ABSTRACT
This chapter discusses questions concerning gases; liquids; solids; and questions concerning changes between different phases. It works out the coefficient of thermal expansion of a molecularly-bonded solid. When a magnetic field is applied perpendicular to a wafer of conducting material carrying a current along its length, then a potential difference appears across its width. The Einstein model of vibrations in solids assumes that all atoms are identical and all vibrate with a single frequency. The Debye model is more realistic, allowing for a spectrum of allowed vibrational frequencies. However, in between the two models there were historically a plethora of modifications of the Einstein model, which assumed ‘a few’ vibrational frequencies. The electrical resistivity of a sample of copper which contains small amounts of zinc impurity is shown. At absolute zero, lattice vibrations are unable to scatter electrons. The scattering which gives rise to the so-called residual resistivity is due solely to impurities and defects in the crystal lattice.
