Gas Laws

Gas molecules in the vessel are in constant random motion, at high speed, colliding with one another and with the walls of the container. This causes some force being exerted on the walls of the container. This force that a gas exerts on the walls of the container per unit area is known as gas pressure. This pressure which is constant for every unit area can be either raised or reduced by altering certain factors such as temperature, the amount of gas, or the volume of the container.

There are important gas laws which show the relationship between the volume and pressure of gases as well as effect of temperature on them.

1. Boyle’s law
2. Charles’ law
3. Combined gas law
4. Graham’s law of diffusion.

All these gas laws exploit aspects of the kinetic theory of matter. Kinetic theory of matter states:

1. Matter is made up of particles (molecules or ions)
2. The particles in liquids and gases are in continual motion in straight lines in every direction. They continually collide with one another and with sides of the containing vessel. Bombardment of walls of the vessel, explains the pressure of a gas. The speeds and distances between collisions of the particles in a liquid are much smaller than those in a gas.
3. The distances between particles in a gas are on average much greater than the size of the particles themselves. The particles are closer together in a liquid.
4. The particles are completely elastic and therefore no energy is lost when two particles collide.
5. Increase in temperature causes the average speed of particles to increase, that is, the kinetic energy increases.