Name = Water (H2O)
ImageFileL1 = Water-2D-labelled.png
ImageSizeL1 = 120px
ImageNameL1 = The water molecule has this basic geometric structure
ImageFileR1 = Water molecule 3D.svg
ImageSizeR1 = 100px
ImageNameR1 = Space filling model of a water molecule
IUPACName = Water
OtherNames = Aqua
Section1 = Chembox Identifiers
CASNo = 7732-18-5
RTECS = ZC0110000
Section2 = Chembox Properties
Formula = H2O or HOH
MolarMass = 18.01528(33) g/mol
Appearance = white solid or almost colourless, transparent, with a slight hint of blue, crystalline solid or liquid [cite journal|last=Braun|first=Charles L.|coauthors=Sergei N. Smirnov|title=Why is water blue?|journal=J. Chem. Educ.|volume=70|issue=8|pages=612|date=1993|url=http://www.dartmouth.edu/~etrnsfer/water.htm|format=HTML]
Density = 1000 kg·m−3, liquid (4 °C)
917 kg·m−3, solid
MeltingPt = 0 °C, 32 °F (273.15 K)
Vienna Standard Mean Ocean Water(VSMOW), used for calibration, melts at 273.1500089(10) K (0.000089(10) °C, and boils at 373.1339 K (99.9839 °C)]
BoilingPt = 100 °C, 212 °F (373.15 K)
pKa = 15.74
pKb = 15.74
Viscosity = 0.001 Pa·s at 20 °C
Section3 = Chembox Structure
MolShape = bent
CrystalStruct = Hexagonal
Dipole = 1.85 D
Section7 = Chembox Hazards
water intoxication, drowning(see also Dihydrogen monoxide hoax)
NFPA-H = 0
NFPA-F = 0
NFPA-R = 1
Section8 = Chembox Related
water vapor ice heavy water
Water (H2O, HOH) is the most abundant
moleculeon Earth's surface, composing of about 70% of the Earth's surface as liquid and solid state in addition to being found in the atmosphere as a vapor. It is in dynamic equilibriumbetween the liquidand vaporstates at standard temperature and pressure. At room temperature, it is a nearly colorless(with a hint of blue), tasteless, and odorless liquid. Many substances dissolve in water and it is commonly referred to as "the universal solvent". Because of this, water in nature and in use is rarely pure, and may have some properties different from those in the laboratory. However, there are many compounds that are essentially, if not completely, insoluble in water. Water is the only common substance found naturally in all three common states of matter—for other substances, see Chemical properties. Water also makes up 55% to 78% of the human body. [ [http://www.madsci.org/posts/archives/2000-05/958588306.An.r.html Re: What percentage of the human body is composed of water?] Jeffrey Utz, M.D., The MadSci Network ]
Forms of water
:"See Types of Water"Water can take many forms. The solid state of water is commonly known as
ice; the gaseous stateis known as water vapor(or steam), and the common liquid phase is generally taken as simply water. Above a certain critical temperatureand pressure (647 K and 22.064 MPa), water molecules assume a "supercritical" condition, in which liquid-like clusters float within a vapor-like phase.
There are many different
crystaland amorphousforms of ice; see icefor a complete listing. Heavy wateris water in which the hydrogen is 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.
