I call students to the gathering area. We review what vocabulary we know about waves. We review the definition of amplitude and frequency. I have two tuning forks that I have borrowed from the music department. They are two different pitches. I hit one and allow it to play until the sound dies. I hit the other to produce a sound that is approximately the same volume, but a different pitch. I ask students to identify the difference between the two sounds.
I explain to students that the difference was the pitch of the sound. Pitch is caused by the speed of the vibrations causing the sound. I show students the tuning forks vibrating using an overhead projector. This allows students to see the movement of the forks and the differences between them. After the second demonstration, I explain to students that we know that sound moves in waves and causes vibrations in the material it moves through, creating the sound. Pitch is determined by the frequency of the vibrations. Faster vibrations produce higher pitches.
I split students into four groups. Each group has three glass bottles. One bottle is full of water, one is half-full of water, one bottle is empty. Each group also has a metal spoon. Students predict which bottle will have the highest frequency and the lowest frequency when struck with the metal spoon. Students record their prediction on their exploration sheets. Students hypothesize whether blowing or tapping will change the sound made by the bottle.
Students work in their groups to complete the experiment as outlined on their exploration sheets. I walk around the room observing students’ work and answering questions as needed. Students work for about 20 minutes to conduct the explorations and to complete their sheets for our class discussion. By this time in the year they should be able to independently work through an investigation as a group.
I call students back to the gathering area. We discuss our findings. Students share their exploration set-up drawings as well as a review of how to draw scientifically. We talk about the components of a scientific drawing. See my lesson on drawing scientifically for information.
I ask students who they could change this exploration to further investigate pitch. Students usually offer ideas such as different liquids, different amounts of liquid, bottles made of different materials. We make a note of these and post them on our “I Wonder” board for potential further investigation.