Pressure is an indicator characterizing the ratio of the force acting on a surface perpendicular to it to the surface area.
A distinctive property of a gas is its ability to fill an entire container or vessel within a limited space. That is, the vessel is filled with gas evenly. As it fills, gas presses on the walls of the tank. If you do not go into the structural analysis of gas, then we can say that the gas pressure is balanced throughout the vessel. But, given the molecular structure of the gas, one cannot speak of its calm state. Molecules are always in motion and hit walls, colliding with each other. In one place, these strikes can be more intense, and in another they can be absent altogether. This movement of molecules is chaotic.
Faced with an obstacle, a molecule acts on it with a force equal to the product of the mass of the molecule and its speed. Based on the wall, the molecule doubles this indicator. This result must be multiplied by the number of beats per second per square centimeter. The obtained indicator according to Newton's law is equal to the force that acts on this site, multiplied by the duration of the action. The obtained value is the pressure of the gas mixture.
What factors determine gas pressure?
The most important is the indicator of gas compression. In other words, this is the number of molecules that are in this vessel. An example is the tire inflation process.
The second indicator is the temperature of the gas mixture. 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 optimal gas pressure, i.e., its equilibrium, occurs at balanced temperatures and mechanical stress.
When the gas pressure in the entire tank becomes uniform, mechanical equilibrium sets in. At this moment, the movement in different parts of the gas mixture stops. Thermal equilibrium is observed at the moment when the temperature becomes the same for different parts of the tank and there is no heat transfer between the parts of the gas.
From the foregoing, we can conclude that the gas pressure is determined by the movement of molecules and their impact on the walls of the vessel. If you reduce the amount of gas in the vessel, then the pressure will increase. Conversely, with an increase in the amount of gas in the tank, the pressure decreases. This rule is valid for constant temperature and gas masses.
With increasing temperature, an increase in gas pressure is observed. This occurs only at constant gas masses.
Measurement of gas pressure occurs without the use 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 gas pressure in a sealed container, some auxiliary devices are required: a barometer, a thermometer, a balance, and a manometer.
Air is also a mixture of gases. To measure air pressure , you can use an ordinary aneroid barometer. On its scale, such units of measure as the atmosphere or millimeters of mercury are used. You can use a mercury barometer, which is less convenient, but more accurate.
To measure the pressure in a closed container, usually use a pressure gauge. For more accurate measurements, an electronic pressure gauge is used, on which you can adjust the measurement range.
If the main characteristics of the gas are known, then you can use the formula to calculate its pressure.