Make a lava lamp

Make a lava lamp

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Light up your life with lava lamps...

Impress your friends with this lava lamp - the perfect distraction from homework!

What you need:

  • Plastic or glass bottle
  • Water
  • Vegetable oil
  • Food colouring
  • Alka-Seltzer or other antacid tablets
  • Glitter (optional)
  • Torch (optional)

How to:

  1. Fill the bottle a quarter full with water.
  2. Add a few drops of food colouring until you like the colour you see. You can add glitter too.
  3. Fill the bottle almost to the top with vegetable oil. Let the mixture separate.
  4. Break up two Alka-Seltzer tablets and drop them in the mixture. Watch your lava lamp bubble!

You can shine a torch behind or underneath your lava lamp to see it glow. If you want to keep your lava lamp, use a bottle with a lid. When you've finished with your lava lamp for the day, put the lid back on. To use it again, take the lid off and add more Alka-Seltzer tablets!

Here's Science Bob showing you how to make a lava lamp:

What's happening?

Oil is less dense than water, so it sits on top of the water and food colouring mix. The water and oil separate into two layers. Alka-Seltzer tablets dissolve in the water and react to make bubbles of carbon dioxide gas. The gas bubbles rise up and take some of the coloured water with them to the surface of the oil. When the gas in the bubbles escape through the top of the bottle, the water droplets fall back to the bottom. When all the gas has escaped, the water and oil separate into two layers again. Add more Alka-Seltzer to restart your lava lamp!