When the composition of a substance is not altered but its state is, this is called?

When the composition of a substance remains unchanged while its state transforms, this is referred to as a physical change. This type of change involves alterations in the form or appearance of a substance without affecting its chemical makeup. Common examples include the processes of melting, freezing, boiling, and dissolving. During these transformations, the molecules of the substance retain their identity, even though they may move differently or exist in various states, such as solid, liquid, or gas.

The other options focus on different concepts. A chemical change, for instance, involves a transformation where the original substance is converted into one or more new substances with different chemical properties. Chemical and physical properties relate to the behaviors and characteristics of substances rather than to changes in their states or compositions. Thus, the characteristics of a substance are not altered in a physical change, clearly distinguishing it from chemical changes or properties.