Physical and chemical properties of water

Chemically, water is a compound of hydrogen and oxygen, having the formula H2O. It is chemically active, reacting withcertain metals and metal oxides to form bases, and with certain oxides of nonmetals to form acids. It reacts with certainorganic compounds to form a variety of products, e.g., alcohols from alkenes. Because water is a polar compound, it is agood solvent.

Although completely pure water is a poor conductor of electricity, it is a much better conductor than mostother pure liquids because of its self-ionization, i.e., the ability of two water molecules to react to form a hydroxide ion, OH−, and a hydronium ion, H3O+. Its polarity and ionization are both due to the high dielectric constant of water.

Water a substance composed of the chemical elements hydrogen and oxygen and existing in gaseous, liquid, and solid states. It is one of the most plentiful and essential of compounds. A tasteless and odourless liquid at room temperature, it has the important ability to dissolve many other substances.

Indeed, the versatility of water as a solvent is essential to living organisms. Life is believed to have originated in the aqueous solutions of the world’s oceans, and living organisms depend on aqueous solutions, such as blood and digestive juices, for biological processes.

In small quantities water appears colourless, but water actually has an intrinsic blue colour caused by slight absorption of light at red wavelengths.



A molecule that can act as either an acid or a base depending on its chemical environment. For example, water (H2O) is amphoteric.


Any molecule or radical that has delocalized positive and negative charges.

phase diagram

A graph showing the phase a sample of matter has under different conditions of temperature and pressure.