Explanation of Gas Law using Kinetic theory

Kinetic molecular theory  of gases states that:

1. All matters are made up of Molecules  and Atom.
2. The molecules are in a constant state of motion.
3. The molecules possess kinetic energy because of their constant motion.
4. The molecules exert attractive force on one another.
5. The nearer the next molecule, the greater the attractive force.

We can use the above kinetic theory of gases to explain the behaviour of gases;

1. Under pressure
2. Charles’ Law
3. Boyle’s law
4. Pressure Law

1. Explanation of Gases under pressure  with kinetic theory.

When a gas is in container, the molecules of the gases exerted pressure through the wall of the container, thereby exerting pressure on itself. The molecules are like sphere and move about in the container with random velocity colliding with one another and with the wall of the container. As the molecules hit the walls of the container, they rebound. The velocity and the momentum changed. The walls of the container experience some force due to the change in momentum. Pressure is force per unit area; some pressure is therefore experienced at the point of collision with the wall of the vessel. This is the kinetic theory explanation of the pressure exerted by the molecules of gas.

2. Explanation of Charles’ Law with kinetic theory.

Charles’ Law states that the volume of a given mass of a gas is directly proportional to its absolute temperature at constant pressure. When the temperature of a fixed mass of gas is increase the volume increases.  The molecules gain kinetic energy as a result of increase in temperature, hence the velocity increases. As the velocity increases, they hit the walls of the container more frequently which brings about the increase in pressure. The volume must be increased to keep the pressure constant; therefore, the molecules will travel further before hitting the wall of the vessels. An increase in temperature increases the volume because to keep the pressure constant then the volume must be increased.

3. Explanation of Boyle’s Law with kinetic theory.

From Boyle’s Law, increase in volume of a given mass of gas decreases the pressure of the gas. The molecules of gases move with certain velocity and momentum.  When these molecules collide with the wall of the vessel, the velocity changes and momentum also changes. The change in momentum produces force on the wall of the vessel. This force per unit area is the pressure that the gas molecules exerted on the wall of the vessel. When the vessel size is increased the gas molecules have more space to travel before they hit the wall of the vessel thereby reduces the pressure. Increase in volume or the size of the vessel will eventually reduce the pressure. This explains the Boyle’s Law with kinetic theory.

4. Explanation of Pressure Law with kinetic theory.

Pressure law states that the pressure of a given mass of a gas is directly proportional to its temperature at constant volume. This means increase in temperature of a gas increases the pressure. When the temperature of a gas in a vessel is increased, the molecules gain more kinetic energy and are able to move at higher speed. As they move at higher speed, it takes less time to hit the wall of the vessel to create pressure on the vessel. The higher the temperature the less the time it takes the molecules to create pressure. This explains pressure law. On the other hands, if the temperature is reduced, the molecules loss kinetic energy. The average kinetic energy is reduced. It takes more time to hit the wall of the vessel to create pressure. Increase in temperature at constant volume increases the pressure.

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