Mpemba effect

Last updated
Temperature vs time plots, showing the Mpemba Effect. Mpemba Effect temperatures plot.png
Temperature vs time plots, showing the Mpemba Effect.

The Mpemba effect is the name given to the observation that a liquid (typically water) which is initially hot can freeze faster than the same liquid which begins cold, under otherwise similar conditions. There is disagreement about its theoretical basis and the parameters required to produce the effect. [1] [2]

Contents

The Mpemba effect is named after Tanzanian scientist Erasto Bartholomeo Mpemba, who described it in 1963 as a secondary school student. The initial discovery and observations of the effect originate in ancient times; Aristotle said that it was common knowledge. [3]

Definition

The phenomenon, when taken to mean "hot water freezes faster than cold", is difficult to reproduce or confirm because it is ill-defined. [4] Monwhea Jeng proposed a more precise wording: "There exists a set of initial parameters, and a pair of temperatures, such that given two bodies of water identical in these parameters, and differing only in initial uniform temperatures, the hot one will freeze sooner." [5]

Even with Jeng's definition, it is not clear whether "freezing" refers to the point at which water forms a visible surface layer of ice, the point at which the entire volume of water becomes a solid block of ice, or when the water reaches 0 °C (32 °F; 273 K). [4] Jeng's definition suggests simple ways in which the effect might be observed, such as if a warmer temperature melts the frost on a cooling surface, thereby increasing thermal conductivity between the cooling surface and the water container. [4] Alternatively, the Mpemba effect may not be evident in situations and under circumstances that at first seem to qualify. [4]

Observations

Historical context

Various effects of heat on the freezing of water were described by ancient scientists, including Aristotle: "The fact that the water has previously been warmed contributes to its freezing quickly: for so it cools sooner. Hence many people, when they want to cool water quickly, begin by putting it in the sun." [6] Aristotle's explanation involved antiperistasis : "...the supposed increase in the intensity of a quality as a result of being surrounded by its contrary quality."[ citation needed ]

Francis Bacon noted that "slightly tepid water freezes more easily than that which is utterly cold." [7] René Descartes wrote in his Discourse on the Method , relating the phenomenon to his vortex theory: "One can see by experience that water that has been kept on a fire for a long time freezes faster than other, the reason being that those of its particles that are least able to stop bending evaporate while the water is being heated." [8]

Scottish scientist Joseph Black investigated a special case of the phenomenon by comparing previously boiled with unboiled water; [9] he found that the previously boiled water froze more quickly. Evaporation was controlled for. He discussed the influence of stirring on the results of the experiment, noting that stirring the unboiled water led to it freezing at the same time as the previously boiled water, and also noted that stirring the very-cold unboiled water led to immediate freezing. Joseph Black then discussed Daniel Gabriel Fahrenheit's description of supercooling of water, arguing that the previously boiled water could not be as readily supercooled.[ citation needed ]

Mpemba's observation

The effect is named after Tanzanian scientist Erasto Mpemba. He described it in 1963 in Form 3 of Magamba Secondary School, Tanganyika; when freezing a hot ice cream mix in a cookery class, he noticed that it froze before a cold mix. He later became a student at Mkwawa Secondary (formerly High) School in Iringa. The headmaster invited Dr. Denis Osborne from the University College in Dar es Salaam to give a lecture on physics. After the lecture, Mpemba asked him, "If you take two similar containers with equal volumes of water, one at 35 °C (95 °F) and the other at 100 °C (212 °F), and put them into a freezer, the one that started at 100 °C (212 °F) freezes first. Why?" Mpemba was at first ridiculed by both his classmates and his teacher. After initial consternation, however, Osborne experimented on the issue back at his workplace and confirmed Mpemba's finding. They published the results together in 1969, while Mpemba was studying at the College of African Wildlife Management. [10]

Mpemba and Osborne described placing 70 ml (2.5 imp fl oz; 2.4 US fl oz) samples of water in 100 ml (3.5 imp fl oz; 3.4 US fl oz) beakers in the icebox of a domestic refrigerator on a sheet of polystyrene foam. They showed the time for freezing to start was longest with an initial temperature of 25 °C (77 °F) and that it was much less at around 90 °C (194 °F). They ruled out loss of liquid volume by evaporation and the effect of dissolved air as significant factors. In their setup, most heat loss was found to be from the liquid surface. [10]

