1. Sound waves Lesson objectives state that: sound cannot travel through a vacuum but can travel through solids, liquids and gases describe how sounds travel through solids, liquids and gases explain in terms of the particle model why sound needs a medium. explain how sound travels at different speeds in different types of material explain everyday phenomena in terms of the different speeds at which sound travels in air and solids Key words: vibrations, molecules, medium, vacuum, solid, liquid, gas, longitudinal, wavelength

2. Sound waves Sound can travel through solids, I know this because ………………………….. ………………………………………………. …………………………………………………. Sound can travel through liquids, I know this because ………………………….. …………………………………………………. Sound can travel through gases, I know this because ………………………….. ………………………………………………….

3. Sound waves In a sound wave the molecules vibrate backwards and forwards C C C R R R Compression; air molecules are squashed together Rarefaction; air molecules are further apart

4. Sound waves speaker cone vibrates. Sound waves spread like ripples on a pond. Air molecule

5. Sound waves

7. If you listen carefully you might. Explain how! Can you hear a space craft explode in space or on the moon? Explain!

8. P 3 2.6 SOUND For a C grade you should be able to: State the range of hearing for a typical human. Describe the properties of a sound wave, including its longitudinal nature. Describe the behaviour of a sound wave, including reflection and refraction. For an a grade you should also be able to: Explain why mechanical vibrations produce sound waves.

10. Mechanical waves electromagnetic waves

11. electromagnetic waves Mechanical waves

12. electromagnetic waves Mechanical waves

13. Mechanical waves electromagnetic waves

22. Reflecting sound Echoes

23. Hard, flat surface

24. Soft, absorbing surface

25. Uneven surface