chemical change

[kem-i-kuhl cheynj]

noun

1. Chemistry.,  a usually irreversible chemical reaction involving the rearrangement of the atoms of one or more substances and a change in their chemical properties or composition, resulting in the formation of at least one new substance.

   The formation of rust on iron is a chemical change.

Word History and Origins

Origin of chemical change¹

First recorded in 1755–65

When To Use

What is a chemical change?

A chemical change happens when one chemical substance is transformed into one or more different substances, such as when iron becomes rust.Chemical changes occur through the process of chemical reactions, and the resulting substances have different properties because their atoms and molecules are arranged differently.A chemical change is different from a physical change, which doesn’t rearrange atoms or molecules and produce a completely new substance. Ice melting into water is an example of a physical change.