Modern experimental work

David Auerbach has described an effect that he observed in samples in glass beakers placed into a liquid cooling bath. In all cases the water supercooled, reaching a temperature of typically −6 to −18 °C (21 to 0 °F; 267 to 255 K) before spontaneously freezing. Considerable random variation was observed in the time required for spontaneous freezing to start and in some cases this resulted in the water which started off hotter (partially) freezing first. [11]

In 2016, Burridge and Linden defined the criterion as the time to reach 0 °C (32 °F; 273 K), carried out experiments, and reviewed published work to date. They noted that the large difference originally claimed had not been replicated, and that studies showing a small effect could be influenced by variations in the positioning of thermometers: "We conclude, somewhat sadly, that there is no evidence to support meaningful observations of the Mpemba effect." [1]

In controlled experiments, the effect can entirely be explained by undercooling and the time of freezing was determined by what container was used. [12] Experimental results confirming the Mpemba effect have been criticized for being flawed, not accounting for dissolved solids and gasses, and other confounding factors. [13]

Philip Ball, a reviewer for Physics World wrote: "Even if the Mpemba effect is real — if hot water can sometimes freeze more quickly than cold — it is not clear whether the explanation would be trivial or illuminating." [4] Ball wrote that investigations of the phenomenon need to control a large number of initial parameters (including type and initial temperature of the water, dissolved gas and other impurities, and size, shape and material of the container, and temperature of the refrigerator) and need to settle on a particular method of establishing the time of freezing, all of which might affect the presence or absence of the Mpemba effect. The required vast multidimensional array of experiments might explain why the effect is not yet understood. [4]

New Scientist recommends starting the experiment with containers at 35 and 5 °C (95 and 41 °F; 308 and 278 K), respectively, to maximize the effect. [14]

Suggested explanations

While the actual occurrence of the Mpemba effect is disputed, [13] several theoretical explanations could explain its occurrence.

In 2017, two research groups independently and simultaneously found a theoretical Mpemba effect and also predicted a new "inverse" Mpemba effect in which heating a cooled, far-from-equilibrium system takes less time than another system that is initially closer to equilibrium. Zhiyue Lu and Oren Raz yielded a general criterion based on Markovian statistical mechanics, predicting the appearance of the inverse Mpemba effect in the Ising model and diffusion dynamics. [15] Antonio Lasanta and co-authors also predicted the direct and inverse Mpemba effects for a granular gas in a far-from-equilibrium initial state. [16] Lasanta's paper also suggested that a very generic mechanism leading to both Mpemba effects is due to a particle velocity distribution function that significantly deviates from the Maxwell–Boltzmann distribution. [16]

James Brownridge, a physicist at Binghamton University, has said that supercooling is involved. [17] [12] Several molecular dynamics simulations have also supported that changes in hydrogen bonding during supercooling take a major role in the process. [18] [19] In 2017, Yunwen Tao and co-authors suggested that the vast diversity and peculiar occurrence of different hydrogen bonds could contribute to the effect. They argued that the number of strong hydrogen bonds increases as temperature is elevated, and that the existence of the small strongly-bonded clusters facilitates in turn the nucleation of hexagonal ice when warm water is rapidly cooled down. The authors used vibrational spectroscopy and modelling with density functional theory-optimized water clusters. [2]

The following explanations have also been proposed:

Similar effects

Other phenomena in which large effects may be achieved faster than small effects are:

See also

Related Research Articles

<span class="mw-page-title-main">Cryogenics</span> Study of the production and behaviour of materials at very low temperatures

In physics, cryogenics is the production and behaviour of materials at very low temperatures.

<span class="mw-page-title-main">Frost</span> Coating or deposit of ice

Frost is a thin layer of ice on a solid surface, which forms from water vapor that deposits onto a freezing surface. Frost forms when the air contains more water vapor than it can normally hold at a specific temperature. The process is similar to the formation of dew, except it occurs below the freezing point of water typically without crossing through a liquid state.

<span class="mw-page-title-main">Ice</span> Frozen water: the solid state of water

Ice is water that is frozen into a solid state, typically forming at or below temperatures of 0 °C, 32 °F, or 273.15 K. It occurs naturally on Earth, on other planets, in Oort cloud objects, and as interstellar ice. As a naturally occurring crystalline inorganic solid with an ordered structure, ice is considered to be a mineral. Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaque bluish-white color.

<span class="mw-page-title-main">Melting point</span> Temperature at which a solid turns liquid

The melting point of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at a standard pressure such as 1 atmosphere or 100 kPa.

