Hot water freezes faster than cold water. Video: which water freezes faster - hot or cold
Water- a fairly simple substance from a chemical point of view, however, it has a number of unusual properties that never cease to amaze scientists. Below are some facts that few people know about.
1. Which water freezes faster - cold or hot?
Take two containers of water: pour hot water into one and cold water into the other, and place them in the freezer. Hot water will freeze faster than cold water, although logically, cold water should have turned into ice first: after all, hot water must first cool down to cold temperature, and then turn into ice, while cold water does not need to cool down. Why is this happening?
In 1963, a Tanzanian student named Erasto B. Mpemba, while freezing a prepared ice cream mixture, noticed that the hot mixture solidified in freezer faster than cold. When the young man shared his discovery with a physics teacher, he only laughed at him. Fortunately, the student was persistent and persuaded the teacher to conduct an experiment, which confirmed his discovery: in certain conditions hot water really freezes faster than cold.
Now this phenomenon of hot water freezing faster than cold water is called " Mpemba effect". True, long before it unique property water was noted by Aristotle, Francis Bacon and Rene Descartes.
Scientists do not fully understand the nature of this phenomenon, explaining it either by the difference in hypothermia, evaporation, ice formation, convection, or the effect of liquefied gases on hot and cold water.
2. She is able to freeze instantly
Everyone knows that water always turns to ice when cooled to 0 °C ... except in some cases! Such a case is, for example, supercooling, which is the property of very pure water to remain liquid even when cooled to a temperature below freezing. This phenomenon becomes possible due to the fact that the environment does not contain crystallization centers or nuclei that could provoke the formation of ice crystals. And so water remains in liquid form, even when cooled to temperatures below zero degrees Celsius.
crystallization process can be provoked, for example, by gas bubbles, impurities (contaminants), uneven surface containers. Without them, the water will remain in liquid state. When the crystallization process starts, you can watch how the super-cooled water instantly turns into ice.
Note that "superheated" water also remains liquid even when heated above its boiling point.
3. 19 states of water
Without hesitation, name how many different states does the water have? If you answered three: solid, liquid, gaseous, then you are mistaken. Scientists distinguish at least 5 different states of water in liquid form and 14 states in frozen form.
Remember the conversation about super-chilled water? So, no matter what you do, at -38 ° C, even the purest super-cooled water will suddenly turn into ice. What happens as the temperature drops further? At -120°C, something strange begins to happen to water: it becomes super-viscous or viscous, like molasses, and at temperatures below -135°C, it turns into "glassy" or "glassy" water - a solid that lacks crystalline structure.
4. Water surprises physicists
At the molecular level, water is even more surprising. In 1995, a neutron scattering experiment conducted by scientists gave an unexpected result: physicists found that neutrons directed at water molecules “see” 25% fewer hydrogen protons than expected.
It turned out that at the speed of one attosecond (10 -18 seconds) an unusual quantum effect takes place, and chemical formula water instead H2O, becomes H1.5O!
5. Water memory
Alternative to official medicine homeopathy states that a dilute solution medicinal product can provide healing effect on the organism, even if the dilution factor is so great that there is nothing left in the solution but water molecules. Proponents of homeopathy explain this paradox with a concept called " water memory”, according to which water at the molecular level has a “memory” of a substance once dissolved in it and retains the properties of a solution of the initial concentration after not a single ingredient molecule remains in it.
An international team of scientists led by Professor Madeleine Ennis of Queen's University of Belfast, who criticized the principles of homeopathy, conducted an experiment in 2002 to disprove the concept once and for all. The result was the opposite. After that, scientists said that they managed to prove the reality of the effect " water memory". However, experiments conducted under the supervision of independent experts did not bring results. Disputes about the existence of the phenomenon " water memory» continue.
Water has many other unusual properties that we have not covered in this article. For example, the density of water varies with temperature (the density of ice is less than that of water); water has quite big size surface tension; in a liquid state, water is a complex and dynamically changing network of water clusters, and it is the behavior of clusters that affects the structure of water, etc.
About these and many other unexpected features water can be read in the article Anomalous properties of water”, the author of which is Martin Chaplin, professor at the University of London.
21.11.2017 11.10.2018 Alexander Firtsev
« Which water freezes faster cold or hot?”- try asking your friends a question, most likely most of them will answer that cold water freezes faster - and make a mistake.
In fact, if you simultaneously put two vessels of the same shape and volume in the freezer, one of which will contain cold water and the other hot, then hot water will freeze faster.
Such a statement may seem absurd and unreasonable. Logically, hot water must first cool down to cold temperature, and cold water should already turn into ice at this time.
So why does hot water overtake cold water on its way to freezing? Let's try to figure it out.
History of observations and research
People have observed the paradoxical effect since ancient times, but no one attached much importance to it. So inconsistencies in the rate of freezing of cold and hot water were noted in their notes by Arestotel, as well as by Rene Descartes and Francis Bacon. An unusual phenomenon often manifested itself in everyday life.
For a long time, the phenomenon was not studied in any way and did not arouse much interest among scientists.
The study of the unusual effect began in 1963, when an inquisitive student from Tanzania, Erasto Mpemba, noticed that hot milk for ice cream freezes faster than cold milk. Hoping to get an explanation of the reasons for the unusual effect, the young man asked his physics teacher at school. However, the teacher only laughed at him.
