The mass density or density of a material is defined as its mass per unit volume.
The symbol most often used for density is 'ρ' (rho).
Mathematical Expression is
Density
The density depends on external factors such as temperature and pressure.
Aso, density depends on the nature of the substance.
When the density of a substance is lower than that of water, it tends to float, whereas when the density of a substance is greater than water, it sinks into the water.
This is illustrated below:
Object Q has density > water, hence it sinks.
Object R has density < water, hence it floats.
Explanation:
Metals generally are hard solids and have high density.
Hence, most metals like iron, copper, steel will float on water.
However, some metals which are soft like sodium, have low density.
Having a lower density than water, sodium tends to float on it.
Hence, the metal that will float on water is Sodium (Na).