Fill the jar about three-quarters full of cold water. Add a few drops of food colouring until you like the colour you see. A few drops go a long way! Sprinkle in glitter for an extra sparkle.
Add cooking oil until you have about a half-inch layer of oil on top of the water. Wait until the oil and water have separated into two layers before the next step.
Sprinkle a little salt on top of the oil.
It will magically begin to sink in great blobs and hang at the bottom for a moment before wobbling back up.
To keep your lava rolling, you'll need to sprinkle more salt when the bubbles start diminishing.
Shine a flashlight behind the jar to watch your lava lamp really glow!
WHAT HAPPENED?
At first, the oil floats on the water because it's lighter - or, more accurately, it's less dense than the water. It also doesn't mix with water, so it won't dissolve. The salt, however, is denser than the water and does dissolve. As the salt passes through the oil layer, it clings and drags blobs of oil to the bottom of the jar. In time, however, the salt starts to dissolve in the water. At a certain point, it can no longer hold down the oil blob which breaks free and floats back up to the surface.
SIMPLE SCIENCE
Make your own
WHAT YOU’LL NEED
WHAT HAPPENED?