Later, Mpemba repeated the experiment, but in his experiment he no longer used milk, but water, and the paradoxical effect was repeated again.
Six years later, in 1969, Mpemba asked this question to physics professor Dennis Osborne, who came to his school. The professor was interested in the observation of the young man, as a result, an experiment was conducted that confirmed the presence of the effect, but the reasons for this phenomenon were not established.
Since then, the phenomenon has been called Mpemba effect.
Throughout the history of scientific observations, many hypotheses have been put forward about the causes of the phenomenon.
So in 2012, the British Royal Society of Chemistry would announce a competition of hypotheses to explain the Mpemba effect. Scientists from all over the world participated in the competition, in total 22,000 were registered scientific works. Despite such an impressive number of articles, none of them clarified the Mpemba paradox.
The most common version was according to which, hot water freezes faster, since it simply evaporates faster, its volume becomes smaller, and as the volume decreases, its cooling rate increases. The most common version was eventually refuted, since an experiment was conducted in which evaporation was excluded, but the effect was nevertheless confirmed.
Other scientists believed that the reason for the Mpemba effect is the evaporation of gases dissolved in water. In their opinion, during the heating process, gases dissolved in water evaporate, due to which it acquires a higher density than cold water. As is known, an increase in density leads to a change physical properties water (increase in thermal conductivity), and hence increase the cooling rate.
In addition, a number of hypotheses have been put forward that describe the rate of water circulation as a function of temperature. In many studies, an attempt was made to establish the relationship between the material of the containers in which the liquid was located. Many theories seemed very plausible, but they could not be scientifically confirmed due to a lack of initial data, contradictions in other experiments, or due to the fact that the identified factors were simply not comparable with the rate of water cooling. Some scientists in their works questioned the existence of the effect.
In 2013, researchers at the Nanyang Technological University in Singapore claimed to have solved the mystery of the Mpemba effect. According to their study, the reason for the phenomenon lies in the fact that the amount of energy stored in hydrogen bonds between cold and hot water molecules differs significantly.
Computer simulation methods have shown the following results: the higher the temperature of the water, the greater the distance between the molecules due to the fact that the repulsive forces increase. And consequently, the hydrogen bonds of molecules are stretched, storing large quantity energy. When cooled, the molecules begin to approach each other, releasing energy from hydrogen bonds. In this case, the release of energy is accompanied by a decrease in temperature.
In October 2017, Spanish physicists in the course of another study found that big role in the formation of the effect, it is precisely the removal of the substance from equilibrium (strong heating before strong cooling) that plays. They determined the conditions under which the likelihood of the effect is maximum. In addition, scientists from Spain have confirmed the existence of the reverse Mpemba effect. They found that when heated, a colder sample can reach high temperature faster than warm.
Despite exhaustive information and numerous experiments, scientists intend to continue studying the effect.
Mpemba effect in real life
Have you ever wondered why winter time the skating rink is flooded hot water and not cold? As you already understood, they do this because a skating rink filled with hot water will freeze faster than if it were filled with cold water. For the same reason, slides in winter ice towns are poured with hot water.
Thus, knowledge of the existence of the phenomenon allows people to save time in preparing sites for winter views sports.
In addition, the Mpemba effect is sometimes used in industry - to reduce the freezing time of products, substances and materials containing water.
In the good old formula H 2 O, it would seem that there are no secrets. But in fact, water - the source of life and the most famous liquid in the world - is fraught with many mysteries that sometimes even scientists cannot solve.
Here are the 5 most interesting facts about water:
1. Hot water freezes faster than cold water
Take two containers of water: pour hot water into one and cold water into the other, and place them in the freezer. Hot water will freeze faster than cold water, although logically, cold water should have turned into ice first: after all, hot water must first cool down to cold temperature, and then turn into ice, while cold water does not need to cool down. Why is this happening?
In 1963, Erasto B. Mpemba, high school student high school in Tanzania, when freezing a prepared ice cream mix, I noticed that the hot mix hardens faster in the freezer than the cold one. When the young man shared his discovery with a physics teacher, he only laughed at him. Fortunately, the student was persistent and convinced the teacher to conduct an experiment, which confirmed his discovery: under certain conditions, hot water really freezes faster than cold water.
Now this phenomenon of hot water freezing faster than cold water is called the Mpemba effect. True, long before him, this unique property of water was noted by Aristotle, Francis Bacon and Rene Descartes.
Scientists do not fully understand the nature of this phenomenon, explaining it either by the difference in hypothermia, evaporation, ice formation, convection, or the effect of liquefied gases on hot and cold water.
Note from Х.RU to the topic "Hot water freezes faster than cold water".
Since cooling issues are closer to us, refrigeration specialists, we will allow ourselves to go deeper into the essence of this problem and give two opinions about the nature of such a mysterious phenomenon.
1. A University of Washington scientist has offered an explanation for a mysterious phenomenon known since the time of Aristotle: why hot water freezes faster than cold water.
The phenomenon, called the Mpemba effect, is widely used in practice. For example, experts advise motorists to pour cold rather than hot water into the washer reservoir in winter. But what underlies this phenomenon? for a long time remained unknown.
Dr. Jonathan Katz of the University of Washington investigated this phenomenon and concluded that substances dissolved in water play an important role in it, which precipitate when heated, reports EurekAlert.
