Ice water sits on a plate in a vacuum chamber. With the pressure lowered, the liquid water begins to boil while ice cubes remain. This is the triple point of water, as shared in this silent video by the UC Santa Cruz Physics Demonstration Lab at UCSC Physics.
The triple point occurs where the solid, liquid, and gas transition curves meet. The triple point is the only condition in which all three phases can coexist, and is unique for every material. Water reaches its triple point at just above freezing (0.01° C) and at a pressure of 0.006 atm.
Related reading: Thermodynamic equilibrium.
Learn more about triple points with this cyclohexane video from Outrageous Acts of Science.
Plus, videos about freezing, boiling, and pressure. And why is water one of the weirdest things in the universe?
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