Can hot water freeze? Why does hot water freeze faster than cold water? Why does distilled water not freeze?

AT modern conditions the human body experiences water starvation: for the most part, this is due to the characteristics of the artificial environment in which we live, the dehydrating effect of conditioned air and the food we eat. We are accustomed not only to quench our thirst, but to extract some additional effect from drinking: a pleasant taste soft drinks, tonic properties of coffee or tea. We have forgotten how to just drink water.

My drink

DRINK ROOM TEMPERATURE WATER OFTEN AND LITTLE LITTLE, WITHOUT WAITING TO FEEL STRONGLY THIRD

Sodas often contain corn syrup, which contains a large number of fructose, which is transformed directly into triglycerides (the building material for fat), and not into glucose, which is the fuel for the brain. Now about milk: its protein is digested for quite a long time, and for the breakdown of lactose ( milk sugar) requires the enzyme lactase, which is not produced by all people. Freshly squeezed juices are healthier, but this is also a kind of super-concentrated artificial drink - it would be much more useful to eat the whole fruit, along with the fiber and ballast substances contained in it. In a word, no other liquids - even those that we used to consider healthy and natural - will not replace ordinary drinking water for us.

One water

Chemistry lessons for many left only the formula of water H2O in their memory, as well as the confidence that without water life would not have arisen on our planet at all. This is so: with its direct participation, almost all biochemical reactions take place. After all, water is a universal solvent. Construction material for constant renewal of the body (that is, for the synthesis of proteins) and energy sources (carbohydrates), oxygen, hormones and enzymes circulate in the intercellular space and enter the cells, being dissolved in water. And metabolic products are excreted from the cells and from the body also in solution.

Water "enters and exits" through special water channels located in the plasma membrane of cells and called "aquaporins" (for their discovery by two American scientists - Peter Agree (Peter Agree) and Roderick McKinnon - was awarded in 2003 Nobel Prize in chemistry). If other substances are attached to the water molecule - after all, the dissolution process is accompanied by complex interactions with salts, sugars, acids, alcohol, chemicals that have arisen in the process of assimilation of drugs or food additives, then these bulky formations are not able to pass through a small water pore. There seems to be water in the body (sometimes there is even too much of it, and we call it fluid retention, edema), but it does not penetrate the cells, as a result of which metabolic processes are inhibited, toxins are not removed. Naturally, a person feels an incomprehensible malaise, fatigue, the cause of which is literally dissolved in water.

Choose a good filter

With all the variety of water filters, they perform the same task: they purify water from mechanical impurities (sand, scale, rust), partly from chemical impurities (chlorine, salts). heavy metals, herbicides, pesticides, petroleum products), as well as from bacteria and viruses. The principle of operation is also similar: water passes through replaceable cassettes with a filter medium. In most of them, a universal adsorbent "works" - activated carbon and ion-exchange resins, which are different for each manufacturer. The slower the water passes through the filter, the cleaner it is. For those who want to be sure that the water will be 97-99% pure, there are filters based on the reverse osmosis system. There, purification occurs by passing water through a multilayer membrane at a pressure of 3.5–4 atmospheres. The dimensions of the cells in the membrane are so small that only H2O molecules and hydrogen and oxygen dissolved in water can pass through them. The advantage of such water is that you can be really sure of its purity. Disadvantages: it has no taste, it can be considered close to distilled, from which the body has no benefit.

From the tap and from the bottle

Tap water may not be healthy (after all, it passes through miles of pipes), but at least it is safe - primarily due to the chlorine ions that are used to disinfect it. The action of chlorine is detrimental to any living cell - from bacteria to the cells of our body, therefore, before drinking tap water, it is better to filter it. “In principle, there are two ways out: filter tap water or buy bottled water, but I have not decided for myself what would be more correct,” Valery Sergeev admits. - On the one hand, bottled water is expensive, and there is not always confidence in its quality: did they slip filtered tap water instead of artesian water? And on the other hand, the filtered water becomes unbalanced, "idle". During the filtration process, it is deprived of almost all salts, including the necessary ones, such as calcium salts (which can lead to brittle bones), as well as essential trace elements.

