Water is a common chemical substance that is essential
for the survival of all known forms of life. In typical usage, water
refers only to its liquid form or state, but the substance also has
a solid state, ice, and a gaseous state, water vapor. About 1,460 tera
tones (Tt) of water covers 71% of the Earth's surface, mostly in oceans
and other large water bodies, with 1.6% of water below ground in aquifers
and 0.001% in the air as vapor, clouds (formed of solid and liquid water
particles suspended in air), and precipitation. Some of the Earth's
water is contained within man-made and natural objects near the Earth's
surface such as water towers, animal and plant bodies, manufactured
products, and food stores.
Water is the chemical substance with chemical formula H2O: one molecule of water has two hydrogen atoms covalently bonded to a single oxygen atom.
• Water is a tasteless, odorless liquid at ambient temperature and pressure. The color of water and ice are, intrinsically, a very light blue hue, although water appears colorless in small quantities. Ice also appears colorless, and water vapor is essentially invisible as a gas.
• Water is transparent, and thus aquatic plants can live within the water because sunlight can reach them. Only strong UV light is slightly absorbed.
• Water is a liquid under standard conditions.
• Since oxygen has a higher electro negativity than hydrogen, water is a polar molecule. The oxygen has a slight negative charge while the hydrogen has a slight positive charge giving the article a strong effective dipole moment. The interactions between the different dipoles of each molecule cause a net attraction force associated with water's high amount of surface tension.
• Another very important force that causes the water molecules to stick to one another is the hydrogen bond.
Copyright 2008 by Grup Scolar Industrial Nicolae Iorga