What defines a chemical reaction?

The definition of a chemical reaction is centered around the concept of transformation, particularly the conversion of reactants into products. In a chemical reaction, the substances involved (reactants) undergo a rearrangement of atoms and bonds resulting in the formation of new substances (products) with distinct chemical properties. This change typically involves the making or breaking of chemical bonds, which is a fundamental characteristic differentiating it from physical changes, where no new substances are formed, and the original substances retain their chemical properties.

The transformation during a chemical reaction is often accompanied by observable changes, such as color changes, gas production, or temperature changes, underscoring the creation of different substances. The focus on the alteration of chemical identity emphasizes the core nature of chemical reactions as a means of producing new chemical compounds, reflecting the dynamic processes that define chemistry as a science.