What You Need:
What You Do:
- Line up your vessels in a row. Make sure they're clean, empty, and all the same size.
- Gently tap the base of each bottle with the metal spatula. Do they all sound the same?
- Use the graduated cylinder to measure and pour different amounts of water into each of the vessels. Fill the first vessel with just a little water. Fill the second with slightly more than the first, and so on, until you reach the last vessel, which will be almost full.
- Add a drop of food coloring (if desired) to each vessel so the water levels on your liquid xylophone are easier to see.
- Number the vessels so the one with the most water is 1, the next highest water level is 2, and so on until the vessel with the least water is marked with the highest number.
- Use the metal spatula to tap each vessel towards the base of the bottle. Does each bottle sound different?
- Try using the wooden spoon and glass stirring rod instead to hear a very different noise.
When you tapped the empty vessels, they all made the same sound. But when you added different amounts of water, the noise changed. You probably noticed that the more water the test tube held, the lower the pitch produced. The highest pitch came from striking the test tube with the least water. Since sound waves travel through liquid, by altering the amount of water in the test tube, the sound waves is altered as well. Sound waves can also move through other liquids like juice or milk. Liquids with varying densities will produce different sounds since the sound waves travel through them in varying speeds. Likewise, different materials make different sounds. too! Strike your xylophone with plastic and wood. You'll notice that these materials absorb a lot of sound waves, dampening the pitch produced. Striking your xylophone with metal and glass creates the clearest sound.
For further experimentation:
- Try tapping the vessel in a different spot. How does the sound change when you tap closer to the top?
- Use vessels of different shapes and sizes. Do they produce different pitches even when the same amount of water is used?
- Vary the amount of water used in each vessel, or just in one.
- Use liquids of varying densities (syrup, ketchup, vinegar, milk) to see how it affects the sounds waves. When finished, pour all your liquids into one vessel then let them separate for a bonus density demonstration!
- Play "Twinkle, Twinkle Little Star" by striking the vessels in this order:
1,1,5,5,6,6,5 4,4,3,3,2,2,1 5,5,4,4,3,3,2 5,5,4,4,3,3,2 1,1,5,5,6,6,5 4,4,3,3,2,2,1
- Play "Mary Had a Little Lamb" like this:
3,2,1,2,3,3,3 2,2,2 3, 4,4 3,2,1,2,3,3,3, 3,2,2,3,2,1
- Can you figure out how to play other simple songs on your liquid xylophone?
Liquid Xylophone Demonstration Video