Watch this short video to find out how to make a lava lamp.

Items you'll need are:

• Water
• Oil
• Plastic bottle
• Food colouring
• Effervescent tablet (or vitamin tablet)

The science behind the experiment

The water and the food colouring are the same density, the food colouring is water soluble and so changes the water’s colour.

Oil is hydrophobic so actively moves away from water molecules.

The tablet reacts with the water, creating carbon dioxide bubbles.

These bubbles float to the surface carrying with them some water.

Once the carbon dioxide bubbles pop the water sinks back down below the oil.

Key Terms:

• Carbon Dioxide – A colourless gas containing one carbon and two oxygen molecules.
• Density – The mass per volume of an object.
• Hydrophobic – Molecules that will repel water.
• Water Soluble – Can be dissolved in water.