Water
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From Wikipedia, the free encyclopedia
For other uses, see Water (disambiguation).
"H2O" redirects here. For other uses, see H2O (disambiguation).
Water
Oxygen, O
Hydrogen, H
Names
IUPAC name
Water
Systematic IUPAC name
Oxidane
Other names
Hydrogen oxide
Hydrogen hydroxide (HH or HOH)
Hydroxylic acid
Dihydrogen monoxide (DHMO) (parody name[1])
Dihydrogen oxide
Hydric acid
Hydrohydroxic acid
Hydroxic acid
Hydroxoic acid
Hydrol[2]
μ-Oxidodihydrogen
κ1-Hydroxylhydrogen(0)
Aqua
Neutral liquid
Identifiers
CAS 7732-18-5
Number
3D model Interactive image
(JSmol)
Beilstein 3587155
Reference
ChEBI CHEBI:15377
ChEMBL ChEMBL1098659
ChemSpide 937
DrugBank DB09145
ECHA 100.028.902
InfoCard
EC Number 231-791-2
Gmelin 117
Reference
KEGG C00001
PubChem 962
CID
RTECS ZC0110000
number
UNII 059QF0KO0R
CompTox DTXSID6026296
Dashboard
(EPA)
show
InChI
show
SMILES
Properties
Chemical H
formula
2 O
Molar mass 18.01528(33) g/mol
Appearance Almost colorless or white crystalline solid, almost
colorless liquid, with a hint of blue, colorless gas[3]
Odor Odorless
Density Liquid (1 atm, VSMOW):
0.99984283(84) g/mL at 0 °C[4]
0.99997495(84) g/mL at 3.983035(670) °C (temperature
of maximum density, often 4 °C)[4]
0.99704702(83) g/mL at 25 °C[4]
0.96188791(96) g/mL at 95 °C[5]
Solid:
0.9167 g/mL at 0 °C[6]
Melting 0.00 °C (32.00 °F; 273.15 K) [b]
point
Boiling 99.98 °C (211.96 °F; 373.13 K)[16][b]
point
Solubility Poorly soluble
in haloalkanes, aliphatic and aromatic hydrocarbons, ether
s.[7] Improved solubility
in carboxylates, alcohols, ketones, amines. Miscible
with methanol, ethanol, propanol, isopropanol, acetone, gl
ycerol, 1,4-dioxane, tetrahydrofuran, sulfolane, acetaldehy
de, dimethylformamide, dimethoxyethane, dimethyl
sulfoxide, acetonitrile. Partially miscible with diethyl
ether, methyl ethyl ketone, dichloromethane, ethyl
acetate, bromine.
Vapor 3.1690 kilopascals or 0.031276 atm at 25 °C[8]
pressure
Acidity (p 13.995[9][10][a]
K a)
Basicity (p 13.995
Kb)
Conjugate Hydronium H3O+ (pKa = 0)
acid
Conjugate Hydroxide OH– (pKb = 0)
base
Thermal 0.6065 W/(m·K)[13]
conductivit
Refractive 1.3330 (20 °C)[14]
index (nD)
Viscosity 0.890 mPa·s (0.890 cP)[15]
Structure
Crystal Hexagonal
structure
Point group C2v
Molecular Bent
shape
Dipole 1.8546 D[17]
moment
Thermochemistry
Heat 75.385 ± 0.05 J/(mol·K)[16]
capacity (
C)
Std molar 69.95 ± 0.03 J/(mol·K)[16]
entropy (S
⦵
298 )
Std −285.83 ± 0.04 kJ/mol[7][16]
enthalpy of
formation (
ΔfH⦵298)
Gibbs free −237.24 kJ/mol[7]
energy (Δf
G⦵)
Hazards
Occupational safety and health (OHS/OSH):
Main Drowning
hazards
Avalanche (as snow)
Water intoxication
NFPA
704 (fire di
amond)
0
0
0
Flash point Non-flammable
Safety data SDS
sheet (SDS)
Related compounds
Other catio Hydrogen sulfide
ns
Hydrogen selenide
Hydrogen telluride
Hydrogen polonide
Hydrogen peroxide
Related sol Acetone
vents
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 is an inorganic compound with the chemical formula H2O. It is a transparent,
tasteless, odorless,[c] and nearly colorless chemical substance, and 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]
"Water" is also the name of the liquid state of H2O at standard temperature and
pressure.
Because Earth's environment is relatively close to water's triple point, water exists on
Earth as a solid, a liquid, and a gas.[21] It forms precipitation in the form
of rain and aerosols in the form of fog. Clouds consist of suspended droplets of water
and ice, its solid state. When finely divided, crystalline ice may precipitate in the form
of snow. The gaseous state of water is steam or water vapor.
Water covers about 71% of the Earth's surface, with seas and oceans making up most
of the water volume (about 96.5%).[22] Small portions of water occur
as groundwater (1.7%), in the glaciers and the ice
caps of Antarctica and Greenland (1.7%), and in the air as vapor, clouds (consisting of
ice and liquid water suspended in air), and precipitation (0.001%).[23][24] Water moves
continually through the water
cycle of evaporation, transpiration (evapotranspiration), condensation, precipitation,
and runoff, usually reaching the sea.
Water plays an important role in the world economy. Approximately 70% of the fresh
water used by humans goes to agriculture.[25] Fishing in salt and fresh water bodies has
been, and continues to be, a major source of food for many parts of the world, providing
6.5% of global protein.[26] Much of the long-distance trade of commodities (such as oil,
natural gas, and manufactured products) is transported by boats through seas, rivers,
lakes, and canals. Large quantities of water, ice, and steam are used for cooling and
heating in industry and homes. Water is an excellent solvent for a wide variety of
substances, both mineral and organic; as such, it is widely used in industrial processes
and in cooking and washing. Water, ice, and snow are also central to many sports and
other forms of entertainment, such as swimming, pleasure boating, boat racing, surfing,
sport fishing, diving, ice skating, snowboarding, and skiing.
Etymology
The word water comes from Old English wæter, from Proto-Germanic *watar (source
also of Old Saxon watar, Old Frisian wetir, Dutch water, Old High
German wazzar, German Wasser, vatn, Gothic 𐍅𐌰𐍄𐍉 (wato)), from Proto-Indo-
European *wod-or, suffixed form of root *wed- ('water'; 'wet').[27] Also cognate, through
the Indo-European root, with Greek ύδωρ (ýdor; from Ancient Greek ὕδωρ (hýdōr),
whence English 'hydro-'), Russian вода́ (vodá), Irish uisce, and Albanian ujë.
