Lava Lamp — Convection in Motion
A lava lamp is a simple demonstration of convection. Heat from the lamp warms the wax at the bottom, causing it to expand and become less dense than the surrounding liquid. The warmer wax rises. As it cools near the top, it becomes denser and sinks again.
This continuous cycle of rising and falling material forms a convection current — the same basic process that occurs in fluids such as air and water.
Additional Information
The wax and liquid are chosen specifically so they never actually mix, no matter how much they touch or blend visually.
A bulb at the base heats the wax, making it expand and become less dense so it floats up; as it rises away from the heat it cools, contracts, and sinks back down.
This heating-and-sinking cycle is a small-scale example of convection, the same process that drives ocean currents and weather patterns on a much larger scale.