about 1800, Standard German was almost only a written language. In this time, people in urban northern Germany, who spoke dialects very different from Standard German, learnt it almost like a foreign language and tried to pronounce it as close to the spelling as possible. Prescriptive pronunciation guides used to consider that northern German pronunciation to be the standard. However, the actual pronunciation of standard German varies from region to region. Media and written works are almost all produced in standard German (often called Hochdeutsch in German), which is understood in all areas of German languages (except by pre-school children in areas which speak only dialect, for example Switzerland — but in this age of TV, even they now usually learn to understand Standard German before school age). The first dictionary of the Brothers Grimm, the 16 parts of which were issued between 1852 and 1960, remains the most comprehensive guide to the words of the German language. In 1860, grammatical and orthographic rules first appeared in the Duden Handbook. In 1901, this was declared the standard definition of the German language. Official revisions of some of these rules were not issued until 1998, when the German spelling reform of 1996 was officially promulgated by governmental representatives of all German-speaking countries. Since the reform, German spelling has been in an eight-year transitional period where the reformed spelling is taught in most schools, while traditional and reformed spelling co-exist in the media. See German spelling reform of 1996 for an overview of the heated public debate concerning the reform. During the 1870s, the German language successfully replaced Latin as the dominant language in all major European and North American universities, thanks to the prominence of German universities at the time. Most important research in the sciences for some decades afterward was published in German, and new universities preferred German instead of Greek or Latin mottoes (for example, Stanford University).

Classification and related languages

Stanford University is divided into Upper German (blue) and Central German (green), and the Dutch/Plattdüütsch (yellow). The main isoglosses, the Benrath and Speyer lines are marked in red.]] German is a member of the western branch of the Germanic family of languages, which in turn is part of the Indo-European language family.

Neighboring languages

German forms together with Dutch, its closest relative, a coherent and well-defined language area that is separated from its neighbors by language borders. These neighbors are: in the north Frisian and Danish; in the east Polish, Sorbian, Czech, Slovak, and Hungarian; in the south Slovenian, Italian, Friulian, Ladin, and Romansh; in the west French. Except for Frisian, none of these languages are West Germanic, and so they are clearly distinct from German and Dutch. While Frisian is closely related to German and Dutch, it is generally considered not to be mutually intelligible with them. The situation is more complex with respect to the distinction between German and Dutch. Until recently, there has been a dialect continuum throughout the whole German-Dutch language area, with no language borders. In such a dialect continuum, dialects are always mutually intelligible with their neighbors, but dialects that are further apart from each other are often not. The German-Dutch continuum lent itself to a classification of dialects into Low German and High German based on their participation in the High German consonant shift; Dutch is part of the Low German group. However, because of the political separation between Germany and the Netherlands, Low German dialects in the Netherlands and Low German dialects in Germany have started to diverge during the 20th century. Additionally, both in northern Germany and in the Netherlands, many dialects are close to extinction and are being replaced by the German and Dutch standard languages. In this way, a language border between Dutch and German is currently forming. While German is grammatically similar in many ways to Dutch, it is very different in speech. A speaker of one may require some practice to effectively understand a speaker of the other. Compare, for example: :De kleinste kameleon is volwassen 2 cm groot, de grootste kan wel 80 cm worden. (Dutch) :Das kleinste Chamäleon ist ausgewachsen 2 cm groß, das größte kann gut 80 cm werden. (Standard German) : (English: "The smallest chameleon is fully grown 2 cm long, the longest can easily attain 80 cm.") Dutch speakers are generally able to read German, and German speakers who can speak Low German or English are generally able to read Dutch, but have problems understanding the spoken language, although Germans who speak High German, or, even better, Low German, can cope with Dutch much better than people from Southern Germany, Switzerland and Austria who have grown up with the Alemannic or Bavarian dialects.

