A student performed an experiment to verify Boyle's law by investigating how the volume V varied with pressure p of a fixed mass of gas - Leaving Cert Physics - Question 2 - 2021

The pressure is varied in this experiment using a piston or a pump that compresses the gas in the enclosed container. By adjusting the position of the piston, the volume of the gas changes, which subsequently alters the pressure according to Boyle's law.

The student must wait to ensure that the gas reaches thermal equilibrium before taking a reading for volume. If the pressure is changed too quickly, the gas may not adjust its volume immediately due to inertia, which could lead to inaccurate readings. Waiting allows the system to stabilize.

To plot the graph:

• Use graph paper and label the x-axis as '1/V (cm⁻³)' and the y-axis as 'Pressure (kPa)'.
• Plot each point corresponding to the values from the earlier table.
• Draw a best-fit straight line through the points. Ensure accuracy up to the significant figures indicated.

From the graph, find the value of 1/V when the pressure equals 140 kPa. If the corresponding value is, for example, 0.07 (as per the marking scheme), then:

• Calculate the volume using the relationship:

  $V = \frac{1}{(1/V)}$

Substituting the value: $V = \frac{1}{0.07} \approx 14.3 cm³$ Thus, the volume of the gas when its pressure is 140 kPa is approximately 14.3 cm³.