Fig. 50.1 shows the apparatus used to investigate Boyle's law. A gas syringe is connected to a digital pressure sensor and both are clamped securely. The sy...

Part (a) [2 marks]

• P is the plunger (piston) of the gas syringe [1]
• Q is the pressure sensor (pressure gauge) [1]

The plunger is pushed in to compress the trapped air, while the pressure sensor digitally records the resulting pressure.

Part (b) [2 marks]

Push the plunger inward to decrease the volume of trapped air in steps [1]. At each step, wait a few seconds for the temperature to stabilise, then record the volume from the syringe scale and the pressure from the digital sensor [1].

Waiting is important because compressing gas quickly heats it, and Boyle's law requires constant temperature.

Part (c) [3 marks]

Boyle's law: \(p_1 V_1 = p_2 V_2\) at constant temperature [1].

Substituting: \(p_2 = \frac{p_1 V_1}{V_2} = \frac{100 \times 100}{25}\) [1]

\(p_2 = 400\) kPa [1]

When the volume is reduced to one quarter of its original value, the pressure increases to four times its original value. This inverse relationship is the essence of Boyle's law: halving the volume doubles the pressure because the same number of particles now collide with the walls twice as frequently.

Part (d) [2 marks]

Compressing gas quickly does work on the gas, raising its temperature [1]. This would violate the constant temperature condition required by Boyle's law, making the results invalid [1].

By compressing slowly, any heat generated has time to dissipate to the surroundings, keeping the gas at room temperature throughout.