Official status

Standard German is the only official language in Germany, Liechtenstein, and Austria; it shares official status in Switzerland (with French, Italian and Romansh), and Luxembourg (with French and Luxembourgish). It is used as a local official language in German-speaking regions of Belgium, Italy, Denmark, and Poland. It is one of the 20 official languages of the European Union. It is also a minority language in Canada, France, Russia, Kazakhstan, Tajikistan, Poland, Romania, Togo, Cameroon, the USA, Namibia, Brazil, Paraguay, Hungary, the Czech Republic, Slovakia, the Netherlands, Slovenia, Ukraine, Croatia, Moldavia, Australia, Latvia, Estonia, and Lithuania. German was once the lingua franca of central, eastern and northern Europe. Increasing influence from the English language has affected German recently. However, German remains one of the most popular foreign languages taught world-wide, and is more popular than French as a foreign language in Europe. 8% of citizens of the EU-15 countries say they can converse in German, in addition to the 24% who speak German as a mother tongue.[http://europa.eu.int/comm/education/policies/lang/languages/index_en.html] This is assisted by the availability of German TV by cable or satellite, where series like Star Trek are shown dubbed into German. German is also the second language of the Internet, more than 8% of the websites are in German (English 50%, French 6%, Japanese 5%, Spanish 3% and Portuguese 2%).

Dialects

The term "German" is used for the dialects of Germany, Austria, German-speaking Switzerland (that is, outside the French-, Italian-, and Romansch-speaking areas) and some areas in the surrounding countries, as well as for several colonies and other ethnic concentrations founded by German-speaking people (for example German in the United States). The variation among the German dialects is considerable. Only the neighbouring dialects are mutually understandable. Most dialects are not understandable for someone who knows standard German. However, all German dialects belong to the dialect continuum of the continental West Germanic languages because any pair of neighbouring dialects is perfectly mutually intelligible. The dialect continuum of the continental West Germanic languages is typically divided into Low Germanic languages and High Germanic languages. Low Germanic is defined as the varieties that were not affected by the High German consonant shift. They consist of two subgroups, Low Franconian and Plattdüütsch (Low German). Low Franconian includes Dutch and Afrikaans, spoken primarily in the Netherlands, Belgium and South Africa; Plattdüütsch includes dialects spoken primarily in the German Lowlands and in the eastern Netherlands. The Plattdüütsch varieties are considered dialects of the German language by some, but a separate language by others; the Low Franconian varieties are not considered a part of the German language (see above for a discussion of the distinction between German and Dutch). High Germanic is divided into Central German and Upper German. Central German dialects include Ripuarian, Moselle Franconian, Rhine Franconian, Hessian, Thuringian and Upper Saxon. It is spoken in the southeastern Netherlands, eastern Belgium, Luxembourg, parts of France, and in Germany approximately between the River Main and the southern edge of the Lowlands. Modern Standard German is mostly based on Central German. The Moselle Franconian varieties spoken in Luxembourg have been officially standardized and institutionalized and are therefore usually considered a separate language, Luxembourgish language. Upper German dialects include Alemannic (for instance Swiss German), Swabian, East Franconian, and Austro-Bavarian. They are spoken in parts of the Alsace, southern Germany, Liechtenstein, Austria, and in the German-speaking parts of Switzerland and Italy. The High German varieties spoken by Ashkenazi Jews (mostly in the former Soviet Union) have several unique features, and are usually considered as a separate language, Yiddish. The dialects of German which are or were primarily spoken in colonies founded by German speaking people resemble the dialects of the regions the founders came from (for example Pennsylvania German resembles dialects of the Palatinate, or Hutterite German resembles dialects of Carinthia). In the United States, the teaching of the German language to latter-age students has given rise to a pidgin variant which combines the German language with the grammar and spelling rules of the English language. It is often understandable by either party. The speakers of this language often refer to it as Amerikanisch or Amerikanischdeutsch, although it is known in English as American German.

