Mpemba Effect....!

Have you ever heard about this concept...?

Mpemba Effect....

Before telling you the concept, I want to convey you the words of Mpemba after his discovery......because its worth to read it once....so read till the end if you really want to catch up the interesting thing and how a normal kid turned into a researcher.....!!! 

“My name is Erasto B Mpemba, and I am going to tell you about my discovery, which was due to misusing a refrigerator.”

Read it again.....do you notice the words " .....I am going to tell you about my discovery, which was due to misusing a refrigerator" .

Ofcourse, it is an accidental incident which lead for the discovery of a mystery concept.......!!!! 

Okay....what is Mpemba Effect...???

It is the theory that warmer water can freeze faster than colder water under certain circumstances.

The effect has been noted since ancient times but scientists have struggled to explain why it occurs....From here onwards, it is a selected copy paste work from the published article of Mpemba Effect....so forgive it....

 The story of the discovery, and the consequent mystery, is worth a bit of exploration — and the Mpemba effect carries numerous important lessons about the nature and method of scientific discovery.

Mpemba made his accidental discovery in Tanzania in 1963, when he was only 13 years old and in secondary school.  In spite of widespread disdain from his classmates, he surreptitiously continued experiments on the phenomenon until he had the good fortune in high school to interact with Professor Denis Osborne of the University College Dar es Salaam.  Osborne was intrigued, carried out his own experiments, and in 1969 the two published a paper in the journal Physics Education.

This article is, in my opinion, one of the most remarkable in all of the history of physics.  Aside from its title, “Cool?”, it is also unusual in being presented in two parts: Mpemba gives a first person account in his own words of his discovery in the first half, and Osborne picks up the story and describes the follow-up experiments in the second half.  Mpemba’s own account is so charming and fascinating that it is worth quoting from liberally:

My name is Erasto B Mpemba, and I am going to tell you about my discovery, which was due to misusing a refrigerator. All of you know that it is advisable not to put hot things in a refrigerator, for you somehow shock it; and it will not last long.

In 1963, when I was in form 3 in Magamba Secondary School, Tanzania, I used to make ice-cream. The boys at the school do this by boiling milk, mixing it with sugar and putting it into the freezing chamber in the refrigerator, after it has first cooled nearly to room temperature. A lot of boys make it and there is a rush to get space in the refrigerator.

One day after buying milk from the local women, I started boiling it. Another boy, who had bought some milk for making ice-cream, ran to the refrigerator when he saw me boiling up milk and quickly mixed his milk with sugar and poured it into the icetray without boiling it; so that he may not miss his chance. Knowing that if I waited for the boiled milk to cool before placing it in the refrigerator I would lose the last available ice-tray, I decided to risk ruin to the refrigerator on that day by putting hot milk into it. The other boy and I went back an hour and a half later and found that my tray of milk had frozen into ice-cream while his was still only a thick liquid, not yet frozen.

I asked my physics teacher why it happened like that, with the milk that was hot freezing first, and the answer he gave me was that “You were confused, that cannot happen”. Then I believed his answer.

Here we have the beginnings of a classic story of science — an accidental discovery, scoffed at by the “establishment scientists”.

Mpemba might have given up at that point, but he encountered a friend who sold ice cream for a living, and that friend happened to mention that many vendors would use boiling water to make their ice cream!  It was already common knowledge amongst them, apparently, that a boiling mixture could freeze quicker.

After passing my O level examination, I was chosen to go to Mkwawa High School in Iringa. The first topics we dealt with were on heat. One day as our teacher taught us about Newton's Law of Cooling, I asked him the question, “Please, sir, why is it that when you put both hot milk and cold milk into a refrigerator at the same time, the hot milk freezes first?” The teacher replied: “I do not think so, Mpemba.” I continued: “It is true, sir, I have done it myself” and he said: “The answer I can give is that you were confused.” I kept on arguing, and the final answer he gave me was that: “Well, all I can say is that that is Mpemba’s physics and not the universal physics.” From then onwards if I failed in a problem by making a mistake in looking up the logarithms this teacher used to say: “That is Mpemba’s mathematics.”