Physics and chemistry of water
Water is the
chemical substancewith chemical formulaH2O: one moleculeof water has two hydrogen atoms covalently bonded to a single oxygenatom. Water is a tasteless, odorless liquid at ambient temperature and pressure, and appears colorless in small quantities, although it has its own intrinsic very light blue hue. Ice also appears colorless, and water vapor is essentially invisible as a gas. [cite journal|last=Braun|first=Charles L.|coauthors=Sergei N. Smirnov|title=Why is water blue?|journal=J. Chem. Educ.|volume=70|issue=8|pages=612|date=1993|url=http://www.dartmouth.edu/~etrnsfer/water.htm|format=HTML] Water is primarily a liquid under standard conditions, which is not predicted from its relationship to other analogous hydrides of the oxygen family in the periodic table, which are gases such as hydrogen sulfide. Also the elements surrounding oxygen in the periodic table, nitrogen, fluorine, phosphorus, sulfurand chlorine, all combine with hydrogento produce gases under standard conditions. The reason that oxygen dihydride (water) forms a liquid is that it is more electronegativethan all of these elements (other than fluorine). Oxygen attracts electrons much more strongly than hydrogen, resulting in a net positive charge on the hydrogen atoms, and a net negative charge on the oxygen atom. The presence of a charge on each of these atoms gives each water molecule a net dipole moment. Electrical attraction between water molecules due to this dipole pulls individual molecules closer together, making it more difficult to separate the molecules and therefore raising the boiling point. This attraction is known as hydrogen bonding. Water can be described as a polar liquid that dissociates disproportionately into the hydroniumion (H3O+(aq)) and an associated hydroxideion (OH−(aq)).Water is in dynamic equilibriumbetween the liquid, gasand solidstates at standard temperature and pressure(0°C, 100.000 kPa) , and is the only pure substance found naturally on Earth to be so.
Water, ice and vapor
Heat capacity and heats of vaporization and fusion
Water has the second highest
specific heat capacityof any known chemical compound, after ammonia, as well as a high heat of vaporization(40.65 kJ mol−1), both of which are a result of the extensive hydrogen bonding between its molecules. These two unusual properties allow water to moderate Earth's climateby buffering large fluctuations in temperature.
enthalpy of fusionof water is 333.55 kJ kg−1 at 0 °C. Of common substances, only that of ammonia is higher. This property confers resistance to melting upon the ice of glaciers and drift ice. Before the advent of mechanical refrigeration, ice was in common use to retard food spoilage.
Density of water and ice
temperatureand pressureat which solid, liquid, and gaseous water coexist in equilibrium is called the triple pointof water. This point is used to define the units of temperature (the kelvin, the SI unit of thermodynamic temperature and, indirectly, the degree Celsiusand even the degree Fahrenheit). As a consequence, water's triple point temperature is a prescribed value rather than a measured quantity. The triple point is at a temperature of 273.16 K (0.01 °C) by convention, and at a pressure of 611.73 Pa. This pressure is quite low, about 1/166 of the normal sea level barometric pressure of 101,325 Pa. The atmospheric surface pressure on planet Marsis remarkably close to the triple point pressure, and the zero-elevation or "sea level" of Mars is defined by the height at which the atmospheric pressure corresponds to the triple point of water.
Although it is commonly named as "the" triple point of water", the stable combination of liquid water,
ice I, and water vapour is but one of several triple points on the phase diagramof water. Gustav Heinrich Johann Apollon Tammann in Göttingen produced data on several other triple points in the early 20th century. Kamb and others documented further triple points in the 1960s. [cite paper|title=The States Of Aggregation|date=1925|author=Gustav Heinrich Johann Apollon Tammann|publisher=Constable And Company Limited] [cite book|title=A System of Physical Chemistry|author=William Cudmore McCullagh Lewis and James Rice|date=1922|publisher=Longmans, Green and co.]
Water drops are stable, due to the high
surface tensionof water, 72.8 mN/m, the highest of the non-metallic liquids. This can be seen when small quantities of water are put on a surface such as glass: the water stays together as drops. This property is important for life. For example, when water is carried through xylemup 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.
Pure water containing no ions is an excellent insulator, but not even "deionized" water is completely free of ions. Water undergoes auto-ionisation at any temperature above
absolute zero. Further, because water is such a good solvent, it almost always has some solutedissolved in it, most frequently a salt. If water has even a tiny amount of such an impurity, then it can conduct electricity readily, as 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 an electric current through it. This process is called
electrolysis. Water molecules naturally dissociate into H+ and OH− ions, which are pulled toward the cathodeand 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 kΩ·m²/m (or 18.2 MΩ·cm²/cm) at 25 °C. This figure agrees well with what is typically seen on reverse osmosis, ultrafiltered and deionized ultrapure watersystems used, for instance, in semiconductor manufacturing plants. A salt or acid contaminant level exceeding even 100 parts per trillion (ppt) in ultrapure water begins to noticeably lower its resistivity level by up to several kilohm-square meters per meter (a change of several hundred nanosiemens per meter of conductance).
