The air around us plays an important role in the life of biological organisms that inhabit planet Earth. But human activity associated with a wide variety of technological processes, identified this substance in the category of technically important gases. He underwent a thorough study for physical properties. During the experiments, the physical properties of air, a number of their features and dependencies were revealed.
The difficulty of working with air is that it is a heterogeneous substance and is a solution of a huge number of components. But all the same, a certain stability of its composition is present.
A natural recipe for a vital gas (air) includes an almost stable set of ingredients. Today they have the following percentage: nitrogen occupies 78 percent, oxygen - 20, carbon dioxide - 0.03 percent. Steam, other gases and even solid particles occupy about one and a half percent. The specific heat of air depends not only on other physical factors, but also varies depending on the internal content (composition) of the gas.
For the collection and analysis of data on the thermodynamic properties of air, the work of the teams of the largest world laboratories was spent. These studies originate from the end of the XIX century and are actively conducted to this day. Their results are used in the calculation of a wide variety of energy and air separation plants, apparatus for the chemical industry and other devices.
The specific heat of air is a value that determines the amount of thermal energy that needs to be spent so that one kilogram of this gas changes its temperature by one degree (kelvin). Given the previously indicated dependence of this value on many factors, various graphs and tables are created for engineering purposes. They indicate how the specific heat of the air changes depending on temperature or humidity.
For a deeper study of this substance, experiments were carried out for which dry air, purified from carbon dioxide, was used. In the first case, specific heat was determined at constant pressure (Cp), in the second case at a constant volume (Cv) and the thermometer readings were the same. Interestingly, at 0 ° Cp was 0.2402 cal / g · deg, and Cv of the same gas was 0.1713 cal / g · deg. The ratio of these quantities gives the following thermodynamic indicator, which is important in thermodynamics.
To determine the gas constant (R), the difference in specific heat capacities of the gas under study is calculated at constant pressure (Cp) and at constant volume (Cv). The physical meaning of this quantity is to determine the work of expansion, for example, one kilogram of gas (air) with an increase in its temperature by one degree (kelvin).
In previous experiments, the physical properties of dry air were studied. In real practice, you have to take into account the percentage of steam (humidity) in it. The specific heat of air containing a certain amount of water (steam) has its own dependencies and patterns of change.
Wet air has become the subject of a whole trend in physical research, because the vapor content in it has an effect on a number of physical and even chemical processes. Living organisms are no exception. Changing air humidity not only affects the comfort of the microclimatic conditions of the room (office, workshop, laboratory), but also affects the performance of employees, the safety of a number of substances, and even the functioning of some devices.
Not only a statement of facts, but also the search for various ways to influence the properties of air is the subject of scientific research. They are of great importance in various fields of human activity, from the chemical industry to the construction of residential premises.