Term: Water
**Physical and Chemical Properties of Water:**
– Water is transparent, tasteless, odorless, and nearly colorless.
– Chemical formula H2O indicates two hydrogen atoms connected to one oxygen atom.
– Water covers about 71% of Earth’s surface.
– Water exists in solid, liquid, and gaseous states on Earth.
– Water plays a vital role in the global economy, agriculture, and food supply.
– Water is used as a solvent in various industrial processes and cooking.
– Water has specific thermal properties like boiling point, vapor pressure, thermal conductivity, refractive index, and viscosity.
– Water has a hexagonal crystal structure and a bent molecular shape.
– Water has a dipole moment and acidity/basicity properties.
– Water is a polar inorganic compound and the universal solvent.
**States and Properties of Water:**
– Water molecule consists of two hydrogen atoms and one oxygen atom.
– Water has three common states: solid (ice), liquid, and gas (water vapor).
– Water becomes less dense as it freezes.
– Ice has a density of 917kg/m³.
– Water boils at 100°C and freezes at 0°C at 1 atm pressure.
– Water can remain liquid at high temperatures in specific conditions.
– Water is a diamagnetic material and exhibits phase transitions like melting and boiling.
– Pressure affects the melting and boiling points of water.
– Water has triple and critical points, including a supercritical fluid phase.
**Chemical Properties and Solubility of Water:**
– Water is poorly soluble in haloalkanes, aliphatic, and aromatic hydrocarbons.
– Water has improved solubility in carboxylates, alcohols, ketones, and amines.
– Water is miscible with substances like methanol, ethanol, and acetone.
– Water is partially miscible with diethyl ether, methyl ethyl ketone, and ethyl acetate.
– Water is a good polar solvent due to hydrogen bonding and molecular polarity.
**Water Cycle and Resources:**
– Water cycle involves processes like evaporation, transpiration, precipitation, and runoff.
– Water resources include stocks like glaciers, groundwater, and flows like rivers and lakes.
– Aquifers can store water for thousands of years, while lake volumes fluctuate seasonally.
– Unsustainable groundwater withdrawals for irrigation lead to depletion.
– Global freshwater distribution: glaciers (69%), groundwater (30%), other sources (1%).
**Importance of Water in Life and Society:**
– Water is essential for all known forms of life, metabolic processes, and replication.
– Water is crucial for anabolism, catabolism, photosynthesis, respiration, and enzyme function.
– Water supports diverse aquatic life forms and is central to ecosystems.
– Access to safe drinking water is vital for human health and development.
– Water scarcity, sanitation issues, and competition for water resources pose global challenges.
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.
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| Names | |||
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| IUPAC name
Water
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| Systematic IUPAC name
Oxidane | |||
Other names
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| Identifiers | |||
3D model (JSmol)
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| 3587155 | |||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider | |||
| DrugBank | |||
| ECHA InfoCard | 100.028.902 | ||
| EC Number |
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| 117 | |||
| KEGG | |||
PubChem CID
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| RTECS number |
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| UNII | |||
CompTox Dashboard (EPA)
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| Properties | |||
| 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 |
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| 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)
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1.3330 (20 °C) | ||
| Viscosity | 0.890 mPa·s (0.890 cP) | ||
| Structure | |||
| Hexagonal | |||
| C2v | |||
| Bent | |||
| 1.8546 D | |||
| Thermochemistry | |||
Heat capacity (C)
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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⦵)
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−237.24 kJ/mol | ||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards
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Drowning Avalanche (as snow) Water intoxication | ||
| NFPA 704 (fire diamond) | |||
| Flash point | Non-flammable | ||
| Safety data sheet (SDS) | SDS | ||
| Related compounds | |||
Other cations
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Related solvents
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| 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).
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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.