What does a chemical reaction usually signify?

A chemical reaction typically signifies an interaction between substances, where the atoms and molecules of the reactants rearrange to form new products with different chemical properties. This interaction is central to the concept of a chemical reaction, as it involves the breaking and forming of chemical bonds.

In this context, while some chemical reactions may result in observable changes or a change in physical state, the fundamental characteristic that distinguishes a chemical reaction is this interaction at the molecular level. Products formed from such reactions often have distinct properties and compositions compared to the reactants, highlighting the transformative nature of chemical interactions. Thus, the essence of a chemical reaction lies in the interplay of different substances leading to new substances being created.