We remember physics - what is the heat capacity of water?

Ode is one of the most amazing substances. Despite widespread use and widespread use, it is a real mystery of nature. Being one of the compounds of oxygen, water, it would seem, should have very low characteristics such as boiling and freezing points , the heat of vaporization, etc. But this does not happen. Only the heat capacity of water, in spite of everything, is extremely high.

Water is capable of absorbing a huge amount of heat, while itself practically not heating - this is its physical feature. Specific heat of water above the heat capacity of sand is about five times, and ten times - iron. Therefore, water is a natural coolant. Its property to accumulate a large amount of energy makes it possible to smooth out temperature fluctuations on the Earth's surface and regulate the thermal regime within the whole planet, and this happens regardless of the season.

This unique property of water makes it possible to use it as a cooling agent in industry and at home. In addition, water is generally available and relatively cheap raw materials.

What is meant by the heat capacity? As is known from the course of thermodynamics, heat transfer always occurs from hot to cold. In this case, we are talking about the transition of a certain amount of heat, and the temperature of both bodies, being a characteristic of their state, shows the direction of this exchange. In the process of heat exchange, for example, a metal body with water of equal mass at the same initial temperatures, the metal changes its temperature several times more than water.

If we accept for the postulate the basic statement of thermodynamics - from two bodies (isolated from others), with one exchange of heat, and the other receives an equal amount of heat, it becomes clear that the metal and water have completely different heat capacities.

Thus, the heat capacity of water (as well as of any substance) is an indicator characterizing the ability of a given substance to give (or receive) a certain amount of heat upon cooling (heating) per unit temperature.

Specific heat capacity of the substance is the amount of heat required to heat a unit of this substance (1 kilogram) by 1 degree.

The amount of heat released or absorbed by the body is equal to the product of the specific heat, mass, and temperature difference. It is measured in calories. One calorie is exactly the amount of heat that is enough to heat 1 g of water per 1 degree. For comparison: specific heat of air - 0.24 cal / g ∙ ° C, aluminum - 0.22, iron - 0.11, mercury - 0.03.

The heat capacity of water is not constant. With an increase in temperature from 0 to 40 degrees, it slightly decreases (from 1.0074 to 0.9980), whereas for all other substances this characteristic increases in the process of heating. In addition, it can decrease with increasing pressure (at depth).

As is known, water has three aggregate states - liquid, solid (ice), and gaseous (vapor). The specific heat of ice is approximately 2 times lower than that of water. In this - the main difference between water and other substances, the specific heat capacity of which does not change in the solid and molten state. What is the secret here?

The fact is that ice has a crystalline structure that does not immediately break down when heated. Water contains small particles of ice, consisting of several molecules and called associates. When water is heated, some of the heat energy is expended on the destruction of hydrogen bonds in these formations. This explains the unusually high heat capacity of water. Completely the bonds between its molecules are destroyed only by the transition of water to steam.

The specific heat of water vapor at a temperature of 100 ° C almost does not differ from that of ice at 0 ° C. This again confirms the correctness of this explanation. The heat capacity of steam, like the heat capacity of ice, has now been studied much better than water, in relation to which scientists have not yet come to a consensus.