A colourful explosion that will mesmerise you again and again!
You will need
- A shallow plate
- Full fat milk
- Food colouring
- Washing up liquid
- Ear bud
- Fill your plate with full fat milk so the surface of the plate is just covered.
- Drop 1 or 2 drops of food colouring into the centre of the plate.
- With the end of an ear bud collect some washing up liquid and place it into the food colouring
- As you hold the ear bud there, watch as it explodes outwards from the centre of the plate.
- What happens if you add 2 or more colours to the plate?
- What happens if you use different milk (semi-skimmed or skimmed)? Does it work as well?
- Try using double cream in this experiment. How does increasing the fat content effect the experiment?
- What happens if you use water instead?
The important component in this experiment is the presence of the fat and protein in the milk. This is why the higher the fat content the better the experiment works. When we add soap to the milk it reduces the surface tension (the strong bonds between the milk molecules at the surface of the liquid which is in contact with the air). By reducing the surface tension on the milk, the molecules begin to invisibly race around the milk. The food colouring is dragged about by these currents and produces the colourful explosions we see. Once the surface tension settles again, the process stops.