What type of change does a physical alteration represent?

A physical alteration represents a change in physical appearance because it involves modifications to the form or structure of a substance without altering its chemical composition. For instance, when ice melts into water, the shape and state of the substance change, but it remains H2O at the molecular level. This type of change is reversible; the substance can return to its original form without any changes to the underlying chemical identity. Therefore, focusing on how physical alterations affect appearance aligns perfectly with the definition of physical change.

In contrast, other options refer to different kinds of changes, such as changes in chemical composition, which occur during chemical reactions, transformations into different materials that imply a more extensive change beyond mere appearance, and permanent modifications that suggest irreversibility and significant alterations to substance properties. These aspects are not applicable to the nature of physical alterations.