Density of substances

The two bodies (on the left: wood, on the right: aluminium) in the right picture each have a mass of 200 g. Nevertheless they differ widely in their sizes (volume).
If one cut off a piece from the wooden piece which was as big as the aluminium piece, one would notice that the wooden piece would weigh less than the aluminium piece.
If several substances are compared in this way (e. g. iron with plastic, ice with copper, etc.) the observation can be summarised as follows:

Bodies that are made of different kinds of material do not have the same masses even though they have the same volume.

The ratio between the mass of a body and its volume is called density.

whereby it applies that:

• The density of solid and liquid substances also depends on their temperature.
• The density of gaseous substances depends both on their temperature and their pressure.

Some examples of the density of substances: