The gas laws
3 marks · NormalDescribe how you could investigate the relationship between the pressure and volume of a trapped gas in a school laboratory, stating the measurements you would take to confirm Boyle's law.
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Use a sealed syringe to trap a fixed amount of air. Vary the volume by adjusting the plunger, measuring the volume using syringe markings, and reading the pressure using a pressure sensor or gauge attached to the end. Record several pressure and volume values at constant temperature and plot p against 1/V to check for a straight line.
Also accept: Use of a different apparatus (e.g., oil manometer, Bourdon gauge) but measures pressure and volume changes.; Plotting values to confirm the law.
Common mistakes: Not mentioning constant temperature; Not measuring both pressure and volume
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Marking points
B1 · 1 mark · Describes trapping gas in a syringe or similar apparatus.
B2 · 1 mark · Explains how to vary and measure volume and pressure.
B3 · 1 mark · States need to keep temperature constant and/or describes plotting p against 1/V to establish law.
Worked solution
You can trap a fixed amount of air in a sealed syringe. Adjust the plunger to change the volume, measuring it from the syringe's scale. Attach a pressure sensor to measure the pressure. Record several pairs of volume and pressure readings. Ensure the experiment is done at constant temperature. Plot pressure against 1/volume to see if there is a linear relationship, confirming Boyle’s law.