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Science lesson plan · 7th grade (Year 8 in England) · 30 minutes

How sound travels through solids, liquids and gases

Light, sound and waves

CCSS NGSS.MS-PS4-2England: KS3 Physics: Waves (sound)

Objective and success criteria

Students will: How sound travels through solids, liquids and gases.

  • I can answer questions on today's skill on my own, without help.
  • I can explain each step and say why it works.
  • I can check my answer and spot a mistake.

Before and after

Needs first: Sound comes from vibrations; The particle model

Leads to: Transverse and longitudinal waves

Materials: Slinky or rope, Mirrors and torches, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 4 min

  • Quick retrieval from earlier learning (Sound comes from vibrations; The particle model). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. What makes the sound when you pluck a guitar string? (the wood breathing / light from the string / the string getting hot / the string vibrating) → the string vibratingPrompt: Touch the string gently after plucking it.
  2. Which state is described: particles packed in a regular pattern? (solid / liquid / gas) → solidPrompt: How close are the particles, and how do they move?
  3. Sound: which statement is true? (Sound cannot travel through water. / Sound travels through space between planets. / Loud sounds do not involve vibrations. / Sound cannot travel through empty space (a vacuum).) → Sound cannot travel through empty space (a vacuum).Prompt: Can sound travel where there is nothing at all?

Hook · 3 min

  • Ask the class to make a wave with a rope or slinky and describe what moves and what doesn't.
  • Share the objective: How sound travels through solids, liquids and gases. Read the success criteria together.

I do: model it · 7 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: Why does sound travel faster in steel than in air?
  • Step 1: Sound travels at about 340 m/s in air, 1500 m/s in water and over 5000 m/s in steel.
  • Step 2: So the answer is: Particles in solids are close together and strongly linked, so vibrations pass on quickly
  • Answer: Particles in solids are close together and strongly linked, so vibrations pass on quickly
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 6 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.
  1. Astronauts on a spacewalk talk by radio. Why can't they just shout? (Their voices are too quiet / Space is a near vacuum, so sound cannot travel between them / Radio waves are a type of sound / Space is too cold for sound) → Space is a near vacuum, so sound cannot travel between themPrompt: Radio waves are electromagnetic waves.
  2. Sound travels at about 1500 m/s in water. How far does it travel in 0.5 s, in m? → 750 mPrompt: distance = speed × time

You do: independent practice · 7 min

  • Students work on the student sheet. Circulate and check the first two answers of every student early.
  • Students who finish: write a question of their own for a partner, with the answer.

The 6 questions are on the student sheet below, with answers in the key.

Exit ticket · 3 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. Sound travels at about 1500 m/s in water. How far does it travel in 4 s, in m? → 6000 mPrompt: distance = speed × time
  2. How sound travels: which statement is NOT true? (Sound travels fastest in gases. / Sound travels faster in water than in air. / Sound waves are longitudinal. / Whales can communicate over long distances underwater.) → Sound travels fastest in gases.Prompt: Why do we see lightning before we hear thunder?

Watch out for

  • Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
  • Remembering facts without the reason: ask "why?" and "what is the evidence?"

Support and stretch

Support

  • Review first: Sound comes from vibrations.
  • Use concrete materials: slinky or rope.
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • Move on to: Transverse and longitudinal waves.
  • Explain a common mistake in writing and how to fix it.
  • Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-7.

Free lesson plan from eurekami.com/lesson-plan-builder

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How sound travels through solids, liquids and gases

Name

Date

Score/ 6

  1. Question 1

    How sound travels: which statement is NOT true?

    • A. Sound waves are longitudinal.
    • B. Sound travels faster than light.
    • C. Sound travels faster in water than in air.
    • D. Whales can communicate over long distances underwater.

  2. Question 2

    An alarm clock rings inside a jar. As the air is pumped out, the ringing gets quieter. Why?

    • A. The clock stops ringing
    • B. Glass absorbs all sound
    • C. Sound needs particles to travel through, and there are fewer left
    • D. Air makes sound quieter

  3. Question 3

    Sound travels at about 340 m/s in air. How far does it travel in 3 s, in m?

    Answerm

  4. Question 4

    Astronauts on a spacewalk talk by radio. Why can't they just shout?

    • A. Space is a near vacuum, so sound cannot travel between them
    • B. Their voices are too quiet
    • C. Radio waves are a type of sound
    • D. Space is too cold for sound

  5. Question 5

    Sound travels at about 1500 m/s in water. How far does it travel in 5 s, in m?

    Answerm

  6. Question 6

    In which direction do air particles vibrate when a sound wave passes?

    • A. in circles
    • B. up and down, at right angles to the wave
    • C. they do not move
    • D. backwards and forwards, parallel to the direction the sound travels

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Answer key: How sound travels through solids, liquids and gases

  1. 1. B. Sound travels faster than light.

  2. 2. C. Sound needs particles to travel through, and there are fewer left

  3. 3. 1020 m

  4. 4. A. Space is a near vacuum, so sound cannot travel between them

  5. 5. 7500 m

  6. 6. D. backwards and forwards, parallel to the direction the sound travels