Under dissolved substances dr Katz refers to the calcium and magnesium bicarbonates found in hard water. When the water is heated, these substances precipitate, forming scale on the walls of the kettle. Water that has never been heated contains these impurities. As it freezes and ice crystals form, the concentration of impurities in water increases 50 times. This lowers the freezing point of water. "And now the water has to cool down in order to freeze," explains Dr. Katz.
There is a second reason that prevents freezing of unheated water. Lowering the freezing point of water reduces the temperature difference between the solid and liquid phases. "Because the rate at which water loses heat depends on this temperature difference, water that has not been heated is less likely to cool down," says Dr. Katz.
According to the scientist, his theory can be tested experimentally, because. the Mpemba effect becomes more pronounced for harder water.
2. Oxygen plus hydrogen plus cold creates ice. At first glance, this transparent substance seems very simple. In fact, the ice is fraught with many mysteries. The ice created by the African Erasto Mpemba did not think about glory. The days were hot. He wanted fruit ice. He took a carton of juice and put it in the freezer. He did this more than once and therefore noticed that the juice freezes especially quickly, if you hold it in the sun before that - just heat it up! This is strange, thought the Tanzanian schoolboy, who acted contrary to worldly wisdom. Is it possible that in order for the liquid to turn into ice faster, it must first ... be heated? The young man was so surprised that he shared his guess with the teacher. He reported this curiosity in the press.
This story happened back in the 1960s. Now the "Mpemba effect" is well known to scientists. But for a long time this seemingly simple phenomenon remained a mystery. Why does hot water freeze faster than cold water?
It wasn't until 1996 that physicist David Auerbach found a solution. To answer this question, he conducted an experiment for a whole year: he heated water in a glass and cooled it again. So what did he find out? When heated, air bubbles dissolved in water evaporate. Water devoid of gases freezes more easily on the walls of the vessel. "Of course, water with a high air content will also freeze," says Auerbach, "but not at zero degrees Celsius, but only at minus four to six degrees." Of course, you will have to wait longer. So, hot water freezes before cold water, this is a scientific fact.
There is hardly a substance that would appear before our eyes with the same ease as ice. It consists only of water molecules - that is, elementary molecules containing two hydrogen atoms and one oxygen. However, ice is perhaps the most mysterious substance in the universe. Scientists have not been able to explain some of its properties so far.
2. Supercooling and "flash" freezing
Everyone knows that water always turns to ice when it cools down to 0 °C... except in some cases! Such a case is, for example, "supercooling", which is the property of very pure water to remain liquid even when cooled below freezing. This phenomenon becomes possible due to the fact that the environment does not contain crystallization centers or nuclei that could provoke the formation of ice crystals. And so water remains in liquid form, even when cooled to temperatures below zero degrees Celsius. The crystallization process can be triggered, for example, by gas bubbles, impurities (pollution), uneven surface of the container. Without them, water will remain in a liquid state. When the crystallization process starts, you can watch how the super-cooled water instantly turns into ice.
Watch the video (2 901 Kb, 60 c) by Phil Medina (www.mrsciguy.com) and see for yourself >>
Comment. Superheated water also remains liquid even when heated above its boiling point.
3. "Glass" water
Quickly and without hesitation, name how many different states water has?
If you answered three (solid, liquid, gas), then you are wrong. Scientists distinguish at least 5 different states of water in liquid form and 14 states of ice.
Remember the conversation about super-cooled water? So, no matter what you do, at -38 ° C, even the purest super-cooled water suddenly turns into ice. What happens with a further decrease
temperature? At -120 °C, something strange begins to happen to water: it becomes super-viscous or viscous, like molasses, and at temperatures below -135 °C it turns into "glassy" or "glassy" water - a solid substance in which there is no crystalline structure.
4. Quantum properties of water
At the molecular level, water is even more amazing. In 1995, a neutron scattering experiment conducted by scientists gave an unexpected result: physicists found that neutrons directed at water molecules “see” 25% fewer hydrogen protons than expected.
It turned out that at the speed of one attosecond (10 -18 seconds) an unusual quantum effect takes place, and the chemical formula of water instead of the usual one - H 2 O, becomes H 1.5 O!
5. Does water have a memory?
Homeopathy, an alternative to conventional medicine, claims that a dilute solution of a medicinal product can have a healing effect on the body, even if the dilution factor is so great that there is nothing left in the solution but water molecules. Proponents of homeopathy explain this paradox with a concept called "memory of water", according to which water at the molecular level has a "memory" of the substance once dissolved in it and retains the properties of the solution of the original concentration after not a single molecule of the ingredient remains in it.
An international team of scientists led by Professor Madeleine Ennis from Queen's University of Belfast, who criticized the principles of homeopathy, conducted an experiment in 2002 to disprove this concept once and for all. The result was the opposite. After which, scientists said that they were able to prove the reality of the effect of "memory of water. However, experiments conducted under the supervision of independent experts, did not bring results. Disputes about the existence of the phenomenon of "memory of water" continue.
Water has many other unusual properties that we have not covered in this article.
Literature.
1. 5 Really Weird Things About Water / http://www.neatorama.com.
2. The mystery of water: the theory of the Aristotle-Mpemba effect was created / http://www.o8ode.ru.
3. Nepomniachtchi N.N. Secrets of inanimate nature. The most mysterious substance in the universe / http://www.bibliotekar.ru.
