At a high level I understand the concept of the triple point of a substance, the combination of temperature and pressure that can result in a substance existing in all 3 states, but practically I always had trouble understanding it. I think this was because I’d take it to it’s logical conclusion, I.E. that essentially the substance would exist in all 3 states simultaneously something which seems impossible. Of course in practical terms this never occurs with whatever substance existing in one of those 3 states, with the added ability to quickly change to another one. Explaining the concept is one thing though, seeing it in motion makes everything far more clear:
The liquid in the video is called cyclohexane which has four distinct solid phases. I don’t think we’re seeing a transition between any of those specifically though, the temperatures required to meet them are below freezing and that appears to be room temperature, but this video does show how the triple point functions. Slight variations in pressure and temperature cause the substance to rapidly change from solid to a liquid and even straight to boiling (which you assume is producing gas). You probably wouldn’t want to reproduce this experiment as a demonstration to kids, cyclohexane is a derivative of benzene and likely carries the same nasty health effects, but you can do similar things as long as you have a vacuum pump.
