Water (H2O)
IUPAC name	Water
Other names	Aqua Hydrogen oxide Hydrogen hydroxide Hydrate Oxidane Hydroxic acid Dihydrogen monoxide Hydronium hydroxide Hydroxyl acid Dihydrogen oxide Hydrohydroxic acid μ-Oxido dihydrogen Light Water
Identifiers
CAS number	[7732-18-5]
RTECS number	ZC0110000
Properties
Molecular formula	H2O or HOH
Molar mass	18.01524 g/mol
Appearance	white solid or almost colourless, transparent, with a slight hint of blue, crystalline solid or liquid [1]
Density	1000 kg·m−3, liquid (4 °C) 917 kg·m−3, solid
Melting point	0 °C, 32 °F (273.15 K)[2] Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... Look up water in Wiktionary, the free dictionary. ... H2O is the chemical formula for Water (molecule) and is also used as an abbreviation for water itself. ... HOH could refer to: Harrow-on-the-Hill station, England; National Rail station code HOH. Head of Household Water (molecule) Category: ... Image File history File links Download high-resolution version (1100x481, 42 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Water (molecule) ... Image File history File links Water_molecule_3D.svg‎ Molecule of water SVG version of Image:Water-3D-vdW.png. ... IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. ... Dihydrogen monoxide (DHMO) and hydrogen hydroxide (HOH) are technically accurate but rarely-used names for water. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... RTECS, also known as Registry of Toxic Effects of Chemical Substances, is a database of toxicity information compiled from the open scientific literature that is available for charge. ... A chemical formula is an easy way of expressing information about the atoms that constitute a particular chemical compound. ... Molar mass is the mass of one mole of a chemical element or chemical compound. ... For other uses, see Density (disambiguation). ... The melting point of a solid is the temperature range at which it changes state from solid to liquid. ... For other uses, see Celsius (disambiguation). ... For other uses, see Fahrenheit (disambiguation). ... For other uses, see Kelvin (disambiguation). ...
Boiling point	100 °C, 212 °F (373.15 K)[2] Italic text This article is about the boiling point of liquids. ...
Acidity (pKa)	15.74 ~35-36
Basicity (pKb)	15.74
Viscosity	0.001 Pa·s at 20 °C
Structure
Crystal structure	Hexagonal See ice
Molecular shape	bent
Dipole moment	1.85 D
Hazards
Main hazards	water intoxication, drowning (see also Dihydrogen monoxide hoax)
NFPA 704	0 0 1
Related compounds
Related solvents	acetone methanol
Related compounds	water vapor ice heavy water
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Water (H₂O, HOH) is the most abundant molecule on 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 equilibrium between the liquid and vapor states at standard temperature and pressure. At room temperature, it is 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 75 % of the human body. An acid dissociation constant, denoted by Ka, is an equilibrium constant for the dissociation of a weak acid. ... An acid dissociation constant, denoted by Ka, is an equilibrium constant for the dissociation of a weak acid. ... For other uses, see Viscosity (disambiguation). ... The pascal second (symbol Pa·s) is the SI unit of dynamic viscosity. ... Enargite crystals In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... This article is about water ice. ... Four sp3 orbitals. ... The Earths magnetic field, which is approximately a dipole. ... The debye (symbol: D) is a non-SI and non-CGS unit of electrical dipole moment. ... The examples and perspective in this article or section may not represent a worldwide view. ... Water intoxication (also known as hyperhydration or water poisoning) is a potentially fatal disturbance in brain function that results when the normal balance of electrolytes in the body is pushed outside of safe limits, ironically by that which makes up the majority of it - common water. ... Water is made from 2 hydrogen and one oxygen atom, giving the name dihydrogen monoxide. ... NFPA 704 is a standard maintained by the U.S. National Fire Protection Association. ... Image File history File links NFPA_704. ... For other uses, see Solvent (disambiguation). ... For other uses, see Acetone (disambiguation). ... Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a chemical compound with chemical formula CH3OH (often abbreviated MeOH). ... Water vapor or water vapour (see spelling differences), also aqueous vapor, is the gas phase of water. ... This article is about water ice. ... Heavy water is dideuterium oxide, or D2O or 2H2O. It is chemically the same as normal water, H2O, but the hydrogen atoms are of the heavy isotope deuterium, in which the nucleus contains a neutron in addition to the proton found in the nucleus of any hydrogen atom. ... The plimsoll symbol as used in shipping In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals exactly). ... This article is about the chemistry of hydrogen. ... This article is about the chemical element and its most stable form, or dioxygen. ... Hydroxide is a polyatomic ion consisting of oxygen and hydrogen: OH− It has a charge of −1. ... 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ... This article is about Earth as a planet. ... A dynamic equilibrium occurs when two reversible processes occur at the same rate. ... For other uses, see Liquid (disambiguation). ... This article is about the chemical use. ... Temperature and air pressure can vary from one place to another on the Earth, and can also vary in the same place with time. ... For other uses, see Room temperature (disambiguation). ... For alternative meanings, see color (disambiguation). ... Taste (or, more formally, gustation) is a form of direct chemoreception and is one of the traditional five senses. ... ... For other uses, see Solvent (disambiguation). ... In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ...

Forms of water

See the Water#Overview of types of water

Water can 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. 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. Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... This box:      For other uses, see Solid (disambiguation). ... This article is about water ice. ... When water is cooled below its normal freezing point, it normally freezes to form hexagonal ice, or Ice I, though it can exist in other solid forms. ... -1... Water vapor or water vapour (see spelling differences), also aqueous vapor, is the gas phase of water. ... For other uses, see Steam (disambiguation). ... In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i. ... The critical temperature, Tc, of a material is the temperature above which distinct liquid and gas phases do not exist. ... For other uses, see Kelvin (disambiguation). ... For other uses, see Pascal. ...

Heavy water is 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. Heavy water is dideuterium oxide, or D2O or 2H2O. It is chemically the same as normal water, H2O, but the hydrogen atoms are of the heavy isotope deuterium, in which the nucleus contains a neutron in addition to the proton found in the nucleus of any hydrogen atom. ... For other uses, see Isotope (disambiguation). ... Deuterium, also called heavy hydrogen, is a stable isotope of hydrogen with a natural abundance in the oceans of Earth of approximately one atom in 6500 of hydrogen (~154 PPM). ... Core of a small nuclear reactor used for research. ... This article or section does not adequately cite its references or sources. ...

Physics and chemistry of water

Water is the chemical substance with chemical formula H₂O: one molecule of water has two hydrogen atoms covalently bonded to a single oxygen atom. 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.^[3] 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, sulfur and chlorine, all combine with hydrogen to produce gases under standard conditions. The reason that oxygen dihydride (water) forms a liquid is that it is more electronegative than 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 hydronium ion (H₃O⁺_(aq)) and an associated hydroxide ion (OH⁻_(aq)). Water is in dynamic equilibrium between the liquid, gas and solid states at standard temperature and pressure (0°C, 100.000 kPa) , and is the only pure substance found naturally on Earth to be so. Water and steam are two different forms of the same chemical substance A chemical substance is a material with a definite chemical composition. ... A chemical formula is an easy way of expressing information about the atoms that constitute a particular chemical compound. ... This article is about the chemistry of hydrogen. ... This article is about the chemical element and its most stable form, or dioxygen. ... 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ... This article is about the chemistry of hydrogen. ... For other uses, see Atom (disambiguation). ... Covalent bonding is a form of chemical bonding characterized by the sharing of one or more pairs of electrons between atoms, in order to produce a mutual attraction, which holds the resultant molecule together. ... A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds. ... This article is about the chemical element and its most stable form, or dioxygen. ... Temperature and air pressure can vary from one place to another on the Earth, and can also vary in the same place with time. ... The chalcogens (with the ch pronounced with a hard c as in chemistry) are the name for the periodic table group 16 (old-style: VIB or VIA) in the periodic table. ... The Periodic Table redirects here. ... Hydrogen sulfide (or hydrogen sulphide) is the chemical compound with the formula H2S. This colorless, toxic and flammable gas is responsible for the foul odour of rotten eggs and flatulence. ... The Periodic Table redirects here. ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... Distinguished from fluorene and fluorone. ... General Name, symbol, number phosphorus, P, 15 Chemical series nonmetals Group, period, block 15, 3, p Appearance waxy white/ red/ black/ colorless Standard atomic weight 30. ... This article is about the chemical element. ... General Name, symbol, number chlorine, Cl, 17 Chemical series nonmetals Group, period, block 17, 3, p Appearance yellowish green Standard atomic weight 35. ... This article is about the chemistry of hydrogen. ... It has been suggested that this article or section be merged with electronegativity. ... Dipole moment refers to the quality of a system to behave like a dipole. ... In chemistry, a hydrogen bond is a type of attractive intermolecular force that exists between two partial electric charges of opposite polarity. ... In chemistry, hydronium is the common name for the cation H3O+ derived from protonation of water. ... Hydroxide is a polyatomic ion consisting of oxygen and hydrogen: OH− It has a charge of −1. ... A dynamic equilibrium occurs when two reversible processes occur at the same rate. ... For other uses, see Liquid (disambiguation). ... For other uses, see Gas (disambiguation). ... This box:      For other uses, see Solid (disambiguation). ... In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i. ... Temperature and air pressure can vary from one place to another on the Earth, and can also vary in the same place with time. ...

Water, ice and vapor

Heat capacity and heats of vaporization and fusion

Main article: Enthalpy of vaporization

Water has the second highest specific heat capacity of 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 climate by buffering large fluctuations in temperature. The heat of vaporization is a physical property of substances. ... Specific heat capacity, also known simply as specific heat, is the measure of the heat energy required to increase the temperature of a unit quantity of a substance by a certain temperature interval. ... For other uses, see Ammonia (disambiguation). ... The heat of vaporization is a physical property of substances. ... An example of a quadruple hydrogen bond between a self-assembled dimer complex reported by Meijer and coworkers. ...

The specific enthalpy of fusion of water is 333.55 kJ kg⁻¹ at 0 ºC. 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. Standard enthalpy change of fusion of period three. ... Perito Moreno Glacier Patagonia Argentina Aletsch Glacier, Switzerland Icebergs breaking off glaciers at Cape York, Greenland This article is about the geological formation. ... Drift ice consists of slabs of ice that float on the surface of the water in cold regions. ... Refrigeration is the process of removing heat from an enclosed space, or from a substance, and rejecting it elsewhere for the primary purpose of lowering the temperature of the enclosed space or substance and then maintaining that lower temperature. ...

Density of water and ice

The solid form of most substances is more dense than the liquid phase; 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 (3.98 more precisely), 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, lead, uranium, neon and silicon are some of the few materials which expand when they freeze; most other materials contract. Not all forms of ice are less dense than liquid water however, HDA and VHDA for example 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. For other uses, see Density (disambiguation). ... In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i. ... This article is about water ice. ... For other uses, see Room temperature (disambiguation). ... Density is the average amount of mass (measured in grams) in each unit of volume (mesured in cubic centimeters). ... Enargite crystals In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... This article is about water ice. ... In crystallography, the hexagonal crystal system is one of the 7 lattice point groups. ... Ice Ih is the hexagonal crystal form of ordinary ice, or frozen water. ... General Name, Symbol, Number lead, Pb, 82 Chemical series Post-transition metals or poor metals Group, Period, Block 14, 6, p Appearance bluish gray Standard atomic weight 207. ... This article is about the chemical element. ... For other uses, see Neon (disambiguation). ... Not to be confused with Silicone. ... When water is cooled below its normal freezing point, it normally freezes to form hexagonal ice, or Ice I. If it is very pure and cooled carefully, it may be supercooled to about -42°C. If water is cooled very rapidly then it forms an amorphoric glass. ... When water is cooled below its normal freezing point, it normally freezes to form hexagonal ice, or Ice I. If it is very pure and cooled carefully, it may be supercooled to about -42 °C. If water is cooled very rapidly then it forms an amorphoric glass. ... An example of a quadruple hydrogen bond between a self-assembled dimer complex reported by Meijer and coworkers. ...

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 conformation 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. Although the H-bond length is actually shorter in solid ice than between molecules of liquid water, the rigidity of the ice crystalline structure ensures that each given H₂O molecule has fewer neighbors, and thus the solid is less dense. This effectively reduces the density ρ of water when ice is formed under standard conditions. Geometry of the water molecule Molecules have fixed equilibrium geometries--bond lengths and angles--that are dictated by the laws of quantum mechanics. ... Elasticity is a branch of physics which studies the properties of elastic materials. ... For other uses, see Crystal (disambiguation). ... Rose des Sables (Sand Rose), formed of gypsum crystals In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... This article is about rotation as a movement of a physical body. ... Oscillation is the variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. ...

Water shares the higher-density liquid state with only a few materials like gallium, germanium, bismuth and antimony. Not to be confused with Galium. ... General Name, Symbol, Number germanium, Ge, 32 Chemical series metalloids Group, Period, Block 14, 4, p Appearance grayish white Standard atomic weight 72. ... General Name, Symbol, Number bismuth, Bi, 83 Chemical series poor metals Group, Period, Block 15, 6, p Appearance lustrous pink Standard atomic weight 208. ... This article is about the element. ...

The importance of this property cannot be overemphasized for its role on the ecosystem of Earth. For example, if water were 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. For other uses, see Ecological Systems Theory. ...

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 increases in density 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 decreases in density as it chills further and remains 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. An example of a quadruple hydrogen bond between a self-assembled dimer complex reported by Meijer and coworkers. ... Convection in the most general terms refers to the movement of currents within fluids (i. ... A current, in a river or stream, is the flow of water influenced by gravity as the water moves downhill to reduce its potential energy. ... In physics and chemistry, freezing is the process whereby a liquid turns to a solid when cold enough. ... Riverbed may refer to: Stream bed, the channel bottom of a stream or river or creek Wadi, a dry riverbed that contains water only during times of heavy rain Riverbed Technology, an American technology company Category: ...

Water will freeze at 0 °C (32 °F, 273 K), however, it can be supercooled in a fluid state down to its crystal homogeneous nucleation at almost 231 K (−42 °C) ^[5]. Supercooling is the process of chilling a liquid below its freezing point, without its becoming solid. ... Bubbles in a soft drink each nucleate independently, responding to a decrease in pressure. ...

Water expands significantly as the temperature increases. The density is 4% less than maximum as the temperature approaches boiling.

Density of saltwater and ice

The density of water is dependent on the dissolved salt content as well as the temperature of the water. Ice still floats in the oceans, otherwise they would freeze from the bottom up. However, the salt content of oceans lowers the freezing point by about 2 °C and lowers the temperature of the density maximum of water to the freezing point. That is why, in ocean water, the downward convection of colder water is not blocked by an expansion of water as it becomes colder near the freezing point. 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 the winter. For the village on the Isle of Wight, see Freshwater, Isle of Wight. ...

As the surface of salt water begins to freeze (at −1.9 °C for normal salinity seawater, 3.5%) the ice that forms is essentially salt free with a density approximately equal to 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, in a process known as brine rejection. 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 causes it to sink towards the bottom. An open surface with X-, Y-, and Z-contours shown. ... Annual mean sea surface salinity for the World Ocean. ... Annual mean sea surface salinity for the World Ocean. ... For the sports equipment manufacturer, see Brine, Corp. ...

Miscibility and condensation

Main article: Humidity

Water is miscible with many liquids, for example ethanol in all proportions, forming a single homogeneous liquid. On the other hand water and most oils are immiscible usually forming layers according to increasing density from the top. The term humidity is usually taken in daily language to refer to relative humidity. ... The chemistry term miscible refers to the property of various liquids that allows them to be mixed together. ... Grain alcohol redirects here. ... Synthetic motor oil For other uses, see Oil (disambiguation). ...

Red line shows saturation

As a gas, water vapor is completely miscible with air. On the other hand the maximum water vapor pressure that is thermodynamically stable with the liquid (or solid) at a given temperature is relatively low compared with total atmospheric pressure. For example, if the vapor partial pressure^[6] is 2% of atmospheric pressure and the air is cooled from 25 °C, starting at about 22 °C water will start to condense, defining the dew point, and creating fog or dew. The reverse process accounts for the fog burning off in the morning. If one raises the humidity at room temperature, say by running a hot shower or a bath, and the temperature stays about the same, the vapor soon reaches the pressure for phase change, and condenses out as steam. A gas in this context is referred to as saturated or 100% relative humidity, when the vapor pressure of water in the air is at the equilibrium with vapor pressure due to (liquid) water; water (or ice, if cool enough) will fail to lose mass through evaporation when exposed to saturated air. Because the amount of water vapor in air is small, relative humidity, the ratio of the partial pressure due to the water vapor to the saturated partial vapor pressure, is much more useful. Water vapor pressure above 100% relative humidity is called super-saturated and can occur if air is rapidly cooled, say by rising suddenly in an updraft.^[7] Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... The chemistry term miscible refers to the property of various liquids that allows them to be mixed together. ... In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. ... The dew point (or dewpoint) is the temperature which a given parcel of air must be cooled, at constant barometric pressure, for water vapor to condense into water. ... For other uses, see Fog (disambiguation). ... Dew on a spider web Dew is water in the form of droplets that appears on thin, exposed objects in the morning or evening. ...

Vapor Pressures of Water

^[8]

Compressibility

The compressibility of water is a function of pressure and temperature. At 0 °C in the limit of zero pressure the compressibility is 5.1×10^-5 bar⁻¹.^[9] In the zero pressure limit the compressibility reaches a minimum of 4.4×10^-5 bar⁻¹ around 45 °C before increasing again with increasing temperature. As the pressure is increased the compressibility decreases, being 3.9×10^-5 bar⁻¹ at 0 °C and 1000 bar. The bulk modulus of water is 2.2×10⁹ Pa.^[10] The low compressibility of non-gases, and of water in particular, leads to them often being assumed as incompressible. The low compressibility of water means that even in the deep oceans at 4000 m depth, where pressures are 4×10⁷ Pa, there is only a 1.8% decrease in volume.^[10] Fluid Dynamics Compressibility (physics) is a measure of the relative volume change of fluid or solid as a response to a pressure (or mean stress) change: . For a gas the magnitude of the compressibility depends strongly on whether the process is adiabatic or isothermal, while this difference is small in... The bar (symbol bar), decibar (symbol dbar) and the millibar (symbol mbar, also mb) are units of pressure. ... The bulk modulus (K) of a substance essentially measures the substances resistance to uniform compression. ... For other uses, see Pascal. ... Animated map exhibiting the worlds oceanic waters. ... This article is about the unit of length. ...

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, the SI unit of thermodynamic temperature and, indirectly, the degree Celsius and 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 Mars is 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. Ice Ih is the hexagonal crystal form of ordinary ice, or frozen water. ... A tetragonal crystalline ice, formed by cooling water down to 250 K at 300 MPa. ... For other uses, see Temperature (disambiguation). ... This article is about pressure in the physical sciences. ... Water vapor or water vapour (see spelling differences), also aqueous vapor, is the gas phase of water. ... In physics, the triple point of a substance is the temperature and pressure at which three phases (gas, liquid, and solid) of that substance may coexist in thermodynamic equilibrium. ... For other uses, see Kelvin (disambiguation). ... For other uses, see Celsius (disambiguation). ... For other uses, see Fahrenheit (disambiguation). ... For other uses, see Pascal. ... Adjectives: Martian Atmosphere Surface pressure: 0. ...

water phase diagram: Y-axis = Pressure in Pascal (10ⁿ), X-axis = Temperature in Kelvin, S = Solid, L = Liquid, V = Vapour, CP = Critical Point, TP = 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 diagram of 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.^[12][11][13] In physical chemistry, mineralogy, and materials science, a phase diagram is a type of graph used to show the equilibrium conditions between the thermodynamically-distinct phases. ... In physics, the triple point of a substance is the temperature and pressure at which three phases (gas, liquid, and solid) of that substance may coexist in thermodynamic equilibrium. ... In physical chemistry, mineralogy, and materials science, a phase diagram is a type of graph used to show the equilibrium conditions between the thermodynamically-distinct phases. ...

