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**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)

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.

The water molecule has this basic geometric structure
Ball-and-stick model of a water molecule
Ball-and-stick model of a water molecule
Space filling model of a water molecule
Space filling model of a water molecule
  Oxygen, O
  Hydrogen, H
A drop of water falling towards water in a glass
IUPAC name
Systematic IUPAC name
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
3D model (JSmol)
ECHA InfoCard 100.028.902 Edit this at Wikidata
EC Number
  • 231-791-2
RTECS number
  • ZC0110000
  • InChI=1S/H2O/h1H2 checkY
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
  • 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)
1.3330 (20 °C)
Viscosity 0.890 mPa·s (0.890 cP)
1.8546 D
75.385 ± 0.05 J/(mol·K)
69.95 ± 0.03 J/(mol·K)
−285.83 ± 0.04 kJ/mol
−237.24 kJ/mol
Occupational safety and health (OHS/OSH):
Main hazards
Avalanche (as snow)
Water intoxication
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g. sodium chlorideFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
Flash point Non-flammable
Safety data sheet (SDS) SDS
Related compounds
Other cations
Related solvents
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).
checkY verify (what is checkY☒N ?)

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.

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