When looking at tiny pollen grains suspended in a drop of water under a microscope, they are observed to undergo random, erratic movements.
What causes this random motion of the pollen grains?
The pollen grains are hit by the rapidly moving water molecules.
Convection currents in the water carry the pollen grains randomly.
The pollen grains actively swim in search of nutrients.
The pollen grains repel each other due to static electric charges.
151 exam-style questions on CIE IGCSE Physics 2.1.2a Particle structure and motion in solids, liquids and gases. Each one has a worked solution and a mark scheme showing where the marks go.