An experiment is set up to observe Brownian motion by looking at a diluted suspension of tiny fat droplets in water under a microscope.
Describe two features of the observed path of a single fat droplet.
Explain, in terms of collisions, relative masses, and the motion of water molecules, the cause of the motion of the fat droplets.
A sample of helium gas is sealed inside a rigid metal cylinder of constant volume. The cylinder is heated, increasing the temperature of the gas.
Explain, in terms of the helium atoms, why heating the cylinder increases the internal energy of the gas.
Explain, in terms of atomic collisions, why the pressure exerted by the gas on the cylinder walls increases.
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.