| Energy & Forces - Properties & uses of energy - Light & Sound - G10 |
  Teacher's
Guide
EF-C1.3 |
ISE 5-14 Curriculum Support Materials Overview advice |
| 1. The children will be willing and able to produce a wide range of sounds with little prompting from you! Allow them to try out the school instruments paying particular attention to the way the sound is produced. |
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2. Remember for this lesson the
important point is that sound is linked to vibration. A surface vibrating causes
the air above it to vibrate. That in turn causes the next layer of air to
vibrate - a bit like ripples spreading out in a pond.
When the vibrating air reaches our ears, it enters through the outer ear and makes a membrane inside our ear vibrate - the ear drum. Tiny bones touching the ear-drum pick up the vibration transmitting it mechanically to another membrane. On the other side of this second membrane is an inner chamber filled with fluid. Very sensitive hairs with nerve cells attached to them move with the vibrations. These nerve cells transmit signals to the brain and it these signals which are interpreted as sound. Another useful demonstration is to take a drum - or make one using a cut off balloon stretched over a cardboard tube - and place a few grains of salt or sugar on the stretched surface. With your mouth about 10 cm from the surface, sing a low note - you should see the grains jumping about as the skin vibrates. Try making other noises nearby - which gives the most vibration? The children can use worksheet C11 (G) to record what they made a noise with, describe the sound they made and what was actually vibrating. |
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Air cannon
Take a sturdy cardboard tube such as a whisky bottle or ‘Pringles’ tube and cut off the fixed end. Replace it with a cardboard disk from which a small circle - about 2 cm diameter has been cut out of the middle.
Fix in place with an elastic band. By tapping on the stretched balloon, a ‘bullet ‘ of air can be sent out of the other end of the tube and used to blow out a nightlight or candle (see Safety ) from a distance of about 50 cm. If you are not happy about using naked flames in the classroom then make a clothes lines with pieces of tissue strung along it which will flutter. See Safety. |
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What do you think about what is happening to the air inside and out of the Air cannon. This has also been called a "sound cannon" by some people. A pulse of air is used to definitely blow out a candle. What we would like you and the children to think about is :- What happens to the air inside the tin as you
draw the balloon skin back? How could you adapt the experiment to investigate (see) what is happening to the air? Sound waves travel through the air by vibrations in a material (e.g. the balloon) which successively squeezes and releases the air in front of it. The air molecules then squeeze and release the next layer of air and so on until the molecules of the candle flame experience the fast moving molecules. Therefore it is not the actual molecules of air that travel from the vibrating balloon skin but the waves of squeezing (compression) and releasing (decompression). |
This
possibly (
Cut the neck off a round balloon and stretch the remaining bit over the open
end of the tube.
