Chapters / Chapter 1 · Solid state / Topic 1 of 14

Crystalline and amorphous solids

Chapter 1 · Solid state and crystal structures

Regular order against irregular order. The drawing is a schematic, not a photograph of atoms.

Crystalline

Definite, repeating, long range order of particles.
Definite characteristic shape.
Sharp and fixed melting point.
Breaks along a definite plane, giving smooth surfaces.
A definite value of heat of fusion.

Examples: NaCl, diamond.

Amorphous

Irregular; only short range order.
Irregular shape.
Softens gradually over a range of temperature.
Breaks irregularly.
No definite value of heat of fusion.

Examples: glass, rubber, pitch.

Glass is the usual exam example of an amorphous solid: it has no long range order, so it has no sharp melting point.