Explain sound as vibrations traveling as waves through matter, and connect amplitude to loudness and wavelength to pitch.
Sound is a wave made of vibrations traveling through matter, usually air. When you pluck a stretched rubber band, it vibrates back and forth very quickly, and those vibrations push the surrounding air into a wave that travels to your ear. No matter to vibrate means no sound at all, which is why sound cannot travel through empty space.
The amplitude and wavelength of a sound wave connect to what you actually hear. A bigger pluck makes a bigger vibration, a larger amplitude, and a louder sound. A tighter, shorter rubber band vibrates faster, giving a shorter wavelength and a higher pitch, while a looser band vibrates slower, giving a longer wavelength and a lower pitch.
Mastery looks like: They can explain sound as vibration traveling through matter and connect amplitude to loudness and wavelength to pitch using a real pluck test.
Common stumbles: Believing sound can travel through empty space; mixing up which wave property, amplitude or wavelength, controls loudness versus pitch.