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Science lesson plan · 7th grade (Year 8 in England) · 45 minutes

Speed of sound and echoes

Light, sound and waves

CCSS NGSS.MS-PS4-1England: KS3 Physics: Waves (sound waves)

Objective and success criteria

Students will: Speed of sound and echoes.

  • 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; Speed = distance ÷ time

Leads to: the next skill in this area.

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

Warm-up · 5 min

  • Quick retrieval from earlier learning (Sound comes from vibrations; Speed = distance ÷ time). 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 string vibrating / the wood breathing / the string getting hot / light from the string) → the string vibratingPrompt: Touch the string gently after plucking it.
  2. A cyclist travels 10 m in 5 s. What is the average speed, in m/s? → 2 m/sPrompt: speed = distance ÷ time
  3. Sound: which statement is true? (Sound cannot travel through water. / Sound travels through space between planets. / Loud sounds do not involve vibrations. / Sounds are made by vibrations.) → Sounds are made by vibrations.Prompt: Can sound travel where there is nothing at all?

Hook · 5 min

  • Ask the class to make a wave with a rope or slinky and describe what moves and what doesn't.
  • Share the objective: Speed of sound and echoes. Read the success criteria together.

I do: model it · 10 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: You see lightning and hear the thunder 2 seconds later. Sound travels at about 340 m/s. About how far away is the storm, in metres?
  • Step 1: 340 × 2 = 680
  • Step 2: So the answer is: 680 m
  • Answer: 680 m
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 10 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. You see lightning and hear the thunder 4 seconds later. Sound travels at about 340 m/s. About how far away is the storm, in metres? → 1360 mPrompt: Light arrives almost instantly; the delay is the sound travelling.
  2. You shout towards a cliff and hear the echo 1 s later. Sound travels at 340 m/s. How far away is the cliff, in metres? → 170 mPrompt: The sound goes to the cliff and back.

You do: independent practice · 10 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 8 questions are on the student sheet below, with answers in the key.

Exit ticket · 5 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. You shout towards a cliff and hear the echo 1 s later. Sound travels at 340 m/s. How far away is the cliff, in metres? → 170 mPrompt: The sound goes to the cliff and back.
  2. How do bats find insects in the dark? (They send out high-pitched sounds and listen for echoes / They glow / They smell them from far away / They use magnets) → They send out high-pitched sounds and listen for echoesPrompt: This is called echolocation.

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

  • 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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Speed of sound and echoes

Name

Date

Score/ 8

  1. Question 1

    You see lightning and hear the thunder 3 seconds later. Sound travels at about 340 m/s. About how far away is the storm, in metres?

    Answerm

  2. Question 2

    Why do you see lightning before you hear thunder?

    • A. Light travels much faster than sound
    • B. Sound travels faster than light
    • C. Your eyes are faster than your ears
    • D. Thunder is made later

  3. Question 3

    You shout towards a cliff and hear the echo 1 s later. Sound travels at 340 m/s. How far away is the cliff, in metres?

    Answerm

  4. Question 4

    You see lightning and hear the thunder 2 seconds later. Sound travels at about 340 m/s. About how far away is the storm, in metres?

    Answerm

  5. Question 5

    How do bats find insects in the dark?

    • A. They glow
    • B. They use magnets
    • C. They smell them from far away
    • D. They send out high-pitched sounds and listen for echoes

  6. Question 6

    You shout towards a cliff and hear the echo 3 s later. Sound travels at 340 m/s. How far away is the cliff, in metres?

    Answerm

  7. Question 7

    You see lightning and hear the thunder 4 seconds later. Sound travels at about 340 m/s. About how far away is the storm, in metres?

    Answerm

  8. Question 8

    What is ultrasound?

    • A. very loud sound
    • B. light we cannot see
    • C. sound that travels in a vacuum
    • D. sound with a frequency too high for humans to hear

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Answer key: Speed of sound and echoes

  1. 1. 1020 m

  2. 2. A. Light travels much faster than sound

  3. 3. 170 m

  4. 4. 680 m

  5. 5. D. They send out high-pitched sounds and listen for echoes

  6. 6. 510 m

  7. 7. 1360 m

  8. 8. D. sound with a frequency too high for humans to hear