Trivia

The Correct answer is:

Convection, the transfer of heat through a liquid by circulation of currents, is very apparent in lava lamps. When the wax is heated it becomes less dense than its surroundings and rises. As the wax travels up through the water it begins to cool, by dissipating heat into its surroundings, and by the time it reaches top it begins to sink again.

Watch how a lava lamp is made!