1. Key words: Medium, particles, reflection
The speed of sound
Thursday, 06 December 2018
Key words: Medium, particles, reflection
Starter: Some animals communicate by echolocation. What is an echo and how does it form?

2. To describe how echoes are formed.
The big picture: “Why does sound travel at different speeds in different mediums?”
Learning outcomes
To describe how echoes are formed.
To compare the speed of sound in solids, liquids and gases.
To evaluate why sound travels at different speeds using the particle model.

3. Echoes
An echo is a reflection of sound. The listener hears the sound after it has been made. Shouting down a well or into a cave are typical examples of echoes.
Echoes are also used by ships/submarines (sonar) and for baby scans (ultrasound).

4. Task
Copy and complete the sentences about echoes. Echoes are caused when ……………. is ……………… off of a surface. Shouting into a ………… creates a big echo. Echoes can be very ……………….., some examples are ……………….. and ………………….. . An unpleasant sound is called …………………. SONAR WELL REFLECTED SOUND USEFUL ULTRASOUND NOISE Extra challenge: Draw a diagram to show why some animals use echolocation. You should explain your picture using the following words: PREY, REFLECTION, SOUND WAVE
LO: To describe how echoes are formed.

5. Discuss:
Sounds cause particles to vibrate, this causes the sound to travel. Do you think a sound travels quicker in a solid, liquid or a gas?
Think of reasons for your opinion and be ready to share.

6. Copy and complete the sentences (Level 4)
Sound can travel at different ………………. depending on the …………………… it is travelling through. Sound travels faster in a ……………… than it does in a ………………. or ………………. . This is because the particles in a solid are …………………… together than they are in a gas.
CLOSER SPEEDS LIQUID GAS MEDIUM SOLID
2) Draw particle models of a solid, liquid and gas and answer questions 1,2 and 3 about the bar chart (L5)
Extra challenge: Question 4a and 4b (L6)
LO: To compare the speed of sound in solids, liquids and gases.
To evaluate why sound travels at different speeds using the particle model.

7. Plenary: If this is the answer what could the question be? MEDIUM ECHO
AMPLITUDE
PITCH
Extra challenge: DENSITY