According to the therapist Sergey Stebletsov, even spring water from the foothills of the Alps or obtained as a result of melting glaciers does not always bring guaranteed benefits: it is better to drink local water, to the electrolyte composition of which a person has adapted. The most reasonable compromise seems to be: do not be afraid of filtered tap water, but outside the home make it a rule to drink high-quality bottled water.

Quantity and quality

When and how, and most importantly, how much water to drink - the opinions of experts on this matter differ. According to Ayurveda, you should drink two to three liters of water a day, and its temperature should be as high as you can endure. “If you drink a lot of water at once, then the main goal of cleansing the body will not be achieved,” explains Mohammed Ali, a doctor from the Kerala Ayurvedic Center. “Therefore, you need to drink constantly, but little by little: two or three sips in 10-15 minutes.” Morning, according to him, you need to start with a glass of water at room temperature. It, like a medicine, must be taken on an empty stomach, without getting out of bed. Moreover, the water should not stand in a glass overnight - in this case it becomes "dead" - and should not be tap water. According to Mohammed Ali, the ancient teachers of Ayurveda advised to drink rainwater, but now you should not do this for obvious reasons - it is too polluted. It is probably best to drink water from a freshly opened bottle in the morning.

A FEELING OF COMFORT IS THE MAIN SIGN THAT WILL MAKE YOU UNDERSTAND WHAT AMOUNT OF WATER THE ORGANISM NEEDS

When we drink water during the day, according to Ayurveda, it is worth taking into account: if we want to lose weight, it is better to drink it before meals, and if we want to gain weight, then after. Accordingly, those who want to keep their kilograms intact can drink water during meals.

Representative of another Eastern school, professor Chinese medicine Gao Yan believes that it is best to drink water at room temperature. "It's a little cooler than body temperature, and it kicks off the body's cleansing processes," he explains. European experts also believe that we need two to three liters of water a day - especially in summer, when it's hot. “It should be slightly mineralized, with a predominance of chlorine anions and calcium, magnesium, and potassium cations,” explains Valery Sergeev. “This makes up for the natural loss of salts during increased sweating.” So water like "Slavyanovskaya", "Smirnovskaya", "Kashinskaya", "Novoterskaya" can be drunk without restrictions. But highly mineralized waters, such as Essentuki-17, are a remedy for diseases of the gastrointestinal tract, which stimulates the secretion of gastric juice and intestinal motility. "If you like carbonated mineral water, then to health, - says Valery Sergeev. - It quenches thirst better, stimulates the activity of the gastrointestinal tract. But if there are any disturbances in the activity of the stomach, heartburn and discomfort, it is better to switch to still water.

Trust the Feelings

So, drinking about two liters of water a day is considered a physiological norm. But, if we have not yet developed the habit of drinking water, should we count the glasses we have drunk, as if we were following the prescription of doctors? “The body itself knows how much water it needs,” says Sergey Stebletsov. - One and a half liters a day is enough, the other is not enough and two and a half. It all depends on the mode in which the kidneys, lungs, skin and gastrointestinal tract through which water leaves the body. The main indicator that you should focus on is the feeling of comfort.

The properties of water never cease to amaze scientists. Water is a fairly simple substance from a chemical point of view, but at the same time 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 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 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 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 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.

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.

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 water has? 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-cooled 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 of H2O becomes H1.5O!

5. Water 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 by 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 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, the scientists said that they were able to prove the reality of the "memory of water" effect. 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. For example, the density of water changes with temperature (the density of ice is less than the density of water)

water has a fairly high 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.

You can read about these and many other unexpected features of water in the article "The Anomalous Properties of Water" by Martin Chaplin, a professor at the University of London.

This is true, although it sounds incredible, because in the process of freezing, preheated water must pass the temperature cold water. Meanwhile, this effect is widely used. For example, ice rinks and slides are filled with hot water instead of cold water in winter. 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.
Under dissolved substances dr Katz refers to 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. Thus, in 2012, the Royal Society of Chemistry of Great Britain announced international competition to solve the scientific mystery of 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.