Standard German

In German linguistics, only the traditional regional varieties are called dialects, not the different varieties of standard German. Standard German has originated not as a traditional dialect of a specific region, but as a written language. However, there are places where the traditional regional dialects have been replaced by standard German (especially in major cities of Germany, and to some extent in Vienna). Standard German differs regionally, especially between German-speaking countries, especially in vocabulary, but also in some instances of pronunciation and even grammar. This variation must not be confused with the variation of local dialects. Even though the regional varieties of standard German are to a certain degree influenced by the local dialects, they are very distinct. German is thus considered a pluricentric language. In most regions, the speakers use a continuum of mixtures from more dialectical varieties to more standard varieties according to situation. In the German-speaking parts of Switzerland, mixtures of dialect and standard are very seldom used, and the use of standard German is almost entirely restricted to the written language. Therefore, this situation has been called a medial diglossia. Standard German is rarely spoken, for instance when speaking with people who do not understand the Swiss German dialects at all, and it is expected to be used in school.

Grammar

Main article: German grammar German is an inflected language.

Noun inflection

German nouns inflect into:
- one of four declension classes
- one of three genders: masculine, feminine, or neuter. Word endings indicate some grammatical genders; others are arbitrary and must be memorised.
- two numbers: singular and plural
- four cases: nominative, genitive, dative, and accusative case. Although German is usually cited as an outstanding example of a highly inflected language, it should be noted that the degree of inflection is considerably less than in Old German, or in Icelandic today. The three genders have collapsed in the plural, which now behaves, grammatically, somewhat as a fourth gender. With four cases and three genders plus plural there are 16 distinct possible combinations of case and gender/number, but presently there are only six forms of the definite article used for the 16 possibilities. Inflection for case on the noun itself is required in the singular for strong masculine and neuter nouns in the genitive and sometimes in the dative. This dative ending is considered somewhat old-fashioned in many contexts and often dropped, but it is still used in sayings and in formal speech or written language. Weak masculine nouns share an common case ending for genitive, dative and accusative in the singular. Feminines are not declined in the singular. The plural does have an inflection for the dative. In total, six inflectional endings (not counting plural markers) exist in German: -s, -es, -n, -en, -ns, -e In the German orthography, unlike any other orthography, nouns and most words with the syntactical function of nouns are capitalised, which makes it quite easy for readers to find out what function a word has within the sentence. On the other hand, things get more difficult for the writer. Like most Germanic languages, German forms left-branching noun compounds, where the first noun modifies the category given by the second, for example: Hundehütte (eng. doghouse). Unlike English, where newer compounds or combinations of longer nouns are often written in open form with separating spaces, German (like the other German languages) always uses the closed form without spaces, for example: Baumhaus (eng. tree house). Like English, German allows arbitrarily long compounds, but these are rare. (See also English compounds.) The longest official German word is Rindfleischetikettierungsüberwachungsaufgabenübertragungsgesetz. There is even a child's game played in kindergartens and primary schools where a child begins the spelling of a word (which is not told) by naming the first letter. The next one tells the next letter, the third one tells the third and so on. The game is over when the a child can not think of another letter to be added to the word.

Verb Inflection

Standard German verbs inflect into:
- one of two conjugation classes, weak and strong (like English). (note: in fact there is a third class, called "gemischte Verben", which can be either weak ("active meaning") or strong ("passive meaning")) There are about 200 irregular verbs.
- three persons: 1st, 2nd, 3rd.
- two numbers: singular and plural
- three moods: Indicative, Subjunctive, Imperative
- two genera verbi: active and passive; the passive being composed and dividable into static and dynamic.
- 2 non-composed tenses (Present, Preterite) and 4 composed tenses (Perfect, Plusquamperfect, Future I, Future II)
- no distinction between aspects (in English, perfect and progressive; in Polish between completed and incompleted form; in Turkish between first-hand and second-hand information) There are also many ways to expand, an sometimes radically change, the meaning of a base verb through several prefixes. Example: haften=to stick, verhaften=to imprison The word order is much more flexible than in English. The word order can be changed for subtle changes of a sentence's meaning. In normal positive sentences the verb always has position 2, in questions it has position 1. Most German vocabulary is derived from the Germanic branch of the Indo-European language family, although there are significant minorities of words derived from Latin, French, and most recently English.

