According to Gay-Lussac's law (at constant volume), what happens to pressure when temperature increases?

• A. Pressure increases in direct proportion to Temperature
• B. Pressure decreases
• C. Pressure stays the same
• D. Pressure is independent of temperature

Answer: (A)

Direct proportionality of pressure to temperature at constant volume is what Gay-Lussac's law describes. As temperature rises, gas molecules move faster and collide with container walls more forcefully, so the pressure increases. For an ideal gas, P is proportional to T when volume is fixed, so P2 = P1(T2/T1) with temperatures in Kelvin. Using Kelvin is essential because 0 K corresponds to zero molecular motion and provides a meaningful zero point. Therefore, increasing temperature results in a higher pressure, in direct proportion. The other statements—pressure decreasing, staying the same, or being independent of temperature—do not align with this relationship.