What causes the waxy substance in a lava lamp to rise?

In a lava lamp, the waxy substance rises due to the change in temperature affecting its density. When the wax is warmed, it becomes less dense than the surrounding liquid. As the wax heats up, it expands and its density decreases, allowing it to rise through the cooler, denser liquid. This process is a result of convection currents, where warmer, lighter fluid moves up and cooler, denser fluid sinks. The wax's behavior in the lamp creates a mesmerizing display, as it continuously cycles through this process of heating and cooling, rising and falling.