Gas molecules move randomly. Due to this movement, some special properties are produced in the gaseous state of matter. In order to explain these features , the theories of scientists like Gassendi, Newton, Bernoulli, Clausius and Maxwell have come up with a theory known as the kinetic theory of gas. Kinetics consists of a number of acknowledgments. Postulates of Kinetic theory 1. Structure of gas: All gases are composed of innumerable small , spherical and elastic particles . These particles are called molecules. However, in the case of inert gases, these particles are atoms. The size and mass of each molecule of a gas is the same. 2. Molecular mobility: Gas molecules move around endlessly. During this rush the molecules collide with each other and on the vessel. The path between any two collisions is straight linear. 3. Average free path: The average of the distances between two collisions is called the average free path of a gas molecule. 4. Time of collision: The time spent between the molecules just for collision is negligible compared to the time between two collisions. 5. Velocity: Since gas molecules are fully elastic, their velocity does not change as a result of collisions. . Pressure: The pressure of gas is caused by the collision of gas molecules with the vessel. Gas pressure is the force exerted on a single field on a vessel as a result of a collision. . Volume: Gas molecules are so small that the total actual (own) volume of the molecules is negligible compared to the volume of the gas vessel and the total volume of the gas. . Gravity / repulsion: Gas molecules are so far apart from each other that they are considered to have no attraction or repulsion towards each other. 9. Kinetic energy: The kinetic energy of a gas is proportional to the absolute temperature. 10. Effect of gravitational force: Gravitational force has no effect on the motion of gas molecules.