aka...science room
lave lamps
Lava Lamps contain a liquid and a wax that don't mix with each other.
When the lamp is turned off, the wax is cold and stays at the bottom of the lamp. Turning the lamp on heats up the wax, which then floats towards the top. As the wax rises up through the liquid it gradually cools down. Near the top of the lamp, the wax becomes cold again and sinks back to the bottom.
Lava lamps work because the liquid and the wax have different densities and less dense objects float on denser ones. When the wax is cold, it is denser than the liquid, so it sinks to the bottom. Heating the wax makes it expand and become less dense than the liquid so it starts to float up through the liquid.
The liquid and the wax have different densities – the same volume of each weighs a different amount. The density of any substance is its mass divided by its volume.
When the wax gets hot, it expands, ie its volume increases. However, its mass must stay the same, so this means that it must become less dense. As the wax cools down, its volume reduces meaning that the density increases.
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