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

Question

A. the change cannot be reversed
B. a reaction occurs
C. the shape changes
D. state of matter changes

Answer 1

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

A. the change cannot be reversed.

Chemical changes typically result in the formation of new substances that cannot easily be reverted back to their original form. While the other options can occur during physical changes as well, the irreversibility of a change is a strong indicator of a chemical change.