A model is developed for the activation energy for diffusion from considerations of the energy required for water molecules to become dissociated from their sites and the energy required to overcome the attraction of water molecules for themselves. The model confirms that equations for bound water movement based on fluid mechanics and those based on thermodynamics are identical when the driving force for diffusion is defined as the moisture flux per unit transport coefficient, as discussed in Part 1. Theoretical activation energies compared well with experimental values in the literature. -- AATA