Water

**1. Water Properties and States:**
– Chemical formula: H2O
– Transparent, tasteless, odorless
– Covers 71% of Earth’s surface
– Exists in solid, liquid, and gaseous states
– Moves through the water cycle continuously
– Boiling point: 99.98°C
– Thermal conductivity: 0.6065 W/(m·K)
– Viscosity: 0.890 mPa·s
– Dipole moment: 1.8546 D
– Crystal structure: hexagonal
– Diamagnetic material
– Triple point: 273.16K, 611.657 pascals
– Critical point: 647.096K, 22.064 megapascals
– Tasteless and odorless
– Appears blue due to light absorption
– Molecular polarity: tetrahedral structure, forms hydrogen bonds
– Self-ionization: weak solution of hydronium hydroxide
– Electrical conductivity: low, increases with ionic material dissolution
– Mechanical properties: mostly incompressible, viscosity, speed of sound
– Water cycle: evaporation, transpiration, precipitation, runoff

**2. Water Importance and Usage:**
– Vital for all life forms
– 70% of fresh water used for agriculture
– Fishing provides 6.5% of global protein
– Crucial for the world economy and industrial processes
– Chemical and physical properties support various applications
– Water resources: stored in lakes, groundwater, ice
– Unsustainable groundwater withdrawals lead to depletion
– Seawater properties and tides
– Effects on life: essential for proliferation, metabolic processes, photosynthesis, respiration
– Human uses: agriculture, irrigation, concerns about water scarcity

**3. Water Health and Pollution:**
– Drinking water/potable water is fit for human consumption
– Safe water for swimming/bathing
– Water reclamation: converts wastewater into reusable water
– Millions lack access to safe water globally
– Water pollution and its impact on health
– Water quality standards and sanitation issues

**4. Water Historical and Global Significance:**
– Civilization flourished around rivers and waterways
– Major cities’ success linked to accessibility via water
– Historical significance of water in Rome, Mesopotamia, Egypt, Indus Valley
– Clean drinking water’s impact on human development
– Global water challenges: UN goals, water-related deaths, water scarcity

**5. Water Scientific Standards and Measurements:**
– Water’s role in defining mass and volume standards
– Historical scientific standards based on water
– Water’s importance in scientific measurements and experiments
– Water’s role in scientific advancements and discoveries
– Water as a crucial element in scientific research and analysis

Water (Wikipedia)

For other uses, see Water (disambiguation).

"H2O" redirects here. For other uses, see H2O (disambiguation).

Water is an inorganic compound with the chemical formula H₂O. It is a transparent, tasteless, odorless, 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). 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°. In liquid form, H₂O is also called "Water" at standard temperature and pressure.

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) Dihydrogen oxide Hydric acid Hydrohydroxic acid Hydroxic acid Hydroxoic acid Hydrol μ-Oxidodihydrogen κ1-Hydroxylhydrogen(0) Aqua Neutral liquid
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
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 Y
CompTox Dashboard (EPA)	DTXSID6026296
InChI InChI=1S/H2O/h1H2 Y Key: XLYOFNOQVPJJNP-UHFFFAOYSA-N Y
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 cations	Hydrogen sulfide Hydrogen selenide Hydrogen telluride Hydrogen polonide Hydrogen peroxide
Related solvents	Acetone 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). Y verify (what is YN ?) Infobox references

Because Earth's environment is relatively close to water's triple point, water exists on Earth as a solid, a liquid, and a gas. 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%). 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%). 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. 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. 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.