According to the British New Scientist magazine, sometimes the freezing speed of hot water is much faster than that of cold water. This bizarre phenomenon has hurt the scientific world.
Explain why the hot water is faster than cold water
Over hundreds of experiments, eventually James Bulangliqi from State University, New York, USA has demonstrated this phenomenon.
According to James Bulangliqi, the phenomenon is related to some impurities in the water.
It is known that the fast freezing hot water phenomenon is called the ' Mpemba effect ,' which is named after the high school student Erasto Mpemba of Tanzania.
Physicists have proposed many theories about the Mpemba effect. However, the different explanations do not convince people, because this effect is not reliable, the freezing speed of cold water is always faster than hot water.
Scientist James Bulangliqi said that it is the impurities in the water that are the key to the fast freezing speed of hot water.
During the 10-year period, James Bulangliqi conducted hundreds of experiments related to the Mpemba effect. Finally, he discovered evidence that the Mpemba effect comes from supercool (unstable).
James Bulangliqi said: 'It seems that the water has not frozen when the temperature is at 0 degrees Celsius, but normally lower temperatures start to freeze, ie supercool phenomenon. The freezing point decided in the impurity that formed the relationship between water and ice. Under normal circumstances, water may have some types of impurities, including dust, soluble salts and bacteria. Each impurity can affect the freezing mechanism under special temperatures. '
James Bulangliqi conducted experiments on two samples of tap water at the same temperature of 20 degrees Celsius.
First he put the water sample into the test tube, then put it in the refrigerator to freeze. The random mixture of impurities has caused two samples to have different freezing points, including one with a higher freezing point. If this difference is large enough, the Mpemba effect will appear.
James Bulangliqi selected a sample with a higher natural freezing point and proceeded to raise the temperature to 80 degrees Celsius, the remaining water sample only increased heat with the indoor temperature, then put the two test tubes back into the refrigerator.
James Bulangliqi said, if the freezing point of hot water is at least 5 degrees Celsius, its freezing speed will be much faster than cold water.
As we all know, each water molecule consists of an oxygen atom covalently attached to two hydrogen molecules. Separate water molecules are also linked together by hydrogen bonds, which are created when a hydrogen atom is located near another oxygen atom of another water molecule.
Hydrogen bonds pull water molecules closer together, triggering the natural repulsive force between them, causing the covalent oxygen-hydrogen bonds to stretch as well as energy reserves. When the water is heated, the atoms move farther apart, causing the link to stretch.
The binding force causes water molecules to shrink back and release energy, leading to cooling, which means that hot water freezes faster than cold water, helping to solve the Mpemba effect.
However, some physicists note that the explanation currently cannot be used to predict the new properties of water, which can be generated by shortening covalent bonds . Therefore, there is still a step to be solved before the mystery is satisfactorily answered.
