Gas Laws – Explained Using Kinetic Molecular Theory

Pressure varies inversely with the volume of a fixed amount of gas at a constant temperature --- this is known as Boyle’s Law of gases.
Use a molecular model to explain pressure
A gas is composed of a large number of particles in rapid motion. Each particle occasionally collides with a wall of the container. As a result of that collision, the particle exerts a force on the wall. This creates pressure (ratio of force to area).
Use a molecular model to explain Boyle’s law
Gases can be compressed because most of the volume of a gas is empty space. If we compress a gas without changing its temperature, the average kinetic energy of the gas particles stays the same. There is no change in the speed with which the particles move, but the container is smaller. Thus, the particles travel from one end of the container to the other in a shorter period of time. This means that they hit the walls more often. Any increase in the frequency of collisions with the walls must lead to an increase in the pressure of the gas. Thus, the pressure of a gas becomes larger as the volume of the gas becomes smaller.

For a fixed amount of gas at a uniform volume, the pressure of the gas varies directly with the absolute temperature of the gas --- this is known as Gay-Lussac’s Law of gases.
Use a molecular model to explain temperature
Temperature is the average kinetic energy of a collection of gas particles.
Use a molecular model to explain Gay-Lussac’s law
The average kinetic energy of a gas particle depends only on the temperature of the gas. Thus, the average kinetic energy of the gas particles increases as the gas becomes warmer. Because the mass of these particles is constant, their kinetic energy can only increase if the average velocity of the particles increases. The faster these particles are moving when they hit the wall, the greater the force they exert on the wall. Since the force per collision becomes larger as the temperature increases, the pressure of the gas must increase as well. In addition, because the volume is constant, the increased speed creates an increased frequency of collisions, which leads to more pressure.
What is “absolute zero” according to the molecular model?
Absolute zero is the point where no more heat can be removed from a system, according to the absolute or thermodynamic temperature scale. This corresponds to 0 K or -273.15°C. There should be no movement of individual molecules at absolute zero. Theoretically, the molecules also exert no pressure at this