Why does water freeze and become larger

Hydrogen bonding. In general, objects obey thermal expansion and contraction, that is, for the same object, "the density of the solid should be greater than that of the liquid".

But water is the opposite, and the reason for this involves chemistry.

Since water molecules are highly polar molecules, they can be combined into associative molecules (groups of water molecules combined) by hydrogen bonding. Liquid water, in addition to simple water molecules (H2O), also contains association molecules, the most typical two are (H2O)2 and (H2O)3, the former is called bimolecular association water molecule. The density of a substance is determined by the average spacing of molecules within a substance.

When the temperature is 0 when the water is not frozen, most of the water molecules exist as (H2O)3 association molecules, and when the temperature rises, the water molecules mostly exist in the form of bimolecular association water molecules (in the process of water temperature rising from 0 to 4, the effect of increasing water density caused by the breaking of hydrogen bonds of associated water molecules is greater than the decrease of water density caused by the acceleration of molecular thermal movement, so in this process, the density of water increases with the increase of temperature. ), the molecules occupy a relatively small space, and the density of water is at its highest. If the temperature continues to rise above this, the law of thermal expansion and cold contraction of general matter will prevail.

When the water temperature drops to 0, the water freezes, and when the water freezes, almost all the molecules are associated together to become a huge association molecule, and the arrangement of water molecules in the ice is that each oxygen atom has four hydrogen atoms as close neighbors (two covalent bonds, two hydrogen bonds), so this arrangement leads to an open structure, that is to say, there are large voids in the structure of the ice, so the density of the ice is inversely smaller than that of water at the same temperature.

Because the density of water and ice is different.

The density of water is greater than that of ice, and when water turns into ice, the mass does not change, only the volume increases.

The mass is equal, the density of ice is less than that of water, and the mass is the product of density and volume, so the volume of ice is greater than that of water.

It's all about chemistry.

Liquid water has hydrogen bonds between its molecules, which makes it have a higher boiling point and a comparatively smaller molecular spacing. When water becomes solid, the hydrogen bonds disappear and the molecular spacing becomes larger, so it becomes larger in volume.

The density is different, and I didn't study physics.

It seems to be getting smaller...

Thermal expansion and contraction???

Categories: Education, Science, >> Science & Technology.

Analysis: The fact that water turns into ice and becomes larger is due to the strong hydrogen bonding force between water molecules in liquid water. It is more than the intermolecular force (van der Waals force).

When the water is in the state of liquid absorption, under the action of hydrogen bonding force, the water molecules are close together, and the volume is small on the macroscopic level. When it becomes solid, water becomes crystalline, the molecular arrangement becomes regular, the force of hydrogen bonding is weakened, and the macroscopic manifestation becomes larger.

Most liquids become solid because the molecules are more closely packed when the object is solid. However, there is an exception to one category, which is substances that have hydrogen bonds between molecules in the liquid state.

Such substances are water, liquid ammonia, liquid hydrogen fluoride. There are only a few holes thick, and the principle is a bit complicated, just remember it.

The increase in the freezing volume of water is due to a special change in the density of water and the coefficient of thermal expansion and early expansion around 0.

A water molecule is formed by the covalent bonding of one oxygen atom and two hydrogen atoms. Due to the shift between the electron cloud of the hydrogen atom and the electron cloud of the oxygen atom, the molecule has a polar structure. This polar structure causes a force similar to "hydrogen bonding" between water molecules, so that water molecules can move closer to each other and form a relatively compact structure.

In general, liquid water is denser than solid water, due to its molecular structure and hydrogen bonding forces. But when the temperature drops below 0, the water molecules gradually reduce their thermal motion and at the same time gradually approach their alignment. When the temperature reaches 0, the hydrogen bonding force is increased due to the shortening of the intermolecular distance, resulting in a gradual increase in the density of water.

The coefficient of thermal expansion of water

The coefficient of thermal expansion of water refers to the amount of volume change per unit volume of water due to the change in temperature. Normally, the coefficient of thermal expansion of liquid water is normal, but when the temperature drops to 0, the coefficient of thermal expansion changes dramatically.

This is due to the fact that when the temperature is reduced to 0, the hydrogen bond distance between the water molecules is gradually shortened, so that the interaction force between the molecules is enhanced, resulting in the volume of the water molecules increasing at the same time as crystallization.

In addition to the above-mentioned factors, there are other influencing factors that can lead to an increase in the volume of water freezing. For example, impurities or dissolved substances in water can affect the density and structure of water, causing its volume to change when it freezes. In addition, adding some chemicals to water, such as glycerol, ethylene glycol, etc., can also affect the crystallization of water, which in turn affects its volume change when it freezes.

In summary, the reason for the increase in the freezing volume of water is mainly due to the special changes in the molecular structure, density, and thermal expansion coefficient of water. Understanding these reasons can help us better understand the nature and behavior of water, as well as enable more precise design and control in real-world applications.