Pikabu

. Thanks to him, the freezing time of some products and materials is reduced, which contains water.

. Thanks to him, the freezing time of some products and materials is reduced, which contains water.

. Thanks to him, the freezing time of some products and materials is reduced, which contains water.

. Thanks to him, the freezing time of some products and materials is reduced, which contains water.

. Thanks to him, the freezing time of some products and materials is reduced, which contains water.

. Thanks to him, the freezing time of some products and materials is reduced, which contains water.
. Thanks to him, the freezing time of some products and materials is reduced, which contains water.
. Thanks to him, the freezing time of some products and materials is reduced, which contains water.

. Thanks to him, the freezing time of some products and materials is reduced, which contains water.
. Thanks to him, the freezing time of some products and materials is reduced, which contains water.
. Thanks to him, the freezing time of some products and materials is reduced, which contains water.
. Thanks to him, the freezing time of some products and materials is reduced, which contains water.

The aqueous shell of the Earth of the hydrosphere is about 71% of the earth's surface. In the bound state, water is both in the mortal crust of the lithosphere, and it is estimated that the reserves of such water (for a second !!) are approximately equal to the mass of free water in the hydrosphere. It was found that 1 km³ of granite during melting can be allocated 26 million tons of water. Women's more "reserves" V., prisonered in the in-depth weekly of the Earth - in the mantle. They hold that there are up to 13 billion km³ of water, that is, more than in the hydrosphere. But only 1 km³ of such a water is carried out on the surface of the volcanoes annually. The industry has played and plays the decisive role of the geological history of the Earth, in the formation of its thermal regime, climate and weather. It is far from everything is known about this interesting, long known, but in many ways mysterious, so abundant and such a deficient matter, about simple water.

. Thanks to him, the freezing time of some products and materials is reduced, which contains water.
. Thanks to him, the freezing time of some products and materials is reduced, which contains water.
. Thanks to him, the freezing time of some products and materials is reduced, which contains water.
Video on the topic

Cold weather is characteristic of most of our country. In addition to skiing at this time, some experiments with water can be carried out. For example, throw hot water into the air, thus making snow. This spectacular trick is based on an interesting fact known since the time of Aristotle.

It is described simply - hot water freezes faster than cold. This property received the name of the effect of the MPEMB. Tanzanian schoolboy discovered this phenomenon in 1963. So why does hot water freeze faster than cold?

Experiments with ice cream

Erasto Mpembea and other children in his school often made ice cream using a school freezing chamber. The process was as follows: they boiled milk and mixed it with sugar. After that, this mixture was placed in the freezer. And once MPemba hurried and put the resulting substance to cool in the heated state.

Video on the topic

It turned out that his ice cream turned out faster than a classmate. But there few people believed a schoolboy, and in 1969, MPemba, together with professor physicists published Article. on this occasion. This effect is not always observed, so if you try to repeat it at home, far from the fact that it will happen. Probably there is a few reasons .

Explanation versions of this effect

The detection of the effect of the MPEMBA did not allow with absolute accuracy to explain this phenomenon. To fully understand this process has not yet succeeded, but scientific disputes are conducted a lot. And there are several versions of explaining the effect of the MPEMBA.

The most frequently advanced hypothesis - hot water evaporates due to mass loss. As a result, the liquid freezes, losing less heat. However, there were cases when the effect of the MPEMBI was observed in closed containers, where evaporation was not.

Another assumption is that water develops convection streams and temperature gradients as it is cooling. A fast cooling glass with hot water will have large temperature differences and faster to remove heat from the surface. While a uniformly cooled glass of water has a smaller temperature difference. Also obtained less convection accelerating the process.

Video on the topic

There are also other theories. For example, according to one of them, the effect of dissolved gases in water on the freezing process. In 2013, a group of researchers from Singapore suggested Your version of the explanation of the effect of the MPEMBA. According to them, the solution lies in the unique properties of chemical ties in water.

As is known, the standard water molecule contains one oxygen atom and two hydrogen atoms. They are connected by covalent bonds. But when a compound of several molecules occurs, hydrogen atoms also form connections with oxygen atoms in other molecules. These hydrogen bonds give water some of its properties, such as a relatively high boiling point and a reduced density during freezing.