And the whole class adopted this, and anytime I did something wrong they used to say to me “That is Mpemba’s…”, whatever the thing was.

Here the high school teacher failed miserably — ridiculing a student is pretty much the worst thing one can do in a science classroom!  Fortunately, Mpemba was not deterred:

Then one afternoon found the biology laboratory open, and there was no teacher. I took two 50 cm³ beakers, one I filled with cold water from the tap and the other with hot water from a boiler and quickly put them in the freezing chamber of the laboratory refrigerator. After one hour I came back to look and I found that not all the water had been changed into ice, but that there was more ice in the beaker which had hot water to start with than in the one which had cold water. This was not really conclusive. So, I planned to try it again when I had the chance.

Before he had this chance, however, Professor Osborne came to lecture on physics, giving Mpemba a valuable opportunity:

When Dr Osborne visited our school we were allowed to ask him some questions, mainly in physics. I asked: “If you take two similar containers with equal volumes Of water, one at 35 °C and the other at 100 °C, and put them into a refrigerator, the one that started at 100 °C freezes first. Why?” He first smiled and asked me to repeat the question. After I repeated it he said: “Is it true, have you done it?” I said: “Yes.” Then he said: “I do not know, but I promise to try this experiment when I am back in Dar es Salaam.” Next day my classmates in form six were saying to me that I had shamed them by asking that question and that my aim was to ask a question which Dr Osborne would not be able to answer. Some said to me: “But Mpemba did you understand your chapter on Newton’s law of cooling?” I told them: “Theory differs from practical.” Some said : “We do not wonder, for that was Mpemba’s physics.”

There are many remarkable points in this short passage.  First of all, we see an admirable open-mindedness of Professor Osborne in his dealings with Mpemba, and that open-mindedness would quickly benefit them both.  Conversely, we see a dangerous “groupthink” amongst Mpemba’s classmates regarding science, in which they are genuinely offended by Mpemba questioning the status quo.  Mpemba shows great wisdom in his answer: “Theory differs from practical”.  This is an important point for anyone studying physics: we like to create simplified models to explain nature, but those models often lose real-world aspects in the process of stripping them down.

Mpemba actually continued his experiments in a kitchen refrigerator, with the permission of kitchen staff, and convinced his classmates and the headmaster of his school of the accuracy of his findings.

At Dar es Salaam, Osborne was true to his word and looked into the phenomenon himself.  As he notes in the continuation of the paper,

It seemed an unlikely happening, but the student insisted that he was sure of the facts. I confess that I thought he was mistaken but fortunately remembered the need to encourage students to develop questioning and critical attitudes. No question should be ridiculed. In this case there was an added reason for caution, for everyday events are seldom as simple as they seem and it is dangerous to pass a superficial judgment on what can and cannot be. I said that the facts as they were given surprised me because they appeared to contradict the physics I know. But I added that it was possible that the rate of cooling might be affected by some factor I had not considered.

Osborne sets a great example for all physics educators!  It can be difficult at times, but “No question should be ridiculed” would be a great part of a “Hippocratic oath” for teachers. 

What happened after was the thing which got the place in the history book....!!!!

Some people who argued for the existence of a Mpemba effect in the 13th century, and in the 17th century.  But it was Mpemba and Osborne, however, who brought it to the attention of modern science.

After the deep confusion of 40+ years, a team of scientists in Singapore believe they have finally revealed the mystery of the Mpemba Effect and it lies in the unique properties of the bonds that hold water together....!

If you want to know deeply what is the scientific thing behind the Mpemba Effect means I would suggest you to follow this link http://www.dailymail.co.uk/sciencetech/article-2483383/Mystery-hot-water-freezes-faster-cold-solved--strange-behaviour-atom-bonds.html

Thank You for reading till the last...take a deep breath, it is over....!!!!