Manuel asks:
Mpemba effect, estimated Manuel and readers, says that hot water freezes before cold in certain circumstances. But do not worry: if we put water in the freezer at 5 degrees and water at 50 degrees, water at 5 degrees before the water freezes at 50 degrees. Common sense prevails. So says the Mpemba effect is that water to, say, 95 degrees before the water freezes at 80 degrees. Yes you can surprise there, but less.
The cause: warmer water evaporates more. If we put in the freezer for a glass of water at 95 ยบ C, when the freeze will have lost 16% of their mass through evaporation, more or less. A glass at 80 ° C, by contrast, have lost only 7%, again approximately (depending on the free surface having the container, freezer power ...). Of course, when there are fewer Water is easier to freeze. If you put plastic over the vessels to prevent evaporation, freezing before the glass is warmer, but now with less difference. The cause may be as much internal convection (and longer) of the cup warmer, which promotes heat transfer to the freezer. It may also influence the fact that the more heat a liquid less remaining dissolved gases, which may make it easier to freeze later. But the bottom
Mpemba effect is that not apply to any two temperatures, which I guess was what stung your curiosity.
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