Statistical Mechanics/The Two-State Problem
Although the two-state model has directly useful applications (as we will see in binary mixtures), it is really useful as an introductory model to Statistical Mechanics. For example, calculating entropy and other thermodynamic properties, and their meaning in certain contexts.
The two-state problem itself deals with a number of sites that can have either of two configurations: material A or material B, up or down, 0 or 1.
To keep with a good example that has thermodynamic properties, we will choose up or down spin statistics.