ABSTRACT
Scientists searching for evidence of life on other planets only bother to look at planets or moons where liquid water might exist. Water must therefore have unexpectedly strong intermolecular forces; these arise from what are called ‘hydrogen bonds’. For water, being a small, light molecule with two OH groups, this means that, proportionately, hydrogen bonding makes more difference to its properties than for any other molecule. The oxygen atom in an isolated water molecule is surrounded by four electron pairs, two in O–H bonds and two non-bonding pairs. Ice has a very ordered structure, with the molecules lining up in an open, hexagonal structure to give four hydrogen bonds per water molecule. Water has its greatest density at about 4°C, which is why there is usually liquid water at the bottom of an apparently frozen lake, even in the depths of winter. No, polywater was an exercise in scientific self-delusion. Water also dissolves some gases.
