A lava lamp

A cool lava lamp

Watch coloured bubbles bobbing up and down with this neat homemade lava lamp.

Ingredients and equipment that you will need

A tall, thin jar
Cooking oil – use the cheapest possible because you need quite a lot
Food colouring if you like
An effervescent tablet – vitamin C, Steradent, Alka Seltzer all work

Method and further information

Fill the jar a third full of water. Add about the same amount of oil. Note that the oil floats in the water.

Mix the food colouring with a little water and add it. The food colouring colours only the water, not the oil.

Break up an effervescent tablet into bits and drop it in. The Alka-Seltzer dissolves in the water producing carbon dioxide gas, which rises to the surface giving a lava lamp effect.

It looks wonderful if you shine a torch underneath this in a darkened room.

Be careful – you should ask an adult to help you with these experiments. Do your experiments in old yoghurt pots, jam jars or bottle tops. Don’t use cups or glasses in case someone thinks it’s a drink.