The phenomenon of hot water solidifying at a faster rate than cold water is known in science as the Mpemba effect. Such great minds as Aristotle, Francis Bacon and Rene Descartes pondered over this paradoxical phenomenon, but for millennia no one has yet been able to offer a reasonable explanation for this phenomenon.
Only in 1963, a schoolboy from the Republic of Tanganyika, Erasto Mpemba, noticed this effect on the example of ice cream, but none of the adults gave him an explanation. Nevertheless, physicists and chemists seriously thought about such a simple, but so incomprehensible phenomenon.
Since then, different versions have been expressed, one of which was as follows: part of the hot water simply evaporates at first, and then, when a smaller amount remains, the water solidifies faster. This version, due to its simplicity, became the most popular, but scientists were not completely satisfied.
Now a team of researchers from Nanyang Technological University in Singapore, led by chemist Xi Zhang, says they have solved the age-old mystery of why warm water freezes faster than cold. As Chinese experts found out, the secret lies in the amount of energy stored in hydrogen bonds between water molecules.
As you know, water molecules are made up of one oxygen atom and two hydrogen atoms held together by covalent bonds, which at the particle level looks like an exchange of electrons. Another known fact is that hydrogen atoms are attracted to oxygen atoms from neighboring molecules - this forms hydrogen bonds.
At the same time, water molecules as a whole repel each other. Scientists from Singapore noticed that the warmer the water, the greater the distance between the molecules of the liquid due to the increase in repulsive forces. As a result, hydrogen bonds are stretched, and therefore store more energy. This energy is released when the water cools - the molecules approach each other. And the return of energy, as you know, means cooling.
As the chemists write in their article, which can be found on the arXiv.org preprint site, hydrogen bonds are stretched more strongly in hot water than in cold water. Thus, it turns out that more energy is stored in the hydrogen bonds of hot water, which means that more of it is released when cooled to sub-zero temperatures. For this reason, freezing is faster.
To date, scientists have solved this riddle only theoretically. When they present convincing evidence of their version, then the question of why hot water freezes faster than cold water can be considered closed.
This is true, although it sounds incredible, because in the process of freezing, preheated water must pass the temperature of cold water. Meanwhile, this effect is widely used. For example, ice rinks and slides are filled with hot water in winter, not cold water. Experts advise motorists to pour cold rather than hot water into the washer reservoir in winter. The paradox is known worldwide as the "Mpemba Effect".
This phenomenon was mentioned at one time by Aristotle, Francis Bacon and Rene Descartes, but only in 1963 did physics professors pay attention to it and try to investigate it. It all started when Tanzanian schoolboy Erasto Mpemba noticed that the sweetened milk he used to make ice cream solidified faster if it was preheated and suggested that hot water freezes faster than cold water. He turned to the physics teacher for clarification, but he only laughed at the student, saying the following: "This is not world physics, but the physics of Mpemba."
Fortunately, Dennis Osborn, a professor of physics from the University of Dar es Salaam, visited the school one day. And Mpemba turned to him with the same question. The professor was less skeptical, said that he could not judge what he had never seen, and upon returning home asked the staff to conduct appropriate experiments. It looks like they confirmed the boy's words. In any case, in 1969, Osborne spoke about working with Mpemba in the magazine "Eng. PhysicsEducation". In the same year, George Kell of the Canadian National Research Council published an article describing the phenomenon in English. AmericanJournalofPhysics».
There are several possible explanations for this paradox:
- Hot water evaporates faster, thereby reducing its volume, and a smaller volume of water with the same temperature freezes faster. In airtight containers, cold water should freeze faster.
- The presence of snow lining. The hot water container melts the snow underneath, thereby improving thermal contact with the cooling surface. Cold water does not melt snow under it. With no snow lining, the cold water container should freeze faster.
- Cold water begins to freeze from above, thereby worsening the processes of heat radiation and convection, and hence the loss of heat, while hot water begins to freeze from below. With additional mechanical agitation of the water in the containers, the cold water should freeze faster.
- The presence of crystallization centers in the cooled water - substances dissolved in it. With a small number of such centers in cold water, the transformation of water into ice is difficult, and even its supercooling is possible when it remains in a liquid state, having a sub-zero temperature.
Another explanation has recently been published. Dr. Jonathan Katz of the University of Washington investigated this phenomenon and concluded that substances dissolved in water play an important role in it, which precipitate when heated.
By solutes, Dr. Katz means the calcium and magnesium bicarbonates found in hard water. When the water is heated, these substances precipitate, the water becomes "soft". Water that has never been heated contains these impurities and is "hard". As it freezes and ice crystals form, the concentration of impurities in water increases 50 times. This lowers the freezing point of water.
This explanation does not seem convincing to me, because. we must not forget that the effect was found in experiments with ice cream, and not with hard water. Most likely, the causes of the phenomenon are thermophysical, and not chemical.
So far, no unambiguous explanation of the Mpemba paradox has been 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 because of his curiosity and perseverance.
Added February 2014
The note was written in 2011. Since then, new studies of the Mpemba effect and new attempts to explain it have appeared. So, in 2012, the Royal Society of Chemistry of Great Britain announced an international competition to unravel the scientific mystery “The Mpemba Effect” with a prize fund of 1000 pounds. The deadline was set on July 30, 2012. The winner was Nikola Bregovik from the laboratory of the University of Zagreb. He published his work, in which he analyzed previous attempts to explain this phenomenon and came to the conclusion that they were not convincing. The model he proposed is based on the fundamental properties of water. Those interested can find a job at http://www.rsc.org/mpemba-competition/mpemba-winner.asp
The research didn't end there. In 2013, physicists from Singapore theoretically proved the cause of the Mepemba effect. The work can be found at http://arxiv.org/abs/1310.6514.
