What describes a chemical change?

A chemical change is characterized by the process in which substances combine, break down, or rearrange to form entirely different substances, with new chemical properties. This process often involves the making or breaking of chemical bonds, resulting in the formation of products that differ from the reactants in composition and behavior.

For example, when iron rusts, it combines with oxygen from the air to form iron oxide, a completely different substance from elemental iron. This type of change typically accompanies a transfer of energy, whether it be in the form of heat or light, as chemical bonds are formed or broken during the reaction. This is what distinguishes a chemical change from a physical change, which merely affects the form or appearance of a substance without altering its chemical structure.

The other descriptions, while related to physical or other types of changes, do not capture the essence of a chemical change as accurately.