Amorphous solids neither have ordered arrangement (i.e, no definite shape) nor have sharp melting point like crystals, but when heated they become pliable until they assume the properties usually related to liquids. It is therefore, they are regarded as super cooled aliquids. Quartz glass $\left({\mathrm{SiO}}_2\right)$ is amorphous solid whereas quartz is crystalline solid.