In an experiment to observe Brownian motion, tiny pollen grains are suspended in water and viewed through a microscope. The pollen grains are seen to undergo continuous, erratic, and random movements.
Which of the following statements correctly explains this observation?
Water molecules have much larger masses than pollen grains and they move in random directions.
Water molecules move at much higher average speeds than pollen grains and collide with them from random directions.
Water molecules move at much higher average speeds than pollen grains and they all move in a single, coordinated direction.
Water molecules have comparable masses to pollen grains and move in fixed, vibrational paths.
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.