Energy, Light and Sound (Lesson 4)

 FOCUS QUESTION

How does sound behave?

SPECIFIC OBJS.

1.       Investigate some properties of sound

2.       Describe sounds using scientific language

3.       Work cooperatively in groups

CONTENT SUMMARY

Sound is a form of energy. It travels as waves in all direction. Sound can travel through all states of matter (solid, liquid, gas). Sounds travel fastest through solids as the molecules in solids are more closely packed, therefore they collide faster.

For sounds to be heard, something must be vibrating. Vibration is a back and forth movement. For a sound to be heard, air must be present. Therefore, sound cannot travel through a vacuum/empty space.

The science of sounds is called acoustics

The bounce of sound is called echo. 

ENGAGE

Students I want you to close your eyes and listen quietly as I play  play an audio clip (Musical instruments) they will describe what they are hearing. (sounds of musical instruments)

Students will tell what sound is and how sound is made. Watch youtube video entitled “What is sound?” to glean information  on sounds.

EXPLORE

Tell if you believe sound has properties as light does. What do you think the properties of sound are?

In groups, I want you to hold one end of a plastic ruler on the edge of your desk and pluck the other end as depicted below.

I want you to record what you observe. (Vibration is taking place, sound is heard) Measure the length of the ruler and record same in a table as depicted below. Repeat the steps with the ruler at varying lengths hanging over the edge, each time trying to flick/pluck the ruler with the same force. Record your observation.

NB. Students will discuss the principles of a test fair. 

(a)   (They will also identify the following):

Materials used

(b)   What will be measured

(c)    What they will keep the same

(d)   What will change

(e)   Method of investigation

Hence: the

Control / constant Variable (materials that don’t change) -

Dependent/Responding Variable (effect) -

Manipulative Variable (what will change) -

Formulate a hypothesis -

Place a tick [ü] in the relevant box.

                                    Table showing the speed and pitch of a vibrating ruler

Length of Ruler /cm	Speed			Pitch
	Fast	Medium	Slow	High	Medium	Low
25			ü			ü

EXPLAIN

Let's discuss your results to ascertain any patterns/relationships between the length of the ruler and the speed and pitch of the vibrations. Share your concluding statements and discuss your ideas with the class.

EXTEND/ELABORATE

In groups, repeat the activity above using rulers made from different materials, eg, a wooden ruler and a metal ruler. Compare the results from all investigations and make suggestions about the relationship between the type of material and the sound produced. (Remember the rules for fair testing)

EVALUATE

1.The diagrams below show an investigation conducted by a student. The student fixed one end of a ruler to a table, and then plucked the other end of the ruler. The pitch of the sound made by vibrating ruler was noted. (Each time the ruler was plucked with the same force. This was what the student did.

(i) From the option below select the most likely prediction for the investigation above.

(a)  When an object is plucked it will make a sound

(b)  The speed of a vibrating object affects the pitch of the sound made

(c)  The length of a ruler affects the pitch of the sound made

(d)   When an object is plucked it will vibrate.

1.      (ii)The student later performed the experiment again, this time using a metal ruler and a board ruler. Do you believe the different materials used will affect the speed and pitch of the vibrations? Yes/No

       Justify your answer to (i) above. ________________________________________________

     (2)  Define the following terms.

(a)    What is sound?

(b)   Define ‘Pitch”

(c)    What is vibration?

(3) Explain in a few sentences how sound is made.