At what temperature water has the highest density

The highest density of water at 4 is determined by the special structure of hydrogen bond association between water molecules. According to recent X-ray studies, it has been proved that 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" (that is, some associated molecules formed by the association of hydrogen bonds), 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 H2O molecules can enter another microcrystalline from one tetrahedral. In this way, the voids between the molecules are reduced, and the density increases.

When the temperature increases, the tetrahedral group of water molecules is continuously destroyed, and the disordered arrangement of the molecules increases, so that the density increases. But at the same time, the thermal motion between molecules also increases the distance between molecules, which reduces the density. These two contradictory factors reach equilibrium at 4 o'clock, therefore, the density of water is highest at 4 o'clock.

After 4, the thermal motion of the molecules increases the distance between the molecules, and the density of the water begins to decrease again.

The density of the water. The lower the temperature, the smaller the volume and the greater the density, while the water has the smallest volume and the highest density at 4, which is 1kg·m-3

4 degrees Celsius. Water forms hydrogen bonds at low temperatures, resulting in volume expansion, and thermal expansion at high temperatures, and 4 degrees Celsius happens to be the extreme point of both effects, so the density is the highest.

Water is one of the most peculiar substances, and it's an abnormal expansion!! Density is greatest at 4 degrees.

4. The reason is that the microstructure of water is relatively special.

Water is most dense at 4 degrees Celsius. The density of water we commonly use refers to the density of water at 4 degrees, which is 1000kg m3. Generally speaking, most objects have the property of thermal expansion and contraction, and the higher the temperature, the less dense the substance.

But water is an exception, its thermal expansion is also inflated, and only at 4 times is the smallest volume. Above 4 or below 4, the volume expands. This phenomenon is known as the "anomalous inflation phenomenon".

If a certain mass of water is heated from 0 to 10, the volume of water decreases first and then increases, and 4 is the turning point, when the volume is the smallest and the density is the largest. This singular property of water is easily seen in nature, such as when the water in a river pond freezes in winter, always starting from the surface of the water. That is to say, first of all, the water temperature of the river surface drops to 0, the water temperature below is higher than 0, the temperature gradually increases from top to bottom, the temperature of the river bottom is about 4, the density gradually increases, and the density of the river bottom is the largest.

It is precisely because of this singular property of water that the natural scene of "people walking on the ice and fish swimming on the ice" has emerged.

So far, the research on water molecules is still insufficient, and there is no unified explanation for the abnormal expansion of water.

This property of water causes some losses in people's daily life, such as the force generated by the expansion of the volume when the water freezes, which is enough to break water pipes, cement parts, etc. Of course, there are also benefits for humans, especially in the protection of fish and other aquatic organisms.

Physical properties of water:

The boiling point of water at 1ATM is 100

Freezing point of water: The freezing point of water under 1atm is 0

Density of water: 4 The density of water is the highest, which is 1g ml

The specific heat of water: 1k cal g, which is larger than that of ordinary substances, so the temperature of water is less likely to change than that of other general substances.

Chemical properties of water:

Water is a good solvent:

Heavy water: Water in nature contains very small amounts of heavy water.

Water as a reactant:

Water reacts with alkali metals to produce hydrogen and hydroxides.

Water reacts with most metal oxides to form basic oxides.

Water reacts with most non-metallic oxides to form acidic oxides.

Ion product of water: Water is a very weak electrolyte, and the higher its temperature, the greater the ion product of water.

The density of water is highest at 4 degrees.

It is related to hydrogen bonding.

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 When the water is not frozen, most of the water molecules exist as (H2O)3 association molecules, when the temperature rises to (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 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), as shown in the figure.

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.

In addition, it takes a certain amount of energy to disassemble the associated molecules, which is enough to explain why water has a large specific heat.

The "associative molecules" referred to here are formed by hydrogen bonding.

The main reason for the formation of hydrogen bonds is that the anion has a strong ability to seize electrons, so that the hydrogen atoms of non-homogeneous molecules are also close to it, it is a much stronger force than the intermolecular force, so that many molecules can be concentrated together to form a super-large molecular group, which can increase the melting and boiling point of the substance.

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The question is incorrect: how can the temperature resistance or degree be related to the density?

It should be changed to the relationship between the density of water and temperature.

We know that usually objects have the property of thermal expansion and cold contraction;

Water is special: there is an 'abnormal swelling'That is, at 0-4, the heat shrinks and expands, at this time, the temperature increases, and the density of water increases; Above 4 is normal, the temperature increases, and the density of the water decreases.

As a result, the fish can survive in the cold winter. Because from the bottom to the top, the temperature decreases from 4 to 0 (ice water and orange interface), and then ice.