Pressure of Gases

Understanding Gas Pressure

Pressure in gases is caused by gas particles hitting the walls of its container. It is measured in Pascal (Pa).
The concept of pressure is closely related to the idea of force. As gas particles hit and push against the sides of their container, they exert a force on it, which results in pressure.
If gas particles hit the walls more often, or with more force, they create a greater pressure.

Calculating Gas Pressure

The formula for pressure is pressure = force / area. It entails that pressure increases with increasing force and decreases with increasing area.
For gases, the relevant ‘area’ is often the inside surface area of the container in which the gas is held.

Factors Influencing Gas Pressure

Temperature: Increasing the temperature of a gas increases its pressure. This is because heating a gas gives its particles more energy, which makes them move faster and hit the walls of their container harder and more frequently, thereby increasing the pressure.
Volume: Decreasing the volume of a container holding a gas (while keeping the temperature constant) increases the pressure. This is because when you squeeze a gas into a smaller volume, its particles hit the walls more often (because they have less space to move around in), which increases pressure.
Number of Particles: Increasing the number of gas particles in the same volume increases the pressure. More particles mean more collisions with the container walls.

Describing Gas Pressures

The pressure of a gas can range from a total vacuum to many millions of pascals.
It can be described in various ways. For example, the term ‘vacuum’ refers to a place where the gas pressure is much lower than atmospheric pressure.
Standard atmospheric pressure (at sea level) is 101325 Pa.

Pressure and Changes of State

If you keep reducing the pressure of a gas (while keeping its temperature constant) eventually it will become a liquid.
Conversely, if you keep increasing the pressure on a liquid (while keeping its temperature constant), it will eventually become a gas.

Practical Applications of Gas Pressure

Gas pressure has numerous practical applications such as in car tyre inflation, weather forecasting, brewing, and deep-sea diving among others.
Knowledge of gas pressure is particularly important for designing and using pressure-operated devices such as gas cylinders and aerosol cans.

Understanding Pressure Changes

Changes in gas pressure can be dangerous. For instance, a rapid decrease in atmospheric pressure is associated with storms.
In industry, precautionary measures are required to handle pressurised gases to prevent unwanted incidences.

Remember, a solid understanding of the concept of gas pressure is not only essential for this exam, but also for many real-world applications. Regular practice of problems relating to gas pressure will help you with this.