Wednesday, 14 June 2017

CBSE Class 12 - Chemistry - Chapter 1 - Solid State - Crystalline vs Amorphous Solids (#cbseNotes)

Crystalline Solids vs Amorphous Solids

Class 12 - Chemistry - Chapter 1 - Solid State

CBSE Class 12 - Chemistry - Chapter 1 - Solid State - Crystalline vs Amorphous Solids (#cbseNotes)

Crystalline Solids Amorphous Solids
1. They have definite and regular geometry due to definite and orderly arrangement of atoms, ions or molecules in three dimensional space. 1. They do not have any pattern of arrangement of atoms, ions or molecules and thus, do not have any definite geometrical shape.
2. They have sharp melting points and change abruptly into liquids. 2. Amorphous solids do not have sharp melting points and do not change abruptly into liquids.
3. Crystalline solids are anisotropic. Some of their physical properties are different in different directions. 3. Amorphous solids are isotropic. Their physical properties are same in all directions.
4. These are considered as true solids. 4. These are considered pseudo solids or supercooled liquids.
5. Crystalline solids are rigid and their shape is not distorted by mild distoring forces. 5. Amorphous solids are not very rigid. These can be distorted by bending or compressing forces.
6. Crystals are bound by plane faces. The angle between any two faces is called interfacial angle. For a given crystalline solid, it is definite angle and remains always constant no matter how the faces develop. When a crystalline solid is hammered, it breaks up into smaller crystals of the same geometrical shape. 6. Amorphous solids do not have well defined planes. When an amorphous solid is broken, the surfaces of the broken pieces are generally not flat and intersect at random angles.
7. Crystals have some sort of symmetry. (i) plane of symmetry, (ii) axis of symmetry or (iii) centre of symmetry 7. Amorphous solids do not have any symmetry.
8. Copper Sulphate (CuSO₄), NiSO₄, Diamond, Graphite, NaCl, Sugar etc. 8. Coal, Coke, Glass, Plastic, rubber etc.