What is the difference between a physical change and a chemical change in a substance?

A physical change alters the form or appearance of a substance without creating a new chemical substance (for example, melting ice, or wetting and drying hair to temporarily change its shape). A chemical change produces one or more new substances with different properties (for example, the action of a permanent wave or haircolor, which permanently alters the hair's structure). Many cosmetology services rely on chemical changes. Distinguishing physical from chemical changes is a basic chemistry concept on the exam.