CBSE Class 11-science Answered

The kinetic theory of matter has limitations when it comes to the condensed state of matter:

Liquid state - kinetic theory does not fully explain the properties of liquids. This is due to the fact that in liquids, molecules are close together, but still retain certain degree of constant, random motion. Thus, liquids have no definite shape, and can diffuse (e.g. a drop of ink in water spreads until it is uniformly distributed throughout the volume of water).

In liquids, the kinetic energy of the molecules is proportional to the absolute temperature. The rise in temperature increases the molecular motion in the liquid and consequently weakens the intermolecular forces.

Therefore, the volume of liquids increase with increasing temperature, but not as much as in gases.

Note: the properties of liquids : indefinite shape, diffusion and increase in volume with increase in temperature can be explained using the kinetic theory; while the properties: fixed volumes and incompressibility cannot be explained by the kinetic theory.

Solid state - in the solid state, the molecules are in fixed positions. I.e., they are unable to move over and beyond one another to assume new positions. Therefore, the kinetic theory does not explain the properties of solids. Solids have definite shapes and fixed volumes, and cannot diffuse.