Water

A water molecule consists of two hydrogen atoms and one oxygen atom
The three common states of matter
Phase diagram of water (simplified)
Tetrahedral structure of water
Model of hydrogen bonds (1) between molecules of water
Water cycle
Overview of photosynthesis (green) and respiration (red)
Water fountain
An environmental science program – a student from Iowa State University sampling water
Total water withdrawals for agricultural, industrial and municipal purposes per capita, measured in cubic metres (m³) per year in 2010
A young girl drinking bottled water
Water availability: the fraction of the population using improved water sources by country
Roadside fresh water outlet from glacier, Nubra
Hazard symbol for non-potable water
Water is used for fighting wildfires.
San Andrés island, Colombia
Water can be used to cook foods such as noodles
Sterile water for injection
Band 5 ALMA receiver is an instrument specifically designed to detect water in the universe.
South polar ice cap of Mars during Martian south summer 2000
An estimate of the proportion of people in developing countries with access to potable water 1970–2000
People come to Inda Abba Hadera spring (Inda Sillasie, Ethiopia) to wash in holy water
Icosahedron as a part of Spinoza monument in Amsterdam.
Water requirement per tonne of food product
Irrigation of field crops
Specific heat capacity of water

Inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a solvent ).

- Water
A water molecule consists of two hydrogen atoms and one oxygen atom

139 related topics

Alpha

The Space Shuttle Main Engine burnt hydrogen with oxygen, producing a nearly invisible flame at full thrust.

Hydrogen

Chemical element with the symbol H and atomic number 1.

Chemical element with the symbol H and atomic number 1.

The Space Shuttle Main Engine burnt hydrogen with oxygen, producing a nearly invisible flame at full thrust.
Depiction of a hydrogen atom with size of central proton shown, and the atomic diameter shown as about twice the Bohr model radius (image not to scale)
Hydrogen gas is colorless and transparent, here contained in a glass ampoule.
Phase diagram of hydrogen. The temperature and pressure scales are logarithmic, so one unit corresponds to a 10x change. The left edge corresponds to 105 Pa, which is about atmospheric pressure.
A sample of sodium hydride
Hydrogen discharge (spectrum) tube
Deuterium discharge (spectrum) tube
Antoine-Laurent de Lavoisier
Hydrogen emission spectrum lines in the visible range. These are the four visible lines of the Balmer series
NGC 604, a giant region of ionized hydrogen in the Triangulum Galaxy
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Most of the hydrogen on Earth exists in molecular forms such as water and organic compounds.

Joseph Priestley is usually given priority in the discovery.

Oxygen

Chemical element with the symbol O and atomic number 8.

Chemical element with the symbol O and atomic number 8.

Joseph Priestley is usually given priority in the discovery.
Antoine Lavoisier discredited the phlogiston theory.
Robert H. Goddard and a liquid oxygen-gasoline rocket
An experiment setup for preparation of oxygen in academic laboratories
Orbital diagram, after Barrett (2002), showing the participating atomic orbitals from each oxygen atom, the molecular orbitals that result from their overlap, and the aufbau filling of the orbitals with the 12 electrons, 6 from each O atom, beginning from the lowest-energy orbitals, and resulting in covalent double-bond character from filled orbitals (and cancellation of the contributions of the pairs of σ and σ* and π and π* orbital pairs).
Liquid oxygen, temporarily suspended in a magnet owing to its paramagnetism
Space-filling model representation of dioxygen (O2) molecule
Oxygen discharge (spectrum) tube
Late in a massive star's life, 16O concentrates in the O-shell, 17O in the H-shell and 18O in the He-shell.
Cold water holds more dissolved.
500 million years of climate change vs. 18O
Photosynthesis splits water to liberate and fixes into sugar in what is called a Calvin cycle.
build-up in Earth's atmosphere: 1) no produced; 2) produced, but absorbed in oceans & seabed rock; 3)  starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4–5)  sinks filled and the gas accumulates
Hofmann electrolysis apparatus used in electrolysis of water.
Oxygen and MAPP gas compressed-gas cylinders with regulators
An oxygen concentrator in an emphysema patient's house
Low pressure pure is used in space suits.
Most commercially produced is used to smelt and/or decarburize iron.
Water is the most familiar oxygen compound.
Oxides, such as iron oxide or rust, form when oxygen combines with other elements.
Main symptoms of oxygen toxicity
The interior of the Apollo 1 Command Module. Pure at higher than normal pressure and a spark led to a fire and the loss of the Apollo 1 crew.

Most of the mass of living organisms is oxygen as a component of water, the major constituent of lifeforms.

Ball-and-stick model of the diamminesilver(I) cation, [Ag(NH3)2]+

Ammonia

Compound of nitrogen and hydrogen with the formula NH3.

Compound of nitrogen and hydrogen with the formula NH3.