Pure water has a "low"
electrical conductivity, but this increases significantly upon solvation of a small amount of ionic material water such as hydrogen chloride. Thus the risks of electrocution are much greater in water with the usual impurities not found in pure water. (It is worth noting, however, that the risks of electrocution decrease when the impurities increase to the point where the water itself is a better conductor than the human body. For example, the risks of electrocution in sea water are lower than in fresh water, as the sea has a much higher level of impurities, particularly common salt, and the main current path will seek the better conductor. This is, nonetheless, not foolproof and substantial risks remain in salt water.) Any electrical properties observable in water are from the ions of mineral salts and carbon dioxidedissolved in it. Water does self-ionize where two water molecules become one hydroxideanion and one hydroniumcation, but not enough to carry enough electric currentto do any work or harm for most operations. In pure water, sensitive equipment can detect a very slight electrical conductivity of 0.055 µS/cm at 25 °C. Water can also be electrolyzed into oxygen and hydrogen gases but in the absence of dissolved ions this is a very slow process, as very little current is conducted. While electrons are the primary charge carriers in water (and metals), in ice (and some other electrolytes), protonsare the primary carriers (see proton conductor).
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
electronegativitythan 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. Certain molecules, such as carbon dioxide, also have a difference in electronegativity between the atoms but the difference is that the shape of carbon dioxide is symmetrically aligned and so the opposing charges cancel one another out. This phenomenon of water can be seen if you hold an electrical source near a thin stream of water falling vertically, causing the stream to bend towards the electrical source.
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 pointtemperatures; more heatenergy 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 temperatureeven though it has twice the molecular mass 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 structureof 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 almost 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 —the pressure exerted by an ice skater on the ice would only reduce the melting point by approximately 0.09 °C (0.16 °F).
;Electronegative PolarityWater has a partial negative charge (δ-) near the oxygen atom due to the unshared pairs of electrons, and partial positive charges (δ+) near the hydrogen atoms. In water, this happens because the oxygen atom is more
electronegativethan the hydrogen atoms — that is, it has a stronger "pulling power" on the molecule's electrons, drawing them closer (along with their negative charge) and making the area around the oxygen atom more negative than the area around both of the hydrogen atoms.
Water sticks to itself (cohesion) because it is polar.Water also has high
adhesionproperties because of its polar nature. On extremely clean/smooth glassthe water may form a thin film because the molecular forces between glass and water molecules (adhesive forces) are stronger than the cohesive forces.In biological cells and organelles, water is in contact with membrane and protein surfaces that are hydrophilic; that is, surfaces that have a strong attraction to water. Irving Langmuirobserved a strong repulsive force between hydrophilic surfaces. To dehydrate hydrophilic surfaces—to remove the strongly held layers of water of hydration—requires doing substantial work against these forces, called hydration forces. These forces are very large but decrease rapidly over a nanometer or less. Their importance in biology has been extensively studied by V. Adrian Parsegianof the National Institute of Health. [ [http://www.biophysics.org/education/parsegian.pdf Physical Forces Organizing Biomolecules (PDF)] ] They are particularly important when cells are dehydrated by exposure to dry atmospheres or to extracellular freezing.
Water has a high
surface tensioncaused by the strong cohesion between water molecules. This can be seen when small quantities of water are put onto a non-absorbent surface such as polytheneand the water stays together as drops. Just as significantly, air trapped in surface disturbances forms bubbles, which sometimes last long enough to transfer gas molecules to the water.Another surface tension effect is capillary waves, which are the surface ripples that form around the impacts of drops on water surfaces, and sometimes occur with strong subsurface currents flowing to the water surface. The apparent elasticity caused by surface tension drives the waves.
Capillary actionrefers to the process of water moving up a narrow tube against the force of gravity. It occurs because water adheres to the sides of the tube, and then surface tension tends to straighten the surface making the surface rise, and more water is pulled up through cohesion. The process is repeated as the water flows up the tube until there is enough water that gravity counteracts the adhesive force.
Water as a solvent
" from the water, and do not dissolve. Contrary to the common misconception, water and hydrophobic substances do not "repel", and the hydration of a hydrophobic surface is energetically, but not entropically, favorable.
