Overview
- Researchers reported in Science on Thursday, March 26, that water has a second critical point near 210 K and about 1,000 atmospheres.
- Scientists melted amorphous ice with an infrared pulse and used X-ray shots at the Pohang facility to probe the liquid in the “no man’s land” before it froze.
- The measurements show two supercooled liquid states, a high-density and a low-density form, become one at that point in line with long-standing theory.
- The finding helps tie water’s density peak at 4 °C and its unusual heat capacity and compressibility to fluctuations that spread out from this critical region.
- Experts note the ultrafast snapshots assume the liquid reached equilibrium, so new tests will check that assumption and explore impacts across chemistry, geology, biology, and climate.