Researchers believe that during boiling water molecules spread, extending hydrogen bonds. But due to limited volume, covalent bonds in individual molecules are compressed, accumulating energy. If water freezes in this state, the links release the energy in the form of a "unlocked spring", cooling much faster.

Video on the topic

But not all experts agree with such an interpretation of the effect of the MPEMB. Someone accuses experts in the fact that their theory could predict a new property of water. However, it is not in the usual understanding. Chemist Richard Dawn from Stanford University considers at all that the rapid freezing of hot water mainly depends on evaporation.

Most likely, precisely because of this, the effect of MPEMBE occurs. Perhaps in the future scientists will be able to fully prove it or bring some amendments to the explanation.

MPEMBA effect or why hot water freeze faster than cold?

Mpemba effect (Paradox of MPEMBI) - a paradox that says that hot water at some conditions freezes faster than cold, although it must undergo the temperature of the cold water in the freezing process. This paradox is an experimental fact that contradicts the usual ideas, according to which, with the same conditions, the more heated body for cooling to a certain temperature requires more time than the less heated body for cooling to the same temperature.

This phenomenon was noticed at one time Aristotle, Francis Bacon and Rene Descart, but only in 1963, Tanzanian schoolboy Erassto Mpembea found that the hot mixture of ice cream freezes faster than cold.

As a student of Magambaba High School in Tanzania, Erasto Mpembea did practical work on the cook case. He needed to make homemade ice cream - boil milk, dissolve sugar in it, cool it to room temperature, and then put it in the fridge for freezing. Apparently, MPembba was not particularly a diligent student and priedered with the fulfillment of the first part of the task. Fearing that he would not have time for the end of the lesson, he put in the refrigerator still hot milk. To his surprise, it froze even earlier than the milk of his comrades cooked according to a given technology.

After that, MPEMBA experimented not only with milk, but also with ordinary water. In any case, already as a student of the Mkvava high school, he asked the question of Professor Dennis Osborne from the University College in Dar Es Salama (to read the students a lecture on physics in the university classroom: "If you take two identical containers with equal volumes of water So, in one of them, water has a temperature of 35 ° C, and in the other - 100 ° C, and put them in the freezer, then in the second water freezes faster. Why? " Osborne became interested in this issue and soon in 1969, together with Mpemba published the results of their experiments in the magazine "Physics Education". Since then, the effect found is called The effect of Mpemba .

Until now, no one knows how to explain this strange effect. Scientists have no single version, although there are many. It's all about the difference in the properties of hot and cold water, but it is not yet clear which properties play a role in this case: the difference in supercooling, evaporation, ice formation, convection or the effects of discharged gases on water at different temperatures.

The paradoxicality of the effect of the MPEMBA is that the time during which the body cools up to the ambient temperature should be in proportion to the difference in the temperatures of this body and the environment. This law was still established by Newton and since then many times confirmed in practice. In this effect, water with a temperature of 100 ° C cools to a temperature of 0 ° C faster than the same amount of water with a temperature of 35 ° C.

Nevertheless, it does not imply a paradox, since the effect of the MPEMBA can be found an explanation and within the framework of the famous physics. Here are a few explanations of the effect of MPEMBU:

Evaporation

Hot water faster evaporates from the container, thereby reducing its volume, and the smaller volume of water with the same temperature freezes faster. Heated to 100 with water loses 16% of its mass during cooling to 0 C.

Effect of evaporation - double effect. First, the mass of water is reduced, which is necessary for cooling. And secondly, the temperature is reduced due to the fact that the heat of evaporation of the transition from the water phase to the steam phase is reduced.

Temperature difference

Due to the fact that the temperature difference between hot water and cold air is more - therefore heat exchange in this case there is more intense and hot water is cooled faster.

Supercooling

When the water is cooled below 0 C It does not always freeze. Under some conditions, it can undergo hypothermia, continuing to remain liquid at temperatures below the temperature of the freezing point. In some cases, water can remain liquid even at a temperature of -20 C.

