A sealed glass flask of gas is cooled from 80 ∘C80\ ^\circ\text{C}80 ∘C to 20 ∘C20\ ^\circ\text{C}20 ∘C. The volume of the flask does not change. What happens to the number of collisions each second between the molecules and the walls?
It decreases, because the molecules move more slowly.
It decreases, because some molecules stop moving completely.
It increases, because the molecules are closer together.
It increases, because the molecules have more kinetic energy.
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.