solides

Solids are one of the fundamental states of matter, characterized by definite shape and volume, low compressibility, and strong interparticle forces. At the microscopic level the particles vibrate about fixed positions, giving a rigid structure.

Crystalline solids have long-range order and defined repeating unit cells; examples include salts, metals, and quartz. Amorphous solids lack long-range order and do not have a sharp melting point; they gradually soften when heated, as in glass and many polymers.

Solids can also be classified by bonding, including ionic, covalent-network, metallic, and molecular solids, each with characteristic properties such as hardness, brittleness, and electrical behavior.

Physically, solids are distinguished by mechanical and thermal properties. They may exhibit elastic deformation and, with sufficient stress, plastic flow or fracture. Thermal properties include melting points and coefficients of thermal expansion.

In geometry, solids are three-dimensional figures with volume and surface area, such as cubes, spheres, pyramids, and polyhedra. The study covers volume formulas, symmetry, and basic lattice concepts in crystallography.

Solids include everyday materials such as metals, ice, minerals, ceramics, and polymers, and they underpin fields from construction and engineering to electronics and geology.