Mpemba effect

The Mpemba effect is the surprising phenomenon whereby hot water can, under certain conditions, freeze sooner 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. The Mpemba effect is the observation that, in some specific, fairly common circumstances, hotter water freezes faster than colder water. ... Vaporization redirects here. ... Convection in the most general terms refers to the movement of currents within fluids (i. ... Supercool redirects here. ... Thermal insulation on the Huygens probe The term thermal insulation can refer to materials used to reduce the rate of heat transfer, or the methods and processes used to reduce heat transfer. ... Frost on black pipes Frost is a solid deposition of water vapor from saturated air. ...

Freezing transition at room temperature

Hot ice is the name given to another surprising phenomenon in which water at room temperature can be turned into ice that remains at room temperature by alignment of water dipoles and crystallization into polar cubic ice through supplying an electric field in the order of 10⁶ volts per meter.^[14] This phenomenon was later discounted as not being due to voltage-induced freezing and attributed to an artifact. ^[15]

The effect of such electric fields has been suggested as an explanation of cloud formation. The first time cloud ice forms around a clay particle, it requires a temperature of −10 °C, but subsequent freezing around the same clay particle requires a temperature of just −5 °C, suggesting some kind of structural change.^[16]

Surface tension

Water drops are stable, due to the high surface tension of 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 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. This box:      Surface tension is an effect within the surface layer of a liquid that causes that layer to behave as an elastic sheet. ... In vascular plants, xylem is one of the two types of transport tissue, phloem being the other one. ... Transpirational pull is the main phenomenon driving the flow of sap in the xylem tissues of large plants. ...

Electrical properties

Pure water containing no ions is an excellent insulator, however, 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 solute dissolved 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. This article or section is in need of attention from an expert on the subject. ... The self-ionization of water is the chemical reaction in which two water molecules react to produce a hydronium (H3O+) and a hydroxide ion (OH-): The reaction is also known as the autoionization or autodissociation of water. ... For other uses, see Absolute Zero (disambiguation). ... A substance is soluble in a fluid if it dissolves in the fluid. ... This article is about common table salt. ... This article is about the electrically charged particle. ...

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 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 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-square meters per meter (a change of several hundred nanosiemens per meter of conductance). In chemistry and manufacturing, electrolysis is a method of separating chemically bonded elements and compounds by passing an electric current through them. ... Diagram of a copper cathode in a Daniells cell. ... Diagram of a zinc anode in a galvanic cell. ... The ohm is the SI derived unit of electrical resistance (derived from the ampere and the watt). ... Reverse osmosis (RO) is a separation process that uses pressure to force a solution through a membrane that retains the solute on one side and allows the pure solvent to pass to the other side. ... The siemens (symbol: S) is the SI derived unit of electric conductance. ...

Electrical conductivity

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 dioxide dissolved in it. Water does self-ionize where two water molecules become one hydroxide anion and one hydronium cation, but not enough to carry enough electric current to 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), protons are the primary carriers (see proton conductor). Not to be confused with electrical conductance, a measure of an objects or circuits ability to conduct an electric current between two points, which is dependent on the electrical conductivity and the geometric dimensions of the conducting object. ... R-phrases , S-phrases , , , , Flash point non-flammable Supplementary data page Structure and properties n, εr, etc. ... Sign warning of possible electric shock hazard An electric shock can occur upon contact of a humans body with any source of voltage high enough to cause sufficient current flow through the muscles or hair. ... This article is about the electrically charged particle. ... Carbon dioxide (chemical formula: ) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... The self-ionization of water is the chemical reaction in which two water molecules react to produce a hydronium (H3O+) and a hydroxide ion (OH-): The reaction is also known as the autoionization or autodissociation of water. ... Hydroxide is a polyatomic ion consisting of oxygen and hydrogen: OH− It has a charge of −1. ... In chemistry, hydronium is the common name for the cation H3O+ derived from protonation of water. ... This box:      Electric current is the flow (movement) of electric charge. ... Not to be confused with electrical conductance, a measure of an objects or circuits ability to conduct an electric current between two points, which is dependent on the electrical conductivity and the geometric dimensions of the conducting object. ... The siemens (symbol: S) is the SI derived unit of electric conductance. ... This article is being considered for deletion in accordance with Wikipedias deletion policy. ... In chemistry and manufacturing, electrolysis is a method of separating chemically bonded elements and compounds by passing an electric current through them. ... For alternative meanings see proton (disambiguation). ... A proton conductor is an electrolyte where movable hydrogen ions are the primary charge carriers. ...

