What is produced as a result of a chemical change?

A chemical change occurs when the composition of a substance is altered, resulting in the formation of one or more new substances that have different chemical properties and characteristics. This distinctive transformation involves the breaking and forming of bonds between atoms, leading to the creation of compounds or molecules that were not present before the reaction.

For example, when iron reacts with oxygen, a new substance—iron oxide (rust)—is formed, indicating that a chemical change has taken place. This new substance differs from the original elements, highlighting the key feature of a chemical change: the production of new substances that are fundamentally different from the reactants.

This understanding clarifies why the production of a new substance is the hallmark of a chemical change, distinguishing it from processes that either do not change the chemical makeup of the materials involved or simply result in a physical change without altering the identities of the substances.