What is a characteristic of a chemical change?

A characteristic of a chemical change is that it alters matter to a completely different form. This transformation occurs at a molecular or atomic level, resulting in the formation of new substances with different chemical properties than the original materials. For example, when iron rusts, it reacts with oxygen to form iron oxide, a substance that has entirely different properties from metallic iron.

In contrast, other aspects of chemical changes, such as reversibility, are typically not straightforward. Many chemical changes are irreversible under normal conditions, meaning they cannot simply revert back to their original state without a significant intervention. Moreover, chemical changes are distinct from physical changes, which may alter the physical appearance but do not change the chemical composition of the matter involved. Ultimately, energy changes are involved in chemical reactions, but the notion that they require minimal energy is not characteristic; many reactions can require substantial energy input to occur. This highlights the unique nature of chemical changes compared to other types of transformations.