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  • Srimoyee Mukherjee

How Heat Helps Cool Us

Mumbai is infamously associated with hot, scorching summers. On the plus side, though, is the adaptability. Golas (or ice-candies), nimbu sharbat, rooh afza, coke float, the list of cool things to complement the heat are simply endless. For most of these delicacies, ice is the main ingredient. It, obviously, provides the cold factor to the dish. Freezing of ice takes about 3-4 hours in a normal freezer. It does get pretty frustrating to have a craving to drink (or eat) something cold and not have ice at home. However, the mpemba effect makes this slightly easier.

The most common mistake most people do, is to put already cold water in the freezer and assume that it will freeze faster. In reality, it is quicker to cool water to a given temperature when the initial temperature is higher. Scientists have dwelled on this phenomenon, the mpemba effect, for a long time. Radiation safety officer with the State University of New York, James Brownridge, says that supercooling is the factor. Water supercools at 0°C and begins freezing only below this temperature. In his experiments, he took two water samples at the same temperature and placed them in a freezer. He found that one would usually freeze before the other, due to slightly different impurities. Once he removed the samples from the freezer, warmed one to room temperature and the other to 80°C, he then froze them again. The results were that if the difference in freezing point was at least 5°C, the one with the highest freezing point always froze before the other if it was heated to 80°C and then put back to freeze, again.

This proved that hot water cools faster because of the bigger difference in temperature between the water and the freezer, and this helps it reach its freezing point before the cold water reaches its natural freezing point, which is at least 5°C lower. All the conditions must be controlled, such as the location of the samples in the freezer, and the type of container, which he said other researchers had not done.

While we will not necessarily divulge into the scientific reasons behind a common mistake we would have been making for a long time, it is kind of ironic how heat allows water to essentially cool faster.

“Mpemba effect”

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