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Comments:
Alexey Mishnev. , 06.10.2012 04:14
Why does hot water evaporate faster? Scientists have practically proved that a glass of hot water freezes faster than cold water. Scientists cannot explain this phenomenon for the reason that they do not understand the essence of phenomena: heat and cold! Warmth and cold is physical sensation, which causes the interaction of particles of Matter, in the form of a counter compression of magnetic waves that move from the side of space and from the center of the earth. Therefore, the greater the potential difference of this magnetic voltage, the faster the energy exchange is carried out by the method of counter-penetration of one wave into another. That is, by diffusion! In response to my article, one opponent writes: 1) “..Hot water evaporates FASTER, as a result of which there is less of it, so it freezes faster” Question! What energy makes water evaporate faster? 2) In my article, we are talking about a glass, and not about a wooden trough, which the opponent cites as a counterargument. What is not correct! I answer the question: “FOR WHAT REASON DOES WATER EVAPORATION IN NATURE?” Magnetic waves, which always move from the center of the earth into space, overcoming the counter pressure of magnetic compression waves (which always move from space to the center of the earth), at the same time, spray water particles, since moving into space, they increase in volume. That is, expand! In case of overcoming the magnetic waves of compression, these water vapors are compressed (condensed) and under the influence of these magnetic compression forces, the water returns to the ground in the form of precipitation! Sincerely! Alexey Mishnev. October 6, 2012.
Alexey Mishnev. , 06.10.2012 04:19
What is temperature. Temperature is the degree of electromagnetic stress of magnetic waves with the energy of compression and expansion. In the case of an equilibrium state of these energies, the temperature of the body or substance is in a stable state. If the equilibrium state of these energies is disturbed, towards the energy of expansion, the body or substance increases in the volume of space. In case of exceeding the energy of magnetic waves in the direction of compression, the body or substance decreases in the volume of space. The degree of electromagnetic stress is determined by the degree of expansion or contraction of the reference body. Alexey Mishnev.
Moiseeva Natalia, 23.10.2012 11:36 | VNIIM
Alexey, you are talking about some article that outlines your thoughts on the concept of temperature. But no one read it. Please give me a link. In general, your views on physics are very peculiar. I have never heard of "electromagnetic expansion of the reference body".
Yuri Kuznetsov , 04.12.2012 12:32
A hypothesis is proposed that this is the work of intermolecular resonance and the ponderomotive attraction between molecules generated by it. In cold water, molecules move and vibrate randomly, with different frequencies. When water is heated, with an increase in the oscillation frequency, their range narrows (the frequency difference from liquid hot water to the point of vaporization decreases), the oscillation frequencies of the molecules approach each other, as a result of which a resonance occurs between the molecules. When cooled, this resonance is partially preserved, it does not die out immediately. Try pressing one of the two guitar strings that are in resonance. Now let go - the string will begin to vibrate again, the resonance will restore its vibrations. So in frozen water, the outer cooled molecules try to lose the amplitude and frequency of oscillations, but the “warm” molecules inside the vessel “pull” the oscillations back, act as vibrators, and the outer ones act as resonators. It is between the vibrators and the resonators that the ponderomotive attraction* arises. When the ponderomotive force becomes greater than the force caused by the kinetic energy of the molecules (which not only vibrate, but also move linearly), accelerated crystallization occurs - the "Mpemba Effect". The ponderomotive connection is very unstable, the Mpemba effect strongly depends on all accompanying factors: the volume of water to be frozen, the nature of its heating, freezing conditions, temperature, convection, heat exchange conditions, gas saturation, vibration of the refrigeration unit, ventilation, impurities, evaporation, etc. Perhaps even from lighting... Therefore, the effect has a lot of explanations and is sometimes difficult to reproduce. For the same "resonant" reason boiled water boils faster than unboiled - resonance for some time after boiling retains the intensity of vibrations of water molecules (energy loss during cooling is mainly due to the loss of kinetic energy of the linear motion of molecules). With intense heating, vibrator molecules change roles with resonator molecules in comparison with freezing - the frequency of the vibrators is less than the frequency of the resonators, which means that there is not attraction between the molecules, but repulsion, which accelerates the transition to another state of aggregation (pair).
Vlad, 11.12.2012 03:42
Broke my brain...
Anton , 04.02.2013 02:02
1. Is this ponderomotive attraction really so great that it affects the heat transfer process? 2. Does this mean that when all bodies are heated to a certain temperature, their structural particles enter into resonance? 3. Why does this resonance disappear upon cooling? 4. Is this your guess? If there is a source, please indicate. 5. According to this theory, the shape of the vessel will play an important role, and if it is thin and flat, then the difference in freezing time will not be large, i.e. you can check it.
Gudrat , 11.03.2013 10:12 | METAK
Cold water already has nitrogen atoms and the distances between water molecules are closer than in hot water. That is, the conclusion: Hot water absorbs nitrogen atoms faster and at the same time it quickly freezes than cold water - this is comparable to the hardening of iron, since hot water turns into ice and hot iron hardens upon rapid cooling!
