In a chemical reaction, what is the definition of a reactant?

In a chemical reaction, a reactant is defined as the starting material that undergoes change. Reactants are the substances that participate in the reaction and are transformed into different products as a result of the chemical interactions that occur. This transformation is a fundamental aspect of chemical reactions, where the bonds between atoms in the reactants are broken and new bonds are formed, leading to the creation of products with different properties.

The other options refer to different components of a chemical reaction. The product is the end result of the reaction, formed after the reactants have undergone transformation. A catalyst, while it may assist a reaction by lowering the activation energy required, does not undergo change itself; it is not a reactant. Lastly, a byproduct refers to substances that are produced in the course of a reaction, which are not the main products desired but occur as side effects. Understanding these distinctions helps clarify the roles different substances play in chemical reactions.