Sorel’s plates

Students are always asking for model answers. But at some point one has to move beyond such things; research, and indeed real life, requires us to act without someone else knowing the correct answer. This is amply demonstrated by the history of distillation. This ancient technique went from an empirical art to a real science in a tentative process, with false starts and dead ends, largely because of the absence of the key idea of dynamic equilibrium – a model answer we now take for granted.