Emulsions and Emulsification

Oil and water don't mix because water molecules are polar (they have a positive and negative end) while oil molecules are nonpolar. Polar molecules attract each other and exclude nonpolar ones—like two groups at a party that only speak different languages. An emulsifier is a bilingual molecule: one end is hydrophilic (water-loving) and the other is lipophilic (fat-loving). It positions itself at the oil-water interface, reducing surface tension and stabilizing tiny droplets of one liquid dispersed in the other. Mayonnaise is an emulsion of oil droplets suspended in the water phase of egg yolk and vinegar, stabilized by lecithin from the yolk.