Water can boil and freeze simultaneously at its triple point, which occurs at 0.01 degrees Celsius and 611.657 pascals of pressure.
Why it is true
The triple point is a unique combination of temperature and pressure where all three phases of matter (solid, liquid, and gas) coexist in thermodynamic equilibrium. For water, this happens at a very low pressure, allowing ice to melt, water to boil, and vapor to condense at the same time.
Source: MIT
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