Posted on

Lava Buckets

Let’s craft some lava! This activity lets you see:

  • How molecules are attracted to other molecules that are like them, such as oil to oil and water to water.
  • How density affects liquids.
  • What happens when you add water to citric acid and sodium bicarbonate.

Important: These instructions are for a small test tube (10 mL) of lava, which is the perfect size for when we do this at events. You can make a much more impressive “bucket” with a 1-liter bottle, and proportionally more water, oil, and food coloring.

Download a PDF copy of these instructions.

Materials

  • 1 plastic tube with lid
  • oil – Vegetable oil works well
  • water
  • food coloring
  • small piece of a fizzing tablet (citric acid + baking soda AKA Alka Seltzer)

Procedure

  1. Place your tube in a holder, or ask a friend to hold it for you. It’s much easier to add stuff to it when you don’t have to also hold it.
  2. Add about 1/4 teaspoon of water to the plastic tube.
  3. Now add oil to the tube until it’s nearly full . Does it mix with the water?
  4. Add 3-5 drops of food coloring to the tube. Where do those drops go?
  5. Now add the piece of fizzing tablet. What happens?
  6. When your lava bucket stops fizzing, screw the lid on, so it doesn’t spill. You can add more tablet pieces later, to make the lava “flow” again. Please don’t add the lid until the fizzing has mostly stopped, or it might pop off from the pressure!

PLEASE DON’T DRINK THE LAVA!!!