Lesson Plan

The demonstration was presented to a grade 7 class, though I feel that the concepts are better suited for students in grades 8 and up. The lesson was 1-hour long and divided into three parts: sound, resonance and the demonstration. My presentation relied on two key components: a worksheet and PowerPoint. I have attached both below:

Lesson

Part 1: Slides 1-10

The first part of the lesson focused on sound and its properties. Students were first asked to discuss and write down what they knew about sound.

To illustrate vibrations, I asked students to wave their worksheets in the air and notice that the back and forth movement (corresponding to a vibration) produces a sound.
I then distributed cups with rubber bands around them (click here for illustration). Students were asked to pluck the rubber band and see how it moves back and forth. I also asked the students to grab the rubber band while it was moving and note that once the rubber band stops moving, there is no longer any sound.
To explain the movement of air particles during vibrations, I showed students a video (on slide 4). The part of interest is from 1:38 to 1:50.
I demonstrated the difference between amplitude and frequency by playing different sounds (link on slide 5). I then had a brief quiz where I asked students to differentiate between amplitude and frequency.
Returning back to the rubber bands, I asked the students to note that the harder they plucked the rubber band, the louder the sound (and vice versa). This was to help the students visualize amplitude: the rubber band moves at large amplitudes when the sound is loud and small amplitudes when the sound is low. This exercise seemed to help the students really understand the link between amplitude and loudness.

Part 2: Slides 11-18

The second part was devoted to the discussion of natural frequency, resonance and helmholtz resonators.

To illustrate the concept of natural frequency, I had the students pluck the rubber bands very hard and then gently. We then discussed that the frequency, or pitch, of the sound stayed the same no matter what. Students seemed comfortable with the idea after playing with the rubber bands.
I followed this with a brief discussion on the concept of resonance. To illustrate this, I showed the students a video of a wine glass shattering. I asked them to discuss what they saw in terms of amplitude, natural frequency and resonance. I then had a few students volunteer their explanations: most students seemed to have a reasonably good idea about what was happening.
Next, I introduced helmholtz resonators to the students and showed them a video of air being blown across various bottles, producing different frequencies.
To explain the springiness of air within the bottles, I showed a video illustrating the movement of air in and out of the bottles (on slide 18). The part of interest is from 0:45 to 1:40.

Part 3: Slides 18-26

The third part involved the demonstration followed by a discussion period.

IMPORTANT: Before showing the students the demonstration, I distributed hand sanitizer to each student to make sure their hands were clean. I then handed out a pair of earplugs to each student.
To explain why the bottles move and spin in the direction opposite to their openings, I blew up a balloon and asked students to predict where the balloon would go if I let it go. Of course, the students were well-aware that the balloon would go in the opposite direction of its opening and found this explanation satisfactory in understanding why the bottles spun in the direction that they did.
Though the last part was not part of the learning goals, as a bonus I explained to the students how the air moves into the bottle differently than when it leaves, giving the bottle a net thrust. I illustrated the concept by showing them a video of blowing inward and outward on a lighted candle (on slide 23). The parts of interest are from 0:57 to 1:15.
Finally, I had the students jot down what they learned. I then went from student to student and asked them what they found interesting. This was indubitably the most rewarding part: though the concepts were difficult, the students seemed to have a good overall understanding of the material.