Vladimir , 03/13/2013 06:50
or maybe this: the density of hot water and ice is less than the density of cold water, and therefore water does not need to change its density, losing some time on this and it freezes.
Alexey Mishnev , 03/21/2013 11:50 am
Before talking about resonances, attraction and vibrations of particles, it is necessary to understand and answer the question: What forces make particles vibrate? Since, without kinetic energy, there can be no compression. Without compression, there can be no expansion. Without expansion, there can be no kinetic energy! When you start talking about the resonance of strings, you first made an effort to make one of these strings start to vibrate! When talking about attraction, you must first of all indicate the force that makes these bodies attract! I affirm that all bodies are compressed by the electromagnetic energy of the atmosphere and which compresses all bodies, substances and elementary particles with a force of 1.33 kg. not per cm2, but per elementary particle. Since the pressure of the atmosphere cannot be selective! Do not confuse it with the amount of force!
Dodik , 05/31/2013 02:59
It seems to me that you have forgotten one truth - "Science begins where measurements begin." What is the temperature of the "hot" water? What is the temperature of "cold" water? The article doesn't say a word about it. From this we can conclude - the whole article is bullshit!
Grigory, 06/04/2013 12:17
Dodik, before calling an article nonsense, one must think to learn, at least a little. And not just measure.
Dmitry , 12/24/2013 10:57 AM
Hot water molecules move faster than in cold water, because of this there is a closer contact with environment, they seem to absorb all the cold quickly slowing down.
Ivan, 10.01.2014 05:53
It is surprising that such an anonymous article appeared on this site. The article is completely unscientific. Both the author and commentators vied with each other in search of an explanation of the phenomenon, not bothering to find out whether the phenomenon is observed at all, and if it is observed, then under what conditions. Moreover, there is not even an agreement on what we actually observe! So the author insists on the need to explain the effect of rapid freezing of hot ice cream, although from the entire text (and the words "the effect was found in experiments with ice cream") it follows that he himself did not set up such experiments. From the variants of "explanation" of the phenomenon listed in the article, it can be seen that completely different experiments are described, set in different conditions with different aqueous solutions. Both the essence of explanations and subjunctive mood they suggest that even an elementary test of the ideas expressed has not been carried out. Someone accidentally heard a curious story and casually expressed his speculative conclusion. I'm sorry but it's not physical Scientific research, and conversation in a smoking-room.
Ivan , 01/10/2014 06:10
Regarding the comments in the article about filling the rollers with hot water and cold washer reservoirs. Everything is simple from the point of view of elementary physics. The skating rink is filled with hot water just because it freezes more slowly. The rink must be level and smooth. Try to fill it with cold water - you will get bumps and "influxes", because. water will _quickly_ freeze without having time to spread in a uniform layer. And the hot one will have time to spread in an even layer, and it will melt the existing ice and snow bumps. With a washer is also not difficult: pour clean water it makes no sense in frost - it freezes on glass (even hot); and hot non-freezing liquid can lead to cracking of cold glass, plus it will have an increased freezing point on the glass due to the accelerated evaporation of alcohols on the way to the glass (with the principle of operation moonshine still everyone is familiar? - alcohol evaporates, water remains).
Ivan , 01/10/2014 06:34
But in fact the phenomenon, it is silly to ask why two different experiments in different conditions proceed differently. If the experiment is set up cleanly, then you need to take hot and cold water of the same chemical composition- take pre-chilled boiling water from the same kettle. Pour into identical vessels (for example, thin-walled glasses). We put not on the snow, but on the same even dry base, for example, wooden table. And not in a microfreezer, but in a sufficiently voluminous thermostat - I conducted an experiment a couple of years ago in the country, when there was stable frosty weather outside, about -25C. Water crystallizes at a certain temperature after the release of the heat of crystallization. The hypothesis boils down to the assertion that hot water cools faster (this is true, according to classical physics, the heat transfer rate is proportional to the temperature difference), but maintains an increased cooling rate even when its temperature equals the temperature of cold water. The question is, how does water that has cooled to a temperature of +20C outside differ from exactly the same water that has cooled to a temperature of +20C an hour before, but in a room? Classical physics (by the way, based not on chatter in a smoking room, but on hundreds of thousands and millions of experiments) says: yes, nothing, further cooling dynamics will be the same (only boiling water will reach the +20 point later). And the experiment shows the same thing: when there is already a solid crust of ice in a glass of initially cold water, hot water did not even think of freezing. P.S. To the comments of Yuri Kuznetsov. The presence of a certain effect can be considered established when the conditions for its occurrence are described and it is stably reproduced. And when we have incomprehensible experiments with unknown conditions, it is premature to build theories of their explanation and this does not give anything from a scientific point of view. P.P.S. Well, it’s impossible to read Alexei Mishnev’s comments without tears of emotion - a person lives in some kind of fictional world that has nothing to do with physics and real experiments.
Grigory, 01/13/2014 10:58 AM
Ivan, I understand that you refute the Mpemba effect? It does not exist, as your experiments show? Why is it so famous in physics, and why do many try to explain it?
