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. IUPAC Nomenclature is a system of naming Chemical compounds and of describing the science of Chemistry in general "Dihydrogen monoxide" redirects here For the H2O molecule see Water (molecule. CAS registry numbers are unique numerical identifiers for Chemical compounds Polymers biological sequences mixtures and Alloys They are also referred to Registry of Toxic Effects of Chemical Substances ( RTECS) is a Database of Toxicity information compiled from the open scientific literature without reference A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Molar mass, symbol M, is the Mass of one mole of a substance ( Chemical element or Chemical compound) 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. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different The melting point of a solid is the temperature range at which it changes state from solid to Liquid. The Celsius Temperature scale was previously known as the centigrade scale. Fahrenheit is a temperature scale named after Daniel Gabriel Fahrenheit (1686–1736 a German Physicist who proposed it in 1724 15 K)[2]
Boiling point	100 °C, 212 °F (373. The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic The boiling point of a liquid is the temperature at which the Vapor pressure of the liquid equals the environmental pressure surrounding the liquid 15 K)[2]
Acidity (pKa)	15. 74 ~35-36
Basicity (pKb)	15. 74
Viscosity	0. Viscosity is a measure of the resistance of a Fluid which is being deformed by either Shear stress or Extensional stress. 001 Pa·s at 20 °C
Structure
Crystal structure	Hexagonal See ice
Molecular shape	bent
Dipole moment	1. Viscosity is a measure of the resistance of a Fluid which is being deformed by either Shear stress or Extensional stress. In Mineralogy and Crystallography, a crystal structure is a unique arrangement of Atoms in a Crystal. Ice is a Solid phase, usually crystalline, of a Non-metalic substance that is liquid or gas at Room temperature, such as Ammonia Molecular geometry or molecular structure is the three- Dimensional arrangement of the Atoms that constitute a Molecule. In Chemistry, the term " bent " can be applied to certain Molecules to describe their Molecular geometry. In physics there are two kinds of dipoles ( Hellènic: di(s- = two- and pòla = pivot hinge An electric dipole is a 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. The debye (symbol D) is a non- SI, CGS unit of electrical dipole moment. Occupational safety and health is a cross-disciplinary area concerned with protecting the Safety, Health and welfare of people engaged in Water intoxication (also known as hyperhydration or water poisoning) is a potentially fatal disturbance in Brain functions that results when the Drowning is Death as caused by suffocation when a liquid causes interruption of the body's absorption of oxygen from the air leading to Asphyxia. "Dihydrogen monoxide" redirects here For the H2O molecule see Water (molecule. Symbolism The four divisions are typically color-coded with blue indicating level of Health Hazard, red indicating A solvent is a liquid or gas that dissolves a solid liquid or gaseous Solute, resulting in a Solution. Acetone (also known as propanone, dimethyl ketone, 2-propanone, propan-2-one and β-ketopropane) is a colorless mobile flammable Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a Chemical compound General properties of water vapor Evaporation/sublimation Whenever a water molecule leaves a surface it is said to have evaporated Ice is a Solid phase, usually crystalline, of a Non-metalic substance that is liquid or gas at Room temperature, such as Ammonia Heavy water is water which contains a higher proportion than normal of the Isotope Deuterium, as deuterium oxide, D2O or ²H2O In Chemistry, the standard state of a material is its state at 1 bar (100 Kilopascals exactly Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the In Chemistry, hydroxide is the most common name for the diatomic Anion OH− consisting of Oxygen and Hydrogen In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 It is in dynamic equilibrium between the liquid and vapor states at standard temperature and pressure. A dynamic equilibrium occurs when two opposing Processes proceed at the same rate Liquid is one of the principal States of matter. A liquid is a Fluid that has the particles loose and can freely form a distinct surface at the boundaries of A vapor or vapour (see Spelling differences) is a substance in the Gas phase at a Temperature lower than its Critical temperature In Physical sciences standard conditions for temperature and pressure are Standard sets of conditions for experimental measurements to allow comparisons to be made At room temperature, it is a nearly colorless (with a hint of blue), tasteless, and odorless liquid. Room temperature (also referred to as ambient temperature) is a common term to denote a certain Temperature within enclosed space at which humans are accustomed Black-and-white is a number of Monochrome forms in Visual arts. Taste (or more formally gustation) is a form of direct Chemoreception and is one of the traditional five Senses Many substances dissolve in water and it is commonly referred to as the universal solvent. A solvent is a liquid or gas that dissolves a solid liquid or gaseous Solute, resulting in a Solution. 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. A state of matter (or physical state, or form of matter) has physical properties which are qualitatively different from other states of matter Water is a common Chemical substance that is essential for the survival of all known forms of Life. Water also makes up 55% to 78% of the human body. ^[3]

