Which law describes the inverse relationship between pressure and volume of a gas at constant temperature?

• A. Charles's Law
• B. Avogadro's Law
• C. Boyle's Law
• D. Gay-Lussac's Law

Answer: (C)

Fixed amount of gas at the same temperature shows an inverse relationship between pressure and volume: as the volume goes up, the pressure goes down, and as the volume goes down, the pressure goes up. This is Boyle's Law, which can be summarized by PV = constant. When you squeeze a syringe or compress a gas, the volume decreases and the gas molecules collide with the container walls more often, raising pressure; letting the space expand lowers those collisions and the pressure drops. The other gas laws describe different conditions: Charles's Law ties volume to temperature at constant pressure, Avogadro's Law links volume to the amount of gas at fixed temperature and pressure, and Gay-Lussac's Law relates pressure to temperature at constant volume.