Boyle's law
2 marks · NormalThe graph below shows the relationship between the pressure and volume of a fixed mass of gas at constant temperature.
Describe the relationship shown by the graph and explain why this relationship occurs using Boyle's law.
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Common mistakes: Saying direct proportionality; Not referencing Boyle's law
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Marking points
B1 · 1 mark · Describes that as volume increases, pressure decreases.
B1 · 1 mark · Links to Boyle's law (the product of p and V is constant for a fixed mass at constant temperature).
Worked solution
The graph shows that as the volume of the gas increases, the pressure decreases. This is an inverse relationship. According to Boyle's law, for a fixed mass of gas at constant temperature, the pressure and volume are inversely proportional (pV = constant).