Ideal Gas Molecules

Ideal gas molecules are defined as perfect, point-sized particles which obey the ideal gas law.
These molecules interact via elastic collisions, meaning the total kinetic energy within the system remains constant.
They are in constant, random motion and this movement is what we perceive as temperature.
All ideal gas molecules, regardless of their size or mass, have the same average kinetic energy at the same temperature.

Ideal Gas Law

The ideal gas law is PV = nRT, where P is the pressure, V is the volume, n is the number of moles of the gas, R is the ideal gas constant, and T is the temperature in Kelvin.
The law allows us to predict the behaviour of a gas under different conditions of pressure, volume and temperature.
According to this law, the volume of an ideal gas is directly proportional to its temperature, provided pressure remains constant. This is known as Charles’ law.
Also, for a fixed amount of gas at a constant temperature, the volume is inversely proportional to the pressure – as the pressure on a gas increases, the volume decreases, and vice versa. This is Boyle’s law.

The pressure exerted by an ideal gas depends on the number of collisions between the gas molecules and the container’s walls. More frequent collisions increase the pressure.
When a gas is heated, the molecules move faster and collide with each other and the container walls more frequently. Therefore, the temperature of a gas is directly related to the average kinetic energy of its molecules.
If the volume of a gas is increased, the molecules have more space to move in and they hit the walls less frequently, hence the pressure decreases.