What is Solid? One of the 4 main states of matter is the solid state (the others being liquid, gas, and plasma). A solid’s molecules are tightly packed and hold the least amount of kinetic energy. A solid’s structural rigidity and resistance to pressure applied to its surface are its distinguishing characteristics. A solid substance, unlike a liquid, does not flow to take on the shape of its container or increase to completely cover available volume, as gas does.
A solid’s atoms are held together either in a regular geometric lattice (crystalline solids, such as metals and typical ice) or in an irregularity lattice (an amorphous solid such as common window glass). Solids cannot be squeezed at low pressures, however, gases can be compressed at low pressures due to the loose packing of the molecules in a gas.
Solid-state physics is the branch of physics that deals with solids, and it is the most important branch of materials science (which also includes liquids). The physical and chemical properties of solids are the focus of materials science. The creation of novel materials, and also the science of recognition and elemental makeup, are all areas of solid-state chemistry.