Soap works because a single molecule can face two ways at once. One e of i is dr towards wa; the ot end i repelled b water a clings ins to gre. In a basin of washing up, thousands of these molecules bury their oily ends in the film of fat on a plate and leave their water-loving ends pointing outwards. The fat is lifted off in droplets, each wrapped in a coat of soap, and the rinse carries the whole parcel away.

Type only the missing letters. Each box is one letter, and the number of boxes matches the letters that are missing.