When an ionic or polar compound enters water, it is surrounded by water molecules (
Hydration). 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.
Water as a ligand
The water molecule can also be used as a
ligandin transition metalcomplexes; one example is perrhenic acid, which forms when Re2O7 is exposed to water. It contains two water molecules coordinated to a rheniumatom.
Amphoteric nature of water
Chemically, water is
amphoteric— i.e., it is able to act as either an acidor 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 hydroxideions (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-Lowrysystem, 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 stronger base, it acts as an acid. For instance, it receives an H+ ion from HCl in the equilibrium:
:HCl + H2O unicode|⇌ H3O+ + Cl−
Here water is acting as a base, by receiving an H+ ion.
In the reaction with
ammonia, NH3, water donates an H+ ion, and is thus acting as an acid:
:NH3 + H2O unicode|⇌ NH4+ + OH−
Acidity in nature
In theory, pure water has a
pHof 7 at 298 K. 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 nitrogenand sulfuroxides are present in the air, they too will dissolve into the cloud and rain drops producing more serious acid rainproblems.
Hydrogen bonding in water
A 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, methanolform hydrogen bonds but they do not show anomalous behaviour of thermodynamic, kineticor 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 stericeffects in bulky residues. In water local tetrahedralorder 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 silicain 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 Paulingin the 1930s is yet to be 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 has shown that at certain scales, water may act more like H3/2O than H2O at the quantum level. [cite news | publisher = Physics News Update |date=31 Jul 03 | author = Phil Schewe, James Riordon, and Ben Stein | title = A Water Molecule's Chemical Formula is Really Not H2O | url = http://www.aip.org/enews/physnews/2003/split/648-1.html] This result could have significant ramifications at the level of, for example, the
hydrogen bondin biological, chemical and physical systems. The experiment shows that when neutronsand electronscollide with water, they scatter in a way that indicates that they only are affected by a ratio of 1.5:1 of hydrogento oxygenrespectively. However, the time-scale of this response is only seen at the level of attoseconds (10-18 seconds), and so is only relevant in highly resolved kineticand dynamical systems. [cite journal | author = C. A. Chatzidimitriou-Dreismann, T. Abdul Redah, R. M. F. Streffer and J. Mayers | title = Anomalous Deep Inelastic Neutron Scattering from Liquid H2O-D2O: Evidence of Nuclear Quantum Entanglement | year = 1997 | journal = Physical Review Letters| volume = 79 | issue = 15 | pages = 2839 | doi = 10.1103/PhysRevLett.79.2839] [cite journal | author = C. A. Chatzidimitriou-Dreismann, M. Vos, C. Kleiner and T. Abdul-Redah | title = Comparison of Electron and Neutron Compton Scattering from Entangled Protons in a Solid Polymer | year = 2003 | journal = Physical Review Letters| volume = 91 | issue = 5 | pages = 057403–4 | doi = 10.1103/PhysRevLett.91.057403]
Heavy Water and
Hydrogen has three naturally occurring isotopes. The most common, making up more than 99.98% of the hydrogen in water, has 1 proton and 0 neutrons. A second isotope,
deuterium(short form "D"), has 1 proton and 1 neutron. Deuterium oxide, chem|D|2|O, is also known as heavy waterand is used in nuclear reactors as a neutron moderator. The third isotope, tritium, has 1 proton and 2 neutrons, and is radioactive, with a half-lifeof 4500 days. chem|T|2|O exists in nature only in tiny quantities, being produced primarily via cosmic ray-driven nuclear reactions in the atmosphere. chem|D|2|O is stable, but differs from chem|H|2|O in that it is denser - hence, "heavy water" - and in that several other physical properties are slightly different from those of common, Hydrogen-1 containing "light water". Water with one deuterium atom chem|HDO occurs naturally in ordinary water in very low concentrations (~0.03%) and chem|D|2|O in far lower amounts (0.000003%). Consumption of pure isolated chem|D|2|O may affect biochemical processes - ingestion of large amounts impairs kidney and central nervous system function. However, very large amounts of heavy water must be consumed for any toxicity to be apparent, and smaller quantities can be consumed with no ill effects at all.
