A solid is a material that has a specific shape and volume, as opposed to a liquid or gas, which can change shape and volume. Solids are made up of particles that are packed tightly together in either a crystal-like lattice or a random arrangement called an amorphous solid. This arrangement is necessary for chemical bonds to form. Solids differ from liquids, gases, and air because air, water, and liquid crystals are not solids.
Common solid materials
There are three basic classes of solid materials: glass, plastics and rocks. When combined with other types of solids, they form composite materials that exhibit enhanced properties. A common example of a composite material is plywood. Made from thin layers of wood glued together with glue, it is a composite material. Its grain runs in parallel directions. This makes it a strong and durable material. However, the definition of solids is more complicated than this.
Physical properties of solids
Physical properties of solids include mass, density, and structural rigidity. These properties are derived from the fact that solids have rigid structures and contain a high concentration of molecular forces. Because solids have low molecular mobility and high intermolecular forces, their physical properties are strongly influenced by their chemical composition. In general, solids are more dense than liquids and gases. Furthermore, their melting and boiling points are relatively high.
Molecular structure of solids
Solids are substances made up of atoms, molecules, and ions. The molecular structure of a substance depends on its state. The molecular structure of solids is different from that of liquids and gases, which are characterized by their varying degrees of density, hardness, and conductivity. In a solid, the particles are relatively close together, but they are not closely packed, which results in high kinetic energy.
Chemical bonding in solids
Molecular solids are formed from a combination of atoms that are chemically bonded together. While the type of bonding varies depending on the constituent atoms and prevalent energy states, the goal of all bonds is to provide an attractive force. Atoms form bonds by exchanging or sharing electrons. Think of a pen and a cap: they are bonded together, but can separate without breaking. The same applies to solids.
Molecular lattices are solids with discrete molecules that are bonded together by van der Waals forces and dipole-dipole or quadrupole interactions. These forces act as strong adhesives for the molecules. Molecular lattices are the most common solids in nature, and can be found in most materials. Here’s an explanation of molecular lattices: