Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

What is a defining characteristic of a physical change?

1. Atoms are rearranged into different compounds

2. A new substance is formed

3. The identity of the substance remains the same

4. The change is irreversible

The correct answer is: The identity of the substance remains the same

A defining characteristic of a physical change is that the identity of the substance remains the same. In a physical change, the form or appearance of a substance may change, but its chemical composition does not. For example, when ice melts into water, it undergoes a physical change—it changes state from solid to liquid. However, the substance remains H2O in both forms. This characteristic distinguishes physical changes from chemical changes, where the making or breaking of bonds within molecules results in the formation of new substances with different chemical identities. Thus, during a physical change, substances retain their original properties and can often be reversed, such as freezing water back into ice.