Contents 1 Forms of water 2 Physics and chemistry of water 2.1 Water, ice and vapor 2.1.1 Heat capacity and heats of vaporization and fusion 2.1.2 Density of water and ice 2.1.3 Density of saltwater and ice 2.1.4 Miscibility and condensation 2.1.5 Vapor Pressures of Water 2.1.6 Compressibility 2.1.7 Triple point 2.2 Surface tension 2.3 Electrical properties 2.3.1 Electrical conductivity 2.4 Dipolar nature of water 2.4.1 Adhesion 2.4.2 Surface tension 2.4.3 Capillary action 2.5 Water as a solvent 2.6 Amphoteric nature of water 2.7 Acidity in nature 2.8 Hydrogen bonding in water 2.9 Quantum properties of molecular water 2.10 Heavy Water and isotopologues of water 2.11 Transparency 3 History 4 Systematic naming 4.1 Systematic nomenclature and humor 5 See also 6 References 7 External links

Forms of water

See Water#Types of water

Water can take many forms. Water is a common Chemical substance that is essential for the survival of all known forms of Life. The solid state of water is commonly known as ice; the gaseous state is known as water vapor (or steam), and the common liquid phase is generally taken as simply water. A solid' object is in the States of matter characterized by resistance to Deformation and changes of Volume. Ice is a Solid phase, usually crystalline, of a Non-metalic substance that is liquid or gas at Room temperature, such as Ammonia This page is about the physical properties of gas as a state of matter General properties of water vapor Evaporation/sublimation Whenever a water molecule leaves a surface it is said to have evaporated Uses A Steam engine uses the expansion of steam in order to drive a Piston or Turbine to perform Mechanical work. 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 Above a certain critical temperature and pressure (647 K and 22. The critical temperature, Tc of a material is the Temperature above which distinct Liquid and Gas phases do not exist The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic 064 MPa), water molecules assume a supercritical condition, in which liquid-like clusters float within a vapor-like phase.

There are several different crystal and amorphous forms of ice; see ice for a complete listing. In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating An amorphous solid is a Solid in which there is no Long-range order of the positions of the Atoms (Solids in which there is long-range atomic order are Ice is a Solid phase, usually crystalline, of a Non-metalic substance that is liquid or gas at Room temperature, such as Ammonia

Heavy water is water in which the hydrogen is replaced by its heavier isotope, deuterium. Heavy water is water which contains a higher proportion than normal of the Isotope Deuterium, as deuterium oxide, D2O or ²H2O Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides Deuterium, also called heavy hydrogen, is a Stable isotope of Hydrogen with a Natural abundance in the Oceans of Earth It is chemically almost identical to normal water. Heavy water is used in the nuclear industry to slow down neutrons. This article is a subarticle of Nuclear power. A nuclear reactor is a device in which Nuclear chain reactions are initiated controlled This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron.

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. A chemical substance is a Material with a definite chemical composition. A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny A chemical bond is the physical process responsible for the attractive interactions between Atoms and Molecules and which confers stability to diatomic and polyatomic Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the 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. In Physical sciences standard conditions for temperature and pressure are Standard sets of conditions for experimental measurements to allow comparisons to be made Ice also appears colorless, and water vapor is essentially invisible as a gas. ^[4] 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. See also Gold chalcogenides Periodic table The periodic table of the chemical elements is a tabular method of displaying the Chemical elements Although precursors to this table exist its invention is Hydrogen sulfide (or hydrogen sulphide) is the Chemical compound with the formula H 2 S. 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 periodic table of the chemical elements is a tabular method of displaying the Chemical elements Although precursors to this table exist its invention is Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Fluorine, fluorum meaning "to flow" is the Chemical element with the symbol F and Atomic number 9 Phosphorus, (ˈfɒsfərəs is the Chemical element that has the symbol P and Atomic number 15 Sulfur or sulphur (ˈsʌlfɚ see spelling below) is the Chemical element that has the Atomic number 16 Chlorine (ˈklɔriːn from the Greek word 'χλωρóς' ( khlôros, meaning 'pale green' is the Chemical element with Atomic number 17 and Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 The reason that oxygen dihydride (water) forms a liquid is that it is more electronegative than all of these elements (other than fluorine). " Electronegativity " is the opposite of " Electropositivity," which describes an element's ability to donate electrons 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. A hydrogen bond results from a Dipole-dipole force between an Electronegative atom and a Hydrogen atom bonded to Nitrogen, Oxygen Water can be described as a polar liquid that dissociates disproportionately into the hydronium ion (H₃O⁺_(aq)) and an associated hydroxide ion (OH⁻_(aq)). In Chemistry, hydronium is the obsolete name for the Cation H 3 O + derived from Protonation of Water In Chemistry, hydroxide is the most common name for the diatomic Anion OH− consisting of Oxygen and Hydrogen Water is in dynamic equilibrium between the liquid, gas and solid states at standard temperature and pressure (0°C, 100. A dynamic equilibrium occurs when two opposing Processes proceed at the same rate Liquid is one of the principal States of matter. A liquid is a Fluid that has the particles loose and can freely form a distinct surface at the boundaries of This page is about the physical properties of gas as a state of matter A solid' object is in the States of matter characterized by resistance to Deformation and changes of Volume. A state of matter (or physical state, or form of matter) has physical properties which are qualitatively different from other states of matter In Physical sciences standard conditions for temperature and pressure are Standard sets of conditions for experimental measurements to allow comparisons to be made 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

