Introduction
The phenomenon that hot water freezes faster than cold water had received constant disapproval prior to the year 1969 when a fluke experiment on ice cream echoed the anomaly. An experiment performed by Mpemba, a high school student, confirmed that indeed the phenomenon is true.
In a synopsis, in his experiment, Mpemba investigated the rate of freezing of two batches of ice cream: a hot ice cream mix and a cooled-to-room-temperature ice cream mix. To this end, he concurrently put the batches in a freezer and recorded the time taken for each to freeze. In his results, he established that the hot ice cream mix freezes faster than the cool one. With these results, he pondered what might have happened. To erase any doubts, he carried an identical experiment but with water instead. To his surprise, he obtained a duplicate result; “hot water freezes faster than cold water” (Katz, 2009).
In his quest to find answers behind this phenomenon, Mpemba approached several people including his physics teacher and Prof. Orsborn. To his surprise none of them had an answer to this anomaly. However, after a series of experiments the Prof. confirmed Mpemba’s findings after which, together with Mpemba in the year 1969, published their findings otherwise christened Mpemba effect (Auerbach, 1995). However, even with these findings, most stubborn readers still remain skeptical about the phenomenon. However, their explanations do not agree with scientific principles.
To date, scientists the world over still grapple to establish the reason that is Mpemba effect. As such, many explanations have been fronted to this effect. This is owed to the fact that there is no published, common denominator on the conditions under which individual experiments need to be performed to assert Mpemba effect.
Moreover, there are a host of variables that render results from different laboratory experiments unique. Different mechanisms including evaporation, dissolved gasses, convection, and the surrounding have been published as reasons for Mpemba effect. To this end, “with the limited number of experiments done, and often under very different conditions, none of the proposed mechanisms can confidently be proclaimed as “the” mechanism” (Wojciechowski, 1995).
Project Goals
- To analyzed the mechanisms fronted in the quest to finding the cause of Mpemba effect.
- To briefly analyze the methodology used in each mechanism.
Review of Literature
In the year 1969, through his fluke experiment on ice cream, Mpemba, a high school student, echoed claims believed to have been remarked by the trio of Aristotle, Bacon and Descartes. His claims were that hot ice cream cools faster than cold ice cream. To assert his claims, he engaged a different liquid (water) and the results were similar.
He engaged different personalities including Prof. Osborne who later on published this phenomenon otherwise christened Mpemba effect as true. This would later elicit mixed reactions from the general public on the credibility as well as the actual causes of the same. A number of literatures hitherto trying to disapprove Mpemba’s findings have been published.
In the year 1996, an experiment to assert Mpemba’s claims was carried out by Mathews. As such, he challenges us to obtain water in two pails: one at 95℃ and the other one at 50℃ but on a freezing day (Jearl, 1977). According to him, the hotter water freezes faster than the cold water. In his research, he claims that on a cooling curve, hot water would take a little more time before reaching the initial temperature of relatively colder water eventually following the trend traced by the cold water.
Apparently, the effect is real however, the credibility of these theoretical claims is best explained by Mpemba effect (Auerbach, 1995). Nonetheless, Mathews further explains that this phenomenon has its roots way back in history. As such, he explains that the mystery was a common place in the ancient epoch where wooded pails were popular. To this end, he cites that “Sir Francis Bacon, Descartes and even Aristotle are said to have remarked on it” (Auerbach, 1995).
Description of Research
According scientists, Mpemba effect might have resulted from three mechanisms that include evaporation, dissolved gasses, surroundings and convection. As such, this research centers on these mechanisms. As regards evaporation, scientists believe that evaporation might have staked a claim in Mpemba effect. As such, they believe that hot water loses significant amount of volume in form of evaporation. Consequently, a relatively small volume of water would be available for cooling hence it freezes faster than initially cold water. However, this theory is limited to open containers hence cannot stake a claim as ‘the’ actual mechanism (Esposito, 2008).
With regards to the experimental methodology, twin experiments need to be set up but with different initial temperatures. A data on the actual lose in volume of water need to be tabulated for analysis. Similar arrangements need to be done for closed containers too. Notably, other factor should be held constant.
With respect to dissolved gasses, the advocates of this theory believe that hot water has low capacity with regards to dissolved gasses. As such, they believe that in absence of the gasses the physical characteristics of water change. This in turn enhances faster development of convectional currents vital in enhancing quick freezing of water.
Moreover, they believe that this changes the boiling point of water in favor of hot water. However, this theory is unsupported arithmetically (Esposito, 2008). As regards methodology, an analysis on how fast convectional current develops using an ink in a twin experiment while holding other factors constant need to be done.
The surrounding environment may have an influence on the rate of cooling especially when one is not keen on providing similar environmental conditions to both containers. As such, a hot water container resting on a thin layer of frost may influence its environment in a complex way to freeze faster than initially cold water. However, scientists are kin to provide similar environmental conditions to avert such uncertainty (Esposito, 2008).
Convectional current theorists believe that these currents are responsible for a non-uniform temperature distribution; hence, the temperatures decrease gradually from the top to bottom. This is for the reasons that in liquids the temperature and density are inversely related. As such, its upper layer otherwise ‘hot top’ lose heat relatively faster. To this end, on reaching the initial temperature of the cooler liquid with its ‘hot top’ intact, the rate of cooling remains comparatively faster. As such, the average cooling rate for initially warm water will be faster than that of initially cool water (Esposito, 2008).
The methodology should be based on establishing temperatures longitudinally in twin containers, but concurrently using sensitive probes in both containers while holding other factors constant. As such, graphs of temperature against time need to be plotted to ascertain the difference in cooling rate.
Timeline on how the experiment would be accomplished is shown below.
Budget
The budget allocation for the experiment is relative to how equipped one’s laboratory is, and how available the raw materials are. As such, the budget for the three experiments is not limited to the budget allocations below.
Annotated Bibliography
Mathews, R. (1996). Hot Water Freezes Faster than Cold!Physics FAO, 1. Web.
In the year 1992, while basing on a personal experience Mathews published an article on anomaly of water otherwise Mpemba effect. As such, he dares us to take two volumes of water with different temperatures, and on a freezing day to ascertain Mpemba’s findings. Mathews’s article is meant for the general public. However, the purported causes of this anomaly require scientific knowledge to comprehend.
Mathews focuses on the aftermath rather than pre-Mpemba’s findings. As such, he overlooks other people who are purported to have remarked about the experience before. Here, Mathews work is closely related to Ann Marie who focuses on post-Mpemba’s findings. In a synopsis, Mathews’s personal experience echoed Mpemba effect- “hot water freezes faster than cold water” (Mathews, 1996).
References
Auerbach, D. (1995). Supercooling and the Mpemba effect: When hot water freezes quicker than cold. American Journal Physics, 63, 882-885.
Esposito, D. (2008). Mpemba effect and phase transitions in the adiabatic cooling of water before freezing. Physica America Journal, 387, 757-763.
Jearl, W. (1977). Hot water freezes faster than cold water. Why does it do so? The Amateur Scientist, Scientific American, 237(3), 246-257.
Katz, J. (2009). When hot water freezes before cold. American Journal of Physics, 77, 27-29.
Wojciechowski, O. (1995). Freezing of aqueous solutions containing gases. Cryst. Res. Technol., 23, 843-848.