What you will need:
- Washing up liquid
- Food colouring
- Small bowl
- Disposable pipette
Pour the milk into the bowl. Add a few drops of food colouring into the milk. Using the pipette, drop small amounts of washing up liquid on to the surface of the milk. Watch what happens!
Milk is made up mostly of water.
The patterns formed with the food colouring, are down to a phenomenon called Surface Tension. This occurs because of the force of attraction between the water molecules. The water molecules on the surface, do not have like molecules on all sides, and therefore have a stronger attraction with the molecules around them. This creates a ‘film’ on the surface.
The molecules in the washing up liquid, usually carry a –ve charge, these molecules weaken the forces between the water molecules, thus allowing the ‘film’ to be broken.
Have a go, and try to create different patterns, with different colours!