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. The enthalpy of vaporization, (symbol \Delta{}_{v}H also known as the heat of vaporization or heat of evaporation, is the Energy required 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 Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor The enthalpy of vaporization, (symbol \Delta{}_{v}H also known as the heat of vaporization or heat of evaporation, is the Energy required 65 kJ mol⁻¹), both of which are a result of the extensive hydrogen bonding between its molecules. A hydrogen bond results from a Dipole-dipole force between an Electronegative atom and a Hydrogen atom bonded to Nitrogen, Oxygen These two unusual properties allow water to moderate Earth's climate by buffering large fluctuations in temperature. Climate encompasses the temperatures humidity rainfall atmospheric particle count and numerous other meteorogical factors in a given region over long periods of

The specific enthalpy of fusion of water is 333. The standard Enthalpy of fusion (symbol \Delta{}H_{fus} also known as the heat of fusion or specific melting heat, is the amount of 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. "Glacial" and "Glaciation" redirect here For the geological periods see Glacial period. Drift ice is Sea ice that floats on the surface of the water in cold regions as opposed to Fast ice, which is attached ("fastened" to a shore Before the advent of mechanical refrigeration, ice was in common use to retard food spoilage. Refrigeration is the process of removing Heat from an enclosed space or from a substance and moving it to a place where it is unobjectionable

Density of water and ice

Temp (°C)	Density (g/cm3)
100	0. 9584
80	0. 9718
60	0. 9832
40	0. 9922
30	0. 9956502
25	0. 9970479
22	0. 9977735
20	0. 9982071
15	0. 9991026
10	0. 9997026
4	0. 9999720
0	0. 9998395
−10	0. 998117
−20	0. 993547
−30	0. 983854
The density of water in grams per cubic centimeter at various temperatures in degrees Celsius [5] The values below 0 °C refer to supercooled water. Water - Density and Specific Weight

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. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different 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 But, by contrast, a block of common ice will float in a tub of water because solid water is less dense than liquid water. Ice is a Solid phase, usually crystalline, of a Non-metalic substance that is liquid or gas at Room temperature, such as Ammonia This is an extremely important characteristic property of water. At room temperature, liquid water becomes denser with lowering temperature, just like other substances. Room temperature (also referred to as ambient temperature) is a common term to denote a certain Temperature within enclosed space at which humans are accustomed 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 maximum density of a substance is the highest attainable Density of the substance under given conditions The physical reason for this is related to the crystal structure of ordinary ice, known as hexagonal ice Ih. In Mineralogy and Crystallography, a crystal structure is a unique arrangement of Atoms in a Crystal. Ice is a Solid phase, usually crystalline, of a Non-metalic substance that is liquid or gas at Room temperature, such as Ammonia In Crystallography, the hexagonal is one of the 7 Crystal system, it contains 7 Point groups. Ice Ih is the hexagonal crystal form of ordinary Ice, or frozen water. Water, lead, uranium, neon and silicon are some of the few materials which expand when they freeze; most other materials contract. Characteristics Lead has a dull luster and is a dense, Ductile, very soft highly Uranium (jʊˈreɪniəm is a silvery-gray Metallic Chemical element in the Neon (ˈniːɒn is the Chemical element that has the symbol Ne and Atomic number 10 Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 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. Amorphous ice is an Amorphous solid form of water meaning it consists of Water molecules that are randomly arranged like the atoms of common Glass. Amorphous ice is an Amorphous solid form of water meaning it consists of Water molecules that are randomly arranged like the atoms of common Glass. 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. A hydrogen bond results from a Dipole-dipole force between an Electronegative atom and a Hydrogen atom bonded to Nitrogen, Oxygen

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. Molecular geometry or molecular structure is the three- Dimensional arrangement of the Atoms that constitute a Molecule. A material is said to be elastic if it deforms under stress (e In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating That is, when water cools, it tries to stack in a crystalline lattice configuration that stretches the rotational and vibrational components of the bond. In Mineralogy and Crystallography, a crystal structure is a unique arrangement of Atoms in a Crystal. A rotation is a movement of an object in a circular motion A two- Dimensional object rotates around a center (or point) of rotation Oscillation is the repetitive variation typically in Time, of some measure about a central value (often a point of Equilibrium) or between two or more different states 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.

