Properties of hydrogen bonds may explain the Mpemba effect
It seems logical to expect cold water to freeze faster than hot, but some experiments have suggested the opposite. There’s now a new explanation for why hot water might freeze faster than cold under certain conditions. The phenomenon, known as the Mpemba effect, may be due to the properties of the bonds that link up neighboring water molecules, a team of chemists reports. Yet other researchers contend that the effect doesn’t exist at all.
References to quick-freezing hot water date back to the early days of science: Aristotle reported observing hot water freezing faster than cold. In the 1960s, a Tanzanian student named Erasto Mpemba noticed that ice cream solidified faster when put into the freezer steaming hot. Scientists have proposed a variety of explanations for the phenomenon — now named for the student — including the effects of evaporation, convection currents, and dissolved gasses or other impurities present in the water. But none of the