Question

Use molecular kinetic theory of gas to explain the pressure-volume relationship from an atomic perspective.

Answer 1

The postulates of the Kinetic Molecular theory of gases are:

1. Gases are made of a large number of particles that behave like hard, spherical objects in a state of constant and random motion.

2. These particles move in a straight line until they collide with another particle or with the walls of the container.

3. These particles are much tinier than the distance between particles. Therefore, most of the volume in a gas is empty space.

4. There exists no force of attraction between two gas particles or between the particle and the walls of the container.

5. The collisions between two gas particles or the collisions of particles with the walls of the container are perfectly elastic. Energy of a gas particle is not lost when it collides with another particle or with the walls of the container.

6. The average kinetic energy of a collection of gas particles is dependent only on the temperature of the gas.

So, as the volume of the gas decreases, there are same number of molecules in the container and hence more number of collisions occur due to the decrease in the empty space between gas particles. Therefore the pressure of the gas increases. When the volume of gas increases, this space increases and there are fewer collisions on the walls of the container leading to a lower pressure.

Hence we can conclude that P is inversely proportional to V