Why is there less hydrogen bonding in water than in ice?

1.The microstructure of the ice crystals is unconventional, with four other water molecules around each water molecule, which are linked to each other by hydrogen (o:...).h-o) associate with each other;

2.Hydrogen bonds are directional, roughly along the direction of the extension of lone pairs on oxygen atoms and the axial direction of h-o bonds in adjacent water molecules;

3.There are two lone pairs of electrons and two O-H bonds on the oxygen atom of each water molecule, and the angle between them is nearly fixed;

4.The direction of the hydrogen bond is limited by the bond angle of the water molecule, which leads to the fact that the structure of the ice crystal is mainly determined by the orientation of the hydrogen bond, which cannot be tightly packed and has large voids (which can be regarded as being hydrogen-bonded-o:.).h-o-stretched);

5.Although there are many hydrogen bonds in liquid water, the number is smaller than that of ice, and the position is not fixed, so the accumulation of water molecules is tighter than that of ice.

6.Liquid water is densest at 4. This is because there are more (H2O)3 or larger associated molecules in water below 4, and its microstructure has begun to move closer to ice, or there are already many structures that are similar to ice crystals at the microscopic level.

Hydrogen that is covalently bound to the electronegative atom x (fluorine, chlorine, oxygen, nitrogen, etc.) is close to the electronegative atom y (which is also the same as x), and hydrogen is used as a medium between x and y to generate x-h....Y-shaped keys. This bond is called a hydrogen bond.

Conditions for the formation of hydrogen bonds.

A hydrogen atom that forms a strong polar bond with a very electronegative atom.

Atom b (f, o, n) with a small radius, large electronegativity, lone pairs, and partial negative charge

Both ice and water contain hydrogen bonds present. The melting of ice only breaks a few hydrogen bonds, so less energy is required. So there are fewer hydrogen bonds in the water.

CO2 is a linear molecule that belongs to the non-polar molecule of polar bond formation. The carbon in CO2 has no lone electron pairs and does not meet the conditions for hydrogen bond formation.

In liquid water, it is often several water molecules that are bonded together by hydrogen bonds; In ice, water molecules are connected to each other by hydrogen bonds on a large scale, forming loose crystals, which have many voids in the structure, resulting in volume expansion and less density, so there are far more hydrogen bonds in ice than in water.

The hydrogen atom is clear with the atom x (fluorine, oxygen, nitrogen, etc.) with large electronegativity and small radius in a covalent bond, and if it is close to the atom y with high electronegativity y (the same as x), hydrogen is used as the medium between x and y to generate x-h··· A special intermolecular or intramolecular interaction in the form of y, called hydrogen bonding. [X and Y can be hydrogen bonds between molecules of the same kind, such as water molecules; It can also be hydrogen bonds between different kinds of molecules, such as ammonia monohydrate molecules (NH3·H2O).

Liquid water, in addition to containing simple water molecules (H2O), also contains association molecules (H2O)2 and (H2O)3, etc., when the temperature is 0 water is not frozen, most of the water molecules exist as (H2O)3 association molecules, when the temperature rises to (101 kPa), water molecules mostly exist in the form of (H2O)2 association molecules, the molecules occupy a relatively small space, and the density of water is the largest at this time. If the temperature continues to rise above , the law of thermal expansion and 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 the water molecules in the ice is that each oxygen atom has four hydrogen atoms as close neighbors (two covalent bonds, two hydrogen bonds), as shown in the figure below.

This arrangement results in an open structure, which means that there are large voids in the structure of the ice, so that the density of the ice is inversely smaller than that of water at the same temperature.

The reason why there is a contrast in the void of water molecules between water and ice.

When water freezes, the volume expands and the density decreases, which is another anomalous property of cracking water, which can also be explained by hydrogen bonding.

Hydrogen bonding between water molecules.

In water vapor, water exists as a single monolithic H2O molecule; In liquid water, it is often several water molecules that are combined by hydrogen bonding to form (H2O)N

In solid water (ice), the water is connected to each other by hydrogen bonds on a large scale, forming quite loose crystals, so that there are many voids in the structure, causing volume expansion and density reduction, so that ice can float on the surface of the water.