Ball-and-stick model of the diamminesilver(I) cation, [Ag(NH3)2]+
Ball-and-stick model of the tetraamminediaquacopper(II) cation, [Cu(NH3)4(H2O)2](2+)
Jabir ibn Hayyan
This high-pressure reactor was built in 1921 by BASF in Ludwigshafen and was re-erected on the premises of the University of Karlsruhe in Germany.
A train carrying Anhydrous Ammonia.
Liquid ammonia bottle
Household ammonia
Ammoniacal Gas Engine Streetcar in New Orleans drawn by Alfred Waud in 1871.
The X-15 aircraft used ammonia as one component fuel of its rocket engine
Anti-meth sign on tank of anhydrous ammonia, Otley, Iowa. Anhydrous ammonia is a common farm fertilizer that is also a critical ingredient in making methamphetamine. In 2005, Iowa used grant money to give out thousands of locks to prevent criminals from getting into the tanks.
The world's longest ammonia pipeline (roughly 2400 km long), running from the TogliattiAzot plant in Russia to Odessa in Ukraine
Hydrochloric acid sample releasing HCl fumes, which are reacting with ammonia fumes to produce a white smoke of ammonium chloride.
Production trend of ammonia between 1947 and 2007
Main symptoms of hyperammonemia (ammonia reaching toxic concentrations).
Ammonia occurs in the atmospheres of the outer giant planets such as Jupiter (0.026% ammonia), Saturn (0.012% ammonia), and in the atmospheres and ices of Uranus and Neptune.

Solvent properties: Ammonia readily dissolves in water. In an aqueous solution, it can be expelled by boiling. The aqueous solution of ammonia is basic. The maximum concentration of ammonia in water (a saturated solution) has a density of 0.880 g/cm3 and is often known as '.880 ammonia'.

Tap water is drinking water supplied through indoor plumbing for home use in many countries.

Drinking water

Tap water is drinking water supplied through indoor plumbing for home use in many countries.
Drinking water vending machines in Thailand. One litre of potable water is sold (into the customer's own bottle) for 1 baht.
Diagram of water well types
EPA drinking water security poster from 2003
Water treatment plant
Solar water disinfection application in Indonesia
World map for SDG 6 Indicator 6.1.1 in 2015: "Proportion of population using safely managed drinking water services"
% of the population with access to drinking water
Population in survey regions living without safely managed drinking water as reported by the WHO/UNICEF JMP.
Project in Nepal: unboxing the water filter unit.
Illustration of a typical tap water treatment process

Drinking water is water that is used in drink or food preparation; potable water is water that is safe to be used as drinking water.

An illustration showing groundwater in aquifers (in blue) (1, 5 and 6) below the water table (4), and three different wells (7, 8 and 9) dug to reach it.

Groundwater

An illustration showing groundwater in aquifers (in blue) (1, 5 and 6) below the water table (4), and three different wells (7, 8 and 9) dug to reach it.
Dzherelo, a common source of drinking water in a Ukrainian village
The entire surface water flow of the Alapaha River near Jennings, Florida, going into a sinkhole leading to the Floridan Aquifer groundwater
Groundwater may be extracted through a water well
Diagram of a water balance of the aquifer
Iron (III) oxide staining (after water capillary rise in a wall) caused by oxidation of dissolved iron (II) and its subsequent precipitation, from an unconfined aquifer in karst topography. Perth, Western Australia.
Groundwater withdrawal rates from the Ogallala Aquifer in the Central United States
Center-pivot irrigated fields in Kansas covering hundreds of square miles watered by the Ogallala Aquifer

Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations.

Visualisation of the distribution (by volume) of water on Earth. Each tiny cube (such as the one representing biological water) corresponds to approximately 1400 cubic km of water, with a mass of approximately 1.4 trillion tonnes (235000 times that of the Great Pyramid of Giza or 8 times that of Lake Kariba, arguably the heaviest man-made object). The entire block comprises 1 million tiny cubes.

Fresh water

Visualisation of the distribution (by volume) of water on Earth. Each tiny cube (such as the one representing biological water) corresponds to approximately 1400 cubic km of water, with a mass of approximately 1.4 trillion tonnes (235000 times that of the Great Pyramid of Giza or 8 times that of Lake Kariba, arguably the heaviest man-made object). The entire block comprises 1 million tiny cubes.
A graphical distribution of the locations of water on Earth. Only 3% of the Earth's water is fresh water. Most of it is in icecaps and glaciers (69%) and groundwater (30%), while all lakes, rivers and swamps combined only account for a small fraction (0.3%) of the Earth's total freshwater reserves.

Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids.

Model of hydrogen bonds (1) between molecules of water

Hydrogen bond

Primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group, and another electronegative atom bearing a lone pair of electrons—the hydrogen bond acceptor (Ac).

Primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group, and another electronegative atom bearing a lone pair of electrons—the hydrogen bond acceptor (Ac).

