In an experiment to demonstrate Brownian motion, smoke particles inside a closed cell are observed through a microscope.
What is the reason for the random, jagged movement of the smoke particles?
They are hit by fast-moving but invisible air molecules.
They are carried by convection currents created by the light source.
They collide with each other due to gravitational attraction.
They vibrate about fixed positions within the air cell.
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.