Writing system

German is written using the Latin alphabet. In addition to the 26 standard letters, German has three vowels with Umlaut, namely ä, ö and ü, as well as a special symbol for "ss", which is used only after long vowels or diphthongs (and not used at all in Switzerland), the Eszett or Scharfes-S (sharp "s") ß. Until the early 20th century, German was mostly printed in blackletter typefaces (mostly in Fraktur, but also in Schwabacher) and written in corresponding handwriting (for example Kurrent and Sütterlin). These variants of the Latin alphabet are very different from the serif or sans serif antiqua typefaces used today, and are difficult for the untrained to read. They were abolished by the Nazis (incorrectly claiming that these letters are Jewish) in 1941 but this has been retained for broader and easier usability.

Alphabet

Main article: German alphabet.

Phonology

Main article: German phonology (pronunciation, historical sound changes).

Cognates with English

There are many German words that are cognate to English words. Most of them are easily identifiable and have almost the same meaning. When these cognates have slightly different consonants, this is often due to the High German consonant shift. There are cognates whose meanings in either language have changed through the centuries. It is sometimes difficult for both English and German speakers to discern the relationship. On the other hand, once the definitions are made clear, then the logical relation becomes obvious. There are many English loanwords in German, and a somewhat smaller number of German loanwords in English. Sometimes these also involve semantic changes, for example German Dogge, 'mastiff', from English dog, or German Handy, 'mobile phone'. German and English also share many borrowings from other languages, especially from Latin, French and Greek, but also from many other languages. Most of these word have the same meaning, while a few have subtle differences in meaning. As many of these words have been borrowed by numerous languages, not only German and English, they are called internationalisms in German linguistics.

Examples of German

Names of the German language in other languages

Because of the turbulent history of both Germany and the German language, the names that other peoples have chosen to use to refer to it varies more than for most other languages. In general, the names for the German language can be arranged in five groups according to their origin: Lao is unique in that both under the influence of English "German" (through Thai "yenman") and French (the colonial language) "Allemand", it chose a name in between: ພາສາເຢຍລະມັນ (phaxa yeylaman), which could be ranked both under category 2 and category 5. Note: The Romanian language used to use in the past the Slavonic term "nemţeşte", but "germană" is now widely used. Hungarian "német" is also a Slavonic loan-word. The Arabic name for Austria, النمسا ("an-namsa"), is derived from the Slavonic term. A possible explanation for the use of "mute" to refer to German (and also to Germans) in Slavic languages is that Germans were the first people Slavic tribes encountered, with whom they could not communicate. The corresponding experience for the Germans was with the Volcae, whose name they subsequently also applied to the Slavs, see etymology of Vlach. Hebrew traditionally (nowadays this is not the case) used the Biblical term Ashkenaz (Genesis 10.3) to refer to Germany, or to certain parts of it, and the Ashkenazi Jews are those who originate from Germany and Eastern Europe and formerly spoke Yiddish as their native language, derived from Middle High German.