Related articles on the site:

Comments:

Alexey Mishnev. , 06.10.2012 04:14

Why does hot water evaporate faster? Scientists have practically proven 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! Heat and cold are physical sensations caused by 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, this magnetic voltage, the faster the energy exchange is carried out by the method of counter penetration of some waves into others. 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 more power, 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 “resonance” reason, boiled water boils faster than unboiled water - resonance for some time after boiling preserves 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 an attraction between the molecules, but a 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, cannot be compressed. 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 claim that all bodies are compressed electromagnetic energy 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 the explanations and the subjunctive mood in them suggest that even an elementary verification of the ideas expressed was not 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 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 (is everyone familiar with the principle of operation of the moonshine still? - 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, a 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 statement that hot water cools faster (this is true, in accordance with classical physics, the heat transfer rate is proportional to the temperature difference), but retains increased speed cooling even when its temperature is equal to 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 consequence of an incorrect interpretation or just a myth), people who are far from physics perceive it. So there is no reason to speak as a single physical effect about the results of different experiments set up 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 of 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 popular science literature) exists not as individual H2O molecules, but as clusters of several molecules (even tens). 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 crystal lattice happens 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 the sake of fun, I experimented many times in severe frost. The effect is obvious. Hello theorists!

Eugene , 12/27/2014 08:40

The principle of an evaporative cooler. We take two hermetically sealed 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 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 a 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 on famous scientific journals and prove it personally 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 the Basics of 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 occurs by heating the gas burner to the melting temperature 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 pipes managed to move far from the junction in two minutes. Now about water. We will operate with the concepts of hot and semi-heated vessel. In a hot vessel, a narrow temperature boundary is formed 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) 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 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" :)

miroland, 03/23/2019 07:20 AM

a Tanzanian boy living in the heart of Africa, who, very likely, has never seen snow in his eyes ... ;-D I'm not confusing anything ???)))

Sergey , 04/14/2019 02:02

We take two elastic bands, stretch both, and one is larger than the other (an analogy with the internal energy of cold and warm water) simultaneously release one end of the rubber bands. Which rubber will shrink faster?

Artanis , 05/08/2019 03:34

Just had this experience myself. I put two identical cups of hot and cold water in the freezer. The cold one froze much faster. The hot one was still a little warm. What is wrong in my experience?

Headlab, 05/09/2019 06:21 |

Artanis, With your experience, "everything is right" :) - The "Mpemba effect" does not exist with a correctly performed experiment, which ensures the identity of the cooling conditions for identical volumes of water only with different initial temperatures. Congratulations - you have moved to the side of light, reason and the triumph of basic physical laws and began to move away from the "Mpemba sect", and fans of YouTube videos in the style of "what they lied to us about in physics lessons" ... :)

Moiseeva N.P. , 05/16/2019 04:30 | Ch. editor

You are right, a lot depends on the conditions of the experiment. But if the effect were not observed at all, then there would be no research and publications in serious journals. Did you read the note to the end? There is no mention of YouTube videos here.

Headlab, 08/06/2019 05:26 | SlavOilGas-SouthNorthWestVostok-SintezWhatever

Natalya Petrovna, we are living in an era of a "crisis of reproducibility" in science, when, in order to increase the citation index under the slogan "publish or perish", "unfortunate scientists" prefer to compete in inventing crazy theories to substantiate obviously dubious experimental data instead of spending a little time and resources to verify these data before sitting down to a purely theoretical article. An example of such "unfortunate scientists" is just the "physicists from Singapore" that you mentioned in the article - their publication does not contain their own experimental data, but only bare theoretical arguments about the possible influence of the abstruse phenomenon "O:H-O Bond Anomalous Relaxation" on the process of anomalous freezing of water, which was observed by both Francis Bacon and Rene Descartes and even Aristotle as early as 350 years BC. ... And personally, I am very glad that Nikola Bregovic from the University of Zagreb received his prize 1000 pounds from the Royal Society of Chemistry of Great Britain after he measured quite physically explicable results without any anomalies on good equipment in reproducible conditions and questioned them as clumsy measurements boy Mpemba and his adepts and the adequacy of those who tried to bring these clumsy experiments "theoretical base".

