Water

Water
Ball-and-stick model of a water molecule	Space filling model of a water molecule Oxygen, O Hydrogen, H
Names
	Preferred IUPAC name Water
	Systematic IUPAC name Oxidane (not in common use)
	Other names Hydrogen oxide; Hydrogen hydroxide (HH 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;
ECHA InfoCard	100.028.902
EC Number	231-791-2;
Gmelin Reference	117
KEGG	C00001;
PubChem CID	962;
RTECS number	ZC0110000;
UNII	059QF0KO0R ;
CompTox Dashboard (EPA)	DTXSID6026296 ;
	InChI InChI=1S/H2O/h1H2 Key: XLYOFNOQVPJJNP-UHFFFAOYSA-N ;
	SMILES O;
Properties
Chemical formula	H; 2O
Molar mass	18.01528(33) g/mol
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
Safety data sheet (SDS)	SDS
Related compounds
Other anions	Hydrogen sulfide; Hydrogen selenide; Hydrogen telluride; Hydrogen polonide; Hydrogen peroxide;
	Related

Water is an inorganic compound with the chemical formula H₂O. It is a transparent, tasteless, odorless,^{[lower-alpha 3]} and nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a solvent^[19]). It is vital for all known forms of life, despite not providing food energy or organic micronutrients. Its chemical formula, H₂O, indicates that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. The hydrogen atoms are attached to the oxygen atom at an angle of 104.45°.^[20] In liquid form, H₂O is also called "water" at standard temperature and pressure.

Quick Facts Names, Identifiers ...

[lower-alpha 3]

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[lower-alpha 1]

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[lower-alpha 2]

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