Why does molten magnesium float to the top of an electrolytic cell?

In the electrolytic production of magnesium, the molten metal floats to the top of the salt bath because it is less dense than the molten electrolyte.1

During the electrolysis process, magnesium chloride is dissociated into chlorine gas and molten magnesium metal. The electrolyte, which consists of a mixture of alkaline chlorides, is maintained at high temperatures—typically between 680 and 750 °C (1,260 to 1,380 °F). Because the density of the resulting molten magnesium is lower than that of the surrounding molten salt bath, the metal rises to the surface, where it is collected.12