In a chemical reaction, what are reactants?

Reactants in a chemical reaction are the substances that undergo a change in their chemical composition to form new substances, which are known as products. This means that during a reaction, the reactants are transformed through a variety of chemical interactions, such as bond breaking and formation, resulting in different chemical substances.

When you look at the classification of substances involved in a chemical reaction, reactants are always the starting materials. They are present before the reaction takes place and participate in the transformation process. This is fundamental in understanding how chemical reactions proceed: it begins with reactants that interact to yield products, demonstrating the concept of conservation of mass, where the total mass remains constant.

In contrast, new substances formed represent the products of the reaction, whereas byproducts are secondary products that may result from the reaction but are not the primary focus. Energy released during the reaction refers to the energy changes involved, which may accompany the transformation of reactants but do not define what reactants are.