Properties of water

Properties of water

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"H2O" and "HOH" redirect here. For other uses, see H2O (disambiguation) and HOH (disambiguation).

Water (H
2O)

Names
IUPAC name water, oxidane
Other names Hydrogen oxide, Dihydrogen monoxide(DHMO), Hydrogen monoxide, Dihydrogen oxide, Hydrogen hydroxide (HH or HOH), Hydric acid, Hydrohydroxic acid, Hydroxic acid, Hydrol,[1] μ-Oxido dihydrogen
Identifiers
CAS Number	7732-18-5
3D model (JSmol)	Interactive image
Beilstein Reference	3587155
ChEBI	CHEBI:15377
ChemSpider	937
Gmelin Reference	117
PubChem CID	962
RTECS number	ZC0110000
UNII	059QF0KO0R
InChI[show]
SMILES[show]
Properties
Chemical formula	H 2O
Molar mass	18.01528(33) g/mol
Appearance	White solid or almost colorless, transparent, with a slight hint of blue, crystalline solid or liquid[2]
Odor	None
Density	Liquid:[3] 0.9998396 g/mL at 0 °C 0.9970474 g/mL at 25 °C 0.961893 g/mL at 95 °C Solid:[citation needed] 917 kg/m3 = 0.917 tonne/m3= 0.917 kg/l = 0.917 g/cm3 ≈ 57.2 lb/ft3
Melting point	0.00 °C (32.00 °F; 273.15 K)[a]
Boiling point	99.98 °C; 211.96 °F; 373.13 K [4][a]
Solubility	Poorly soluble inhaloalkanes, aliphatic andaromatic hydrocarbons,ethers.[5] Improved solubility in carboxylates, alcohols,ketones, amines. Miscible with methanol, ethanol,propanol, isopropanol,acetone, glycerol, 1,4-dioxane, tetrahydrofuran,sulfolane, acetaldehyde,dimethylformamide,dimethoxyethane, dimethyl sulfoxide, glycerol,acetonitrile.
Vapor pressure	3.1690 kilopascals or 0.031276 atm[6]
Acidity (pKa)	13.995[7][b]
Basicity (pKb)	13.995
Thermal conductivity	0.6065 W/m·K[9]
Refractive index(nD)	1.3330 (20°C)[10]
Viscosity	0.890 cP[11]
Structure
Crystal structure	Hexagonal
Point group	C2v
Molecular shape	Bent
Dipole moment	1.8546 D[12]
Thermochemistry
Specific heat capacity (C)	75.375 ± 0.05 J/mol·K[13]
Std molar entropy (So298)	69.95 ± 0.03 J/mol·K[13]
Std enthalpy of formation (ΔfHo298)	-285.83 ± 0.040 kJ/mol[5][13]
Gibbs free energy(ΔfG˚)	-237.24 kJ/mol[5]
Hazards
Main hazards	Drowning Water intoxication Avalanche (as snow) (see also Dihydrogen monoxide hoax)
NFPA 704	0 0 0
Flash point	Non-flammable
Related compounds
Other cations	Hydrogen sulfide Hydrogen selenide Hydrogen telluride Hydrogen polonide Hydrogen peroxide
Related solvents	Acetone Methanol
Related compounds	Water vapor Ice Heavy water
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Water (H
2O) is a polar inorganic compound that is at room temperature a tasteless and odorless liquid, nearly colorless with a hint of blue. This simplest hydrogen chalcogenide is by far the most studied chemical compound and is described as the "universal solvent" for its ability to dissolve many substances.^[14][15] This allows it to be the "solvent of life".^[16] It is the only common substance to exist as a solid, liquid, and gas in nature.^[17]

Water molecules form hydrogen bonds with each other and are strongly polar. This polarity allows it to separate ions in salts and strongly bond to other polar substances such as alcohols and acids, thus dissolving them. Its hydrogen bonding causes its many unique properties, such as having a solid form less dense than its liquid form, a relatively high boiling point of 100 °C for its molar mass, and a high heat capacity.

Water is amphoteric, meaning it is both an acid and a base—it produces H+ and OH− ions by self ionization. This regulates the concentrations of H+ and OH− ions in water.

Due to water being a very good solvent, it is rarely pure and some of the properties of impure water can vary from those of the pure substance. However, there are also many compounds that are essentially, if not completely, insoluble in water, such as fats, oils and other non-polar substances.