substancas

Substancas is not a standard term in science; in many Portuguese texts the correct plural is substâncias. The word may appear as an informal or misspelled form. This article treats substancas as referring to the general concept of chemical substances and explains the standard meaning in scientific usage.

A substance is a form of matter with a definite composition and distinct properties. Substances are divided into pure substances and mixtures. Pure substances include elements, which cannot be broken down into simpler substances by chemical means, and compounds, which consist of two or more elements in fixed proportions and can be decomposed only by chemical reactions.

Mixtures are combinations of two or more substances in which each component retains its own properties. They can be homogeneous, such as solutions, or heterogeneous, such as suspensions or alloys. Substances have physical properties (melting and boiling points, density, color, odor) and chemical properties (reactivity, flammability, acidity). They may exist in different phases — solid, liquid, or gas — and can change phase under varying temperature and pressure.

In practice, substances are described in chemical nomenclature, safety data sheets, and regulatory frameworks. Safety data sheets provide information on hazards, handling, storage, and first aid. Regulatory regimes such as REACH in the European Union or TSCA in the United States govern the production and use of chemical substances.

Examples include water (a compound), sodium chloride (table salt, a compound), oxygen (an element), and ethanol (a compound).