Water shares the higher-density liquid state with only a few materials like gallium, germanium, bismuth and antimony. Gallium (ˈgæliəm is a Chemical element that has the symbol Ga and Atomic number 31 Germanium (dʒɚˈmeɪniəm is a Chemical element with the symbol Ge and Atomic number 32 Bismuth (ˈbɪzməθ is a Chemical element that has the symbol Bi and Atomic number 83 Antimony (IPA (Received Pronunciation, /ˈæntɪmoʊni/ (US is a Chemical element with the symbol Sb (stibium meaning "mark" and

The importance of this property cannot be overemphasized for its role on the ecosystem of Earth. An ecosystem is a natural unit consisting of all plants animals and micro-organisms( Biotic factors in an area functioning together with all of the non-living physical ( 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.

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. A hydrogen bond results from a Dipole-dipole force between an Electronegative atom and a Hydrogen atom bonded to Nitrogen, Oxygen 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. Convection in the most general terms refers to the movement of molecules 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 For freezing as a method of food preservation see Frozen food. 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.

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) ^[6]. Nucleation is the onset of a Phase transition in a small region

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. The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region is the smallest and shallowest of the world's five major Freshwater is a word that refers to bodies of water such as Ponds lakes rivers and streams containing low concentrations of dissolved Salts and other Total dissolved

As the surface of salt water begins to freeze (at −1. In Mathematics, specifically in Topology, a surface is a Two-dimensional Manifold. 9 °C for normal salinity seawater, 3. Seawater is Water from a Sea or Ocean. On average seawater in the world's oceans has a Salinity of about 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. Salinity is the Saltiness or dissolved salt content of a body of Water. Brine (lat saltus) is Water saturated or nearly saturated with Salt (NaCl 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.

Miscibility and condensation

Main article: Humidity

Water is miscible with many liquids, for example ethanol in all proportions, forming a single homogeneous liquid. Humidity is the amount of water vapor in the air In daily language the term "humidity" is normally taken to mean Relative humidity. Miscibility is a term commonly used in Chemistry that refers to the property of Liquids to mix in all proportions forming a Homogeneous Solution On the other hand water and most oils are immiscible usually forming layers according to increasing density from the top. An oil is a substance that is in a viscous Liquid state ( "oily") at ambient temperatures or slightly warmer and is

As a gas, water vapor is completely miscible with air. Miscibility is a term commonly used in Chemistry that refers to the property of Liquids to mix in all proportions forming a Homogeneous Solution 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^[7] 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. 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 (sometimes spelled dewpoint) is the Temperature to which a given parcel of Air must be cooled at constant Barometric pressure, Fog is a cloud that is in contact with the ground Stratus clouds are usually the only clouds that touch the ground Formation Water will condense into droplets depending on the temperature 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. ^[8]

Vapor Pressures of Water

^[9]

Temperature (°C)	Pressure (torr)
0	4. 58
5	6. 54
10	9. 21
12	10. 52
14	11. 99
16	13. 63
17	14. 53
18	15. 48
19	16. 48
20	17. 54
21	18. 65
22	19. 83
23	21. 07
24	22. 38
25	23. 76

Compressibility

The compressibility of water is a function of pressure and temperature. In Thermodynamics and Fluid mechanics, compressibility is a measure of the relative volume change of a Fluid or Solid as a response At 0 °C in the limit of zero pressure the compressibility is 5. 1×10^-5 bar⁻¹. ^[10] 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 bar (symbol bar) decibar (symbol dbar) and the millibar (symbol mbar, also mb are units of Pressure. The bulk modulus of water is 2. 2×10⁹ Pa. ^[11] 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. An ocean (from Greek, ''Okeanos'' (Oceanus) is a major body of saline water, and a principal component of the Hydrosphere. The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International 8% decrease in volume. ^[11]

Triple point

The various triple points of water^[12]

Phases in stable equilibrium	Pressure	Temperature
liquid water, ice Ih, and water vapour	611. Ice Ih is the hexagonal crystal form of ordinary Ice, or frozen water. 73 Pa	273. 16 K (0. 01 °C)
liquid water, ice Ih, and ice III	209. Ice III is a Tetragonal crystalline Ice, formed by cooling Water down to 250 K at 300 MPa. 9 MPa	251 K (-22 °C)
liquid water, ice III, and ice V	350. Ice V is Monoclinic crystalline form of Ice formed by cooling water to 253 K at 500 MPa. 1 MPa	-17. 0 °C
liquid water, ice V, and ice VI	632. Ice VI is a Tetragonal crystalline form of Ice formed by cooling water to 270 K at 1 4 MPa	0. 16 °C
ice Ih, Ice II, and ice III	213 MPa	-35 °C
ice II, ice III, and ice V	344 MPa	-24 °C
ice II, ice V, and ice VI	626 MPa	-70 °C

The temperature and pressure at which solid, liquid, and gaseous water coexist in equilibrium is called the triple point of water. Ice II is a Rhombohedral crystalline form of Ice with highly ordered structure Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface General properties of water vapor Evaporation/sublimation Whenever a water molecule leaves a surface it is said to have evaporated In Thermodynamics, the triple point of a substance is the Temperature and Pressure at which three phases (for example Gas, Liquid 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). The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic The Celsius Temperature scale was previously known as the centigrade scale. Fahrenheit is a temperature scale named after Daniel Gabriel Fahrenheit (1686–1736 a German Physicist who proposed it in 1724 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.