The reason for this effect is that in order to begin to form the first ice crystals need crystal formation centers. If they are not in liquid water, then the supercooling will continue until the temperature decreases so much that the crystals will begin to form spontaneously. When they begin to form in a supercooled fluid, they will begin to grow faster, forming a Lorth Shuhuh, which freezing will form ice.

Hot water is most susceptible to supercooling since its heating eliminates dissolved gases and bubbles, which in turn can serve as centers for the formation of ice crystals.

Why does the supercooling cause hot water to stick faster? In the case of cold water, which is not overcooked by the following. In this case, the thin layer of ice will be formed on the surface of the vessel. This layer of ice will act as an insulator between water and cold air and will prevent further evaporation. The rate of formation of ice crystals in this case will be less. In the case of hot water, undergoing supercooling, supercooled water does not have a protective surface layer of ice. Therefore, it loses heat much faster through open top.

When the process of hypothermia ends and water freezes, much more heat is lost and therefore more ice is formed.

Many researchers of this effect consider supercooling to the main factor in the case of the MPEMB effect.

Convection

Cold water begins to freeze from above, thereby worsening the processes of heat emission and convection, and therefore heat loss, while hot water begins to freeze from below.

This effect of water density anomaly is explained. Water has a maximum density at 4 C. If cooling water to 4 s and put it at a lower temperature, the surface layer of water will freeze faster. Because this water is less dense than water at a temperature of 4 s, it will remain on the surface, forming a thin cold layer. Under these conditions, the thin layer of ice will be formed on the surface of the water for a short time, but this layer of ice will be an insulator that protects the lower layers of water, which will remain at a temperature of 4 C. Therefore, the further cooling process will be slower.

In the case of hot water, the situation is completely different. The surface layer of water will be cooled faster due to evaporation and greater temperature difference. In addition, cold water layers are more dense than hot water layers, therefore the cold water layer will fall down, lifting a layer of warm water to the surface. Such water circulation provides a rapid drop in temperature.

But why does this process do not reach the equilibrium point? To explain the effect of the MPEMBA from this point of view of convection, it would be necessary to make that cold and hot water layers are separated and the convection process itself continues after the average water temperature drops below 4 C.

However, there are no experimental data that would confirm this hypothesis that cold and hot water layers are divided during convection.

Dissolved gases

Water always contains gases dissolved in it - oxygen and carbon dioxide. These gases have the ability to reduce water freezing point. When the water is heated, these gases are released from water, since their solubility in water at high temperatures below. Therefore, when hot water is cooled, there are always fewer dissolved gases in it than in non-heated cold water. Therefore, the freezing point of heated water is higher and it freezes faster. This factor is sometimes considered as the main thing when explaining the effect of the MPEMB, although there are no experimental data confirming this fact.

Thermal conductivity

This mechanism can play a significant role when water is placed in the freezer of the refrigeration chamber in small containers. Under these conditions, it is noted that the hot water container is shifted by a freezer ice from a freezer, thereby improving thermal contact with the freezer wall and thermal conductivity. As a result, the heat is removed from the container with hot water faster than from cold. In turn, the container with cold water does not shive below the snow.

All these (as well as others) conditions were studied in many experiments, but a unambiguous answer to the question - which of them provide one hundred percent reproduction of the MPEMBE effect - and was not received.

For example, in 1995, the German physicist David Auerbach studied the effect of water hypothermia on this effect. He found that hot water, reaching a supercooled state, freezes at a higher temperature than the cold, which means faster the latter. But cold water reaches a supercooled state faster than hot, thereby compensating for the previous lag.

In addition, the results of Auerbakh contradicted the data obtained earlier that hot water is capable of achieving greater overcooling due to a smaller number of crystallization centers. When the water is heated from it, the gases dissolved in it are removed, and during its boiling, some salts dissolved in it are precipitated.

You can say so far only one thing is possible - the reproduction of this effect significantly depends on the conditions in which the experiment is carried out. It is precisely because it is not always reproduced.

O. V. Mosin

Literary Sources :

"Hot Water Freezes Faster Than Cold Water. Why Does It Do SO?", Jearl Walker in The Amateur Scientist, Scientific American, Vol. 237, No. 3, pp 246-257; September, 1977.

"The Freezing Of Hot and Cold Water", G .S. Kell in American Journal of Physics, Vol. 37, No. 5, pp 564-565; May, 1969.

