A student uses a microscope to observe the Brownian motion of smoke particles suspended in a closed cell filled with air. Which statement correctly describes and explains the effect of a modification to this experiment?
Increasing the temperature of the air increases the average speed of the air molecules, resulting in more frequent and more energetic collisions with the smoke particles, which increases their random motion.
Using smoke particles of a larger average mass increases the momentum transferred to them per collision, resulting in more rapid and larger observed displacements.
Evacuating the air from the cell would cause the smoke particles to move even more rapidly because there would be no air resistance to oppose their motion.
Decreasing the volume of the cell at constant temperature increases the pressure, which increases the average kinetic energy of the air molecules and makes the smoke particles move more rapidly.
48 exam-style questions on AQA A Level Physics Thermal physics (A-level only), covering Thermal energy transfer (A-level only), Ideal gases (A-level only), and Molecular kinetic theory model (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.