I had a few requests for the instructions on this experiment we did yesterday. 

Firework in a bottle

Equipment

• empty water bottle
• Warm water
• Oil
• Food colouring

Instructions

• Fill the tall bottle with warm water.
• Pour a small amount of oil into another container and add a few drops of food coloring.
• Give it a good stir, if it doesn’t mix, add a bit of water.
• Pour the food colouring and oil mixture into the warm water and watch the fireworks.

The Science Bit

Oil and water don’t mix. Also oil is less dense than water (meaning there is less of it in the same volume) and therefore floats on top of water in a nice layer.

The food colouring we used was water based and therefore does not mix with the oil, instead it sinks through the oil into the water below.

Since the addition of the colouring makes the food colouring heavier than the water it sinks to the bottom leaving trails (resembling fireworks) as some of the colour diffuses into the water