"SuperCooling and The Mpemba Effect", David Auerbach, In American Journal of Physics, Vol. 63, No. 10, pp 882-885; Oct, 1995.

"The MPemba Effect: The Freezing Times Of Hot and Cold Water", Charles A. Knight, in American Journal of Physics, Vol. 64, No. 5, p 524; May, 1996.

"The Final Word", New Scientist, 2nd Decept 1995.

Hi, Habr! I present to your attention the translation of the article "Why Hot Water Freezes Faster Than Cold-Physicists Solve The MoMba Effect".

From the translator: All his life suffered a question, and here you were explained again.

Why boiling water freezes the fastest of cold water, tells the video:

Summary: due to the presence of hydrogen bonds in water molecules, a change in the configuration of covalent bonds of O-H is changed, with the supplies of additional energy in them, released during cooling and working as an additional heating that interferes with freezing. In hot water, hydrogen bonds are stretched, covalent not tense, energy reserve is low-cooling and freezing is faster. There is some characteristic time. Tau. necessary to form hydrogen bonds if the cooling process will go slowly, the effect of the MPEMB will disappear. If the cooling process is relatively fast (up to tens of minutes), the effect is expressed. It should probably be some critical temperature, starting with which the effect appears, but this is not reflected in the article.

An image from the original article, looking at which the reader should see with all the clarity that energy is in covalent bonds, which can then be released in the form of additional heat, preventing cold water.

History of the question

Aristotle first noted that hot water freezes faster than cold, but chemists always refused to explain this paradox. Up to this day.

Water is one of the most ordinary substances on Earth, but at the same time one of the most mysterious. For example, as in most liquids, its density grows during cooling. However, in contrast to the rest, its density reaches a maximum at a temperature of 4c, and then begins to decrease up to the crystallization temperature.

In solid phase, water has a slightly smaller density, which is why ice floats on the surface of the water. This is one of the reasons for the existence of life on Earth - if the ice was denser of water, then during freezing, he would drop the bottom of the lakes and oceans, which would make it impossible many types of chemical processes that make life possible.

So, there is a strange membaby effect, named after Tanzanian student, who found that the hot mixture for ice cream freezes faster than the cold in the freezer of school cuisine somewhere in the early 1960s. (In fact, this effect was noted by many researchers in history, starting with Aristotle, Francis Bacon and Rene of Descartes).

Mpemba effect It is that hot water freezes faster cold. This effect was measured in a variety of cases with various explanations outlined below. One of the ideas is that hot vessels have the best thermal contact with the freezer and remove heat more efficiently. The other is that warm water evaporates faster, and since this process is an endothermic (comes with the absorption of heat) - then it accelerates freezing.

None of these explanations looks plausible, so there was still no real explanation.

A new explanation of the effect (now it is certainly correct)

Today, Chang from Nangang Technology University of Singapore and several of his colleagues provided such. These guys argue that the effect of MPEMS is the result of the unique properties of various types of communication, holding water molecules together.

So what is the same in these connections? Each water molecule consists of a relatively large oxygen atom connected to two low hydrogen atoms with a conventional covalent bond. But if you place a few water molecules, the hydrogen bonds will also begin to play an important role. This is due to the fact that hydrogen atoms of one molecule are located near the oxygen of another molecule, and interact with it. Hydrogen bonds are much weaker than covalent (approx. Per. ~ 10 times), but stronger than van der Wales forces that uses a heckon for sticking to vertical walls.

Chemists have long been aware of the importance of these ties. For example, the boiling point of water is much higher than that of other liquids with similar molecules, due to the fact that hydrogen bonds hold the molecules together.

But in recent years, chemists are increasingly interested in other roles that can play hydrogen bonds. For example, water molecules in thin capillaries form long chains held by hydrogen bonds. This is very important for plants that have evaporation of water through the leaves membranes effectively drags the chain of water molecules from roots up.

Now, with co-authors, they argue that hydrogen bonds also explain the effect of the MPEMBE. Their key idea is that hydrogen bonds lead to a more dense contact of water molecules, and when this occurs, the natural repulsion between molecules leads to the compression of covalent bonds and the accumulation of energy in them.

However, when the liquid is heated, the distance between molecules increases, and hydrogen bonds are stretched. It also allows you to increase the length of covalent bonds and thus draw back energy accumulated in them. An important element of the theory is the fact that a process in which covalent bonds give energy accumulated in them- equivalent to cooling!

In fact, this effect enhances the usual cooling process. Thus, hot water should be cooled faster than cold, the authors argue. And this is exactly what we observe in the effect of the scam.

Why is a new explanation better than previous?

These guys calculated the amount of additional cooling, and showed that it exactly corresponds to the observed difference in the experiments On measuring the difference in hot and cold water cooling rates. Voila! This is an interesting look at the complex and mysterious properties of water that still make chemists do not sleep at night. Despite the fact that the idea of ​​zi and co-authors is convincing, it may be another mistake of theorists, which other physicists will have to refute. This is because theories lack predictive strength (at least - in the original article).

Zi and co-authors need to take advantage of their theory for the prediction of new properties of water, which are not derived from ordinary reasoning. For example, if covalent bonds are shortened, this should lead to some new measured properties of water, which would not have to manifest themselves otherwise. The opening and measurement of such properties would be the last cherry on the cake, which lacks the theory in its current form.

So, despite the fact that the guys may have explained the effect of MPEMB, well, they need a bit podnaping to convince others.

Be that as it may, they have an interesting theory.

P.S. In 2016, one of the co-authors - Chang Sun (Chang Q. SUN) together with Yi Sun (Yi Sun) published a more complete statement of the proposed theory, with the consideration of surface effects, convection, diffusion, radiation and other factors- and seeming good agreement with Experiment (Springer).

Literature

Literature

Ref: arxiv.org/abs/1310.6514: O: H-O Bond Anomalous Relaxation Resolving MPEMBA Paradox

Original: https://medium.com/the-physics-Arxiv-blog/why-hot-water-freezes-faster-than-cold-physicists-solve-the-mpemba-effect-d8a2f611e853.

Why "explained again" - and because it was already:

  1. https://doi.org/10.1103/physrevx.9.021060.
  2. Non-equilibrium Markov processes: can follow some unusual trajectories strongly faster than equilibrium, therefore rapid cooling boiling water falls on such a "accelerated" trajectory, and overtakes cold water (which cools in more equilibrium conditions).
  3. https://pubs.acs.org/doi/abs/10.1021/acs.jctc.6b00735
  4. Clusters (also due to hydrogen bonds) that interfere with crystallization. In boiling water there are no such clusters, and during its freezing, they do not have time to form, and in water, for a long time of the former cold outside the freezer, and they do not give it to freeze it normally.
  5. https://aapt.scitation.org/doi/10/1119/1.18059
  6. The supercooling below the freezing point, which in originally hot water is weaker, because the mess is greater, and it is not enough to organize in the freezer in the freezing process. (But here it is clearly a problem - in experiments, the entire cooling curve of hot water is steeper cold, and not only the freezing process, and this "disorder" on thermal conductivity and cooling if it should be influenced by slowing down cooling, and acceleration).

https://www.sciencedirect.com/science/article/pii/s0140700716302869.

Water evaporates from the surface, and takes heat. Hot water is faster (only it is not clear why, after aligning the temperatures, the water that was hot- continues to evaporate more actively, although it is already colder than that water that was originally cold).

https://www.sciencedirect.com/science/article/pii/s0017931014008072.

Video.

All wine convection, which improves heat exchange (convection flows are spinning over inertia and after the temperature of the glasses leveled and for a long time after that).

American Journal of Physics 77, 27 (2009); https://doi.org/10/1119/1.2996187.

In all, the dissolution of impurities (gases?). In boiling water impurities less, freezing faster.

Conclusion

The phenomenon of hot water frozen with a greater speed than cold, known in science as the effect of scam. Over this paradoxical phenomenon, such great minds as Aristotle, Francis Bacon and René Descartes, were reflected above, but for the Millennium, no one was able to offer a reasonable explanation for this phenomenon.

Only in 1963, a schoolboy from the Republic of Tanganyik, Erasto Mpembe, noticed this effect on the example of ice cream, but none of adults gave him an explanation. Nevertheless, physicists and chemists seriously thought about so simple, but so incomprehensible phenomenon.

