When tiny smoke particles suspended in air are viewed through a microscope, they are observed to be in continuous, rapid, random motion. What causes a smoke particle to move in this way?
Convection currents in the air
Gravitational forces acting unevenly on the smoke particles
Uneven bombardment on different sides by rapidly moving air molecules
Collisions between the smoke particles themselves
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.