H2O

Water (H2O) is a polar inorganic compound that is at room temperature a tasteless and odorless liquid, nearly colorless with a hint of blue. The simplest hydrogen chalcogenide, it 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".[15] It is the only common substance to exist as a solid, liquid, and gas in nature.[16]

Water molecules form hydrogen bonds with each other and are strongly polar. This polarity allows it to separate ions in salts and strongly bond to other polar substances such as alcohols and acids, thus dissolving them. Its hydrogen bonding causes its many unique properties, such as having a solid form less dense than its liquid form, a relatively high boiling point of 100 °C for its molar mass, and a high heat capacity.

Water is amphoteric, meaning it is both an acid and a base - it produces H+ and OH− ions by self ionization. This regulates the concentrations of H+ and OH− ions in water.

Due to water being a very good solvent, it is rarely pure and some of the properties of impure water can vary from those of the pure substance. However, there are also many compounds that are essentially, if not completely, insoluble in water, such as fats, oils and other non-polar substances.