Brownian motion can be observed when viewing a suspension of pollen grains in water under a microscope.
What is the main cause of the random, jerky movement of these pollen grains?
The pollen grains are constantly hit by much smaller, fast-moving water molecules.
Convection currents in the water carry the pollen grains in different directions.
The pollen grains are living organisms that are actively swimming in the water.
Static electrical forces cause the pollen grains to repel one another.
321 exam-style questions on CIE IGCSE Physics 2.1 Kinetic particle model of matter, covering 2.1.1 States of matter and changes of state, 2.1.2a Particle structure and motion in solids, liquids and gases, 2.1.2b Gas pressure and particle collisions, 2.1.2c Brownian motion, 2.1.3a The absolute scale of temperature, and 2.1.3b Pressure, volume and temperature of a gas. Each one has a worked solution and a mark scheme showing where the marks go.