Here's the picture:

The density of water is g cm 3 and the density of ice is g cm 3That's why ice floats on water.

This is because when liquid water solidifies into ice, the interaction between the molecules causes the molecules to be arranged according to a certain rule, and each molecule is surrounded by four molecules to form a crystalline tetrahedron. This arrangement is determined by the van der Waals forces between the molecules. In liquid water, the water molecules are free and can reach the arrangement that forms hydrogen bonds.

The action of hydrogen bonding brings water molecules closer to each other, which counteracts the van der Waals force to a certain extent, resulting in the average distance between water molecules being smaller than the intermolecular distance of ice crystals.

So the density of water is greater than that of ice.

The intermolecular forces include hydrogen bonds, and the melting of the ice not only destroys the van der Waals forces, but also breaks the hydrogen bonds, and the reason is ......Of course, the molecular crystals have van der Waals forces, and of course there are hydrogen bonds in the water, ......Note to students: Intermolecular forces include van der Waals forces and hydrogen bonds.

All destroyed.

Ice has a stable tetrahedral structure that is formed by hydrogen bonds between water molecules. At 0 4 degrees Celsius, most of the destruction is hydrogen bonds, and there are also intermolecular forces, at this time the tetrahedral structure is destroyed, the gap between the tetrahedra will also be inserted into the water molecules, the water density increases, when the temperature rises again, most of the destruction is the intermolecular force, the distance between water molecules is increased due to the thermal movement at one time, and the influence of thermal motion dominates at this time, so the water density becomes smaller, so we say that the water density is the largest at 4 degrees Celsius.

Hydrogen bonding is a special intermolecular force, not a chemical bond, nor a van der Waals force. Water is a molecular crystal, and the intermolecular force is destroyed when the molecular crystal melts and vaporizes; When dissolved in water, ionization occurs or reacts with water to destroy the intramolecular covalent bonds.

The solid state becomes liquid, and the intermolecular distance increases. Ice turns into water, of course, it is necessary to destroy the intermolecular forces to make it smaller, and the distance can be larger. Hydrogen bonding can be between molecules or within molecules.

But there are also hydrogen bonds between the water molecules. Therefore, ice melting or water vaporization not only breaks the intermolecular forces, but also provides additional energy to break the intermolecular hydrogen bonds.

Exist. Hydrogen bonds are usually formed when the substance is in a liquid state, but can sometimes continue to exist in some crystalline or even gaseous substances after they have been formed. For example, hydrogen bonds are present in HF in gaseous, liquid, and solid states.

There are many substances that can form hydrogen bonds, such as water, hydrates, ammonia, inorganic acids, and certain organic compounds. The presence of hydrogen bonds affects certain properties of matter.

The difference in density between ice and water is mainly due to the presence of hydrogen bonds between water molecules, which in the liquid state of water are connected to one water molecule to four water molecules, and when the water solidifies, the hydrogen bonds stretch the water molecules.

Increase the distance between water molecules.

The volume also increases, let the mass of the water be m, and when the water of the m mass condenses into ice, the mass m remains unchanged and the volume becomes larger.

p=m/v.The density is also smaller.

The density of ice is less than that of water because of the presence of hydrogen bonds between water molecules, which in the liquid state of water are that connect one water molecule to four water molecules, and when the water solidifies, the hydrogen bonds stretch the water molecules.

Increase the distance between water molecules.

The volume also increases.

Let the mass of the water be m, when the water of the mass m condenses into ice, the mass m does not change, and the volume becomes larger = m vThe density is also smaller.

The difference in density between ice and water is mainly due to the existence of hydrogen bonds between water molecules, hydrogen bonds in the liquid state of water are to connect a water molecule with 4 water molecules, and when the water solidifies, the hydrogen bonds will stretch the water molecules, so that the distance between the water molecules increases, and the volume increases, let the mass of water be m, when the water of m mass condenses into ice, the mass m remains unchanged, and the volume becomes larger, p=m vThe density is also smaller.