KIN104 Lecture Notes - Lecture 3: Hydrogen Chalcogenide, Pressure Cooking, Chemical Substance
23 May 2020
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Water is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is
the main constituent of Earth's hydrosphere, and the fluids of most living organisms. It is vital for all
known forms of life, even though it provides no calories or organic nutrients. Its chemical formula is
H2O, meaning that each of its molecules contains one oxygen and two hydrogen atoms, connected by
covalent bonds. Water is the name of the liquid state of H2O at standard ambient temperature and
pressure. It forms precipitation in the form of rain and aerosols in the form of fog. Clouds are formed
from 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 moves
continually through the water cycle of evaporation, transpiration, condensation, precipitation, and
runoff, usually reaching the sea.
Water covers 71% of the Earth's surface, mostly in seas and oceans. Small portions of water occur as
groundwater, in the glaciers and the ice caps of Antarctica and Greenland, and in the air as vapor,
clouds, and precipitation .
Water plays an important role in the world economy. Approximately 70% of the freshwater used by
humans goes to agriculture. Fishing in salt and fresh water bodies is a major source of food for many
parts of the world. Much of long-distance trade of commodities 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 and skiing.
Etymology
The word water comes from Old English wæter, from Proto-Germanic watar, from Proto-Indo-European
wod-or, suffixed form of root wed- . Also cognate, through the Indo-European root, with Greek ύδωρ,
Russian вода́, Irish uisce, Albanian ujë.
History
Chemical and physical properties
Water is a polar inorganic compound that is at room temperature a tasteless and odorless liquid, nearly
colorless with a hint of blue. This simplest hydrogen chalcogenide is by far the most studied chemical
compound and is described as the "universal solvent" for its ability to dissolve many substances. This
allows it to be the "solvent of life". It is the only common substance to exist as a solid, liquid, and gas in
normal terrestrial conditions.
States
Water is a liquid at the temperatures and pressures that are most adequate for life. Specifically, at a
standard pressure of 1 atm, water is a liquid between . Increasing the pressure slightly lowers the
melting point, which is about at 600 atm and at 2100 atm. This effect is relevant, for example, to ice
skating, to the buried lakes of Antarctica, and to the movement of glaciers. At pressures higher than
2100 atm the melting point rapidly increases again, and ice takes several exotic forms that do not exist
at lower pressures.
Document Summary
Water is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of earth"s hydrosphere, and the fluids of most living organisms. It is vital for all known forms of life, even though it provides no calories or organic nutrients. H2o, meaning that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. Water is the name of the liquid state of h2o at standard ambient temperature and pressure. It forms precipitation in the form of rain and aerosols in the form of fog. Clouds are formed from 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 moves continually through the water cycle of evaporation, transpiration, condensation, precipitation, and runoff, usually reaching the sea. Water covers 71% of the earth"s surface, mostly in seas and oceans.