<span class="mw-page-title-main">Convection</span> Fluid flow that occurs due to heterogeneous fluid properties and body forces

Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity. When the cause of the convection is unspecified, convection due to the effects of thermal expansion and buoyancy can be assumed. Convection may also take place in soft solids or mixtures where particles can flow.

<span class="mw-page-title-main">Boiling</span> Rapid phase transition from liquid to gas or vapour

Boiling or ebullition is the rapid phase transition from liquid to gas or vapor; the reverse of boiling is condensation. Boiling occurs when a liquid is heated to its boiling point, so that the vapour pressure of the liquid is equal to the pressure exerted on the liquid by the surrounding atmosphere. Boiling and evaporation are the two main forms of liquid vapourization.

<span class="mw-page-title-main">Water vapor</span> Gaseous phase of water

Water vapor, water vapour or aqueous vapor is the gaseous phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Water vapor is transparent, like most constituents of the atmosphere. Under typical atmospheric conditions, water vapor is continuously generated by evaporation and removed by condensation. It is less dense than most of the other constituents of air and triggers convection currents that can lead to clouds and fog.

<span class="mw-page-title-main">Radiative cooling</span> Loss of heat by thermal radiation

In the study of heat transfer, radiative cooling is the process by which a body loses heat by thermal radiation. As Planck's law describes, every physical body spontaneously and continuously emits electromagnetic radiation.

<span class="mw-page-title-main">Heat transfer</span> Transport of thermal energy in physical systems

Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes. Engineers also consider the transfer of mass of differing chemical species, either cold or hot, to achieve heat transfer. While these mechanisms have distinct characteristics, they often occur simultaneously in the same system.

<span class="mw-page-title-main">Freezing</span> Phase transition of liquid to solid

Freezing is a phase transition where a liquid turns into a solid when its temperature is lowered below its freezing point. In accordance with the internationally established definition, freezing means the solidification phase change of a liquid or the liquid content of a substance, usually due to cooling.

<span class="mw-page-title-main">Supercooling</span> Lowering the temperature of a liquid below its freezing point without it becoming a solid

Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid below its freezing point without it becoming a solid. It is achieved in the absence of a seed crystal or nucleus around which a crystal structure can form. The supercooling of water can be achieved without any special techniques other than chemical demineralization, down to −48.3 °C (−54.9 °F). Supercooled water can occur naturally, for example in the atmosphere, animals or plants.

<span class="mw-page-title-main">Liquid nitrogen</span> Liquid state of nitrogen

Liquid nitrogen—LN2—is nitrogen in a liquid state at low temperature. Liquid nitrogen has a boiling point of about −196 °C (−321 °F; 77 K). It is produced industrially by fractional distillation of liquid air. It is a colorless, mobile liquid whose viscosity is about one tenth that of acetone (i.e. roughly one thirtieth that of room temperature water). Liquid nitrogen is widely used as a coolant.

In physics and chemistry, flash freezing is the process whereby objects are rapidly frozen. This is done by subjecting them to cryogenic temperatures, or it can be done through direct contact with liquid nitrogen at −196 °C (−320.8 °F). It is commonly used in the food industry.

<span class="mw-page-title-main">Cloud physics</span> Study of the physical processes in atmospheric clouds

Cloud physics is the study of the physical processes that lead to the formation, growth and precipitation of atmospheric clouds. These aerosols are found in the troposphere, stratosphere, and mesosphere, which collectively make up the greatest part of the homosphere. Clouds consist of microscopic droplets of liquid water, tiny crystals of ice, or both, along with microscopic particles of dust, smoke, or other matter, known as condensation nuclei. Cloud droplets initially form by the condensation of water vapor onto condensation nuclei when the supersaturation of air exceeds a critical value according to Köhler theory. Cloud condensation nuclei are necessary for cloud droplets formation because of the Kelvin effect, which describes the change in saturation vapor pressure due to a curved surface. At small radii, the amount of supersaturation needed for condensation to occur is so large, that it does not happen naturally. Raoult's law describes how the vapor pressure is dependent on the amount of solute in a solution. At high concentrations, when the cloud droplets are small, the supersaturation required is smaller than without the presence of a nucleus.

<span class="mw-page-title-main">Nucleation</span> Initial step in the phase transition or molecular self-assembly of a substance

In thermodynamics, nucleation is the first step in the formation of either a new thermodynamic phase or structure via self-assembly or self-organization within a substance or mixture. Nucleation is typically defined to be the process that determines how long an observer has to wait before the new phase or self-organized structure appears. For example, if a volume of water is cooled below 0 °C, it will tend to freeze into ice, but volumes of water cooled only a few degrees below 0 °C often stay completely free of ice for long periods (supercooling). At these conditions, nucleation of ice is either slow or does not occur at all. However, at lower temperatures nucleation is fast, and ice crystals appear after little or no delay.

