The reasons why hot water freezes into ice more easily than cold water are as follows:

(1) The temperature of hot water is high and the water molecules are constantly moving, which is more intense than the movement of water molecules in cold water. Thermal motion of liquid molecules: Experiments have fully demonstrated that the molecules in liquids move near the equilibrium position like the molecules in crystals and amorphous solids. The vibration modes of liquid molecules in the same unit are basically the same, but the vibration modes of molecules in different units are different, which is somewhat similar to polycrystals. However, this situation can last for a short time in liquids. In the future, due to fluctuations and other factors, units will be destroyed and new units will be reorganized.

We all know that the temperature of hot water is high and the movement of water molecules is intense. The temperature of cold water is low and the movement of water molecules is slow. During the process of water turning into ice, hot water continues to release heat. When 100°C hot water cools to 0°C, it takes a while, that is, the water molecules in the hot water move violently and continue to transfer heat to the parts that are cooled first by collision. Energy, when the entire water part is in the state of cold water at 0°C, it also combines hydrogen bonds. At this time, it is not that 100°C hot water turns into 0°C cold water as people imagine, and 0°C cold water begins to condense into ice. This Obviously, 100°C hot water freezes faster in a refrigerator than 0°C cold water, and 0°C cold water freezes faster. However, the opposite is true. Hot water at 100°C freezes into ice before cold water at 0°C. This may be due to hydrogen bonding. ?

(2) Hydrogen bonds: Since people discovered hydrogen bonds, the special characteristics of water have been revealed. The formation of ice is the association of water (the combination of simple molecules into more complex molecules) The process of forming groups without causing changes in the chemical properties of substances is called molecular association)

The formation and breaking of hydrogen bonds is the main reason why water can associate. To boil water, you need energy, which is to break the hydrogen bonds between water molecules. When the hot water is cooled, the formation of hydrogen bonds forms a huge molecule, thus forming ice.

Water association is a process in which simple molecules contained in water combine to form complex molecular groups without causing changes in the chemical properties of the substance. It can be expressed by the reaction formula of a reversible process: nH2O=(H2O)n. When the associated molecules and simple molecules are in equilibrium, there will be no association process and dissociation process. Once this reversible process is destroyed, water becomes It forms ice, ice turns into water, and the process of repeated cycles of ice and water. ?

Because association is an exothermic process and dissociation is an endothermic process, as the temperature increases, the degree of association of water decreases (n decreases). At high temperatures, water mainly exists in a single molecule state. ; As the temperature decreases, the degree of association of water increases (n becomes larger). Water freezes into ice at 0°C, and all water molecules associate into one huge molecule. ?

When hot water is still 100℃, water mainly exists in a single molecule state. When hot water turns into cold water, single molecules in the water gradually turn into associated molecules, but single molecules still occupy Dominant position, it can be seen that the reaction continues in the direction of associated molecules, which is more conducive to ice formation. However, due to the low temperature of cold water at 0°C, the water components have a single molecule state and an associated molecule state, and when the single molecule state is As the molecular state continues to move toward the associated molecule state, the number of associated molecules gradually increases. When the single molecule state and the associated molecule state reach equilibrium, an equilibrium state will be reached. The 100°C hot water continuously releases heat during the cooling process, thereby providing external energy for the formation of hydrogen bonds. At the same time, the single-molecule state molecules dominate and continue to generate molecules in the associated state, which is the direction of ice generation. occur.

When hydrogen bonds continue to form, associating molecules into a huge molecule, all the hot water turns into ice. As the cold water reaches the balance between the association process and the dissociation process, although hydrogen bonds are formed at this time, it is very slow because cold water at 0°C cannot continuously provide external energy. Only when the hydrogen bonds are slowly formed, the previous stage is broken. At the equilibrium, the cold water still reacts in the direction of forming ice. At this time, the hot water has already associated into a huge molecule, that is, ice due to the rapid formation of hydrogen bonds. Therefore hot water freezes into ice before cold water.

From the above conclusion and the formation process of hydrogen bonding, it can be seen that hot water is easier to form ice than cold water.

(1) The existence of a certain molecular gap in the liquid also creates conditions for unit destruction and reorganization. Although the residence time of any molecule in the unit is different, under a certain temperature and pressure, the average residence time i of liquid molecules in the unit is the same. Generally, molecules vibrate an average of 100 to 1,000 times in a unit. The thermal motion of liquid molecules can be compared as follows: all molecules live a nomadic life, alternating between short-term migrations and longer-term settled lives. The average settlement time i experienced between two migrations is much longer than the period of vibration of the molecules in the unit. The size of i is related to the contradiction between molecular force and thermal motion. The closer the molecules are arranged, the stronger the intermolecular force, the harder it is for the molecules to move, and the larger i is; the higher the temperature, the more intense the thermal motion of the molecules, the smaller i, and the easier it is for the molecules to migrate. Normally, the time the external force acts on the liquid is always much longer than the average settlement time i. During this time, the liquid molecules have traveled through many units, resulting in macroscopic displacements.

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(2) The main reason why water molecules can associate is due to the formation of intermolecular hydrogen bonds. In ice crystals, a hydrogen atom with a single *** valence bond has a strong ability to attract electrons. When the oxygen elements combine to form a positive valence bond, the electron cloud is strongly biased by oxygen toward oxygen, a highly ionic atom with a positive valence bond, so that the hydrogen atom becomes a "naked" proton. At this time, the radius is very small. In addition to combining with oxygen, the partially positively charged "baked" hydrogen ion can also be combined with another negative ion. This bond is called a hydrogen bond. It can be seen that if a hydrogen atom has a hydrogen bond, it can be combined with two atoms through two bonds, one is a polar hydrogen bond, and the other is a hydrogen bond. The energy is about 20KJ/mol, which is much smaller than the valent bond. Hydrogen bonds are the main form of combination between water and ice, and are also the reason why water has many special properties.