Final answer:
In a physical change, the molecular composition of a substance stays the same and the properties of the substance remain unchanged. Physical changes involve moving molecules around without changing them and are usually reversible.
Step-by-step explanation:
In a physical change, the molecular composition of a substance stays the same. This means that the same types of compounds or elements that were present before the change are still present after the change, and the properties of the substance, such as color or boiling point, remain the same. Physical changes involve moving molecules around without changing them and are reversible in most cases.