Ivan , 02/14/2014 01:51
Good afternoon, Gregory! The effect of an impurely staged experiment exists. But, as you understand, this is not a reason to look for new patterns in physics, but a reason to improve the skill of the experimenter. As I already noted in the comments, in all the mentioned attempts to explain the “Mpemba effect”, the researchers cannot even clearly articulate what exactly and under what conditions they are measuring. And you want to say that these are experimental physicists? Do not make me laugh. The effect is known not in physics, but in pseudo-scientific discussions on various forums and blogs, of which the sea is now. As a real physical effect (in the sense as a consequence of some new physical laws, and not as a result of an incorrect interpretation or just a myth) it is perceived by people who are far from physics. So there is no reason to speak as a single physical effect about the results different experiments placed under completely different conditions.
Pavel, 02/18/2014 09:59
hmm, guys... article for "Speed Info"... No offense... ;) Ivan is right about everything...
Gregory, 02/19/2014 12:50 pm
Ivan, I agree that there are a lot of pseudo-scientific sites publishing unverified sensational material now.? After all, the effect of Mpemba is still being studied. Moreover, scientists from universities are researching. For example, in 2013, this effect was studied by a group from the University of Technology in Singapore. Look at the link http://arxiv.org/abs/1310.6514. They believe they have found an explanation for this effect. I will not write in detail about the essence of the discovery, but in their opinion, the effect is associated with the difference in energies stored in hydrogen bonds.
Moiseeva N.P. , 02/19/2014 03:04
For everyone interested in research on the Mpemba effect, I have slightly supplemented the material of the article and provided links where you can get acquainted with the latest results (see text). Thanks for the comments.
Ildar , 02/24/2014 04:12 | it makes no sense to list everything
If this Mpemba effect really takes place, then the explanation must be sought, I think, in the molecular structure of water. Water (as I learned from the popular science literature) exists not as individual H2O molecules, but as clusters of several molecules (even dozens). With an increase in water temperature, the speed of movement of molecules increases, the clusters break up against each other and the valence bonds of the molecules do not have time to assemble large clusters. It takes a little more time to form clusters than to slow down the speed of molecules. And since the clusters are smaller, the formation of the crystal lattice is faster. In cold water, apparently, large, fairly stable clusters prevent the formation of a lattice; it takes some time for their destruction. I myself saw on TV a curious effect, when cold water standing quietly in a jar remained liquid for several hours in the cold. But as soon as the jar was picked up, that is, slightly moved from its place, the water in the jar immediately crystallized, became opaque, and the jar burst. Well, the priest who showed this effect explained it by the fact that the water was consecrated. By the way, it turns out that water greatly changes its viscosity depending on temperature. We, as large creatures, do not notice this, but at the level of small (mm and less) crustaceans, and even more so bacteria, the viscosity of water is a very significant factor. This viscosity, I think, is also given by the size of the water clusters.
GREY , 03/15/2014 05:30
everything around that we see is surface characteristics (properties), so we take for energy only what we can measure or prove existence in any way, otherwise it is a dead end. This phenomenon, the Mpemba effect, can only be explained by a simple volumetric theory that will unite all physical models into a single structure of interaction. actually it's simple
Nikita, 06/06/2014 04:27 | car
but how to make the water stay cold and not be warm when you go in the car!
alexey, 03.10.2014 01:09
And here is another "discovery", on the go. Water in plastic bottle freezes much faster with an open cork. For fun, I experimented many times on severe frost. The effect is obvious. Hello theorists!
Eugene , 12/27/2014 08:40
The principle of an evaporative cooler. We take two sealed closed bottles with cold and hot water. We put it in the cold. Cold water freezes faster. Now we take the same bottles with cold and hot water, open it and put it in the cold. Hot water will freeze faster than cold water. If we take two basins with cold and hot water, then hot water will freeze much faster. This is due to the fact that we increase contact with the atmosphere. The more intense the evaporation, the faster the temperature drop. Here it is necessary to mention the factor of humidity. The lower the humidity, the stronger the evaporation and the stronger the cooling.
gray TOMSK, 03/01/2015 10:55
GREY, 15.03.2014 05:30 - continued What you know about temperature is not everything. There is something else. If you correctly compose a physical model of temperature, then it will become the key to describing energy processes from diffusion, melting and crystallization to such scales as an increase in temperature with an increase in pressure, an increase in pressure with an increase in temperature. Even the physical model of the Sun's energy will become clear from the above. I am in winter. . in the early spring of 20013, after looking at the temperature models, I compiled a general temperature model. After a couple of months, I remembered the temperature paradox, and then I realized ... that my temperature model also describes the Mpemba paradox. This was in May - June 2013. A year late, but that's for the best. My physical model is a freeze frame and it can be scrolled both forward and backward and it has the motor skills of activity, the very activity in which everything moves. I have 8 classes of school and 2 years of college with a repetition of the topic. 20 years have passed. So I can’t ascribe any kind of physical models of famous scientists, as well as formulas. So sorry.
Andrey , 08.11.2015 08:52
In general, I have an idea about why hot water freezes faster than cold water. And in my explanations everything is very simple if you are interested then write me an email: [email protected]
Andrey , 08.11.2015 08:58
I'm sorry I gave the wrong one Mailbox here is the correct email: [email protected]
Victor , 12/23/2015 10:37 AM
It seems to me that everything is simpler, snow falls with us, it is evaporated gas, cooled, so maybe in frost it cools faster hot because it evaporates and immediately crystallizes far from rising, and water in the gaseous state cools faster than in liquid)
Bekzhan , 01/28/2016 09:18
Even if someone revealed these laws of the world that are associated with this effect, he would not write here. From my point of view, it would not be logical to reveal his secrets to Internet users when he can publish it in famous scientific journals and prove it himself in front of the people. So, what will be written about this effect here, all this majority is not logical.)))
