• Quick retrieval from earlier learning (Parts of a wave; How sound travels through solids, liquids and gases). Students answer on mini whiteboards.
• Show answers together and note who needs support in the main task.

1. An alarm clock rings inside a jar. As the air is pumped out, the ringing gets quieter. Why? (The clock stops ringing / Sound needs particles to travel through, and there are fewer left / Glass absorbs all sound / Air makes sound quieter) → Sound needs particles to travel through, and there are fewer leftPrompt: Can sound travel through a vacuum?
2. 20 waves pass a point in 4 seconds. What is the frequency, in hertz (Hz)? → 5 HzPrompt: Frequency is the number of waves per second.
3. In which direction do air particles vibrate when a sound wave passes? (backwards and forwards, parallel to the direction the sound travels / up and down, at right angles to the wave / they do not move / in circles) → backwards and forwards, parallel to the direction the sound travelsPrompt: Sound is a longitudinal wave.

• Ask the class to make a wave with a rope or slinky and describe what moves and what doesn't.
• Share the objective: Transverse and longitudinal waves. Read the success criteria together.

• Work through the example out loud, saying why you do each step, not just what you do.
• Example: Is this a transverse or a longitudinal wave: seismic P waves?
• Step 1: In longitudinal waves, vibrations are parallel to the direction the wave travels.
• Step 2: So the answer is: longitudinal
• Answer: longitudinal
• Pause after each step and ask a student to say what comes next.

• Do these together. Students try each step on whiteboards before you reveal it.
• Use the hints as prompts rather than giving the answer.

1. Is this a transverse or a longitudinal wave: sound? (transverse / longitudinal) → longitudinalPrompt: Compare the direction of vibration with the direction the wave travels.
2. What are compressions and rarefactions? (the peaks and troughs of a transverse wave / regions where particles are squashed together and spread apart in a longitudinal wave / the start and end of a wave / two kinds of light) → regions where particles are squashed together and spread apart in a longitudinal wavePrompt: Think of a slinky being pushed.

• 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.

• Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.

1. A cork floats on a pond as ripples pass. What does the cork do? (bobs up and down but does not travel with the wave / spins in a circle quickly / sinks / moves along with the wave to the edge) → bobs up and down but does not travel with the wavePrompt: Waves transfer energy, not matter.
2. Types of wave: which statement is NOT true? (Seismic P waves are longitudinal and S waves are transverse. / Longitudinal waves have crests and troughs. / Sound waves are longitudinal. / All electromagnetic waves are transverse.) → Longitudinal waves have crests and troughs.Prompt: Which kind of wave is light?

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-8.