Why does iron float in a pool of mercury while gold sinks?

Answer 1

It is function of the density of the three metals. The density of iron is less than that of mercury, but the density of gold is greater.

Density of iron: 7.86 g/cm3

Density of mercury: 13.53 g/cm3

Density of gold: 19.3 g/cm3

Anything more dense than a liquid will sink in that liquid, and anything less dense will float. For comparison, the density of water is only 1 g/cm3, so all three would sink in a pool of water. Styrofoam for instance is less dense than water and so it floats in water.

Answer 2

Iron floats in Mercury because it is less dense than mercury, whereas gold sinks because it is more dense than mercury. The density of a material determines whether it will float or sink in another substance, with denser materials sinking and less dense materials floating.