1 Combining the three laws

For a fixed mass of gas:

• Boyle: V ∝ 1/P (T constant)
• Charles: V ∝ T (P constant) Combining: V ∝ T/P → PV/T = constant.

For two states of the same mass of gas:

P₁V₁/T₁ = P₂V₂/T₂ (T in kelvin; P in any consistent unit; V in any consistent unit)

Special cases: T constant → Boyle's law; P constant → Charles's law; V constant → pressure law.