Kinetic Molecular Theory of Gases:

Kinetic Molecular Theory of Gases:
Scientists use the kinetic molecular theory (KMT) to describe the behavior of gases.
The KMT consists of several postulates:
1. Gases consist of small particles (atoms or molecules) that move randomly with rapid velocities.
2. Gas particles have little attraction for one another. Therefore, attractive
forces between gas molecules can be ignored.
3. The distance between the particles is large compared to their size. Therefore the volume occupied by gas molecules is small compared to the volume of the gas.
4. Gas particles move in straight lines and collide with each other and the
container frequently. The force of collisions of the gas particles with the
walls of the container causes pressure.
5. The average kinetic energy of gas molecules is directly proportional to the absolute temperature (Kelvin).The deviations of a real gas from ideal gas behaviour may be quantified by a parameter called the compression factor, usually given the symbol Z. At a given pressure and temperature, attractive and repulsive intermolecular forces between gas particles mean that the molar volume is likely to be smaller or larger than for an ideal gas under the same conditions. The compression factor is simply the ratio of the molar volume Vm of the gas to the molar volume Vm o of an ideal gas at the
same pressure and temperature.
The value of Z provides information on the dominant types of intermolecular forces acting in a gas.
Z = 1 No intermolecular forces, ideal gas behaviour
Z < 1 Attractive forces dominate, gas occupies a smaller volume than an ideal gas.
Z > 1 Repulsive forces dominate, gas occupies a larger volume than an ideal gas.
All gases approach Z=1 at very low pressures, when the spacing between particles is large on average.