If the amount of water is increased the pitch gets lower. I can make music with the bottles of water.
- eight glass soda bottles of the same size and shape
- paper slips numbered 1 to 8
- Pour water to different levels in the bottles.
- Blow gently across the tops of the bottles until a sound is produced for each one.
- Arrange the bottles in a row according to the pitch of the sound from low to high.
- You may want to add to or remove water from the bottles to make a musical scale.
- Under each bottle put a slip of paper numbered from one to eight.
Try to play a simple tune by blowing across the tops of the bottles. Can you decide what is vibrating to make the sound?
Use a pencil to tap the side of each bottle near the top. What happened? Check the numbers from low to high. What is vibrating to make the sound? What can you say about this?
Troubleshooting : try to tune the bottles to the piano. Can you make one of the bottles produces the same pitch as one of the piano keys? Can you match the piano with one full octave of sounds from the bottles? One octave is eight white keys in a row. If you are using bottles with lids, put the lids on overnight and see if the sounds still match the next morning.
To do this activity, children may need to be reminded of the musical meaning of the term pitch.
In steps 1-4, blowing across the bottle causes the air to vibrate. This is the way pipe organs and musical wind instruments produce sound. A longer column of air will cause a slower vibration and a lower pitch. When the bottles are struck in step 5, it is the glass that vibrates to produce the sound. Water will slow the rate of vibration of the glass. Therefore, the greater the amount of water, the more slowly the glass vibrates, and the lower the pitch
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