The mostajortity of solid substances like high temperature superconductors, biocompatible plastics, silicon chips, etc, are destined to play an ever expanding role in future development of science.
We are mostly surrounded by solid and we use them more often than luquid and gases. For different applications we need solids with widely different properties. These properties depends upon the nature of constituent particles and the binding forces operating between them. Therefore study of the structure of solid is important. The correlation between structure and properties helps in discovering new solid materials with desired properties like high temperature superconductors, magnetic materials, biodegradable polymers for packing, biocompatible solids for surgical implants, etc.
For our earlier studies, we know that luquids and gases are called fluids because of their ability to flow.
The fluidity in both of these states is due to the fact that the molecules are free to move about. On the contrary, the molecules are free to move about. On the contrary, the constituent particles in solids have fixed positions and can only oscillate about their mean positions. This explains the rigidity in solids. In crystalline solids, the constituent particles are arranged in regular patterns.
In this Unit we shall discuss different possible arrangements of particles resulting in serveral types of structures. The correlation between the nature of interactions within the constituent particles and serveral properties of solids will also be explored. How these properties get modified due to the structural imperfections or by the presence of impurities in minute amounts would also be discussed.
General Characteristics of Solid State
Under a given set of conditions of temperature and pressure, which of these would be the most stable state of a given substances depends upon the net effect of two opposing factors.
Intermolecular forces tends to keep the molecules (or atoms or ions) closer, whereas thermal energy tends to keep them apart by making them move faster. At sufficiently lot temperature, the thermal energy is low and intermolecular forces bring them so close still oscillate about their mean positions and the substances exists in solid oscillate about their mean positions and the substances exists in solid state. The following are the characteristics properties of the solid state:
- They have definite mass, volume state:
- Intermolecular distance are short.
- Intermolecular forces are strong.
- Their constituent particles (atoms,molecules or ions) have fixed position and can only oscillate about their mean positions.
- They are incompressible and rigid.