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. In Physical chemistry, Mineralogy, and Materials science, a phase diagram is a type of graph used to show the equilibrium conditions In Thermodynamics, the triple point of a substance is the Temperature and Pressure at which three phases (for example Gas, Liquid Ice Ih is the hexagonal crystal form of ordinary Ice, or frozen water. In Physical chemistry, Mineralogy, and Materials science, a phase diagram is a type of graph used to show the equilibrium conditions 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. ^[13][12][14]

Surface tension

Water drops are stable, due to the high surface tension of water, 72. For the work of fiction see Surface Tension (short story. Surface tension is a property of the surface of a Liquid that causes it to 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. In Vascular plants xylem is one of the two types of transport tissue Phloem being the other 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. Transpirational pull is the main phenomenon driving the flow of Water in the Xylem tissues of large Plants Mechanisms Transpirational 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 containing no ions is an excellent insulator, however, not even "deionized" water, is completely free of ions. An insulator, also called a Dielectric, is a material that resists the flow of Electric current. Water undergoes auto-ionisation at any temperature above absolute zero. The self-ionization of water (also autoionization of water, and autodissociation of water) is the chemical reaction in which two water molecules react to produce a Absolute zero is the point at which molecules do not move (relative to the rest of the body more than they are required to by a quantum mechanical effect called Zero-point Further, because water is such a good solvent, it almost always has some solute dissolved in it, most frequently a salt. In Chemistry, a solution is a Homogeneous Mixture composed of two or more substances Salt is a Dietary mineral composed primarily of Sodium chloride that is essential for Animal life but toxic to most land plants 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. An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge

Water can be split into its constituent elements, hydrogen and oxygen, by passing a current through it. This process is called electrolysis. In chemistry and manufacturing electrolysis is a method of separating chemically bonded elements and compounds by passing an Electric current Water molecules naturally dissociate into H⁺ and OH⁻ ions, which are pulled toward the cathode and anode, respectively. A cathode is an Electrode through which (positive Electric current flows out of a polarized electrical device An anode is an Electrode through which Electric current flows into a polarized electrical device 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. The ohm (symbol Ω) is the SI unit of Electrical impedance or in the Direct current case Electrical resistance, 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. 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 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). 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. Electrical conductivity or specific conductivity is a measure of a material's ability to conduct an Electric current. Thus the risks of electrocution are much greater in water with the usual impurities not found in pure water. "Electrocute" redirects here For the band see Electrocute (band. (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. An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single 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. The self-ionization of water (also autoionization of water, and autodissociation of water) is the chemical reaction in which two water molecules react to produce a In Chemistry, hydroxide is the most common name for the diatomic Anion OH− consisting of Oxygen and Hydrogen In Chemistry, hydronium is the obsolete name for the Cation H 3 O + derived from Protonation of Water Electric current is the flow (movement of Electric charge. The SI unit of electric current is the Ampere. In pure water, sensitive equipment can detect a very slight electrical conductivity of 0. Electrical conductivity or specific conductivity is a measure of a material's ability to conduct an Electric current. 055 µS/cm at 25 °C. The siemens (symbol S is the SI derived unit of Electric conductance. A centimetre ( American spelling: centimeter, symbol cm) is a unit of Length in the Metric system, equal to one hundredth 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. In chemistry and manufacturing electrolysis is a method of separating chemically bonded elements and compounds by passing an Electric current 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). The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive A proton conductor is an Electrolyte, typically a Solid electrolyte, in which movable Hydrogen ions (protons are the primary charge carriers

Dipolar nature of water

An important feature of water is its polar nature. A hydrogen bond results from a Dipole-dipole force between an Electronegative atom and a Hydrogen atom bonded to Nitrogen, Oxygen "Polar molecule" and "Non-polar" redirect here 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. " Electronegativity " is the opposite of " Electropositivity," which describes an element's ability to donate electrons A molecule with such a charge difference is called a dipole. In physics there are two kinds of dipoles ( Hellènic: di(s- = two- and pòla = pivot hinge An electric dipole is a 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. A hydrogen bond results from a Dipole-dipole force between an Electronegative atom and a Hydrogen atom bonded to Nitrogen, Oxygen 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 point temperatures; more heat energy is required to break the hydrogen bonds between molecules. The melting point of a solid is the temperature range at which it changes state from solid to Liquid. The boiling point of a liquid is the temperature at which the Vapor pressure of the liquid equals the environmental pressure surrounding the liquid In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature 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. Room temperature (also referred to as ambient temperature) is a common term to denote a certain Temperature within enclosed space at which humans are accustomed The extra bonding between water molecules also gives liquid water a large specific heat capacity. 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 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. Regular hexagon The internal Angles of a regular hexagon (one where all sides and all angles are equal are all 120 ° and the hexagon has 720 degrees In Mineralogy and Crystallography, a crystal structure is a unique arrangement of Atoms in a Crystal. 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 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. " Electronegativity " is the opposite of " Electropositivity," which describes an element's ability to donate electrons ---- Bold text Coulomb's law', developed in the 1780s by French physicist Charles Augustin de Coulomb, may be stated in scalar form The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J

Adhesion

Water sticks to itself (cohesion) because it is polar. Formation Water will condense into droplets depending on the temperature Cohesion ( n. lat cohaerere "stick or stay together" or cohesive attraction or cohesive force is a Physical property "Polar molecule" and "Non-polar" redirect here Water also has high adhesion properties because of its polar nature. Adhesion is the tendency of certain dissimilar molecules to cling together due to Attractive forces. 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. Glass in the common sense refers to a Hard, Brittle, transparent Solid, such as that used for Windows many 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. In Cell biology, an organelle (pronunciation /ɔː(rgəˡnɛl/ is a specialized subunit within a cell that has a specific function and is usually separately enclosed Hydrophile, from the Greek (hydros "water" and φιλια (philia "friendship" refers to a physical property of a Molecule Irving Langmuir observed a strong repulsive force between hydrophilic surfaces. Irving Langmuir ( January 31, 1881 in Brooklyn New York – August 16, 1957 in Woods Hole Massachusetts) was an 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. "NIH" redirects here For other meanings of NIH see NIH (disambiguation. ^[15] They are particularly important when cells are dehydrated by exposure to dry atmospheres or to extracellular freezing.

Surface tension

Main article: Surface tension

Water has a high surface tension caused by the strong cohesion between water molecules. For the work of fiction see Surface Tension (short story. Surface tension is a property of the surface of a Liquid that causes it to 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. Polyethylene or polythene ( IUPAC name poly(ethene) is a Thermoplastic commodity heavily used in consumer products (notably the 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. A capillary wave is a Wave travelling along the interface between two fluids whose dynamics are dominated by the effects of Surface tension. The apparent elasticity caused by surface tension drives the waves.

Capillary action

Main article: Capillary action

Capillary action refers to the process of water moving up a narrow tube against the force of gravity. Capillary action, capillarity, capillary motion, or wicking is the ability of a substance to draw another substance into it Capillary action, capillarity, capillary motion, or wicking is the ability of a substance to draw another substance into it Gravitation is a natural Phenomenon by which objects with Mass attract one another 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

Water is also a good solvent due to its polarity. A solvent is a liquid or gas that dissolves a solid liquid or gaseous Solute, resulting in a Solution. "Polar molecule" and "Non-polar" redirect here Substances that will mix well and dissolve in water (e. g. salts) are known as "hydrophilic" (water-loving) substances, while those that do not mix well with water (e. A salt, in Chemistry, is defined as the product formed from the neutralisation reaction of Acids and bases. Hydrophile, from the Greek (hydros "water" and φιλια (philia "friendship" refers to a physical property of a Molecule g. fats and oils), are known as "hydrophobic" (water-fearing) substances. Lipids are broadly defined as any fat- Soluble ( lipophilic) naturally-occurring Molecule, such as fats oils waxes cholesterol sterols fat-soluble In Chemistry, hydrophobicity (from the combining form of water in Attic Greek hydro- and for fear phobos) refers to the physical property of The ability of a substance to dissolve in water is determined by whether or not the substance can match or better the strong attractive forces that water molecules generate between other water molecules. In Physics, Chemistry, and Biology, intermolecular forces are forces that act between stable Molecules or between functional groups of If a substance has properties that do not allow it to overcome these strong intermolecular forces, the molecules are "pushed out" from the water, and do not dissolve. Precipitation is the formation of a Solid in a Solution during a Chemical reaction. 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. In Chemistry, a solution is a Homogeneous Mixture composed of two or more substances 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. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are In Chemistry, an alcohol is any Organic compound in which a Hydroxyl group ( - O[[hydrogen H]]) is bound to a Carbon Salt is a Dietary mineral composed primarily of Sodium chloride that is essential for Animal life but toxic to most land plants 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. The Van der Waals equation is an Equation of state that can be derived from a special form of the potential between a pair of molecules (hard-sphere repulsion

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. For sodium chloride in the diet see Salt. Sodium chloride, also known as common salt, table salt, or Halite, is a An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge The ions are then easily transported away from their crystalline lattice into solution. In Mineralogy and Crystallography, a crystal structure is a unique arrangement of Atoms in a Crystal. An example of a nonionic solute is table sugar. Solubility of Pure SucroseTemperature(Cg 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.