The Wegener–Bergeron–Findeisen process, is a process of ice crystal growth that occurs in mixed phase clouds in regions where the ambient vapor pressure falls between the saturation vapor pressure over water and the lower saturation vapor pressure over ice. This is a subsaturated environment for liquid water but a supersaturated environment for ice resulting in rapid evaporation of liquid water and rapid ice crystal growth through vapor deposition. If the number density of ice is small compared to liquid water, the ice crystals can grow large enough to fall out of the cloud, melting into rain drops if lower level temperatures are warm enough.

<span class="mw-page-title-main">Erasto B. Mpemba</span> Tanzanian game warden and scientist (1950–2023)

Erasto Bartholomeo Mpemba (1950–2023) was a Tanzanian game warden who, as a schoolboy, discovered the eponymously named Mpemba effect, a paradoxical phenomenon in which hot water freezes faster than cold water under certain conditions; this effect had been observed previously by Aristotle, Francis Bacon, and René Descartes.

Cryofixation is a technique for fixation or stabilisation of biological materials as the first step in specimen preparation for the electron microscopy and cryo-electron microscopy. Typical specimens for cryofixation include small samples of plant or animal tissue, cell suspensions of microorganisms or cultured cells, suspensions of viruses or virus capsids and samples of purified macromolecules, especially proteins.

Giovanni Marliani was an Italian physicist, doctor, philosopher and astrologer who was born and lived during the Late Medieval period in northern Italy. Marliani specialised in many mathematical fields and lectured on the phenomenon of natural body heat. He was known for experiments attempting to empirically prove that hot water freezes faster than cold water.

Denis Gordon Osborne was a British diplomat and academic.

