Final answer:
A physical change preserves the atomic structure of a substance, while a chemical change involves rearrangement of molecules and atoms to form new substances.
Step-by-step explanation:
The main difference between a physical and chemical change lies in the nature of the changes that occur. In a physical change, the atomic structure of the substance remains the same before and after the change, while the molecules rearrange to form new substances. On the other hand, in a chemical change, the molecules and atoms themselves are rearranged, resulting in the formation of entirely new substances.
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