What’s it about?
Oil and water do not mix because oil has a much lower density compared to water and hence it lies on the top of the water’s surface. Use a patch of oil on top of the surface of water to make a rainbow of colours in the following science experiment:
Rainbow, Density, Colour spectrum, Immiscible
What will I need?
- VEGETABLE OIL
- NON-STICK PAN
- TAP WATER
- EYE DROPPER
How does it work?
Oil and water do not mix – they are described as ‘immiscible’. Oil has a much lower density compared to water and hence it lies on the top of the water’s surface. The layer of oil on the water has a thickness and forms a thin flat film due to the flat surface of the water. In this science experiment, when a drop of oil is placed on the water, a rainbow of colours is visible on the surface, spreading away to the edge of the pan.
When you blow on the surface the colours change. Some of the sunlight shining on the oil is reflected from the top surface, but some penetrates and instead bounces off the bottom of the oil layer. The light waves reaching your eye are no longer in sync due to the different distances traveled, and are perceived by us in different ways forming a ‘colour spectrum’ or rainbow. This ‘floating rainbow’ will change shape if you blow on top of the oil gently, slightly changing the thickness of the oil film.