Density

Density relates mass and volume:

$\rho = \frac{m}{V}$

The SI unit is kg/m$^3$. The density of water is 1000 kg/m$^3$ (or 1.0 g/cm$^3$).

An object floats in a fluid if it is less dense than the fluid. An object sinks if it is denser than the fluid.

Density is a property of the material, not the object. A large block of iron and a small block of iron have the same density.