An investigation of the effect of dissolved gases on the freezing of water

Abstract

The Mpemba Effect has been a much talked-about topic in recent years. The Mpemba Effect is the phenomenon of hot water freezing faster than cold water. The Royal Society of Chemistry (RSC) in London recently organised a competition to challenge people to come up with the most innovative and plausible solution to this problem, a testament to its popularity. The winner, Nikolai Bregovic, was recently announced. His paper along with many other previously written papers on the Mpemba Effect will be discussed in this paper.

How this topic came into mind was during the exploratory stages of the initial topic which was, “ways to keep drinks cold longer”. Around this time, the RSC competition was in its closing stages and with relation to the initial topic, this paper about the Mpemba Effect came about. With the ever growing food and beverage industry, one can say that the ability to know how to create ice in a shorter time will hopefully help improve the lead times related to the creation of ice, which will assist people in keeping their drinks cold longer. There are many reasons given by credible people as to how and why the Mpemba Effect occurs, such as conduction, convection, supercooling, dissolved gas, dissolved minerals and evaporation. In this report the possibility of dissolved gases being a major player in the creation of this effect will be discussed.

Unlike other experiments that can be found on the internet which will be discussed in this report as well, the author sets out to differentiate his research by using two unique phases. The first phase is cooling the water in a household refrigerator over a long period before freezing, and the second phase is freezing the water in a standard household freezer, while using temperature probes to record the temperature versus time graph of this process. The amount of water used in this experiment is of a small volume of 50ml. Both steps are to ensure that the convection current is kept similar and negligible throughout the freezing process. As conduction can affect the experiment results, the author used the same materials for the process of this experiment. This is in hope to keep the factor of cooling by conduction constant. Every step taken in this experiment is to create a controlled environment for the freezing of water, in which convection, conduction and radiation were either eliminated or minimised in order to focus on the effect of dissolved gases.

Results produced are shorter phase transition to ice times, steeper cooling curves, lower temperatures of water that is degassed. The results of this paper confirms that dissolved gases are in fact a cause of the Mpemba Effect.