Dipolar nature of water

model of hydrogen bonds between molecules 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. 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. An example of a quadruple hydrogen bond between a self-assembled dimer complex reported by Meijer and coworkers. ... A commonly-used example of a polar compound is water (H2O). ... Electronegativity is a measure of the ability of an atom or molecule to attract electrons in the context of a chemical bond. ... The Earths magnetic field, which is approximately a dipole. ... An example of a quadruple hydrogen bond between a self-assembled dimer complex reported by Meijer and coworkers. ...

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 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. The melting point of a solid is the temperature range at which it changes state from solid to liquid. ... Italic text This article is about the boiling point of liquids. ... For other uses, see Heat (disambiguation) In physics, heat, symbolized by Q, is energy transferred from one body or system to another due to a difference in temperature. ... For other uses, see Room temperature (disambiguation). ... Specific heat capacity, also known simply as specific heat, is the measure of the heat energy required to increase the temperature of a unit quantity of a substance by a certain temperature interval. ...

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 almost all other materials shrink on solidification. A regular hexagon A hexagon (also known as sexagon) is a polygon with six edges and six vertices. ... Enargite crystals In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ...

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 Polarity

Water has a partial negative charge (σ-) near the oxygen atom due to the unshared pairs of electrons, and partial positive charges (σ+) near the hydrogen atoms. In water, this happens because the oxygen atom is more electronegative than 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. It has been suggested that this article or section be merged with electronegativity. ... In physics, the electrostatic force is the force arising between static (that is, non-moving) electric charges. ... For other uses, see Electron (disambiguation). ...

Adhesion

Dew drops adhering to a spider web

Water sticks to itself (cohesion) because it is polar. Water also has high adhesion properties because of its polar nature. On extremely clean/smooth 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. 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 Langmuir observed 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 Parsegian of the National Institute of Health.^[17] They are particularly important when cells are dehydrated by exposure to dry atmospheres or to extracellular freezing. Dew on a spider web Dew is water in the form of droplets that appears on thin, exposed objects in the morning or evening. ... Spiders web redirects here. ... Mercury sticks together because of the cohesive forces. ... A commonly-used example of a polar compound is water (H2O). ... Dew drops adhering to a spider web For the medical condition see Adhesion (medicine) Adhesion is the molecular attraction exerted between bodies in contact. ... This article is about the material. ... In cell biology, an organelle is a specialized subunit within a cell that has a specific function, and is separately enclosed within its own lipid membrane. ... The adjective hydrophilic describes something that likes water (from Greek hydros = water; philos = friend). ... Irving Langmuir (January 31, 1881 in Brooklyn, New York - August 16, 1957 in Woods Hole, Massachusetts) was an American chemist and physicist. ... The National Institutes of Health is an institution of the United States government which focuses on medical research. ...

Surface tension

Main article: Surface tension

This daisy is under the water level, which has risen gently and smoothly. Surface tension prevents the water from submerging the flower.

Water has a high surface tension caused by the strong cohesion between water molecules. This can be seen when small quantities of water are put onto a non-soluble surface such as polythene; 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 from around the impact of drops on water surfaces, and some times occur with strong subsurface currents flow to the water surface. The apparent elasticity caused by surface tension drives the waves. This box:      Surface tension is an effect within the surface layer of a liquid that causes that layer to behave as an elastic sheet. ... Download high resolution version (1200x900, 61 KB)A daisy. ... Download high resolution version (1200x900, 61 KB)A daisy. ... Look up Daisy in Wiktionary, the free dictionary. ... This box:      Surface tension is an effect within the surface layer of a liquid that causes that layer to behave as an elastic sheet. ... Polyethylene or polyethene is one of the simplest and most inexpensive polymers. ... A capillary wave is a wave travelling along a meniscus, whose dynamics are dominated by the effects of surface tension. ...

Capillary action

Main article: Capillary action

Capillary action refers 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. Capillary Flow Experiment to investigate capillary flows and phenomena onboard the International Space Station Capillary action, capillarity, capillary motion, or wicking is the ability of a substance to draw another substance into it. ...