Tiny pollen grains suspended in water are observed under a microscope. The pollen grains are seen to move in a random, jerky manner.
What is the reason for this observation?
Convection currents are carrying the pollen grains.
The pollen grains are being bombarded by much smaller, fast-moving water molecules.
The pollen grains are alive and moving on their own.
Mutual electrostatic repulsion between the pollen grains forces them to move.
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.