Since then, different versions have expressed, one of which sounded as follows: some of the hot water is first just evaporated, and then, when it remains less than its quantity, water freezes faster. This version, by virtue of its simplicity, became the most popular, but scientists did not fully satisfy. Nowadays, a team of researchers from University of Technological University of Nanyang in Singapore (Nanyang Technological University), headed by Chemist Si Zhanom (XI Zhang) stated that they managed to allow a century-old riddle about why warm water freezes faster than cold. As Chinese specialists found out, the secret lies in the amount of energy stored in hydrogen bonds between water molecules.

As is known, water molecules consist of one oxygen atom and two hydrogen atoms held together with covalent bonds, which looks like an exchange of electrons at the particle level. Another famous fact is that hydrogen atoms are attracted to oxygen atoms from neighboring molecules - at the same time hydrogen bonds are formed.

MPEMBA effect is interesting, so it continues to study. Studies are conducted immediately in several directions. Scientists will definitely find out the cause of the inexplicable paradox and allow people to expand the possibilities of using it.

At the same time, the water molecules are generally repelled from each other. Scientists from Singapore noticed: the warmer water, the larger the distance between the fluid molecules due to the increase in the repellent forces. As a result, hydrogen bonds are stretched, and therefore reserves greater energy. This energy is released when the water is cooled - the molecules come closer to each other. And the return of energy, as you know, and means cooling.

As chemists write in their article, which can be found on the website of Preprints of Arxiv.org, in hot water, hydrogen bonds are tensioning stronger than in the cold. Thus, it turns out that in hydrogen bonds of hot water is stored more energy, which means it is released more during cooling to minus temperatures. For this reason, the frozen is faster.

To date, scientists have solved this mystery only theoretically. When they present convincing evidence of their version, the question of why hot water is frozen faster than cold, it will be possible to be closed. Also on the topic: Scientists of 100 years old could not understand why the teapots American physicist solved the paradox of Cat Schrödinger Physics solved a long-term riddle of the behavior of electron physics proved that the magnetic field changes the heat transfer of the material in diamond saw the quantum effect of Zenon Why does hot water freeze faster than cold? This is true, although it sounds incredible, because in the process of freezing, the warm water must pass the temperature of the cold water. Meanwhile, this effectshire is used. For example, rollers and slides in winter poured hot, not cold water. Specialists advise motorists to fill in winter in the washer tank cold, and not hot water. Paradox is known in the world as the "MPEMB effect". This phenomenon mentioned Aristotle, Francis Bacon and René Descartes, but only in 1963, professors of physics were paid to him and tried to explore. It all started with the fact that Tanzanian schoolboy Erasto Mpembba noted that sweetened milk, which he used to prepare ice cream, freezes faster if it was pre-heated and put forward the assumption that hot water freezes faster than cold. He appealed for clarification to the physics teacher, but he only laughed at the student, saying the following: "This is not a world physics, but a physician of MPEMS." Fortunately, Dennis Osborne was once at school, Professor of Physics from the University of Dar Es Salama. And Mpemba appealed to him with the same question. The professor was set up less skeptical, said he could not judge what he had never seen, and upon returning home asked employees to conduct relevant experiments. Looks like they confirmed the words of the boy. In any case, in 1969, Osborne spoke about working with Mpembo in the magazine "Eng. Physics. Education.

" In the same year, George Kell from the Canadian National Research Council published an article with a description of the phenomenon in "Eng.

  • American.
  • Journal
  • Of.
  • Physics.

"

There are several options for explaining this paradox:

Hot water evaporates faster, thus reducing its volume, and a smaller volume of water with the same temperature freezes faster. In hermetic containers, cold water should freeze faster.

The presence of snow lining. The hot water container is shoaling under itself, it is therefore thermal contact with a cooling surface. Cold water does not shine under it. In the absence of snow lining, the cold water container must freeze faster.

Cold water begins to freeze from above, thereby worsening the processes of heat emission and convection, and therefore heat loss, while hot water begins to freeze from below. With additional mechanical stirring of water in containers, cold water should freeze faster.

