There are four variables of a gaseous sample that can be measured in the laboratory. They are pressure (P), volume (V), temperature (T) and amount of substance (usually expressed as number of moles, n).

The Ideal Gas Law is a mathematical equation that relates these four variables together for an ‘ideal’ gas.

The Ideal Gas Law is derived from empirical relationships, some of which have been known since the 16^th Century, known as Boyle’s Law, Charles’ Law and Avogadro’s Law. These laws are summarized in the following equations;

Boyle’s Law		@ constant T and n
Charles’ Law	V a T	@ constant P and n
Avogadro’s Law	V a n	@ constant T and P

These relationships can be combined into the following equation;

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