Chemistry / Unit 8 Chem 1435 short lesson, about 20 seconds
The Triple Point
Captions available
The idea
A phase diagram's triple point is the single temperature and pressure where solid, liquid, and gas all coexist in equilibrium.
In practice
Freeze-drying holds a frozen sample below its triple-point pressure, so ice sublimes directly to vapor without ever becoming liquid.
Where people slip
Below the triple point's pressure, no temperature at all permits a liquid state — a structural fact, not a rare condition.
Your place on the trail
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