Water (H2O)
IUPAC name	water, oxidane
Other names	Hydrogen hydroxide (HH or HOH), hydrogen oxide, dihydrogen monoxide (DHMO) (systematic name), hydrogen monoxide, dihydrogen oxide, hydric acid, hydrohydroxic acid, hydroxic acid, hydrol, μ-oxido dihydrogen, κ1-hydroxyl hydrogen(0)
Identifiers
CAS number	7732-18-5
PubChem	962
ChEBI	CHEBI:15377
RTECS number	ZC0110000
SMILES	O
Beilstein Reference	3587155
Gmelin Reference	117
Properties
Molecular formula	H2O
Molar mass	18.01528(33) g/mol
Appearance	White crystal-like solid, almost colorless liquid with a hint of blue, colorless gas
Odor	None
Density	Liquid: 0.9998396 g/mL at 0 °C 0.9970474 g/mL at 25 °C 0.961893 g/mL at 95 °C Solid: 0.9167 g/ml at 0 °C
Melting point	0.00 °C, 273 K, 32 °F
Boiling point
Solubility in water	N/A
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
Acidity (pKa)	13.995
Basicity (pKb)	13.995
Thermal conductivity	0.6065 W/(m·K)
Refractive index (nD)	1.3330 (20 °C)
Viscosity	0.890 cP
Structure
Crystal structure	Hexagonal
Point group	C2v
Molecular shape	Bent
Dipole moment	1.8546 D
Thermochemistry
Std enthalpy of formation ΔfHo298	−285.83 ± 0.04 kJ/mol
Standard molar entropy So298	69.95 ± 0.03 J/(mol·K)
Specific heat capacity, C	75.385 ± 0.05 J/(mol·K)
Hazards
Main hazards	Drowning Avalanche (as snow) Water intoxication (see also Dihydrogen monoxide parody)
NFPA 704	0 0 0
Flash point	Non-flammable
Related compounds
Other cations	Hydrogen sulfide Hydrogen selenide Hydrogen telluride Hydrogen polonide Hydrogen peroxide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

Water in three states: liquid (including the clouds, which are aerosols), solid (ice) and gas (water vapour)

Water (H₂O) is a transparent, tasteless, odourless, and almost colourless chemical substance and covers about 71% of Earth's surface.

No known life can live without it. Water is essential for life. This has to be qualified a bit. There are some forms of life which can survive without it, but cannot reproduce without it. Since reproduction is a central part of life, it is clear that water is essential for an organism to survive and reproduce.