In general, solids are characterized by structural rigidity and resistance to changes of shape or volume. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a gas does. Solids have greater interatomic attractions than liquids and gases. However, there are wide variations in the properties of solid materials used for engineering purposes. The properties of materials depend on their interatomic bonds. These same bonds also dictate the space between the configuration of atoms in solids.
Amorphous solids, or non-crystalline solids, have no regular arrangement of their molecules and lack the long-range order that is characteristic of crystalline solids. Amorphous materials have the properties of solids, they are also characterized by structural rigidity and resistance to changes of shape or volume. They have definite shape and volume and diffuse slowly. Materials like glass and paraffin are considered amorphous. These materials also lack sharply defined melting points. In many respects, they resemble liquids that flow very slowly at room temperature.