External links

-
- [http://www.declan-software.com/german German language learning audio software]
- [http://learno.com/german Online Learno german course] Free online German tutorial at Learno.com
- [http://www.washjeff.edu/capl/ Culturally Authentic Pictorial Lexicon] Free online visual lexicon of the German language with authentic photos from German speaking world.
- [http://www.sprachtausch.net Sprachtausch.net] — German website to find someone to teach you, for example german in exchange with your language.
- [http://www.ethnologue.com/show_language.asp?code=deu Ethnologue report for German]
- [http://www.travlang.com/languages/german/ihgg/ Internet Handbook of German Grammar]
- [http://www.lsa.umich.edu/german/hmr/ German resources] at the University of Michigan
- [http://german.languages4everyone.com Learn German Online] with this internet German course for beginners
- [http://www.dw-world.de/dw/0,1595,2469,00.html Deutsche Welle's Online German Courses]
- [http://www.applelanguages.com/en/learn/german.php German courses in Germany]
- [http://www.vds-ev.de Verein Deutsche Sprache] (in German)
- A beginning [http://wikibooks.org/wiki/German German Language Textbook] under development at [http://wikibooks.org/ Wikibooks]
- [http://www.diwa.info/ Digital Wenker-Atlas] Project publishing the 19th century Linguistic Atlas of the German Empire
- [http://www.geocities.com/language_directory/languages/german.htm List of online German-related resources]
- [http://eserver.org/langs/the-awful-german-language.txt That awful German language] — A humourous essay by Mark Twain
- [http://how-to-learn-any-language.com/e/languages/german/index.html Why learn German? A German language profile]
- [http://www.vistawide.com/german/why_german.htm Why learn German?] — 12 reasons to learn German
- [http://www.actilingua.com/german_courses/german_language.php Short summary on German language and varieties with a map!]
- [http://www.ielanguages.com/German.html Free German Language Tutorial from ielanguages.com]
- [http://www.passwort-deutsch.de/ Passwort Deutsch] - A German course
- [http://www.deutsch-lernen.com/ Learn German Online] containing free courses
- [http://www.loecsen.com/travel/discover_pop.php?lang=en&to_lang=1&learn-German/ Learn and listen to useful expressions in German] Each expression is presented with an audio recording and an illustration
- [http://www.expatica.com/source/site_content_subchannel.asp?subchannel_id=37&name=Germany+Education Articles on learning German] Also has a service whereby learners of German can send questions to a German teacher

Dictionary and word translations

- [http://dict.leo.org/ The LEO Online Dictionary] German-English-German dictionary at Leo.org
- [http://dict.tu-chemnitz.de/ TU Chemnitz Dictionary] a 185000+ German-English Dictionary with proverbs and pronounciation
- [http://www.dict.cc/ dict.cc: User-editable German-English-German Dictionary] works similar to Wikipedia, more than 840,000 keywords (420,000 translation pairs)
- [http://odge.info/ Odge.info] uses dict.cc's data according to [http://odge.info/License/ license] page
- [http://www.websters-online-dictionary.org/definition/German-english/ German — English Dictionary]: from [http://www.websters-online-dictionary.org Webster's Online Dictionary] — the Rosetta Edition.
- [http://www.canoo.net/index_en.html German Grammar, Online Dictionary for Spelling, Infection and Wordformation for the German Language]
- [http://www.geodic.de GEODic] German-English-Online-Dictionary
- [http://www.woerterbuch.info woerterbuch.info — Free English-German Online Dictionary] with over 600.000 translations
- [http://www.dwds.de The Digital Dictonary Project]in German - Dictionary, Corpus and Statistics
- http://www.dedict.de - English-German Online Dictionary
- http://www.spell-it.net - Free English-German Online Dictionary

Grammar

- [http://www.wm.edu/modlang/gasmit/grammar/grammnu.html Grammar of German]
- [http://www.arts.uwaterloo.ca/~skidmore/grammarpage.htm German Grammar on the Web]
- [http://io.uwinnipeg.ca/~oberle/courses/review.html German Review Grammar]
- [http://www.cas.muohio.edu/~greal/netzgrammatik/grammar.html German Grammar Charts]

