substancia

Substance is a term used across science and philosophy to denote something with a definite identity. In chemistry, a substance is a form of matter with a fixed composition and distinct properties. Substances are either pure substances, which have a uniform composition, or mixtures, which contain two or more substances that can be separated by physical means.

Pure substances include elements, comprised of a single type of atom, and compounds, formed from atoms in fixed ratios. Substances exhibit physical properties such as melting point and density, and chemical properties such as reactivity. They can undergo physical changes without changing their chemical identity, whereas chemical changes alter the substance into different substances.

In contrast, a mixture is not a pure substance because its composition can vary and its components can be separated by physical methods. Substances can be characterized by intensive properties that do not depend on amount, such as boiling point, and by chemical properties such as reactivity and flammability.

In philosophy, substance refers to an underlying entity that exists independently and bears property ascriptions over time. It is contrasted with properties or predicates, which inhere in substances.

The term substancia is used in several languages to translate substance; while the scientific concept remains consistent, cultural and historical usage may vary. In everyday language, substance can also refer to any material or matter, or more narrowly, to a chemical compound.