A fixed mass of gas is stored beneath the freely moving roof of a variable-volume gas holder. Weights press down on the roof. Before any weights are removed, the roof stays at a steady height. Some of the weights are then removed while the gas temperature remains constant. Once the roof has stopped moving again, which statement describes the pressure of the gas?
It is lower than at the start, and it balances the reduced pressure pushing down on the gas.
It is higher than at the start, because the gas has expanded and pushes harder on the roof.
It is the same as at the start, because the mass and temperature of the gas are unchanged.
It is lower than at the start, because the gas particles now move more slowly than before.
108 exam-style questions on Edexcel GCSE Physics 14.3 Gas pressure and temperature, covering 14.3.1 Gas pressure and particle motion, 14.3.2 Temperature and pressure at constant volume, 14.3.3 Absolute zero and the kelvin scale, 14.3.4 Compressing and expanding gases, 14.3.5 Volume and pressure at constant temperature, and 14.3.6 Doing work on a gas. Each one has a worked solution and a mark scheme showing where the marks go.