A glass of hot water and a glass of cold water. Put it in the fridge. Which one freezes first? Why?Physical problem
A student named Erasto Mpemba put hot cream in the hot milk and prepared to put it in the refrigerator for ice cream. He thought that if the hot milk had been put into the refrigerator, the other students would have filled the refrigerator, so they put hot milk in the refrigerator. It was not long before he opened the fridge and, to his surprise, his own ice cream had turned into a nice ice cream, and the ice cream made by the other students in cold water had not frozen. His discovery did not attract the attention of teachers and students; instead, they were laughing at their jokes. Mpemba told this particular phenomenon to Dr. Aus Boer Hei, a professor of physics at the University of La Salam. After listening to Mpemba's account, Aus Boer Hei was a little surprised, but he believed that Mpemba must have been telling the truth. Respect for Science Aus Boer Hei has conducted experiments, the results are fully consistent with the Mupeiba narrative. This definitely confirms that hot water freezes faster than cold water in a low temperature environment. Since then, many of the world's scientific journal article introduces this natural phenomenon, this phenomenon will also be named as the "Mupeiba effect" (MpembaEffect).
People usually think that when a glass of cold water and a glass of hot water are put into a refrigerator, cold water freezes quickly. That's not the case. One day in 1963, in a middle school in Tanzania, a tropical African country, a group of students wanted to cool down a bit of frozen food
The fact that hot water freezes faster than cold water has been known for centuries. "The earliest data to mention and record this phenomenon can be traced back to Aristotle in 300 BC," he wrote:"Previously heated water helps it to freeze more quickly.". So when people want to cool the hot water, they will put it in the sun first..."But before twentieth Century, this phenomenon was regarded as a folk tale. It was not until 1969 that Mpemba was again presented in the scientific community. Since then, many experiments have confirmed the existence of the Mpemba effect, but there is no single explanation.Around 1461, physicist GiovanniMarliani argued in a debate about how objects cool down, that he had proved that hot water froze faster than cold water. He said he used four ounces of boiling water, and four ounces of unheated water, respectively, in two small containers, placed in a cold winter outside the house, and found that the first boiling water ice. But he has no ability to explain the phenomenon.By the early seventeenth Century, this phenomenon seemed to be common knowledge. In 1620, Bacon wrote, "when water is slightly heated, it freezes more easily than cold water.". Shortly afterwards, Descartes said, "experience has shown that water on the fire is frozen more quickly than other water.". "Until 1969, it was 500 years after the Marliani experiment, and a story about the phenomenon of Mpemba secondary school students in Tanzania's secondary school was published in the new NewScientist magazine. The story tells scientists and teachers not to ignore the observation of non scientists and not to judge too early.
