Specific heat of the air. Physical properties of substances

The Surrounding air plays an important role in the life of biological organisms inhabiting the planet Earth. But human activities related to various technological processes, has identified this substance in the category of technically important gases. He has undergone thorough learning on the subject of physical properties. The experiments have revealed the physical properties of air, some of their characteristics and dependencies.

The Difficulty with air is that it is a substance heterogeneous and represents a solution from a huge number of components. But all the same a certain stability of its members are present.

Natural recipe vital gas (air) includes a relatively stable set of ingredients. Today they have the following percentages: nitrogen is 78%, oxygen 20 and the carbon dioxide-0.03%. Vapor, other gases and even solid particles is about one and a half percent. Specific heat of the air depends not only on physical factors but also changes depending on the internal content (composition) of gas.

To the collection and analysis of data on the thermodynamic properties of air have been spent in the labor collectives of the world's largest laboratories. These studies originate from the late nineteenth century and are actively maintained to this day. Their results find application in the calculation of various energy and air separation plants, equipment for chemical industry and other devices.

Specific heat of air is a quantity that determines the amount of heat energy that must be spend to one kilogram of this gas changed its temperature by one degree (Kelvin). Considering the previously dependence of this quantity on many factors for engineering purposes, are the various graphs and tables. They indicate how to change the specific heat capacity of air depending on temperature or humidity.

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For a deeper study of this substance, experiments were conducted that used dry air, purified from carbon dioxide. In the first case determined the specific heat at constant pressure (Cp), the second at constant volume (Cv) and the same thermometer. Interestingly, when 0° Cp value amounted to 0,2402 cal/g·grad and Cv of the same gas - 0,1713 cal/g·grad. The ratio of these quantities gives the following thermodynamic figure of importance in thermodynamics.

To determine the gas constant (R) calculate the difference of the specific heats of the studied gas at constant pressure (Cp) and constant volume (Cv). The physical meaning of this quantity is the denition of the extension work, for example, one kilogram of gas (air) by raising the temperature by one degree (Kelvin).

In the previous experiments examined the physical properties of dry air. In actual practice, have to take into account the percentage of steam (humidity). Specific heat capacity of air containing a certain amount of water (steam) has its own dependencies and patterns of change.

The Humid air was the subject of a direction in physical studies, because the vapor content in it affects a number of physical and even chemical processes. Living organisms is no exception. The change in humidity not only affects the comfort of the microclimate of premises (office, shop, laboratories), but also affects the efficiency of staff, the safety of a number of substances and even the functioning of some devices.

Not only a statement of facts, but also finding different ways of influence on the properties of air is a subject of scientific research. They are of great importance in various fields of human activity, ranging from the chemical industry, ending with the construction of dwellings.