As has been shown by Boyle's law and Charles' law, the behaviour of gases conforms (to a close approximation) to some simple relationships between the gas volume, pressure and temperature for a given amount of gas. Combining Boyle's law and Charles' law gives the equation of state. Syllabus referenceStructure 1.5.4  The relationship between the pressure, volume, temperature and amount of an ideal gas is shown in the ideal gas equation PV = nRT and the combined gas law P_{1}V_{1}/T_{1}= P_{2}V_{2}/T_{2}.
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The equation of state
The equations of Boyle's law (PV = constant) and Charles' law (V/T = constant) may be combined to give the expression: PV/T = constant. This is called the equation of state. This new combined gas equation can be used to find the new volume, pressure and temperature of a gas if the conditions are changed.