Amphoteric nature of water

Chemically, water is amphoteric — i. e. , it is able to act as either an acid or a base. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are In Chemistry, a base is most commonly thought of as an aqueous substance that can accept Protons This refers to the Brønsted-Lowry theory of acids and 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. In Chemistry, hydroxide is the most common name for the diatomic Anion OH− consisting of Oxygen and Hydrogen In Chemistry, hydronium is the obsolete name for the Cation H 3 O + derived from Protonation of Water Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 If the equilibrium is disturbed, the solution becomes acidic (higher concentration of hydronium ions) or basic (higher concentration of hydroxide ions). In a Chemical process, chemical equilibrium is the state in which the chemical activities or Concentrations of the reactants and products have no net change

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 stronger base, 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.

In the reaction with ammonia, NH₃, water donates an H⁺ ion, and is thus acting as an acid:

NH₃ + H₂O ⇌ NH₄⁺ + OH⁻

Acidity in nature

In theory, pure water has a pH of 7 at 298 K. Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor pH is the measure of the acidity or alkalinity of a Solution. 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. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Carbonic acid (ancient name acid of air or aerial acid) has the formula H2CO3 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. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Sulfur or sulphur (ˈsʌlfɚ see spelling below) is the Chemical element that has the Atomic number 16 Acid rain is Rain or any other form of precipitation that is unusually Acidic It has harmful effects on plants aquatic animals and infastructure

Hydrogen bonding in water

A water molecule can form a maximum of four hydrogen bonds because it can accept two and donate two hydrogens. A hydrogen bond results from a Dipole-dipole force between an Electronegative atom and a Hydrogen atom bonded to Nitrogen, Oxygen 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. Structure HF forms orthorhombic crystals consisting of zig-zag chains of HF molecules Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a Chemical compound In Physics, thermodynamics (from the Greek θερμη therme meaning " Heat " and δυναμις dynamis meaning " 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. See also Intramolecular forces ' Steric effects arise from the fact that each Atom within a Molecule occupies a certain 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. A tetrahedron (plural tetrahedra) is a Polyhedron composed of four triangular faces three of which meet at each vertex. Liquid is one of the principal States of matter. A liquid is a Fluid that has the particles loose and can freely form a distinct surface at the boundaries of 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. The Chemical compound silicon dioxide, also known as silica or silox (from the Latin " Silex " is an Oxide 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. A biological process is a process of a living Organism (either plant or animal

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 the 1930s is yet to be proven unambiguously by experiments and theoretical calculations. Linus Carl Pauling (February 28 1901 – August 19 1994 was an American Scientist, Peace activist, Author and educator.

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 H_3/2O than H₂O at the quantum level. ^[16] This result could have significant ramifications at the level of, for example, the hydrogen bond in biological, chemical and physical systems. A hydrogen bond results from a Dipole-dipole force between an Electronegative atom and a Hydrogen atom bonded to Nitrogen, Oxygen Foundations of modern biology There are five unifying principles Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. The experiment shows that when neutrons and electrons collide with water, they scatter in a way that indicates that they only are affected by a ratio of 1. This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J 5:1 of hydrogen to oxygen respectively. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the 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 kinetic and dynamical systems. In physics the term dynamics customarily refers to the time evolution of physical processes ^[17][18]

Heavy Water and isotopologues of water

Hydrogen has three isotopes. Isotopologues are molecules that differ only in their isotopic composition 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, also called heavy hydrogen, is a Stable isotope of Hydrogen with a Natural abundance in the Oceans of Earth Deuterium, D₂O, is also known as heavy water and is used in nuclear reactors as a neutron moderator. Heavy water is water which contains a higher proportion than normal of the Isotope Deuterium, as deuterium oxide, D2O or ²H2O This article is a subarticle of Nuclear power. A nuclear reactor is a device in which Nuclear chain reactions are initiated controlled In Nuclear engineering, a neutron moderator is a medium which reduces the velocity of Fast neutrons thereby turning them into Thermal neutrons capable The third isotope, tritium, has 1 proton and 2 neutrons, and is radioactive, with a half-life of 4500 days. Tritium (ˈtɹɪtiəm symbol or, also known as Hydrogen-3) is a radioactive Isotope of Hydrogen. Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. Half-Life (computer-game page here It's already listed in the disambiguation page T₂O exists in nature only in tiny quantities, being produced primarily via cosmic ray-driven nuclear reactions in the atmosphere. D₂O is stable, but differs from H₂O in that it is more dense - 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 HDO occurs naturally in ordinary water in very low concentrations (~0. 03%) and D₂O in far lower amounts (0. 000003%). Consumption of pure isolated D₂O 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. ^[19]

Transparency

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.

