(b) The statistical view of entropy
The entry point into the molecular interpretation of the Second Law of thermodynamics
is Boltzmann’s insight, first explored in Section F.5a, that an atom or molecule
can possess only certain values of the energy, called its ‘energy levels’. The continuous
thermal agitation that molecules experience in a sample at T > 0 ensures that they are
distributed over the available energy levels. Boltzmann also made the link between the
distribution of molecules over energy levels and the entropy. He proposed that the
entropy of a system is given by