Define the term ‘amorphous’. Give a few examples of amorphous solids.

Solids having constituent particles with irregular shapes and short range order are called amorphous solids. Amorphous solids are isotropic in nature and melt over a range of temperature. Thus, amorphous solids are also referred as pseudo solids or super cooled liquids.

Amorphous solids do not have definite heat of fusion.

Amorphous solids give irregular surfaces, when cut with sharp tool.

Glass, rubber, plastic, etc. are some examples of amorphous solid.

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What is the co-ordination number of atoms:
(i) in a cubic close packed structure?
(ii) in a body centred cubic structure?

What makes a glass different from a solid such as quartz? Under what conditions could quartz be converted into glass?

Classify each of the following solids as ionic, metallic, molecular, network (covalent) or amorphous:

(i) Tetra phosphorous decoxide (P₄O₁₀)

(ii) Ammonium phosphate (NH₄)₃PO₄

(iii) SiC

(iv) I₂

(v) P₄

(vi) Plastic

(vii) Graphite

(viii) Brass

(ix) Rb

(x) LiBr

(xi) Si

What is meant by the term ‘coordination number’?

(ii) What is the coordination number of atoms:

(a) in a cubic close-packed structure?

(b) in a body-centred cubic structure?

The Solid State

Define the term ‘amorphous’. Give a few examples of amorphous solids.