KS3 Physics Practice Test 2025 – Complete Exam Prep

When the temperature of a gas is increased while keeping its volume constant, the pressure of the gas also increases. This relationship is described by Gay-Lussac's Law, which states that the pressure of a given mass of gas is directly proportional to its absolute temperature, provided that the volume does not change.

As temperature rises, the kinetic energy of the gas molecules increases, causing them to move faster. These faster-moving molecules collide with the walls of the container more frequently and with greater force. Since pressure is defined as the force exerted per unit area, an increase in the frequency and intensity of collisions directly results in higher pressure.

Maintaining a constant volume means that the space available for the gas cannot change, so as the temperature rises and the gas molecules gain more energy and speed, the increase in pressure is an expected outcome of these conditions. The other options would suggest either a decrease in pressure or no change, which does not align with the scientific principles governing gas behavior under temperature changes.