Some of the gas is allowed to escape from a sealed rigid container. The temperature of the gas that is left does not change. Why does the pressure inside the container decrease?
There are fewer molecules, so the walls are hit less often each second.
The molecules that are left behind move more slowly than before.
The molecules that are left behind are spread over a larger volume.
There are fewer molecules, so each collision exerts a smaller force.
40 exam-style questions on AQA GCSE Physics 3.3 Particle model and pressure, covering 3.3.1 Particle motion in gases, 3.3.2 Pressure in gases, and 3.3.3 Increasing the pressure of a gas (HT only). Each one has a worked solution and a mark scheme showing where the marks go.