Solid 

What is a Solid?

A solid can be defined as a substance which exists in the solid-state, which is one of the four fundamental states of matter. Solids feature closely packed atoms whose kinetic energies are much lower than those of liquids and gases. All solids have rigid structures that tend to resist any external forces applied to them. Solids also are known to have a fixed, definite shape (unlike liquids and gases, which assume the shape of the container they are placed in). Furthermore, solids are also known to have a fixed, definite volume (unlike gaseous substances which expand to occupy the entire volume of the container they are placed in).

Solids do not have the ability to flow as liquids and gases do. Another dissimilarity between solids and gases is that gases can be compressed when some external pressure is applied to them, but solids are virtually incompressible. The atoms of a solid can be bound together in either a regular or an irregular manner. The manner in which the atoms of the solid are arranged in three-dimensional space determines the type of the solid.

Types of Solids

Crystalline Solids

A crystalline solid (also known as a crystal) is a solid in which the constituent atoms or molecules (or sometimes ions) are arranged in a highly ordered microscopic structure. This microscopic structure is called a crystal lattice, and it extends in a uniform manner through all points in the crystalline solid. Common examples of crystalline solids include ice, sodium chloride (table salt), potassium chloride, and diamonds.

Amorphous Solids

Amorphous solids (also known as non-crystalline solids) are solids that lack long-range order in the arrangement of their constituent atoms, molecules, or ions in three-dimensional space. It is important to note that amorphous solids feature an internal structure in which different structural blocks of the solids are interconnected. It can also be noted that amorphous solids usually have higher solubilities than crystalline solids. Common examples of amorphous solids include metallic glasses, gels, thin-film lubricants, and certain polymers.