Temperature
Anomalies related to the unusual behavior of water at various temperatures -- from its extraordinarily high melting and boiling points to the Mpemba effect.
Water has an unusually high melting point
The melting point of water is 0 degrees Celsius -- much higher than expected for comparable molecules.
Water has an unusually high boiling point
The boiling point of water at 100 degrees Celsius is anomalously high compared to similar hydrides.
Water has an unusually high critical point
The critical point of water is unusually high at 374 degrees Celsius and 218 atm.
Water has two liquid phases and a second critical point
At approximately -91 degrees Celsius, a second critical point is suspected where two liquid phases coexist.
Liquid water is easily supercooled but difficult to vitrify
Water can remain liquid far below 0 degrees Celsius, yet forming amorphous ice is difficult.
Liquid water exists at extremely low temperatures and freezes upon warming
Under certain conditions, water can be liquid at very low temperatures and crystallize upon warming.
Liquid water can be easily superheated
Water can be heated above its boiling point without boiling.
Hot water can freeze faster than cold water -- the Mpemba effect
Under certain conditions, hot water freezes faster than cold -- a phenomenon known since antiquity.
Warm water vibrates longer than cold water
The OH stretching vibration in warm water decays more slowly than in cold water.
Water molecules shrink with rising temperature and expand with rising pressure
Counterintuitively, individual water molecules become smaller when heated.
A liquid-liquid transition occurs at approximately 330 K
At around 57 degrees Celsius, water shows signs of a transition between two liquid states.