Final answer:
Boyle's law is the gas law that relates pressure to volume, stating that pressure and volume are inversely proportional at a constant temperature for a fixed mass of gas.
Step-by-step explanation:
The gas law that relates pressure to volume is Boyle's law. Boyle's law states that, for a given mass of gas at constant temperature, the volume of the gas is inversely proportional to its pressure. This means that if the volume increases, the pressure decreases, and vice versa, provided the temperature and amount of gas remain unchanged. Mathematically, Boyle's law can be expressed as P₁V₁ = P₂V₂, where P₁ and V₁ are the initial pressure and volume, and P₂ and V₂ are the final pressure and volume, respectively.