Model of hydrogen bonds (1) between molecules of water
AFM image of naphthalenetetracarboxylic diimide molecules on silver-terminated silicon, interacting via hydrogen bonding, taken at 77  K. ("Hydrogen bonds" in the top image are exaggerated by artifacts of the imaging technique. )
An example of intermolecular hydrogen bonding in a self-assembled dimer complex. The hydrogen bonds are represented by dotted lines.
Intramolecular hydrogen bonding in acetylacetone helps stabilize the enol tautomer.
Examples of hydrogen bond donating (donors) and hydrogen bond accepting groups (acceptors)
Cyclic dimer of acetic acid; dashed green lines represent hydrogen bonds
Crystal structure of hexagonal ice. Gray dashed lines indicate hydrogen bonds
Structure of nickel bis(dimethylglyoximate), which features two linear hydrogen-bonds.
The structure of part of a DNA double helix
Hydrogen bonding between guanine and cytosine, one of two types of base pairs in DNA
Para-aramid structure
A strand of cellulose (conformation Iα), showing the hydrogen bonds (dashed) within and between cellulose molecules

The hydrogen bond is responsible for many of the abnormal physical and chemical properties of compounds of N, O, and F. In particular, intermolecular hydrogen bonding is responsible for the high boiling point of water (100 °C) compared to the other group-16 hydrides that have much weaker hydrogen bonds.

The chemical elements ordered in the periodic table

Chemical element

A chemical element refers to all aspects of the species of atoms that have a certain number of protons in their nuclei, including the pure substance consisting only of that species.

A chemical element refers to all aspects of the species of atoms that have a certain number of protons in their nuclei, including the pure substance consisting only of that species.

The chemical elements ordered in the periodic table
Estimated distribution of dark matter and dark energy in the universe. Only the fraction of the mass and energy in the universe labeled "atoms" is composed of chemical elements.
Periodic table showing the cosmogenic origin of each element in the Big Bang, or in large or small stars. Small stars can produce certain elements up to sulfur, by the alpha process. Supernovae are needed to produce "heavy" elements (those beyond iron and nickel) rapidly by neutron buildup, in the r-process. Certain large stars slowly produce other elements heavier than iron, in the s-process; these may then be blown into space in the off-gassing of planetary nebulae
Abundances of the chemical elements in the Solar System. Hydrogen and helium are most common, from the Big Bang. The next three elements (Li, Be, B) are rare because they are poorly synthesized in the Big Bang and also in stars. The two general trends in the remaining stellar-produced elements are: (1) an alternation of abundance in elements as they have even or odd atomic numbers (the Oddo-Harkins rule), and (2) a general decrease in abundance as elements become heavier. Iron is especially common because it represents the minimum energy nuclide that can be made by fusion of helium in supernovae.
Mendeleev's 1869 periodic table: An experiment on a system of elements. Based on their atomic weights and chemical similarities.
Dmitri Mendeleev
Henry Moseley

Air is primarily a mixture of the elements nitrogen, oxygen, and argon, though it does contain compounds including carbon dioxide and water.

A photograph of Earth taken by the crew of Apollo 17 in 1972. A processed version became widely known as The Blue Marble.

Earth

Third planet from the Sun and the only astronomical object known to harbor life.

Third planet from the Sun and the only astronomical object known to harbor life.

A photograph of Earth taken by the crew of Apollo 17 in 1972. A processed version became widely known as The Blue Marble.
Planetary disk of a star, the inner ring has a radius equal to Earth and the Sun
Artist's impression of earth during the Archean eon, showing falling meteor, erupting volcano, round stromatolites, and barren landscape
Earth topological map, the area is redder if it is raised higher in real-life
Global map of heat flow from Earth's interior to the surface
Earth's major plates, which are: · ·  ·  ·  ·
Satellite picture of Upsala Glacier, showing mountains, icebergs, lakes, and clouds
Schematic of Earth's magnetosphere, with the solar wind flows from left to right
Earth's rotation imaged by Deep Space Climate Observatory, showing axis tilt
Illustration of the Earth, Earth's orbit, the Sun and the four seasons
Earth's axial tilt and its relation to the rotation axis and planes of orbit
Earth-Moon system seen from Mars
A model of Vanguard 1, the oldest human-made object in Earth orbit
Water is transported to various parts of the hydrosphere via the water cycle
Top of Earth's blue-tinted atmosphere, with the Moon at the background
Fungi are one of the kingdoms of life on Earth.
The seven continents of Earth:
Earth's land use for human agriculture
Change in average surface air temperature since the industrial revolution, plus drivers for that change. Human activity has caused increased temperatures, with natural forces adding some variability.
Earthrise, taken in 1968 by William Anders, an astronaut on board Apollo 8
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The abundance of water on Earth's surface is a unique feature that distinguishes it from other planets in the Solar System.

Water cycle

Time-mean precipitation and evaporation as a function of latitude as simulated by an aqua-planet version of an atmospheric GCM (GFDL's AM2.1) with a homogeneous “slab-ocean” lower boundary (saturated surface with small heat capacity), forced by annual mean insolation.
Global map of annual mean evaporation minus precipitation by latitude-longitude
Relationship between impervious surfaces and surface runoff
Diagram of the water cycle
Natural water cycle

The water cycle, also known as the hydrologic cycle or the hydrological cycle, is a biogeochemical cycle that describes the continuous movement of water on, above and below the surface of the Earth.