which observation most likely indicates that only a chemical change has taken place?

Question

a. a reaction occurs
b. states of matter change
c. the change cannot be reversed
d. the shape changes

Answer 1

The observation that most likely indicates that only a chemical change has taken place is:

c. the change cannot be reversed

This is because chemical changes typically result in the formation of new substances that cannot easily be converted back to their original forms, unlike physical changes where the original substances can usually be recovered.