Asked by: Gus Mitchell, Hemel Hempstead
Whisky is predominantly water and ethanol. One end of the ethanol molecule is hydrophilic (water-loving) and the other hydrophobic (water-hating). As a result, the ethanol tends to form a thin layer at the surface of the whisky, with the hydrophobic ends pointing up into the air. Elsewhere in the tipple, it clumps together, forming a so-called micelle, with the hydrophilic ends shielding the other parts of the molecule from the water.
Many of the flavours in whisky dissolve better in ethanol, and therefore get locked away in the micelles. When water is added, this disrupts some of the micelles allowing more of the ethanol to migrate to the surface of the drink, along with the volatile flavours. Scientists and whisky connoisseurs agree that to get maximum flavour enhancement, you need more than a drop of water – diluting the whisky to about 25 per cent alcohol is ideal.
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.