(a)[2]
State what is meant by internal energy of a system.
(b(i))[3]
With reference to molecular kinetic and potential energies, describe and explain the change in internal energy of the system when a gas is heated at constant volume so that its temperature increases.
(b(ii))[3]
With reference to molecular kinetic and potential energies, describe and explain how the internal energy of the system changes when a wire is stretched within its elastic limit while the temperature is constant.