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Water Can Boil and Freeze at the Same Time — It's Called the Triple Point
💡 At exactly 0.01°C and very low pressure, water boils, freezes, and flows as liquid simultaneously — a phenomenon so precise it was used to define the kelvin temperature unit.
Under normal conditions, water exists as a solid, liquid, or gas. But at exactly 0.01°C and 611.73 pascals of pressure (about 0.6% of normal atmospheric pressure), something extraordinary happens: water boils, freezes, and remains liquid all at the same time. This is the triple point, and it's not theoretical — you can observe it in a lab.
At the triple point, water molecules have just enough energy that the boundaries between all three phases dissolve. You can literally watch a container of water that is simultaneously bubbling (boiling), forming ice crystals (freezing), and flowing as liquid. It looks like the water is confused about what state it wants to be in.
The triple point is so precisely reproducible that it's actually used as a fundamental calibration standard. The kelvin, the base unit of temperature in the International System of Units, was defined for decades based on water's triple point (1/273.16 of the triple point temperature). When scientists needed an absolutely reliable temperature reference point, they turned to this bizarre state where water can't make up its mind.