References

Notes

  1. 1 2 Burridge, Henry C.; Linden, Paul F. (2016). "Questioning the Mpemba effect: Hot water does not cool more quickly than cold". Scientific Reports. 6: 37665. Bibcode:2016NatSR...637665B. doi:10.1038/srep37665. PMC   5121640 . PMID   27883034.
  2. 1 2 3 Tao, Yunwen; Zou, Wenli; Jia, Junteng; Li, Wei; Cremer, Dieter (2017). "Different Ways of Hydrogen Bonding in Water - Why Does Warm Water Freeze Faster than Cold Water?". Journal of Chemical Theory and Computation. 13 (1): 55–76. doi:10.1021/acs.jctc.6b00735. PMID   27996255.
  3. ↑ Aristotle in E. W. Webster, Meteorologica I , Oxford: Oxford University Press, 1923, pp. 348b–349a.
  4. 1 2 3 4 5 6 Ball, Philip (29 March 2006). "Does hot water freeze first?". Physics World. pp. 19–26. Retrieved 19 March 2024.
  5. 1 2 3 4 Jeng, Monwhea (2006). "Hot water can freeze faster than cold?!?". American Journal of Physics. 74 (6): 514–522. arXiv: physics/0512262 . Bibcode:2006AmJPh..74..514J. doi:10.1119/1.2186331.
  6. ↑ Aristotle. "Meteorology". Book I, part 12, pp. 348b31–349a4. Retrieved 16 October 2020– via MIT.
  7. ↑ Bacon, Francis; Novum Organum, Lib. II, L. In the original Latin: "Aqua parum tepida facilius conglacietur quam omnino frigida."
  8. ↑ Descartes, René. "Les Météores" . Retrieved 19 March 2024.
  9. ↑ Black, Joseph (1 January 1775). "The Supposed Effect of Boiling upon Water, in Disposing It to Freeze More Readily, Ascertained by Experiments. By Joseph Black, M. D. Professor of Chemistry at Edinburgh, in a Letter to Sir John Pringle, Bart. P. R. S.". Philosophical Transactions of the Royal Society of London. 65: 124–128. Bibcode:1775RSPT...65..124B. doi:10.1098/rstl.1775.0014. S2CID   186214388.
  10. 1 2 Mpemba, Erasto B.; Osborne, Denis G. (1969). "Cool?". Physics Education. 4 (3): 172–175. Bibcode:1969PhyEd...4..172M. doi: 10.1088/0031-9120/4/3/312 . S2CID   250771765. republished as Mpemba, Erasto B.; Osborne, Denis G. (1979). "The Mpemba effect". Physics Education. 14 (7): 410–412. Bibcode:1979PhyEd..14..410M. doi:10.1088/0031-9120/14/7/312. S2CID   250736457.
  11. ↑ Auerbach, David (1995). "Supercooling and the Mpemba effect: when hot water freezes quicker than cold" (PDF). American Journal of Physics . 63 (10): 882–885. Bibcode:1995AmJPh..63..882A. doi:10.1119/1.18059.
  12. 1 2 Brownridge, James (2011). "When does hot water freeze faster then [sic] cold water? A search for the Mpemba effect". American Journal of Physics. 79 (78): 78–84. Bibcode:2011AmJPh..79...78B. doi:10.1119/1.3490015. Experimental results confirming the Mpemba effect have been criticized for being flawed, not accounting for dissolved solids and gasses, and other confounding factors.
  13. 1 2 Elton, Daniel C.; Spencer, Peter D. (2021). "Pathological Water Science – Four Examples and What They Have in Common". Water in Biomechanical and Related Systems. Biologically-Inspired Systems. Vol. 17. pp. 155–169. arXiv: 2010.07287 . doi:10.1007/978-3-030-67227-0_8. ISBN   978-3-030-67226-3. S2CID   222381017.
  14. ↑ How to Fossilize Your Hamster: And Other Amazing Experiments for the Armchair Scientist, ISBN   1-84668-044-1
  15. ↑ Lu, Zhiyue; Raz, Oren (16 May 2017). "Nonequilibrium thermodynamics of the Markovian Mpemba effect and its inverse". Proceedings of the National Academy of Sciences. 114 (20): 5083–5088. arXiv: 1609.05271 . Bibcode:2017PNAS..114.5083L. doi: 10.1073/pnas.1701264114 . ISSN   0027-8424. PMC   5441807 . PMID   28461467.
  16. 1 2 3 Lasanta, Antonio; Vega Reyes, Francisco; Prados, Antonio; Santos, Andrés (2017). "When the Hotter Cools More Quickly: Mpemba Effect in Granular Fluids". Physical Review Letters. 119 (14): 148001. arXiv: 1611.04948 . Bibcode:2017PhRvL.119n8001L. doi:10.1103/physrevlett.119.148001. hdl:10016/25838. PMID   29053323. S2CID   197471205.
  17. ↑ Chown, Marcus (24 March 2010). "Revealed: why hot water freezes faster than cold". New Scientist.
  18. 1 2 Jin, Jaehyeok; Goddard III, William A. (2015). "Mechanisms Underlying the Mpemba Effect in Water from Molecular Dynamics Simulations". Journal of Physical Chemistry C . 119 (5): 2622–2629. doi: 10.1021/jp511752n .
  19. ↑ Xi, Zhang; Huang, Yongli; Ma, Zengsheng; Zhou, Yichun; Zhou, Ji; Zheng, Weitao; Jiange, Qing; Sun, Chang Q. (2014). "Hydrogen-bond memory and water-skin supersolidity resolving the Mpemba paradox". Physical Chemistry Chemical Physics. 16 (42): 22995–23002. arXiv: 1310.6514 . Bibcode:2014PCCP...1622995Z. doi:10.1039/C4CP03669G. PMID   25253165. S2CID   119280061.
  20. ↑ Zimmerman, William B. (20 July 2021). "Towards a microbubble condenser: Dispersed microbubble mediation of additional heat transfer in aqueous solutions due to phase change dynamics in airlift vessels". Chemical Engineering Science. 238: 116618. Bibcode:2021ChEnS.23816618Z. doi: 10.1016/j.ces.2021.116618 .
  21. ↑ Whipple, Tom (13 April 2021). "Cracked, the cold case of why boiling water freezes faster". The Times.
  22. ↑ Kell, George S. (1969). "The freezing of hot and cold water". American Journal of Physics. 37 (5): 564–565. Bibcode:1969AmJPh..37..564K. doi: 10.1119/1.1975687 .
  23. ↑ CITV Prove It! Series 1 Programme 13 Archived 27 February 2012 at the Wayback Machine
  24. ↑ Katz, Jonathan (2009). "When hot water freezes before cold". American Journal of Physics. 77 (27): 27–29. arXiv: physics/0604224 . Bibcode:2009AmJPh..77...27K. doi:10.1119/1.2996187. S2CID   119356481.
  25. ↑ Tier, Ren (18 January 2022). "Mpemba Effect Demystified". doi:10.31224/osf.io/3ejnh.

Bibliography

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.