Why are Liquids and gases categorised as Fluids ?
Matter can exits in three physical states, solid, liquid and gas depending upon the conditions of temperature and pressure. The molecules in gases and liquids are relatively free to move, therefore these two state are togather called fluid state. )
on the contrary in solids molecules, ions or atoms are not free to move but have capacity to oscillate ( Vibration only ) around there fixed positions due to strong intermolecular, interionic or interatomic forces.
Why are solids incompressible?
Ans: Thus solids are characterized by incompressibility, rigidity and mechanical strength indicating thereby that the molecules, ions or atoms constituting the solids are closely packed. they are held together by strong interparticle forces and cannot move randomly. solids, therefore have definite volume, shape and mass and also may have a well ordered molecular, ionic or atomic arrangement. )
We are mostly surrounded by solids and we use them more often than liquids and gases. for different applications we need solids with widely different properties, This properties depend upon :
- The nature of constituent particles and
- The attractive forces existing between them. therefore, study of the structure of solid is important. The correlations between structure and properties helps in discovering new solid materials with desired properties like High temperature Superconductors ( HTSC), magnetic materials, biodegradable polymers for packaging, biocomplaint solids for surgical implants etc.
General characteristics of the solid state:
In the previous class ( unit 5), we have studied that matter can exist in three state under given set of conditions of temperature and pressure, which of these would be more stable state of a given substances depends upon the net effect of two opposing factors.
- Intermolecular Forces tend to keep the molecules ( or atoms or ions ) closer.
- Thermal Energy tends to keep them apart by making them move faster. at sufficient low temperature, the thermal energy is low and intermolecular forces bring them so close that they cling to one another and solid state.
The important characteristics of solids are listed :
- They have definite mass, volume and shape.
- The constituent particles are very closely packed i.e., intermolecular distances are very small.
- They have strong interparticle forces.
- Their constituent particles do not possess translatory motion but can only oscillate about their mean position.
- They are rigid and incompressible.
Why are Solids rigid ?
Solid are rigid due to presence of strong intermolecular forces between the constituent particles.
Why do solids have a definite volume ?
Solids are rigid because constituent particles are fixed. that is why they have a definite volume.