Answer:
a. Chemical changes require a change in composition and physical does not
Step-by-step explanation:
The main difference between physical and chemical changes is that chemical changes require a change in composition and physical does not.
A chemical change is the change in composition of a substance which is irreversible and a permanent change.
On the other hand, physical change is a temporary change in a substance and can be easily reversible. The composition of a substance do not change in physical composition.