2. Water

Water represents around 65% of the mass of the adult human body.

Water (H ₂ O), made up of three atoms, is not a linear molecule, but a V-shaped one (angle of 105˚ with O at the point of the V). This angular configuration and the high electronegativity of O mean that the molecule takes the form of a double electric dipole, which explains the remarkable properties of water. In liquid water, the dipoles interact via hydrogen bonds: water is a polar solvent of considerable...