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Year 9

Sound waves

I can describe the movement of particles in a sound wave travelling through a solid, liquid or gas, and explain the relative speed of sound in each state of matter.

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New
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Year 9

Sound waves

I can describe the movement of particles in a sound wave travelling through a solid, liquid or gas, and explain the relative speed of sound in each state of matter.

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Lesson details

Key learning points

  1. Sound waves are caused when objects vibrate, causing nearby air particles to vibrate as well.
  2. As a sound wave travels, each bit of air is vibrating parallel to the direction of wave travel, not travelling forwards.
  3. Sound is a longitudinal wave: the direction of vibration is parallel to the direction of energy transfer.
  4. Sound waves are faster in solids/liquids than gases; the particles are very close so vibrations are easily passed on.
  5. Sound waves are faster in solids than liquids; the strong forces between particles mean vibrations travel even faster.

Keywords

  • Vibrate - to move back and forth

  • Sound wave - a ‘pulse’ that travels through a material caused by the vibrations of particles.

  • Longitudinal wave - a wave, such as a sound wave, where the vibrations are parallel to the direction of energy transfer

  • Medium - the material through which a wave travels

Common misconception

Sound is an entity/substance of some kind that travels through air, or is somehow 'carried' by air particles or passed between them in collisions. Sound involves air moving away from a sound source.

Use moving animations to show pupils how the travelling pulses of a longitudinal wave are created from particles vibrating back and forth without being transported. Give pupils time to observe the motion of different single particles.

Pupils can compare the ease of sound transmission through solids and gases by scratching the desk with and without their ear in contact. Note that linking sound waves to oscilloscope traces or 'waveforms' is left to KS4. The longitudinal motion of particles in sound waves is to be established first.
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Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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Starter quiz

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6 Questions

Q1.
In a wave, the direction of energy transfer is __________ the direction of wave travel.
at 90° to
Correct answer: the same as
opposite to
Q2.
In a transverse wave such as a water wave, the vibrations are __________ to the direction of energy transfer.
Correct answer: at 90°
parallel
diagonal
Q3.
Which of the following words have the same meaning?
acceleration
distillation
Correct answer: oscillation
Correct answer: vibration
Q4.
Which of the following words describes a solid that is not easy to bend, stretch or squash?
compact
flexible
fragile
Correct answer: rigid
Q5.
Which of the following statements about particles in solids, liquids and gases are correct?
Correct answer: The particles in a gas can collide with each other.
The particles in a liquid are in a fixed arrangement.
Correct answer: The particles are much closer together in liquids than in gases.
The particles are much closer together in solids than in liquids.
Q6.
Which of the following statements about scientific models are correct?
Correct answer: They can be used to make predictions.
They must include pictures or 3D objects.
They must exactly match what we know about the real world.
Correct answer: Some details may be left out of a model if that makes it easier to use.

Exit quiz

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6 Questions

Q1.
A sound wave is an example of a wave in which the vibrations are parallel to the direction of energy transfer. This type of wave is called a wave.
Correct Answer: longitudinal
Q2.
The material through which a wave travels, such as air or water, is called the .
Correct Answer: medium
Q3.
Which of the following statements about forces between particles in solids, liquids and gases are correct?
There are no electrostatic forces between the particles in a liquid.
Correct answer: The attractions between particles are stronger in solids than in liquids.
Electrostatic repulsion forces act all the time between the particles in a gas.
Q4.
Which of the following explain why sound waves travel faster in solids than in liquids?
Correct answer: When one particle in a solid is disturbed, many are disturbed.
The particles have higher speeds in solids, so collide more frequently.
The particles are much closer together in solids, so collide more easily.
Q5.
Two astronauts stand on the Moon wearing space suits and helmets because there is no air. They usually communicate using radios, but their radios break. How can they talk to each other?
by talking normally
by shouting loudly
Correct answer: by touching their helmets together when they speak
Correct answer: by resting their heads on the ground, in their helmets, when they speak
Q6.
Starting with the vibrating drum skin, sort the following statements to describe how a vibrating drum skin makes a sound wave.
1 - The drum skin moves upwards, knocking air particles upwards.
2 - These collide with particles in front of them and may slow or change direction.
3 - The drum skin moves downwards, leaving an empty space above it.
4 - Some nearby particles move into the gap, because of their random motions.
5 - This creates a gap further up, which is soon filled by moving particles.