Alex , 02/22/2016 12:48 PM
Hello Experimenters You are right in saying that Science begins where... not Measurements, but Calculations. "Experiment" - an eternal and indispensable argument for those deprived of Imagination and Linear thinking Offended everyone, now in the case of E \u003d mc2 - does everyone remember? The speed of molecules flying out of cold water into the atmosphere determines the amount of energy they carry away from water (cooling - loss of energy) The speed of molecules from hot water is much higher and the energy carried away is squared (the rate of cooling of the remaining mass of water) That's all, if you leave from " experimentation" and remember Basics Science
Vladimir , 04/25/2016 10:53 AM | Meteo
In those days when antifreeze was a rarity, the water from the cooling system of cars in an unheated garage of a car fleet was drained after a working day so as not to defrost the cylinder block or radiator - sometimes both together. Hot water was poured in the morning. In severe frost, the engines started without problems. Somehow, due to the lack of hot water, water was poured from the tap. The water immediately froze. The experiment was expensive - exactly as much as it costs to buy and replace the cylinder block and radiator of a ZIL-131 car. Who does not believe, let him check. and Mpemba experimented with ice cream. In ice cream, crystallization proceeds differently than in water. Try biting off a piece of ice cream and a piece of ice with your teeth. Most likely it did not freeze, but thickened as a result of cooling. And fresh water, whether it is hot or cold, freezes at 0*C. Cold water - fast hot time needed for cooling.
Wanderer , 06.05.2016 12:54 | to Alex
"c" - speed of light in vacuum E=mc^2 - formula expressing the equivalence of mass and energy
Albert , 07/27/2016 08:22
First, an analogy with solid bodies(there is no evaporation process). Recently soldered copper water pipes. The process takes place by heating gas burner to the melting point of the solder. The heating time of one joint with the coupling is approximately one minute. I soldered one joint with the coupling and after a couple of minutes I realized that I soldered it wrong. It took a little to scroll the pipe in the coupling. I began to heat the joint again with a burner and, surprisingly, it took 3-4 minutes to heat the joint to the melting point. How so!? After all, the pipe is still hot and it would seem that much less energy is needed to heat it to the melting point, but everything turned out to be the opposite. It's all about the thermal conductivity, which is much higher for an already heated pipe and the boundary between the heated and cold pipe in two minutes she managed to move far from the junction. Now about water. We will operate with the concepts of hot and semi-heated vessel. In a hot vessel, narrow border temperature separation between hot, highly mobile particles and slow-moving, cold ones, which moves relatively quickly from the periphery to the center, because at this boundary, fast particles quickly give up their energy (cool down) by particles on the other side of the boundary. Since the volume of outer cold particles is greater, then fast particles, giving their thermal energy, cannot significantly warm up the outer cold particles. Therefore, the process of cooling hot water occurs relatively quickly. Semi-heated water, on the other hand, has a much lower thermal conductivity, and the width of the boundary between semi-heated and cold particles is much wider. The displacement to the center of such a wide boundary occurs much more slowly than in the case of a hot vessel. As a result, a hot vessel cools faster than a warm one. I think it is necessary to follow the dynamics of the cooling process of water of different temperatures by placing several temperature sensors from the middle to the edge of the vessel.
Max , 11/19/2016 05:07
It has been verified: in Yamal, in frost, a pipe with hot water freezes and it has to be warmed up, but not cold!
Artem, 09.12.2016 01:25
It is difficult, but I think that cold water is denser than hot water, even better than boiled water, and then there is an acceleration in cooling, i.e. hot water reaches the cold temperature and overtakes it, and if you take into account the fact that hot water freezes from below and not from above, as written above, this speeds up the process a lot!
Alexander Sergeev, 21.08.2017 10:52
There is no such effect. Alas. In 2016, a detailed article on the topic was published in Nature: https://en.wikipedia.org/wiki/Mpemba_effect From it it is clear that if the experiments are carried out carefully (if the samples of warm and cold water are the same in everything except temperature), the effect is not observed .
Headlab, 08/22/2017 05:31
Victor , 10/27/2017 03:52 AM
"It really is." - if the school did not understand what heat capacity and the law of conservation of energy are. It's easy to check - for this you need: a desire, a head, hands, water, a refrigerator and an alarm clock. And the skating rinks, as experts write, are frozen (filled) with cold water, and with warm water they level the cut ice. And in the winter you need to pour anti-freeze fluid into the washer reservoir, not water. Water will freeze anyway, and cold water will freeze faster.
Irina , 01/23/2018 10:58
Scientists all over the world have been struggling with this paradox since the time of Aristotle, and Viktor, Zavlab and Sergeev turned out to be the smartest.
Denis , 02/01/2018 08:51
Everything is right in the article. But the reason is somewhat different. In the process of boiling, the air dissolved in it is evaporated from the water, therefore, as the boiling water cools, as a result, its density will be less than that of raw water of the same temperature. There are no other reasons for different thermal conductivity except for different density.
Headlab, 03/01/2018 08:58 | head lab
Irina :), "scientists of the whole world" do not fight this "paradox", for real scientists this "paradox" simply does not exist - this is easily verified in well-reproducible conditions. The "paradox" appeared due to the irreproducible experiments of the African boy Mpemba and was inflated by similar "scientists" :)
