By Rebekah Crane
Have you ever seen a lava lamp? If you have, you’ve probably stared at it for a while. It’s pretty fascinating. But have you wondered how they actually work? Why does it look like there are bubbles floating in it? Why does it only work when the light is turned on? Well, I have some answers for you.
Lava lamps have two liquids in them with similar densities – we’re going to call them Liquid A and Liquid B to make things more clear. (Density is a fancy word to describe how “heavy” a liquid is.) Similar to oil and water, the two liquids can’t mix. After you have your two liquids, you add some heat to the bottom of the lava lamp. This is usually in the form of a lightbulb. The heavier, denser, Liquid A absorbs the heat and starts to expand and take up more space. This makes that heavier liquid (Liquid A) less dense and lighter! Liquid A then rises above Liquid B because of the density change, and you see what looks like floating bubbles in the lava lamp.
How does Liquid A come back down then? As it gets farther away from the heat it starts to cool back down again and lose some of the heat. This made Liquid A heavier than Liquid B again, so Liquid A falls down and the whole process starts all over again!