Oxygen also has three stable isotopes, with 16O present in 99.76 %, 17O in 0.04% and 18O in 0.2% of water molecules. [Citation | author = IAPWS | title = Guideline on the Use of Fundamental Physical Constants and Basic Constants of Water | year = 2001 | url = http://www.iapws.org/relguide/fundam.pdf]
Water's transparency is also an important property of the liquid. If water were not transparent, sunlight, essential to aquatic plants, would not reach into seas and oceans.
The properties of water have historically been used to define various temperature scales. Notably, the
Kelvin, Celsiusand Fahrenheitscales were, or currently are, defined by the freezing and boiling points of water. The less common scales of Delisle, Newton, Réaumurand Rømerwere defined similarly. The triple pointof water is a more commonly used standard point today. [ [http://home.comcast.net/~igpl/Temperature.html A Brief History of Temperature Measurement ] ]
The first scientific decomposition of water into hydrogen and oxygen, by
electrolysis, was done in 1800 by William Nicholson, an English chemist. In 1805, Joseph Louis Gay-Lussacand Alexander von Humboldtshowed that water is composed of two parts hydrogen and one part oxygen (by volume). Gilbert Newton Lewisisolated the first sample of pure heavy waterin 1933. Polywaterwas 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.
The accepted IUPAC name of water is simply "water" (or its equivalent in a different language), although there are two other systematic names which can be used to describe the molecule.
The simplest and best systematic name of water is hydrogen oxide. This is analogous to related compounds such as
hydrogen peroxide, hydrogen sulfide, and deuterium oxide(heavy water). Another systematic name, oxidane, is accepted by IUPAC as a parent name for the systematic naming of oxygen-based substituent groups, [Leigh, G. J. "et al." 1998. [http://www.iupac.org/publications/books/principles/principles_of_nomenclature.pdf "Principles of chemical nomenclature: a guide to IUPAC recommendations"] , p. 99. Blackwell Science Ltd, UK. ISBN 0-86542-685-6] although even these commonly have other recommended names. For example, the name hydroxylis recommended over "oxidanyl" for the –OH group. The name oxaneis explicitly mentioned by the IUPAC as being unsuitable for this purpose, since it is already the name of a cyclic ether also known as tetrahydropyranin the Hantzsch-Widman system; similar compounds include dioxaneand trioxane.
Dihydrogen monoxide or DHMO is an overly pedantic systematic covalent name of water. This term has been used in parodies of chemical research that call for this "lethal chemical" to be banned. 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".
material safety data sheets for water list the following: Caution: May cause drowning! [ [http://www.davidgray.com.au/files/MSDS%20David%20Grays%20Distilled%20Water%20060106.pdf MSDS David Grays Distilled Water 060106.pdf] , HEALTH EFFECTS - INHALED: "...excessive inhalation may cause drowning."] [ [http://www.setonresourcecenter.com/msds/docs/wcd00008/wcd008c5.htm MSDS for BATTERY WATER] , SECTION VI - Health Hazard Data: "WATER MAY CAUSE DEATH BY DROWNING"]
Other systematic names for water include hydroxic acid or hydroxylic 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.
Double distilled water
Vienna Standard Mean Ocean Water
*Viscosity of Water
Water (data page)
Water absorptionof electromagnetic radiation
* [http://www.iapws.org/relguide/IF97-Rev.pdf Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam] (fast computation speed)
* [http://www.iapws.org/relguide/IAPWS95.pdf Release on the IAPWS Formulation 1995 for the Thermodynamic Properties of Ordinary Water Substance for General and Scientific Use] (simpler formulation)
* [http://www.dhmo.org/ A spoof site on the "dangers" of dihydrogen monoxide]
* [http://water.sigmaxi.org Sigma Xi The Scientific Research Society, Year of Water 2008]
* [http://www.siwi.org/ Stockholm International Water Institute] (SIWI)
* [http://www.lsbu.ac.uk/water/anmlies.html Explanation of the anomalous properties of water]
* [http://www.lsbu.ac.uk/water/phase.html Water phase diagrams]
* [http://www.lsbu.ac.uk/water/vibrat.html Water Absorption Spectrum]
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