Introduction
To most people, the idea that hot water freezes faster than cold water seems illogical. However, this is an absolute fact. This phenomenon had been met with lots of disapproval prior to the year 1969. However, an experiment performed by a Tanzanian high school student, Mpemba, 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 (Auerbach 883). To this end, while holding other factors constant he established that hot ice cream mix freezes faster than a cool one. With these results he pondered what might have happened. To assert his findings, he performed an experiment akin to the former but with water instead. To his surprise he obtained a replica result- “hot water freeze faster than cold water” (Kell 564).
In an effort to search for answers behind this phenomenon Mpemba approached his physics teacher who rebuffed his findings citing experimental errors. His quest to establishing the origin of the anomaly did however not end. He, by chance happened to meet Dr. Orsbone, a physics Prof., whom he shared his findings. To his surprise Dr. Orsbone was as blank too. This challenge motivated the Prof. to carry out investigations to ascertain the phenomenon. Through his laboratory technician Dr. Orsbone echoed Mpemba’s findings. Succeeding experiments reproduced Mpemba’s findings hence; in the year 1969, following these results, the duo published what became to be known as Mpemba effect hitherto (Brewster & Gebhart 331).
To date, given the findings most readers who haven’t gone through a practical experience to attest this still remain skeptical.
Project Goals
- To investigate the mechanisms proposed as the reasons behind Mpemba effect.
- To briefly propose a methodology used in each mechanism to yield a perfect result.
Review of Literature
Way back in history during Aristotle’s era, the anomaly that hot water freezes faster than cold water was remarked but by one Aristotle. Looking at it however simple it may appear Aristotle who boasts a range of scientific inventions could not crack this mystery. He pondered why this is so to no avail. Thousands of years down the line today major milestones have been achieved but Mpemba effect still remains elusive. To this effect today ‘think tanks’ are still grappling with the same.
Later on in1960s, a thirteen year old Tanzanian- Mpemba, 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 stalk his claims he engaged a different liquid (water) and the results were similar. Moreover, he brought Prof. Orsbone on board who later confirmed his findings. This would later be christened Mpemba effect. However, 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 unearth the causes of Mpemba effect have been published.
In the year 1996, as reported by Mathews, an experiment to assert Mpemba’s claims was performed. As such, he challenges us to obtain water in two pails; one at 950 C and the other one at 500 C but on a freezing day (Mathew 1). According to him, the hotter water freezes faster than the cold water. Apparently, the effect is real and, he claims that according to the public notion this is also reproducible in refrigerators. Mathews further reports 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” (Mathews 1).
Description of Research
Scientists the world over have been tasked to unearth the mystery that is Mpemba effect. As such they explain mechanisms including evaporation, dissolved gasses, surroundings and convection as the reasons for the abnormal behavior of water. As such, this research focuses on these mechanisms.
With focus to evaporation, some scientists suppose evaporation to be the reason that is Mpemba effect. To this effect they believe that the process of evaporation leads to a significant loss in the total volume of water. As such, a relatively small volume of water is present for cooling which by fact should freeze faster than a big volume. Nevertheless, this theory does not hold water because it fails to explain the anomaly in closed containers. With respect to the experimental methodology, and while holding other factors constant, a twin experiments need to be setup but with different initial temperatures. A data on the actual loss in volume of water needs to be tabulated for analysis. An analogous arrangement needs to be done for closed containers too.
A correlation between dissolved gases and temperatures reveal an inverse trend. As such, proponents of ‘dissolved gases’ mechanism believes this as the reason behind Mpemba effect. They believe that with devoid of gases the entire physical properties of a liquid is modified. As such, they enhance faster development of convectional currents vital in quicker freezing of water. Moreover, they suppose that this modifies the boiling point of hot water such that on freezing it would take less time as opposed to cold water (Esposito 759). However, this theory lacks mathematical backing. In view of the methodology, an experiment on how fast convectional currents develop with respect to the rate of cooling need to be done. This need to be done while holding other factors constant.
As regards the ‘surrounding environment’ few would reckon it as a mechanism behind Mpemba effect. However, this may influence the freezing rate in a complex manner. For instance, 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 763). As for the experimental approach the experiments need to be performed in different environment including big freezer, small freezer, on a hot day, cold day etc. This needs to be done while holding other factors constant.
Theorists fronting convectional current as a mechanism for Mpemba effect point out at non-uniform temperature distribution vertically across the surface of water to this effect. They believe that temperature decreases gradually from the ‘hot top’ to bottom. This, they explain is owed to an inverse relation between density and temperature common in liquids. As such, the ‘hot top’ which is intact throughout the freezing process loses heat relatively faster. Consequently, the cooling rate for initially warm water would be faster than that of initially cool water (Tankin and Farhadieh 955). With respect to the methodology, using sensitive probes in two containers, temperatures need to be taken vertically across the water while the experiment is ongoing. As such, calibrated container should be used. The results should be compared to a respective rate of cooling.
Timeline of the experiment.
Budget
The budget for the experiment depends on the availability of equipment. However, for these experiments and with an equipped laboratory in place the budget is projected to be less expensive. As such, the budget for the four experiments would be as shown below:
Annotated Bibliography
In an article published by Mathews in the year 1992, his main focus centers on the Mpemba’s phenomenon. As such, he dares us to perform an experiment to experience Mpemba effect. He takes us through a chronology of experiences that stretch back to the heydays of prominent personalities including Aristotle, Sir Francis Bacon and Descartes who supposedly remarked this experience. Eventually, he brings us to the most recent experiences that significantly commences in the year 1969, when this phenomenon which later came to be known as Mpemba effect received worldwide publication courtesy of a Tanzanian- Mpemba. He takes us through ensuing responses and the mechanisms fronted in an effort to unearth the truth. Mathews focuses mainly on the recent experiences from the year 1969, as opposed to ancient times. However, he acknowledges Auerbach’s contributions to the success of his publication.
References
Auerbach, David. “Supercooling and the Mpemba effect: When hot water freezes quicker than cold.” American Journal Physics 63.1 (1995): 882-885. Print.
Brewster, Richard and Gebhart Benjamin. “An experimental study of natural convection effects on downward freezing of pure water.” Int. J. Heat Mass Trans. 31.2 (1988): 331-348. Print.
Esposito, David. “Mpemba effect and phase transitions in the adiabatic cooling of water before freezing.” Physica America Journal 387.1 (2008): 757-763. Print.
Kell, George. “The Freezing of Hot and Cold Water.” American Journal of Physics 37.5 (1996): 564-576. Print.
Mathews, Richards. “Hot Water Freezes Faster than Cold!” Physics FAO. 1992: 1-2. Physics Online. Web.
Tankin, Richard and Farhadieh Rouyentan. “Effects of Thermal Convection currents on Formation of Ice.” Int. J. Heat Mass Trans. 14.1 (1971): 953-961. Print.