History

The properties of water have historically been used to define various temperature scales. Kelvin Celsius (Centigrade Fahrenheit Rankine Delisle Newton Réaumur Notably, the Kelvin, Celsius and Fahrenheit scales were, or currently are, defined by the freezing and boiling points of water. The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic The Celsius Temperature scale was previously known as the centigrade scale. Fahrenheit is a temperature scale named after Daniel Gabriel Fahrenheit (1686–1736 a German Physicist who proposed it in 1724 The less common scales of Delisle, Newton, Réaumur and Rømer were defined similarly. The newton (symbol N) is the SI derived unit of Force, named after Isaac Newton in recognition of his work on Classical "Réaumur" redirects here For other uses see Réaumur (disambiguation. Ole Christensen Rømer (o(ːlə ˈʁœːˀmɐ in Danish 25 September 1644, Århus – 19 September 1710, Copenhagen) The triple point of water is a more commonly used standard point today. In Thermodynamics, the triple point of a substance is the Temperature and Pressure at which three phases (for example Gas, Liquid ^[20]

The first scientific decomposition of water into hydrogen and oxygen, by electrolysis, was done in 1800 by William Nicholson, an English chemist. In chemistry and manufacturing electrolysis is a method of separating chemically bonded elements and compounds by passing an Electric current William Nicholson (1753&mdash May 21, 1815) was a renowned English chemist who was also a writer on natural philosophy and chemistry as well as a translator In 1805, Joseph Louis Gay-Lussac and Alexander von Humboldt showed that water is composed of two parts hydrogen and one part oxygen (by volume). Joseph Louis Gay-Lussac (also Louis Joseph Gay-Lussac, December 6, 1778 – May 9, 1850) was a French chemist (September 14 1769 &ndash May 6 1859 was a German naturalist and explorer, and the younger brother of the Prussian minister philosopher and linguist

Gilbert Newton Lewis isolated the first sample of pure heavy water in 1933. Gilbert Newton Lewis ( October 23, 1875 - March 23, 1946) was a famous American physical chemist known for the discovery Heavy water is water which contains a higher proportion than normal of the Isotope Deuterium, as deuterium oxide, D2O or ²H2O

Polywater was a hypothetical polymerized form of water that was the subject of much scientific controversy during the late 1960s. Polywater was a hypothetical Polymerized form of Water that was the subject of much scientific controversy during the late 1960s A polymer is a large Molecule ( Macromolecule) composed of repeating Structural units typically connected by Covalent Chemical bonds The consensus now is that it does not exist.

Systematic naming

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 IUPAC nomenclature of inorganic chemistry is a systematic method of naming Inorganic Chemical compounds as recommended by the International Union

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). Hydrogen peroxide (H2O2 is a very pale blue liquid which appears colorless in a dilute solution slightly more Viscous than water Hydrogen sulfide (or hydrogen sulphide) is the Chemical compound with the formula H 2 S. Heavy water is water which contains a higher proportion than normal of the Isotope Deuterium, as deuterium oxide, D2O or ²H2O Another systematic name, oxidane, is accepted by IUPAC as a parent name for the systematic naming of oxygen-based substituent groups,^[21] although even these commonly have other recommended names. In Organic chemistry, a substituent is an atom or group of atoms substituted in place of a Hydrogen atom on the Parent chain of a Hydrocarbon For example, the name hydroxyl is recommended over oxidanyl for the –OH group. Hydroxyl in Chemistry stands for a molecule consisting of an Oxygen atom and a Hydrogen atom connected by a Covalent bond. The name oxane is explicitly mentioned by the IUPAC as being unsuitable for this purpose, since it is already the name of a cyclic ether also known as tetrahydropyran in the Hantzsch-Widman system; similar compounds include dioxane and trioxane. Tetrahydropyran, or oxane, is the Organic compound consisting of a saturated six-membered ring containing five carbon atoms and one oxygen atom Trioxane refers to a pair of Isomeric Organic compounds having the Molecular formula C3H6O3

Systematic nomenclature and humor

Main article: Dihydrogen monoxide hoax

Dihydrogen monoxide or DHMO is an overly pedantic systematic covalent name of water. "Dihydrogen monoxide" redirects here For the H2O molecule see Water (molecule. This term has been used in parodies of chemical research that call for this "lethal chemical" to be banned. A parody (ˈpɛɹədiː US, [ˈpaɹədiː] UK) in contemporary usage is a work created to mock comment on or poke fun at an original work its subject 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". Hydrogen sulfide (or hydrogen sulphide) is the Chemical compound with the formula H 2 S. Hydrogen peroxide (H2O2 is a very pale blue liquid which appears colorless in a dilute solution slightly more Viscous than water

Some overzealous material safety data sheets for water list the following: Caution: May cause drowning!^[22][23]

Other systematic names for water include hydroxic acid or hydroxylic acid. A material safety data sheet ( MSDS) is a form containing data regarding the properties of a particular substance 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 (amphoteric). None of these names are used widely outside of DHMO sites.

See also

References

External links

• Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam (fast computation speed)
• Release on the IAPWS Formulation 1995 for the Thermodynamic Properties of Ordinary Water Substance for General and Scientific Use (simpler formulation)
• A spoof site on the "dangers" of dihydrogen monoxide
• Sigma Xi The Scientific Research Society, Year of Water 2008
• Stockholm International Water Institute (SIWI)
• Explanation of the anomalous properties of water
• Computational Chemistry Wiki
• Water phase diagrams
• Water Absorption Spectrum

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