Lava Lamp

You will need:

Clean 1 litre plastic bottle

150ml water

Vegetable Oil

Food colouring

Alka Seltzer tablets

What to do:

• Pour the water into the bottle.
• Use a funnel to pour the oil into the bottle until it is almost full.
• Wait for the water and oil to separate.
• Add 10 drops of food colouring to the bottle. The drops will pass through the oil and then mix with the water below. 
• Break a tablet in half and drop it into the water. The tablet will sink to the bottom.
• To keep the effect going, just add another tablet piece.
• For a true lava lamp effect, shine a flashlight through the bottom of the bottle.

How does is work?

To begin, the oil stays above the water because the oil is lighter than the water or, more specifically, less dense than water. Water molecules are attracted to other water molecules. They get along fine, and can loosely bond together (drops). Oil molecules are attracted to other oil molecules. But the structures of the two molecules do not allow them to bond together.

When you added the tablet piece, it sank to the bottom and started dissolving and creating a gas. As the gas bubbles rose, they took some of the coloured water with them. When the blob of water reached the top, the gas escaped and down went the water.

By the way, you can store your "Lava Lamp” with the cap on, and then anytime you want to bring it back to life, just add another tablet piece.

The School of Chemistry at NUI Galway advise that adult supervision is needed for all experiments. The portions of materials used in the experiments should not be increased from that described and mixtures prepared should not be ingested. The full text should be read before starting any experiment.