SNAL @ Imperial Festival

Fats’ split personality

The aim of this experiment is to demonstrate one of the key properties of fat which makes it a vital biomolecule for life. The ability of fat molecules (lipids) to spontaneously self-assemble in water provides the structural basis for the membranes which surround biological cells, the building blocks of all living organisms. The key characteristic of fat molecules which gives rise to this ability to self-assemble is the contrasting interactions of different parts of the fat molecule with water (‘split personality’). Specifically a water loving “head” region at one end and a water hating “tail” region at the other. The experiment will demonstrate this crucial property of fat by an effect visible to the naked eye: first, a small drop of food colouring or ink is gently added to a dish of milk, resulting in a small, concentrated patch of colour. The tip of a cotton bud is then loaded with washing up liquid. When the cotton bud tip is placed on the surface of the milk, near to the drop of colour, the colour rapidly spreads out, away from the cotton bud as the soap mixes and interacts with the milk. By changing the initial positions of the drops of colour in the milk and touching the cotton bud at different points on the milk surface, complex patterns can be produced which should encourage involvement and creativity. In addition people were able to take home the patterns that they create by transferring them to pieces of card. This experiment is very easy to perform and uses no special equipment or materials. It is therefore something that people attending the festival could very easily reproduce at home to impress family and friends.