Solid State

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Chemistry

12

Science

Central Board of Secondary Education

The three states of matter : solid, liquid and gas are the result of competitive molecular interaction and thermal energy.

For any substance to be in a particular state of matter is a matter of strength of intermolecular forces which when strongest bring the molecules closest (as much as possible) and substance adopts definite volume and shape at room temperature.

The same substance at three different temperatures:

(i) Temperature below its melting point (m.p.).


(ii) Temperature above its m.p. but below b.p.


(iii) Above its b.p.

In solid state, the atoms are arranged in an orderly manner and are at fixed positions. There is only one form of molecular motion in solids, namely, vibration motion, by virtue of which the particles move about their fixed positions and cannot easily leave the solid surface.

Solids can be classified in two major categories on the basis of pattern of arrangement of constituent particles.

(a) Crystalline Solid; (b) Amorphous Solid

(a) Crystalline Solid: Solids in which constituent particles are arranged in a well and long range ordered pattern. e.g. Salt, Diamond, Iodine, etc.

(b) Amorphous Solid: Solids in which pattern is short range ordered or disordered. e.g. Plastic, Glass, Rubber etc. Amorphous solid are also known as super cooled liquid.

Difference between Crystalline and Amorphous Solid
Property Crystalline Solid Amorphous Solid
1. Crystal
Geometry
These have definite crystal
shapes because of ordered
arrangement.
Do not have definite
geometrical shape because
of irregular arrangement
2. Symmetry These can have
(a) plane of symmetry
(b) center of symmetry
(c) axis of symmetry.
Do not have any symmetry.
3. Anisotropic or
isotropic nature
In these, some properties are
direction dependent e.g.
refractive index i.e., these are
anisotropic.
Properties are not direction
dependent i.e.these are ,
Isotropic
4. Melting Point Sharp M.P. These have range of melting
temperature.
5. Physical State Hard and rigid Soft
6. Crystal System These have seven types of
definite crystal systems.
These do not have regular
crystal systems.

Crystalline solids are classified on the basis of interparticle forces.
Types of Solid Constituent particle Nature of Forces Examples

1. Ionic
Positive and Negative
ions
Electrostatic forces Ionic compounds
2. Covalent Covalently bonded
atoms
Covalent forces in
3D cross network
Diamond-graphite
carborundum, silicon
3. Metallic Metal ions (kernels)
surrounded by mobile
electrons.
Metallic bonds Metals and some alloys
4. Molecular Molecules van der Waal forces 12, solid C02, Ice, Sulphur

Note: In this chapter, when we will be talking about solids, it must be understand to be crystalline only.

 

Related Tags Solid State, Atomic Weight, Three States Of Matter, Liquid State, Gas State, Intermolecular Forces, Classification Of Solids, Crystalline Solid, Amorphous Solid, Difference Between Crystalline And Amorphous Solid, Interparticle Forces, Types Of Solids, Crystal Geometry, Melting Point, Physical State, Crystal System, Nature Of Forces, Crystalline Solids

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