What is it called when matter undergoes a transformation and creates new substances?

When matter undergoes a transformation that leads to the creation of new substances, this process is referred to as a chemical change. During a chemical change, the bonds between atoms are broken and reformed, resulting in entirely different substances with distinct properties. This contrasts with other types of changes, such as physical changes, where the form or appearance of the substance may change, but the composition remains the same—like freezing water into ice.

In addition, nuclear changes involve alterations to an atom's nucleus, typically resulting in radioactivity and nuclear reactions, which are different from the type of substantive transformation described in the question. Phase changes pertain specifically to changes in the state of matter—such as solid to liquid or liquid to gas—where no new substances are formed. Therefore, the correct answer highlights the process of creating new substances, which is precisely what occurs during a chemical change.