Material
Material is a substance or mixture of substances that constitutes an object. Materials can be pure or impure, living or non-living matter. Materials can be classified on the bases of their physical and chemical properties, or on their geological origin or biological function. Materials science is the study of materials and their applications. Raw materials can be processed in different ways to influence their properties, by purification, shaping or the introduction of other materials. New materials can be produced from raw materials by synthesis. In industry, materials are inputs to manufacturing processes to produce products or more complex  materials. History. Elements of material. Materials chart the history of humanity. The system of the three prehistoric ages (stone age, bronze age, iron age) were succeeded by historical ages: steel age in the 19th century, polymer age in the middle of the following century (plastic age) and silicon age in the second half of the 20th century. Classification by use. Materials can be broadly categorized in terms of their use, for example: Material selection is a process to determine which material should be used for a given application. Classification by structure. The relevant structure of materials has a different length  scale depending on the material. The structure and composition of a material can be determined by microscopy or spectroscopy. Microstructure. In engineering, materials can be categorised according to their microscopic structure: Larger-scale structure. In foams and textiles, the chemical structure is less relevant to immediately observable properties than larger-scale material features: the holes in foams, and the weave in textiles. Classification by properties. Materials can be compared and classified by their large-scale physical properties. Mechanical properties. Mechanical properties determine how a material responds to applied forces. Examples include: Thermal properties. Materials may degrade or undergo changes of  properties at different temperatures. Thermal properties also include the material's thermal conductivity and heat capacity, relating to the transfer and storage of thermal energy by the material. Other properties. Materials can be compared and categorized by any quantitative measure of their behavior under various conditions. Notable additional properties include the optical, electrical, and magnetic behavior of materials.