“The simplest stable compound of hydrogen with oxygen,” is the definition of water given by the Concise Chemical Encyclopedia. But, if you look, this liquid is not so simple. It has many unusual, amazing and very special properties. A Ukrainian aquatic researcher told us about the unique abilities of water Stanislav Suprunenko.

High heat capacity

Water heats up five times slower than sand and ten times slower than iron. It takes 3300 times more heat to heat a liter of water by one degree than to heat a liter of air. Absorbing a huge amount of heat, the substance itself does not heat up significantly. But when it cools down, it gives off as much heat as it took in when heated. This ability to accumulate and release heat allows you to smooth out sharp temperature fluctuations on the surface of the earth. But that's not all! The heat capacity of water decreases as the temperature rises from 0 to 370C, that is, within this framework it is easy to heat it, it will not take much heat and time. But after a temperature limit of 370C, its heat capacity increases, which means that more efforts will have to be made to heat it. It has been established that water has a minimum heat capacity at a temperature of 36, 790C, and this is - normal temperature human body! So it is this quality of water that ensures the stability of the temperature of the human body.

High surface tension of water

Surface tension is the force of attraction between molecules. Visually, it can be observed in a cup filled with tea. If you slowly add water to it, it will not overflow immediately. Take a closer look: above the surface of the liquid you can see the thinnest film - it does not allow the liquid to pour out. It swells as it is topped up, and only at the “last drop” will it still happen.
All liquids have surface tension, but it's different for everyone. Water has one of the highest surface tensions. Only mercury has more, which is why, when spilled, it immediately turns into balls: the molecules of the substance are firmly “attached” to each other. But alcohol, ether and acetic acid have a much lower surface tension. Their molecules are less attracted to each other and, accordingly, that is why they evaporate faster and spread their smell.

High latent heat of vaporization

Photo Shutterstock

It takes five and a half times more heat to evaporate water than to boil it. If it were not for this property of water - to slowly evaporate - many lakes and rivers would simply dry up in the hot summer.
On a global scale, a million tons of water evaporates from the hydrosphere every minute. As a result, a colossal amount of heat enters the atmosphere, equivalent to the operation of 40,000 power plants with a capacity of 1 billion kW each.

Extension

When the temperature drops, all substances shrink. Everything but water. Until the temperature drops below 40C, the water behaves quite normally - compacting a little, it reduces its volume. But after 3, 980С it behaves, more precisely, it begins to expand, despite the decrease in temperature! The process goes smoothly up to a temperature of 00C, until the water freezes. As soon as ice forms, the volume of already solid water increases dramatically by 10%.

Weak pressure in the faucet can piss off even the most balanced homeowner. After all, the duration of filling the kettle or coffee maker, and the performance of the washing machine or dishwasher depend on the pressure.

In addition, with poor pressure, it is almost impossible to use either the toilet or the shower or bath. In a word, if there is no pressure in the tap, then the house will not have the comfort of living.

We understand the causes of low water pressure in the tap

What weakens the pressure of water in the faucet?

Why weak water pressure in the tap can ruin even the most happy life even in the most perfect house or apartment, we have already discussed. However, moaning will not help grief. Moreover, this problem is not as terrible as it seems. One has only to understand what has weakened the pressure, and you will get an almost ready-made recipe for eliminating this trouble.

