Ode is one of the most amazing substances.Despite the widespread and ubiquitous use of it - a real mystery of nature.As one of the compounds of oxygen, water, it would seem to have very low characteristics such as boiling point and freezing point, heat of vaporization, and so on. N. But this is not happening.One only heat capacity of water, in spite of everything, is extremely high.
Water is able to absorb a huge amount of heat itself with virtually no heating up - this is its physical characteristics.The specific heat of water above the sand of the heat capacity is approximately five times and ten times - iron.Therefore, water is a natural cooler.Her ability to accumulate large amounts of energy allows you to smooth out fluctuations in temperature on the surface of the Earth and to adjust thermal conditions throughout the world, and it happens regardless of the season.
This unique property of water allows its use as a coolant in industry and in everyday life.Besides water it is publicly available and relatively cheap raw materials.
What is meant by heat capacity?As we know from the course of thermodynamics, heat transfer always happens from hot to cold body.This involves passage of a certain amount of heat and the temperature of the two bodies, being their characteristic state indicates the direction of the exchange.The heat exchange process, for example, a metallic body with an equal weight of water at the same initial temperature of the metal changes its temperature is several times more water.
If we accept the postulate of the main statement of thermodynamics - of two bodies (isolated from others), when one gives the heat exchange and the other gets an equal amount of heat, it becomes clear that the metal and the heat capacity of water is completely different.
Thus, the heat capacity of water (or any material) - a measure of the ability of the substance to give (or receive) a certain amount of heat during the cooling (heating) per unit temperature.
specific heat material is considered the amount of heat required to heat the unit of this material (1 kg) is 1 degree.
amount of heat released or absorbed by the body, is the product of the values of specific heat, mass, and temperature difference.It is measured in calories.One calorie - namely the amount of heat which is enough to heat the water of 1 g of 1 degree.For comparison, the specific heat of air - 0.24 cal / g ° C ∙, alumina - 0.22, iron - 0.11, mercury - 0.03.
heat capacity of water is not constant.As temperature increases from 0 to 40 degrees it is slightly reduced (from 1.0074 to 0.9980), whereas all other substances in the heating process, this characteristic increases.Further, it may decrease with increasing pressure (depth).
As is known, water has three aggregate states - liquid, solid (ice) and gaseous (vapor).Whereby the specific heat of ice is about 2 times lower than that of water.This - the main difference between the water from the other substances, values of specific heat in the solid and molten state does not change.What's the secret?
fact that ice has a crystalline structure which is destroyed when heated at once.Water contains small particles of ice, consisting of several molecules and called associates.When heated, the water of the heat energy expended in the destruction of hydrogen bonds in these formations.This explains the extremely high heat capacity of water.Fully connection between its molecules are destroyed only in the transition from water to steam.
Specific heat of steam at a temperature of 100 ° C is not very different from that of ice at 0 ° C. This once again confirms the correctness of this explanation.The heat capacity of steam as the heat of ice, now understood much better than the water, for which scientists have not yet been agreed.
