The video immediately below on Brownian motion explains the background and significance of the discovery fundamental to our understanding of gases and the Gas Laws. It was the key observation made 1827, not fully explained until 1905 by Einstein that was the key to the development of the kinetic theory of gases.
The lesson demonstrates the experimental set up of fine smoke trapped in a small space under a microscope, the motion of the smoke particles is shown and the explanation for it is given by using animations of the molecular collisions.
The concept of an ideal gas is used in our construction of the theory of gases and equations we use to explain the connections between pressure, volume, temperature and the kinetic energy of the molecules. Understanding these ideas is important in A level physics (16 to 19 specialist physics) and is a starter for developing the kinetic theory of gases.
The video lesson below that is on The Kinetic Theory of Gases is a guide through the arguments using simple animation together with the algebra and assumptions made in deriving the base equation of gas laws. These assumptions are that the molecules will act like an "ideal gas".