Reference

Taste

Taste is one of the most common and fundamental of the senses of animals. It is the direct detection of chemical composition, usually through contact with chemoreceptor cells. Taste is very similar to olfaction (the sense of smell), in which the chemical composition of an organism's ambient medium is detected by chemoreceptors. In a liquid medium, taste is often used to describe this act as well. :Main article: Gustatory system. In humans, the sense of taste is transduced by taste buds and is conveyed via three of the twelve cranial nerves. The facial nerve (VII) carries taste sensations from the anterior two thirds of the tongue, the glossopharyngeal nerve (IX) carries taste sensations from the posterior one third of the tongue while a branch of the vagus nerve (X) carries some taste sensations from the back of the oral cavity. Information from these cranial nerves is processed by the gustatory system. :Main article:Basic taste. As a general rule, taste is a holistic assessment of the interaction of the fundamental taste systems of sweetness, sour, bitter, salty, and umami ("savouriness"). Location of the stimulus on the tongue is not important, despite the common misperception of a "taste map" of sensitivity to different tastes thought to correspond to specific areas of the tongue [http://www.med-rz.uni-sb.de/med_fak/physiol1/LDM/chemotopic_1.htm]. The "mouth map" is a myth. It is a misinterperatation of a German medical paper by a Harvard psychology student in 1901 . In reality, the separate populations of taste buds sensing each of the basic tastes are distributed across the tongue. If half of the tongue is blocked from sending information to the brain, people will report that a doubling of psychological perception has occurred for sweet, sour, salty, and bitter. See also Flavor

Terms for disorders of taste

- ageusia (complete loss)
- hypogeusia (partial loss)
- parageusia (unpleasant taste)
- dysgeusia (inaccurate taste)

Taste in aesthetics

:Main article Taste (aesthetics). Taste can also refer to appreciation for aesthetic quality, significantly applying the purely physical term to an intellectual quality. In such contexts Taste begins to be used in a metaphorical sense to refer to certain degrees of cultural competence, closely related to the concept of discrimination; it can set distinctions between "tasteful" and "tasteless" or the embodiments of "good taste" or "bad taste", thus providing categories for social division and reinforcing cultural hierarchy. The modern concept of "taste" is a product of the 16th century Italian Mannerism: the idea of "taste" as a quality that is independent of the style that is simply its vehicle — though the style might be designated a taste, such as "the Antique taste"— was born in the circle of Pope Julius III and first realized at the Villa Giulia he built on the edge of Rome in 1551 - 1555. To the Enlightenment, "taste" was still a universal character, which could be recognized by what pleased any cultured sensibility. With the shift in perspective that Romanticism brought, it began to be thought that, to the contrary, "Beauty is in the eye of the beholder" and could be individually interpreted, with results that might be of equivalent aesthetic value.

Taste as a metaphor for experience or knowledge

To taste is also used metaphorically to describe having a small amount of experience with something that gives a sense of its quality as a whole. For example: "they had not yet tasted the sweetness of freedom" (Livy) or "I tasted in her arms the delights of paradise" (Voltaire). The word is often used as a noun in this sense, typically in such expressions as "I got a taste of it" or "It left a bad taste in my mouth."

Odor

] An odor (American English) or odour (Commonwealth English) is the object of perception of the sense of olfaction. Odors are also called smells. The term stench or pong is used to describe an unpleasant odor. The term fragrance or aroma is used primarily by the food and cosmetic industry to describe a pleasant odor. Odors correspond to the objective phenomenon of chemicals dissolved in air, although, as with other senses, psychological factors can play a part in perception. Certain odors, such as perfumes and flowers, are much sought after and large prices are paid for the most elite ones. Other whole industries have developed products to remove unpleasant odors. See deodorant. Odors that are mostly perceived as "pleasant":
- fresh breath, flowers, trees, some plants, cologne, mint, fresh fruit Odors that are mostly perceived as "unpleasant":
- bad breath, foot odor, feces, vomit, rotting fruit The perception of odors is also very much dependent upon circumstance. The odor of cooking processes may be agreeable while cooking, but not after the meal when one is full. It is also culturally dependent; what smells great to you may be quite unpleasant for your neighbors. The study of odors is a growing field, but is a complex and difficult one. The human olfactory system can detect many thousands of scents based on only very minute airborne concentrations of a chemical. The sense of smell of many animals is ev