Question

How does a gas expand according to the kinetic molecular theory?

Answer 1

To answer this question we should know what expansion means and the kinetic molecular theory. The increase in volume is known as expansion. The kinetic molecular theory deals with the kinetic energy of the particles of gas.

Complete answer:
The kinetic molecular theory is as follows:

1. According to the kinetic molecular theory, the gas is composed of a large number of particles. The particles are hard spheres.
2. The particles move in a straight line. They can collide with another particle or with the wall of the container.
3. The collisions are perfectly elastic.
4. The average kinetic energy of the particle is directly proportional to the temperature.
5. The size of the gas particles is very small.
6. There is no attraction between particles or between particles and walls.
7. According to the kinetic molecular theory, when we increase the temperature of the gas. The gas particles gain energy. So, the kinetic energy of the particle increases. So, the average speed of the gas particles increases. The gas particles now colloid with each other and with the wall of the container more frequently, so the repulsion between particles increases. So, the pressure of the gas increases. Then the volume of the gas increases to reduce the pressure. Thus expansion takes place.
   Therefore, gas expands according to the kinetic molecular theory at constant pressure on increasing temperature.

Note: Elastic collision means there is no loss of energy during a collision. During collision particles exchange energy. Due to the small size of gas particles, the volume occupied by the gas particles is negligible compared to the volume of gas. The pressure is inversely proportional to the volume. Temperature is directly proportional to the volume. The temperature is also directly proportional to the pressure.