* Physical changes alter the form or appearance of a substance, but not its chemical composition. Sound is a form of energy that travels as vibrations through a medium (like air, water, or solids). These vibrations cause molecules to move back and forth, but they don't change the molecules themselves.

* Chemical changes involve the formation of new substances with different chemical properties. Sound doesn't create new substances; it's simply the transmission of energy through a medium.

Examples:

* Physical change: A bell ringing. The bell vibrates, creating sound waves, but the bell itself remains chemically the same.

* Chemical change: Burning wood. Wood reacts with oxygen, producing ash, smoke, and gases, all with different chemical compositions than the original wood.