Water

Water (H
₂O)

Names
IUPAC name water, oxidane
Other names Hydrogen hydroxide (HH or HOH), hydrogen oxide, dihydrogen monoxide (DHMO) (systematic name[1]), hydrogen monoxide, dihydrogen oxide, hydric acid, hydrohydroxic acid, hydroxic acid, hydrol,[2] μ-oxido dihydrogen, κ1-hydroxyl hydrogen(0)
Identifiers
CAS Number	7732-18-5 Y
3D model (JSmol)	Interactive image
Beilstein Reference	3587155
ChEBI	CHEBI:15377 Y
ChEMBL	ChEMBL1098659 Y
ChemSpider	937 Y
ECHA InfoCard	100.028.902
Gmelin Reference	117
PubChem CID	962
RTECS number	ZC0110000
UNII	059QF0KO0R Y
CompTox Dashboard (EPA)	DTXSID6026296
SMILES O
Properties
Chemical formula	H 2O
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:[3] 0.9998396 g/mL at 0 °C 0.9970474 g/mL at 25 °C 0.961893 g/mL at 95 °C Solid:[4] 0.9167 g/ml at 0 °C
Melting point	0.00 °C (32.00 °F; 273.15 K) [a]
Boiling point	99.98 °C (211.96 °F; 373.13 K) [5][a]
Solubility in water	N/A
Solubility	Poorly soluble in haloalkanes, aliphatic and aromatic hydrocarbons, ethers.[6] 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[7]
Acidity (pKa)	13.995[8][9][b]
Basicity (pKb)	13.995
Conjugate acid	Hydronium
Conjugate base	Hydroxide
Thermal conductivity	0.6065 W/(m·K)[12]
Refractive index (nD)	1.3330 (20 °C)[13]
Viscosity	0.890 cP[14]
Structure
Crystal structure	Hexagonal
Point group	C2v
Molecular shape	Bent
Dipole moment	1.8546 D[15]
Thermochemistry
Std enthalpy of formation ΔfHo298	−285.83 ± 0.04 kJ/mol[6][16]
Standard molar entropy So298	69.95 ± 0.03 J/(mol·K)[16]
Specific heat capacity, C	75.385 ± 0.05 J/(mol·K)[16]
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 otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y verify (what is YN ?)
Infobox references

Water (H
₂O) is a transparent, tasteless, odourless, and almost always colourless chemical substance and covers about 71% of Earth's surface.

No known life can live without it. Water is essential for life.^[17] 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.

Lakes, oceans, seas, and rivers are made of water. Precipitation is water that falls from clouds in the sky. It may be rain if it is liquid, or it may be snow or ice frozen if it is cold. When water gets below 0 °C (32 °F), it freezes and becomes ice, the frozen kind of water. If water gets very hot (above 100 °C (212 °F), it boils and becomes steam or water vapor.

There is a water cycle.

1. ↑ "naming molecular compounds". www.iun.edu. Archived from the original on 24 September 2018. Retrieved 1 October 2018. Sometimes these compounds have generic or common names (e.g., H2O is "water") and they also have systematic names (e.g., H2O, dihydrogen monoxide).
2. ↑ "Definition of Hydrol". Merriam-Webster.
3. ↑ Riddick 1970, Table of Physical Properties, Water 0b. pg 67-8. sfn error: no target: CITEREFRiddick1970 (help)
4. ↑ Lide 2003, Properties of Ice and Supercooled Water in Section 6. sfn error: no target: CITEREFLide2003 (help)
5. ↑ Water in Linstrom, Peter J.; Mallard, William G. (eds.); NIST Chemistry WebBook, NIST Standard Reference Database Number 69, National Institute of Standards and Technology, Gaithersburg (MD), http://webbook.nist.gov (retrieved 2016-5-27)
6. ↑ ^{6.0 6.1} Anatolievich, Kiper Ruslan. "Properties of substance: water". Archived from the original on 2014-06-02. Retrieved 2021-02-07.
7. ↑ Lide 2003, Vapor Pressure of Water From 0 to 370° C in Sec. 6. sfn error: no target: CITEREFLide2003 (help)
8. ↑ Lide 2003, Chapter 8: Dissociation Constants of Inorganic Acids and Bases. sfn error: no target: CITEREFLide2003 (help)
9. ↑ Weingärtner et al. 2016, p. 13. sfn error: no target: CITEREFWeingärtner_et_al.2016 (help)
10. ↑ "What is the pKa of Water". University of California, Davis. 2015-08-09.
11. ↑ Silverstein, Todd P.; Heller, Stephen T. (17 April 2017). "pKa Values in the Undergraduate Curriculum: What Is the Real pKa of Water?". Journal of Chemical Education. 94 (6): 690–695. Bibcode:2017JChEd..94..690S. doi:10.1021/acs.jchemed.6b00623.
12. ↑ Ramires, Maria L. V.; Castro, Carlos A. Nieto de; Nagasaka, Yuchi; Nagashima, Akira; Assael, Marc J.; Wakeham, William A. (1995-05-01). "Standard Reference Data for the Thermal Conductivity of Water". Journal of Physical and Chemical Reference Data. 24 (3): 1377–1381. Bibcode:1995JPCRD..24.1377R. doi:10.1063/1.555963. ISSN 0047-2689.
13. ↑ Lide 2003, 8—Concentrative Properties of Aqueous Solutions: Density, Refractive Index, Freezing Point Depression, and Viscosity. sfn error: no target: CITEREFLide2003 (help)
14. ↑ Lide 2003, 6.186. sfn error: no target: CITEREFLide2003 (help)
15. ↑ Lide 2003, 9—Dipole Moments. sfn error: no target: CITEREFLide2003 (help)
16. ↑ ^{16.0 16.1 16.2} Water in Linstrom, Peter J.; Mallard, William G. (eds.); NIST Chemistry WebBook, NIST Standard Reference Database Number 69, National Institute of Standards and Technology, Gaithersburg (MD), http://webbook.nist.gov (retrieved 2014-06-01)
17. ↑ "United Nations". Un.org. 2005-03-22. Retrieved 2010-07-25.