What does a physical/phase change involve?

A physical or phase change involves transformations in the state or form of a substance without altering its chemical composition. In these types of changes, the substance retains its original chemical identity, meaning that even though it might change from solid to liquid or from liquid to gas (for example), it remains the same substance at the molecular level.

Common examples of physical or phase changes include melting (solid to liquid), freezing (liquid to solid), boiling (liquid to gas), and condensation (gas to liquid). During these processes, the arrangement of molecules changes, and so do the intermolecular forces acting upon them, but the actual molecules themselves do not change.

In contrast, a change involving the formation of new substances would indicate a chemical change, where the original substance loses its identity and transforms into different substances with different properties. The options that suggest a reduction in mass or a change of matter into another substance would also imply a chemical change rather than a physical change.