The kinetic-molecular theory explains the properties of the gases in terms of energy, size and motion of their particles.
The assumptions that the kinetic-moletuclar theory makes about the characteristics of gas particles are:
1. Gases are constituted by a large amount of particles (atoms or molecules) symilar to solid spherical sphers, in constant and random motion.
2. Gas particles move in straight line until collide with another particle or the walls of the vessel.
3. Gas particles are so small compared to the distances that separate them, that the volume of the gas is considered empty space: the volume of the particles is neglected.
4. Beside the already mentioned collisions with the walls of the vessels or between the particles, there is no interaction (attractive or repulsive forces) acting on the gas particles.
5. The collisions between gas particles or with the walls of the vessel are elastic: there is not loss of energy.
6. The average kinetic energy of the particles in a gas depends only on the absolute temperature of the gas: at a given temperatue every gas have the same average kinetic energy.
That collection of assumptions are used to explain such things as: the relation of pressure withthe number of particles, the relation of pressure and temperature, the relation of pressure and volume, the relation of volume and temperature, Avogadro's hypothesis (relation of volume and number of particles), Dalton's Law of partial pressures, and both effusion and difusion.
