Finicky Freezing: Investigations into the Causes of the Mpemba Effect

Martha I. Roseberry

2009

A study of the Mpemba effect, the phenomenon of initially hot water freezing faster than initially cold water was performed. Several types of water were frozen in beakers in a domestic freezer and the temperature of the samples was monitored using thermistors placed in the samples. Four thermistors were used to record the temperature of the samples throughout the cooling and freezing process, three at different places within the sample and one monitoring the temperature of the environment. When using nano-pure water, distilled water, and Wooster city tap water, no Mpemba effect was observed. However, data taken with a Millersburg water, a known hard water, demonstrated the Mpemba effect! Water with an initial temperature between 60 degrees C and 80 degrees C had a shorter freezing plateau than water with a higher initial temperature. These results support the theory that the Mpemba effect is caused by impurities within the water which hamper the freeze process. Heating the water removes some of these impurities from the water, causing the hot water to freeze faster.