Properties and pressure of gases
Pressure is an indicator characterizing the ratio of the force acting on the surface perpendicular to it, to the area of this surface.
A distinctive feature of the gas is itsability to fill the entire container or vessel within a confined space. That is, the vessel is filled with gas evenly. As the gas is filled, the gas presses against the walls of the tank. If we do not go into the structural analysis of the gas, then we can say that the pressure of the gases is balanced throughout the vessel. But, given the molecular structure of the gas, one can not speak of its calm state. Molecules are always in motion and strike against the walls, colliding with each other. In one place these blows can be more intense, and in the other - there is no need at all. This movement of molecules is chaotic.
Faced with an obstacle, the molecule actson it with a force equal to the product of the mass of the molecule by its velocity. Starting from the wall, the molecule doubles this index. This result must be multiplied by the number of beats per second per square centimeter. The obtained index according to Newton's law is equal to the force that affects this site, multiplied by the time of action. The value obtained is the pressure of the gas mixture.
What factors determine the pressure of gases?
The most important is the compression ratio of gases. In other words, this is the number of molecules that are in a given vessel. An example is the process of inflating tires.
The second parameter is the temperature of the gas mixture. The pressure can change under the influence of two factors simultaneously: with a change in temperature or a change in volume. But each of these indicators has a negligible effect on the parameters of another factor. The optimum gas pressure, that is, its equilibrium, occurs with balanced temperature and mechanical effects.
When the pressure of gases in the entire container becomesuniform, mechanical equilibrium comes. At this point, movement is stopped in different parts of the gas mixture. Thermal equilibrium is observed at a time when the temperature becomes the same for different parts of the vessel and there is no heat exchange between the parts of the gas.
From all that has been said, we can conclude thatThe pressure of the gases is determined by the movement of molecules and their impacts against the walls of the vessel. If you reduce the amount of gas in the vessel, the pressure will increase. Conversely, when the amount of gas in the tank increases, the pressure decreases. This rule is effective at constant values of temperature and mass of the gas.
As the temperature rises, an increase in the gas pressure is observed. This occurs only when the mass of the gas is unchanged.
Measurement of gas pressure occurs withoutapplication of the formula. This is necessary when conducting practical exercises and experiments. To measure air pressure, only an atmospheric pressure indicator is required. To measure the pressure of gases in a sealed container, some auxiliary devices are required: a barometer, a thermometer, a balance, a manometer.
Air is also a mixture of gases. To measure air pressure, you can use an ordinary barometer-aneroid. On its scale, use units such as atmosphere or millimeters of mercury. You can also use a mercury barometer, which is less convenient, but more accurate.
To measure the pressure in a sealed container, a manometer is usually used. For more accurate measurements, an electronic pressure gauge is used, on which the measuring range can be adjusted.
If the basic characteristics of the gas are known, then we can use the formula to calculate its pressure.