Which of the following best describes a chemical change?

A chemical change is defined as a transformation that results in a change in the composition of matter. This means that during a chemical change, the atoms that make up the substances involved are rearranged to form new substances with different properties. For example, when iron rusts, it reacts with oxygen to form iron oxide, which is a completely different substance compared to its original form. This characteristic of altering the fundamental composition distinguishes chemical changes from physical changes, which may only affect physical properties such as state or appearance without changing the substance itself.

The other choices describe aspects that are more specific or relate to physical changes rather than the broader concept of a chemical change. The correct option captures the essence of a chemical reaction, highlighting the transformation that leads to new material substances being formed.