Water is one of the most used compounds in the world. But water is also a mysterious compound. Analysis of chemical or physical properties reveals various exceptional properties. As water freezes and ice increases in volume, the opposite is true of other compounds.
Again, as with other liquids, they tend to thicken as they cool. But in the case of water the phenomenon is the exception. If it is cooled, the concentration is highest at 4°C, and if the temperature is reduced, its density decreases again.
As a result, when the water freezes and turns into ice, this ice can float in the water.
In addition to such wonderful properties, many people want to know about one more feature of water. Many ask, does hot water freeze faster than cold water?
If the answer is apparently one word, the answer would be “yes”, hot water freezes faster than cold water.
But overall, in some cases it would not be right to say yes. We will know the reason for this at the end of the discussion. Let’s find out first why hot water freezes faster than cold water.
One day in the 1960’s, a Tanzanian schoolboy noticed that a mixture of hot ice cream freezes faster than cold ice cream. However, this phenomenon was first observed by the great sage Aristotle in the fourth century BC. Even people like Rene Descartes and Francis Bacon mention it.
The event is named after the Tanzanian student Mpemba effect.
The mpemba effect is an effect where hot water freezes faster than cold water. Much research has been done so far and many theories have been provided to explain this effect. One explanation is that the warm pot served as a good heat conductor in the fridge. As a result, hot water cools very quickly by releasing heat and ice is cooled faster than cold water.
Another explanation is that hot water quickly evaporates. And we know that the process of evaporation is thermostatic or endothermic. As a result, when water evaporates, the water cools down quickly and helps it to freeze faster.
However, none of these interpretations received sufficient acceptance. For a long time the mystery of the Mpemba effect remained a mystery.
However, the latest explanation has strongly demanded the unraveling of this mystery. This explanation was given by a team of physicists from Nanyang Technological University in Singapore led by Xi Zhang.
According to their research, the main role behind this mystery is the different types of chemical bonds that exist in water.
A large oxygen atom in a water molecule is connected by covalent bonds to two relatively small hydrogen atoms. But hydrogen bonding plays an important role when numerous water molecules are together. When a water molecule comes close to another water molecule, the oxygen atom of one water molecule forms a bond with the hydrogen atom of another water molecule, which is called hydrogen bond.
Hydrogen bonds are weaker than covalent bonds but stronger than Vander Wallace balls. These hydrogen bonds play a very important role in determining the properties of water. Even the boiling point of water determines why it is higher than other liquids.
According to Xi Zhang and his team’s research, hydrogen bonding brings water molecules very close to each other. Since a water molecule is connected to all the water molecules around it by hydrogen bonding, the covalent bond (O-H) between the hydrogen and oxygen atoms in their respective molecules expands for hydrogen bonding. As a result, energy is stored in this expanded covalent bond.
But when the water is heated, the hydrogen bonds in the water begin to expand. This causes the covalent bonds of each molecule in the water to contract due to the force of attraction and the stored energy is released.
Interestingly, the release of this energy is the same as the cooling of the water. This means that as a result of the release of the stored energy, the water cools down quickly and freezes at the appropriate temperature.
Understandably, these phenomena cannot happen so quickly in the case of cold water. The release of energy stored in covalent bonds in cold water does not occur as fast as in warm water. As a result, it freezes when kept at the right temperature, but not as fast as warm water.
Researchers have also shown mathematically that loosening of covalent bonds in water occurs less quickly in hot water than in cold water, which is why hot water condenses faster than cold water.
In this way, the long-held notion that “hot water freezes faster than cold water” is proved true.
Let us now turn to the answer given earlier, where it was said that in some cases it would not be right to say yes directly to the answer to today’s question.
This can happen in many cases where the cold water will freeze first. For example, if hot water and cold water are kept in a container, then the Mpemba effect will not occur if the mouth of both the containers is closed. Because in this case evaporation of hot water will not happen.
Mpemba effect is normally true except in some special cases like this. This means that hot water will freeze faster than cold water.