Why does water get larger when it freezes

The fact that water turns into ice and becomes larger is due to the strong hydrogen bonding force between the water molecules in liquid water. It is much greater than the intermolecular forces (van der Waals force). When water is in a liquid state, under the action of hydrogen bonding force, the water molecules are close together, and it appears to be small in size at the macro 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, and the principle is a bit complicated, just remember it.

When the water freezes, the amount of water does not change, so the quality does not change.

The density of water is, the density of ice is, i.e., the density of ice is less than that of water.

According to the definition of density: density = mass volume, after deformation gives volume = mass density. So when the mass is constant, the density is inversely proportional to the volume, i.e., the smaller the density, the greater the volume. Because ice is less dense than water, it has a larger volume than water.

In general, when the temperature of the object increases, the volume of the object expands and the density decreases, which is commonly referred to as the phenomenon of "thermal expansion and cold contraction". However, when the temperature of water rises by 0, a special phenomenon occurs. The p t curve shown in Figure 2 3 is the curve of water density as a function of temperature.

As can be seen from the figure, the density of water gradually increases as the temperature rises from 0 to 4. The density of the water gradually decreases as the temperature rises from 4 to the same time. Water has its highest density at 4. Water in the range of 0 to 14 exhibits the phenomenon of "cold expansion and heat contraction", which is called abnormal expansion. The anomalous expansion of water can be explained by the theory of hydrogen bonding and associated water molecules.

Why does water get bigger when it freezes? It's not easy for people to know.

The reason why the volume of water increases when it freezes is because there is a strong hydrogen bonding force between the water molecules in liquid water, so the volume is smaller. If the hydrogen atom is close to the atom y y (O, F, N, etc.) with large electronegativity and small radius, hydrogen is used as the medium between x and y to generate a special intermolecular or intramolecular interaction in the form of x-h, which is called hydrogen bonding.

In a typical hydrogen bond, x and y are the very electronegative f, n, and o atoms. But C, S, CL, P, and even Br and I atoms can also form hydrogen bonds in some cases, but usually with lower bond energies. Carbon also has the potential to produce hydrogen bonds when it is attached to several electronegative atoms.

For example, in chloroform CHCL3, the carbon atom is directly connected to three chlorine atoms, and the electron cloud density around the chlorine atom is larger, so the carbon atom is surrounded by a partial positive charge, and the carbon also participates in the formation of hydrogen bonds, playing the role of a proton donor.

First of all, thermal expansion and contraction are only summarized by people's daily experience, although they are applicable to most substances, but not all properties of substances.

Thermal expansion and contraction are caused by the increase in the distance between molecules due to the more intense movement of molecules after being heated; The opposite is true.

But the distance between molecules is not caused by the thermal motion of the molecule alone, so when there are other factors, the situation changes.

Speaking of water, there are probably some reasons for the difference in the density of water from ice

1. Water dissolves a certain amount of air when it is in a liquid state, and the air becomes gaseous when it freezes, so the volume of air becomes larger, but the air is still in water;

2. The molecular structure of ice is an important factor that causes its density to be greater than that of water.

It's like a carbon element.

Similarly, the structure of its molecular composition is different, so the density is also different; In the process of changing from water to ice, the arrangement and structure of its molecules also change, so the density changes.

From the structural point of view: there are hydrogen bonds in the water molecule, at a density of up to 4 grams of cubic centimeters, bimolecular or multiple molecules are associated, and the volume becomes larger.

Under normal conditions, thermal expansion and cold contraction, water abnormal expansion! This is because ice is less dense than water. The density of ice is, and the density of water is 1

When the water freezes, the total mass does not change, but because the density of the ice is low, the volume increases.

The essential reason is because the hydrogen bonding of water makes water different from other substances.

Ice has a tetrahedral crystal structure. This tetrahedron is formed by hydrogen bonding, which is an open relaxation structure, because five water molecules cannot take up the volume of all tetrahedra, and hydrogen bonds in ice connect these tetrahedra into a whole. This directional and orderly arrangement formed by hydrogen bonding has a small space utilization rate, accounting for about 34, so the density of ice is small.

When water dissolves, a large number of hydrogen bonds are disassembled, so that the whole is divided into tetrahedral groups and scattered smaller "water molecule groups" (i.e., some association molecules formed by hydrogen bond association), so liquid water is no longer completely ordered like ice, but has a certain degree of disordered arrangement, that is, the distance between water molecules is not fixed as in ice, and water molecules can enter another microcrystalline from one tetrahedral. In this way, the voids between the molecules are reduced, and the density increases.

Similarly, the presence of hydrogen bonds is also the reason why water is at its densest at 4 degrees Celsius.

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.