The critical point and universality

Todays lecture had two major goals. First, to get students to think about the barrel crush video in terms of temperature-volume phase diagram of water. As an in-class exercise (not assessed) I get them to define the system, and plot on the T-V diagram the history of the system as the video progesses.
The second goal is to introduce the notion of universality via the law of corresponding states. I emphasize that since this holds independent of the chemical and structural details of the fluid, i.e., it is universal. I mention that universality is arguably one of the most important concepts in theoretical physics from the second half of the 20th century.

The figure is adapted from Guggenheim's 1945 Journal of Chemical Physics paper.