BEHAVIOUR AND TYPE OF SOLID

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SOLIDS

BEHAVIOUR OF SOLID:

1.         COMPRESSIBILITY:

The compressibility of solid is nearly zero. In terms of kinetic theory the particles of solid are so tightly bound together that only slight unfilled space is left, hence density of solid is much higher then gases and liquid.

2.            DIFFUSIBILITY:

In term of kinetic theory, there is no translation movement of molecules in solid, but nevertheless panicles are vibrating at then mean position. This vibrational motion is responsible for diffusion in solid.

3.            DEFORMATION:

The ability of solid to maintain their new shape when their shape is changed by any external force is called “DEFORMATION”.

4.            MELTING:

A process in which solid and liquid states of any substance coexist is called melting and the temperature at which it occurs is called Melting Point In term of KMT when solids are heated vibrational energy of their particles increases; unit at melting point some particles are vibrating with sufficient energy to overcome the forces holding them, hence they become mobile.

5.            SUBLIMATION:

Conversion of solid directly in to gases from by heating is called “SUBLIMATION” while the solid are called sublime solids e.g. Iodine, CO2 etc.

TYPES OF SOLID

There are two types of solid.

1. Crystalline solid                          2.            Amorphous solid.

CRYSTALLINE SOLID:

All those solids in which particle arranged themselves in a perfect three dimensional geometrical shape are called CRYSTALLINE SOLID”.

AMORPHOUS SOLID:

“All those solids in which particles cannot arranged themselves in a perfect three dimensional geometrical shape are called “AMORPHOUS SOLID”

1.            GEOMETRY

Crystalline Solid                                                                                               Amorphous solid

Particle of crystalline solids are arranged                             Particles of Amorphous solids are not

in an orderly three dimensional network                             arranged in a definite pattern; hence they

called crystal lattice. Hence they have                                   don’t have a definite shape,

definite shape.

2.            MELTING POINT

Crystalline                                                                                                                          Amorphous

Crystalline solid have sharp melting point,                                         Amorphous solid melt over a. wide range

this is because at reactive forces between                                          of temperature i.e. they don’t have sharp

particles are long range and uniform                                                      melting point because inter molecular

these forces break down at the same                                                     forces vary form place to place.

instant, at melting point.

3.            CLEAVAGE AND CLEAVAGE PLANE

The breakage of a big crystal into smaller                                            Amorphous solid doesn’t break down a

crystal of identical shape is called                                                           fixed cleavage plane.

“CLEAVAGE”. Crystal cleavage along

particular direction of cleavage is called

CLEAVAGE PLANE”.

4.            ANISOTROPY AND ISOTROPY

Physical properties of crystal such as                                                     Amorphous solids are isotropic i.e. their

electrical conductivity refractive index, etc                                        physical properties are same in all

are different in different direction. This                                                               direction.

process is called “ANISOTROPY” e.g.

graphite can aonduct electricity parallel to

its plane but not perpendicular.

5.            SYMMETRY

When crystalline solid are rotated about                                             Amorphous solid does not have

an axis their appearance does not                                                           symmetry,

change i.e. they possess symmetry.

TYPES OF CRYSTAL:

There are four types of crystals.

1.            Atomic crystal                                                                                   2.            Ionic crystal

3.            Covalent crystal                                                                                               3.            Molecular crystal

ATOMIC CRYSTAL:

All those crystals consist of atoms held together by strong Interatomic forces are called Atomic Crystals. The examples of these crystals are observed in metals. They have following characteristic properties.

(1)          Lustre                                                                                                   (2)          High melting point

(3)          Electrical and thermal conductivity                                         (4)          Malleability

(5)          Ductility (drawing in to wires)

1.            IONIC CRYSTALS:

Such crystals consist of (+ve) and (-ve) charged ion, held together by electrostatic forces of attraction. Individual ions have no identity. The examples of these crystals are observed in ionic solids. They are characterized by,

(I) high melting point                                                                                    (2) Brittleness and hardness

(3)          conduction of electricity is fused state; as well as in solution form..

(4)          Indefinite growth of crystal, until it is broken or is stopped from growing.

2.            COVALENT CRYSTAL:

Such crystals consist of atoms held together by covalent bonds. Covalent crystals are very strong. They require large amount of energy to break them. E.g. of covalent crystal are graphite, diamond, silica and carborundum. Covalent crystals are characterized by.

(1)          High melting point                          (2) low density                                  (3) High refractive index

3.            MOLECULAR CRYSTAL:

Such crystals are composed of molecules such as ice, I2, C02. The molecules are held together either by following force.

i.             Hydrogeri bonding (which is an electrostatic force of attraction between partially positive hydrogen atom of one molecule and on electronegative atom of other molecules.)

ii.            Weak Vander Waals forces (which arise due to attraction between atomic nuclei of one molecule and electron of other molecule) such crystal characterized by.

1. Low melting point                      2. Non-conduction of heat and electricity

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