At the same time, the list of TOP 3 reasons for the drop in pressure of hot or cold water is as follows:

Clogged faucet . In this case, the intensity of the water jet is weakened by a cork made of rust and scale, which clogged the aerator, filter insert (mesh) or bushing. Moreover, only one tap in the house suffers from this problem. That is, if your tap water is not flowing well, for example, in the kitchen, but there are no problems in the bathroom, then you will have to disassemble and clean the problematic point of consumption.
. In this case, the same particles of silt, rust or scale are to blame. Only now they block not the faucet aerator or the faucet mesh, but the filter built into the water supply. In the worst case, such deposits can block the flow diameter of the connecting fitting or the pipe fitting itself.

. In this case, the cause of the weakening may be either a failure at the level of the pumping station, or a depressurization of the pipeline. Failure at the station can only be corrected by repair crews of utilities. The indicator of this breakdown is the lack of water in the entire microdistrict. Loss of tightness is diagnosed visually - by a stream of water spouting from the body of plumbing fittings. Any locksmith from a service company can fix this breakdown.
In addition, speaking about the reasons for the weakening of pressure, it is necessary to mention possible miscalculations in the arrangement of a specific water supply line . Incorrect diameter (larger than the previous branch), excessive length (not corresponding to the characteristics of pressure equipment) - these are the main reasons for the pressure drop in new network water supply.

If you don’t want to deal with them, order a water supply project from professionals.

Well, now that you already know the reasons for the drop in pressure in the tap, it's time to figure out how to eliminate this defect in the water supply.

What to do if cold and hot water from the tap does not flow well?

It all depends on the cause of the pressure drop.

For example, if your faucet is clogged, you will need to do the following:

Removing the faucet aerator for cleaning

Take an adjustable wrench and twist it off the "spout" of the crane - Foaming jet of water nozzle. This part has very small nozzles. Therefore, aerators are clogged with a frequency of once every six months. And if we are talking about a mixer tap with hot / cold water, then the frequency of cleaning the nozzles is reduced to 2-3 months. The dismantled aerator is washed under running water.
If the aerator is clean and the water is weak, you will have to dive even deeper into the faucet design. . Indeed, in this case, you need to get close to the locking unit - the box. To do this, dismantle the valve (faucet handle) and unscrew the lock washer holding the locking element in the body seat. Next, you remove the shut-off assembly from the housing and clean off silt or scale deposits from its surface. In the final, you will have to assemble the crane, acting in reverse.

Before dismantling the shut-off valve assembly, be sure to turn off the water supply by closing the water valve closest to the point of consumption. Otherwise, you will flood the entire apartment.

If the source of the problem is not the faucet, but the “sprayer” in the shower or bathroom, you will have to proceed a little differently. First shut off the supply to the atomizer. Then remove it from the rack or metal hose using an adjustable wrench. Immerse the removed part of the atomizer in a saucepan of vinegar. Heat up this medium on a hot plate. Wash off the scale with water. Put the nozzle back in place.

If the smell of vinegar irritates you, try a 10% citric acid solution. To prepare it, it is enough to dissolve 100 grams of dry acid powder - it is sold in any confectionery department - in a liter of water.

If you do not have the desire to mess with the crane - call a locksmith from the management company. He will solve this problem right before your eyes.

What to do if the water pressure in the tap is poor, we hope you already understand.

Now let's move on to pipes:

First of all, turn off the water by turning the central valve near the meter.
Next, dismantle the plug of the coarse filter. Remove the wire cassette and wash it in a container. Then return the filter element to its place, renew the seal and screw the plug.
After the revision of the coarse filter, proceed to check the fine filter system. First, disconnect it from the water supply and check the pressure in the free pipe by slightly opening the central valve. If everything is in order, change the liner, simultaneously washing the filter glass from particles of accumulated dirt. In the final, everything, of course, is mounted in its original place.
If the filters are clean, and the water still does not come out of the tap with the proper force, then the cause of the drop in pressure is a blockage in the pipes themselves. Localization of this problem and its elimination is an extremely time-consuming task. Therefore, after unsuccessfully cleaning the filters, you will have to call the management company and report a problem with the patency of the pipes in the water supply.

If you did not change the wiring of the water supply system in the apartment, you will pay for pipe cleaning Management Company. After all, it is she who should monitor the performance of "native" engineering communications.