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The Solid State

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Chemistry I

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CBSE Gujarat Board Haryana Board

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Class 10 Class 12
How the crystalline solids are classified on the basis of the nature of bonding? Give suitable examples and nature of the forces present in different types of solids.

i) A crystalline solid usually consists of a large number of small crystals, each of them having a definite Characteristic geometrical shape. In a crystal, the arrangement of constituent particles (atoms, molecules or ions) is ordered. It has long range order which means that there is a regular pattern of arrangement of particles which repeats itself periodically over the entire crystal. Sodium chloride and quartz are typical examples of crystalline solids.

ii) Crystalline solid have a sharp melting point.

Crystalline solids can be classified on the basis of nature of intermolecular forces operating in them into four categories.
i) molecular
iv)covalent solids.

i) molecular: Molecules are the constituent particles of molecular solids. These are further sub divided into the following categories:

a) Non polar Molecular Solids: They comprise of either atoms, for example, argon and helium or the molecules formed by non polar covalent bonds for example H2, Cl2.

b) Polar Molecular Solids: The molecules in which solids are held together by relatively stronger dipole-dipole interactions.for example HCl, SO2, etc.

c) Hydrogen Bonded Molecular Solids: The molecules of such solids contain polar covalent bonds between H and F, O or N atoms. Strong hydrogen bonding binds molecules of such solids like H2O (ice).

ii) Ionic solid : Ions are the constituent particles of ionic solids. In ionic solid cations and anions bound by strong coulombic (electrostatic) forces. for example NaCl, KCl etc.

iii) metallic solid: These solids contain metal atoms as constituent particles. As metals have a good tendency to lose their valence electron and change in to positively charged metal ions (kernel). These electrons can easily move throughout the whole crystal and form the sea of free electrons. for example iron, calcium etc.

iv) covalent solids: A wide variety of crystalline solids of non-metals result from the formation of covalent bonds between adjacent atoms throughout the crystal. They are also called giant molecules. for example diamond, silicon carbide, etc.


Why are solids rigid?

Solids are rigid because the internuclear distance between the  molecules of a solid are very less and closely packed and their positions are fixed due to the strong forces of attraction between them.

Refractive index of a solid is observed to have the same value along all directions. Comment on the nature of this solid. Would it show clevage property?

Refractive index of a solid which have the same value along all directions are isotropic in nature. It would not show cleavage property.

Why do solids have a definite volume?

A solid have a definite volume because the inter molecular distance  between its molecules are fixed.

Why is glass considred a super-cooled liquid?

Glass is amorphous solids and  have a tendency to flow, though very slowly. Therefore, these are called pseudo solids or super cooled liquids .

Classify the following as amorphous or crystalline solids: Polyurethane, naphthalene, benzoic acid, teflon, potassium nitrate, cellophane, polyvinyl chloride, fibre glass, copper.

Amorphous solids: Polyurethane, teflon, cellophane, polyvinyal chloride, fibre glass.
Crystalline solids: naphthlene, benzoic acid, potassium nitrate, copper.