How quickly turn water into ice cubes

Immediately open the card: hot or warm water freezes faster than cold or cool. This paradox is called the Mpemba effect. On why it works contrary to logic and what temperature should the water, so that it quickly turned into ice, read our article.

effect Mpemba

This story began over fifty years ago, but did not receive interchange to this day. And all because, no matter how hard thousands of inquisitive minds from around the world, they can not even find the only right decision puzzles Mpemba.

In 1963, African inconspicuous student named Erasto Mpemba (Erasto Mpemba) noticed one oddity: warm ice cream mix freezes faster than chilled.

The observation seemed so implausible that the teacher of physics could only laugh at the opening of the unlucky experimenter. However, Erasto was sure that he was right and did not hesitate to once again become the laughing stock: a little later, he lifted slippery question before Dennis Osborne (Denis Osborne), a professor at the University of Dar es Salaam, Tanzania. The scientist did not rush to hasty conclusions and decided to study the problem. Then in 1969 Physics Education Journal published an article describing the Mpemba paradox.

In scientific circles, then I remembered that something similar has already said the greatest minds of yore. For example, more Aristotle referred to the inhabitants of the Greek Pontus, who during the winter fishing heated water and soaked in her cane, so he quickly solidified. Many centuries later, Francis Bacon wrote: "The slightly cooler water freezes more easily than very cold."

In general, the question is as old as the world, but it only fuels the interest in unraveling. Over the past few decades, we put forward many theories to explain the Mpemba effect. The most likely of which were presented in 2013 at a ceremony conducted by the Royal Chemical Society of Great Britain. Professional Association examined 22 000 (!) Opinions and distinguish among them only one belonging to Nikola Bregovic (Nikola Bregović).

Croatian chemist pointed to the importance of processes of convection and hypothermia liquid at its freezing.

Here's how these phenomena are described in the "Wikipedia":

• Cold water begins to freeze from the top, thereby slowing the process of thermal radiation and convection, and hence the loss of heat, while the hot water begins to freeze from the bottom.
• Supercooling - liquid having a temperature below the crystallization temperature at a given pressure. Supercooling obtained from normal by cooling in the absence of nucleation.

global confession and a check for 1,000 pounds of steel a good reward. By the way, the winner welcomed Erasto Mpemba and Denis Osborne.

What should be the temperature of the water before freezing

This question is still no clear answer. Royal Society of Chemistry, though defined, but not completely stopped arguing. Until now put forward new hypotheses and sound rebuttal.

Although there is a small hitch: the popular science magazine New Scientist conducted a study and came to the concluded that the best conditions for the repetition Mpemba effect - two water tanks at 35 and 5 ° C.

Thus, if the parties to the left quite a bit of time to fill molds for ice water having a temperature comparable to the ambient temperature of the hot summer. Manhole or cool tap water should be avoided.