The presence of crystallization centers in cooled water - substances dissolved in it. With a small number of such centers in cold water, the transformation of water into the ice is difficult and possibly its supercooling when it remains in a liquid state, having a minus temperature.

Recently, another explanation was published. Dr. Jonathan Katz (Jonathan Katz) from Washington University investigated this phenomenon and came to the conclusion that an important role in it is played by dissolved substances in water, which are deposited when heated. Under the dissolved substances, Dr. Katz also implies calcium and magnesium bicarbonates, which are contained in rigid water. When the water is heated, these substances are deposited, water becomes soft. Water that has never heated, contains these impurities, it is "tough." As it freezes and the formation of ice crystals, the concentration of impurities in water increases 50 times. Because of this, the water freezing point is reduced.

This explanation does not seem convincing, because No need to forget that the effect was found in experiments with ice cream, and not with rigid water. Most likely the cause of the phenomenon of thermophysical, and not chemical.

While the unequivocal explanation of the paradox of the MPEMB is not received. I must say that some scientists do not consider this paradox worthy of attention. However, it is very interesting that a simple schoolboy has achieved recognition of the physical effect and gained popularity due to its curiosity and perseverance.

Added in February 2014

The note was written in 2011. Since then, new studies of the effect of MPEMBI and new attempts to explain it have appeared. So, in 2012, the Royal Chemical Society of Great Britain announced an international competition for the solution of scientific secrets "MPEMBI effect" with a prize fund of 1000 pounds. Deadline was installed on July 30, 2012. Nikola Beregovik from the laboratory of the University of Zagreb became the winner. He published his work in which he analyzed previous attempts to explain this phenomenon and concluded that they were not convincing. The model proposed by them is based on the fundamental properties of water. Those who wish can find a job on the link http://www.rsc.org/mpemba-competition/mpemba-winner.asp

Research on this was not completed. In 2013, Physics from Singapore theoretically proved the cause of the Empube effect. The work can be found by reference http://arxiv.org/abs/1310.6514.

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Why the sky is blue? Can it freeze? .

The answer is simple - yes, maybe

. Moreover, boiling water will freeze faster than cold. What faster: boiling or cold H2O?

Scientists have a lot of experiments and proved that the first crystallizes boiling water.

If in the freezer simultaneously put two capacities of the same volume and shape with boiling water and simple water, then

The first will turn into ice precisely boiling water

Although, if you follow logic, it must first cool down, and then crystallize. But it is not.

It is worth noting that such an effect was observed by people for a long time.

  1. foto14818-3. The Aristotle pointed to this in his records, was interested in the phenomenon of R. Dekart. However, a carefully studying this issue at that time, few people did, it was not particularly interested in scientists.
  2. An inquisitive Tanzanskaya schoolboy gave a solid studies of the topic, who found in everyday life that the warm-up liquid, whether milk or water, crystallizes faster.
  3. In 1969, an experiment was conducted by Professor D.Sboron, who proved the approval of the young man. From that moment on, the phenomenon received the name of his "opener", and became known as the effect of the MPEMB.

Why?

It was not yet fully explained and to understand the phenomenon yet, but disputes among scientists under this topic are sufficient. However, some hypotheses still take place: .

When boiling there is evaporation and a decrease in water volume, which means that the crystallization process is activated, i.e. accelerates.

The gases dissolved in water are evaporated, therefore the density of water in a boiling state is higher than that of the water temperature. It is known that the high percentage of density contributes to the cooling rate.

The freezing of hot water begins to go below, and the upper surface layer remains free. This allows the processes of convection and radiation of heat not to stop and not slow down. In the normal state, the upper surface is preserved at the usual state, which slows down the heat yield.

There are other versions that explain the paradoxical phenomenon. One of them was put forward by scientists from Washington by D. Katts. In his opinion, in the boiling process, water from the "tough" turns into a "soft". Part of substances, such as magnesium and calcium bicarbonate, are sedied and do not interfere with crystallization. therefore

The freezing process of boiling water goes at times faster than usual

How does this paradox applied in real life?

The existence of a paradoxical phenomenon saves time to prepare game sites and sports in the winter season.

Used incomprehensible phenomenon and industrial production

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