Density

What is density?

Density ($\rho$) is equal to the total mass (m) of a substance per unit volume (V):

The less mass per unit volume, the less dense, e.g. ``lighter than air'' heliem (He), which tends to rise. Contrarily, the more mass per unit volume, the more dense or heavier the material. This has implications that will be dealt with later in physics (buouancy) and gas phase chemistry.