Sound through solids, liquids and gases
Send a sound along 1 km of air, water, wood and steel, time how long it takes, and see what happens in a vacuum.
Core concept
Sound needs a medium; it travels fastest in solids, slower in liquids and slowest in gases, and not at all in a vacuum
Topic: Sound
Sound is a vibration passed from particle: A tiny piece that matter is made of, far too small to see. All key words to particle. Where the source vibrates, it pushes the particles next to it, which push their neighbours, so a wave of squashed-together particles moves outwards. Sound therefore needs a material (a medium) to travel through. Particles in solids are packed close and firmly linked, so solids pass sound on fastest; liquids are slower and gases slowest. In a vacuum there are no particles, so sound cannot travel at all.
What you will learn
- Explain that sound needs a medium to travel.
- Compare the speed of sound in solids, liquids and gases.
- Calculate the time for sound to travel a distance (time = distance ÷ speed).
Before you start
- Know that sound is made by vibrations.
Materials
- A long metal railing, a wooden plank and a bucket of water (in a real investigation)
Equipment
- Hammer or bell, and a stopwatch
- Bell jar and vacuum pump (teacher demonstration)
Procedure
- Set the distance to 1000 m and tap the bar. Record the time for air, water, wood and steel.
- Choose the vacuum and try again.
- Change the distance and compare.
How this simulation is simplified
- Speeds of sound at room temperature: air 343 m/s, water 1480 m/s, wood 3800 m/s, steel 5960 m/s.