Six original Cambridge-style questions on pV = constant: calculations both ways, the particle explanation, the conditions that must hold, and the shape of the pressure-volume graph.
State Boyle's Law, including the conditions under which it applies.
A gas has a volume of 2.0 litres at a pressure of 200 kPa. At constant temperature it is compressed to a volume of 0.5 litres. Calculate the new pressure.
p₂ = (200 × 2.0) / 0.5 = 400 / 0.5
p₂ = 800 kPa
Volume cut to a quarter, so pressure is four times bigger.
A sealed syringe holds 100 cm³ of gas at a pressure of 300 kPa. The plunger is pulled out, at constant temperature, until the volume is 150 cm³. Calculate the new pressure.
p₂ = (300 × 100) / 150 = 30000 / 150
p₂ = 200 kPa
Volume increased, so pressure dropped, as expected.
Explain, in terms of particles, why reducing the volume of a fixed mass of gas at constant temperature increases its pressure.
Boyle's Law only holds if a particular quantity is kept constant. State this quantity, and explain why the average speed of the particles does not change when the gas is compressed under these conditions.
A student plots a graph of pressure (y-axis) against volume (x-axis) for a fixed mass of gas at constant temperature. Describe the shape of the graph, and state what the product of the two plotted quantities represents.
Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.