GLASS: Glass is amorphous solid which is not true solid, it is rather super cooled liquid which possesses a very high viscosity. It has no fixed melting point, on heating gradually softens and then melts over a wide range of temperature into mobile liquid. The amorphous solid unlike crystalline solid breaks with conchoidal fracture. Glass is fused of silicates of sodium and calcium which is amorphous, hard brittle, transparent or translucent super cooled liquid, having high viscosity.