(A Level) Thermodynamics and internal energy

Learning objectives

Describe the internal energy of a system as the total of the random kinetic energies and intermolecular potential energies of its molecules, and explain that it depends only on the state of the system.

Explain how a temperature rise corresponds to a gain in internal energy, and why the internal energy of an ideal gas is purely the kinetic energy of its molecules and proportional to T.

Calculate the work done in expanding or compressing a gas at constant pressure with W = pΔV, taking care over whether the work is done on the gas or by it.

Apply the first law of thermodynamics ΔU = q + W, with q the energy supplied by heating and W the work done on the system, to heating, compression, expansion and a complete cycle in which ΔU = 0.