Properties of water

Water
	The water molecule has this basic geometric structure
Ball-and-stick model of a water molecule	Space filling model of a water molecule Oxygen, O Hydrogen, H
	A drop of water falling toward water in a glass
Names
	Preferred IUPAC name Water
	Systematic IUPAC name Oxidane (not in common use)
	Other names Hydrogen oxide; Hydrogen hydroxide (H2O or HOH); Hydroxylic acid; Dihydrogen monoxide (DHMO) (parody name); Dihydrogen oxide; Hydric acid; Hydrohydroxic acid; Hydroxic acid; Hydroxoic acid; Hydrol; μ-Oxidodihydrogen; κ1-Hydroxylhydrogen(0); Aqua; Neutral liquid; Oxygen dihydride (may be considered incorrect);
Identifiers
CAS Number	7732-18-5 ;
3D model (JSmol)	Interactive image;
Beilstein Reference	3587155
ChEBI	CHEBI:15377 ;
ChEMBL	ChEMBL1098659 ;
ChemSpider	937 ;
DrugBank	DB09145;
EC Number	231-791-2;
Gmelin Reference	117
KEGG	C00001;
PubChem CID	962;
RTECS number	ZC0110000;
UNII	059QF0KO0R ;
	InChI InChI=1S/H2O/h1H2 Key: XLYOFNOQVPJJNP-UHFFFAOYSA-N ;
	SMILES O;
Properties
Chemical formula	H2O
Molar mass	18.015 g·mol−1
Appearance	Almost colorless or white crystalline solid, almost colorless liquid, with a hint of blue, colorless gas
Odor	Odorless
Density	Liquid (1 atm, VSMOW):; 0.99984283(84) g/mL at 0 °C; 0.99997495(84) g/mL at 3.983035(670) °C (temperature of maximum density, often 4 °C); 0.99704702(83) g/mL at 25 °C; 0.96188791(96) g/mL at 95 °C; Solid:; 0.9167 g/mL at 0 °C;
Melting point	0.00 °C (32.00 °F; 273.15 K)
Boiling point	99.98 °C (211.96 °F; 373.13 K)
Solubility	Poorly soluble in haloalkanes, aliphatic and aromatic hydrocarbons, ethers. ; 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, acetonitrile. ; Partially miscible with diethyl ether, methyl ethyl ketone, dichloromethane, ethyl acetate, bromine.
Vapor pressure	3.1690 kilopascals or 0.031276 atm at 25 °C
Acidity (pKa)	13.995
Basicity (pKb)	13.995
Conjugate acid	Hydronium H3O+ (pKa = 0)
Conjugate base	Hydroxide OH– (pKb = 0)
Thermal conductivity	0.6065 W/(m·K)
Refractive index (nD)	1.3330 (20 °C)
Viscosity	0.890 mPa·s (0.890 cP)
Structure
Crystal structure	Hexagonal
Point group	C2v
Molecular shape	Bent
Dipole moment	1.8546 D
Thermochemistry
Heat capacity (C)	75.385 ± 0.05 J/(mol·K)
Std molar; entropy (S⦵298)	69.95 ± 0.03 J/(mol·K)
Std enthalpy of; formation (ΔfH⦵298)	−285.83 ± 0.04 kJ/mol
Gibbs free energy (ΔfG⦵)	−237.24 kJ/mol
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	Drowning; Avalanche (as snow); Water intoxication;
NFPA 704 (fire diamond)	0 0 0
Flash point	Non-flammable
Related compounds
Other anions	Hydrogen sulfide; Hydrogen selenide; Hydrogen telluride; Hydrogen polonide; Hydrogen peroxide;
Related solvents	Acetone; Ethanol; Methanol; Hydrogen fluoride; Ammonia;
Supplementary data page
	Water (data page)
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Water (H₂O) is a polar inorganic compound that is, at room temperature, a tasteless and odorless liquid, which is nearly colorless apart from an inherent hint of blue. It is by far the most studied chemical compound and is described as the "universal solvent" and the "solvent of life". It is the most abundant substance on the surface of Earth and the only common substance to exist as a solid, liquid, and gas on Earth's surface. It is also the third most abundant molecule in the universe (behind molecular hydrogen and carbon monoxide).

Water molecules form hydrogen bonds with each other and are strongly polar. This polarity allows them to dissociate ions in salts and bond to other polar substances such as alcohols and acids, thus dissolving them. Their hydrogen bonding causes their 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 that it can exhibit properties of an acid or a base, depending on the pH of the solution that it is in; It readily produces both H⁺
and OH⁻
ions. Related to its amphoteric character, it undergoes self-ionization. The product of the activities, or approximately, the concentrations of H⁺
and OH⁻
is a constant, so their respective concentrations are inversely proportional to each other.