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

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

Answer: (A)

Pressure and volume move in opposite directions when temperature stays the same. If you compress a gas and shrink its volume, the molecules hit the container walls more often, boosting pressure; if the gas expands, pressure drops. This inverse relationship is captured by Boyle's law, which can be written as P × V = constant for a fixed amount of gas at constant temperature. In other words, pressure and volume trade off so that their product stays the same. Other laws describe different conditions: Charles's law links volume to temperature at constant pressure, Avogadro's law ties volume to the amount of gas at fixed T and P, and Gay-Lussac's law relates pressure to temperature at constant volume.