W&S Activity III – D3: Changing the Medium

Name: Group: Class Period:

Introduction: In this on-line sample activity, clicking on the link to the “simulators” will open snapshots of the simulator setups in a separate window. The buttons and tools in these snapshots do not work EXCEPT for the two buttons shown to the right (located on the lower left of the simulator image). Clicking on these two buttons allows you to “turn on” or “turn off” the waves simulation.
To change the medium of the sound room (see picture to right), click once on the sound room (make sure the simulation is “off”). In the window Properties of Sound Room, click on the radio button for the medium of your choice. Then click OK or Apply to have the change take effect. For this example, only the sound room medium can be changed.
Finally, clicking on the “Logger Pro” link below opens an image of a Logger Pro window. The image does not display any data.

	What properties of the medium affect the sound transmitted though it?
	Materials: two glass bottles, Alka-seltzer tablets, ULI, microphone probe, temperature probe, 5 m cardboard tube with end caps, hair dryer, hot and cold water
	1. Imagine that you have two glass bottles each half-filled with water. Each bottle has the same level of water in it.
	Suppose you drop one Alka-seltzer tablet into one of the bottles. The carbon dioxide gas generated, which is heavier than air, will push most of the air from the bottle so that one is half-filled with air and one half-filled with carbon dioxide. Each bottle still has the same level of water in it. You will blow across each one simultaneously to produce a tone. Keeping in mind the ideas developed in cycle 2, predict what wave properties will change in the carbon dioxide bottle and what this will sound like to your ear.
		Comparing carbon dioxide to air		What will you hear?
	Pitch
	Wavelength
	Wave Speed
	How did you decide?
	What ideas helped you make your predictions?
	2. Test your prediction by performing the experiment. Fill each bottle with the same amount of water (about half way). Adjust the amount of water until the tones made by the bottles are identical. Drop in one Alka-Seltzer tablet and allow it to completely dissolve. The water level will rise as the tablet fizzes. Allow enough time for the water level to just barely return to normal (the tablet may still be fizzing a little). Now blow across each bottle simultaneously. Describe what you hear.
	Which wave properties changed? Based on what you saw in ActIII-D3 Sim 1 state a general rule relating what you heard with the properties that changed.
	Why does this make sense?
			3. Suppose you have two identical glass soda bottles - one filled with hot water and one with ice water. You quickly empty the two bottles and blow across each one simultaneously to produce a tone. Predict how the sounds in the two bottles will compare.
	How did you decide?
	What about the behavior of sound waves helped you make your prediction?
	4. Test your prediction for the bottle by performing the experiment. Be sure to work quickly as the temperatures will change as soon as you empty the water. Write your observations below.

5. Imagine you send the same sound through various materials, testing the effect each substance has on the wave properties of that sound.

Predict how the wave properties in the materials listed below will change when compared with properties of the same sound in air.

CO2

Helium

Mercury

Granite

Vacuum

Amplitude

Frequency

Wavelength

Speed

How did you decide? What ideas helped you make your predictions?

6. Test your predictions by running the simulation Act III-D3 Sim 1. You can read the amplitude in dB from the top right side meter. The observed frequency can be measured on the bottom right side meter. The wavelength can be determined using the tape measure. To calculate the speed of sound in each material, use the equation you developed in Cycle I. To change the medium, select the pointer and double click on the sound room. Record your observations below.

Air

CO2

Helium

Mercury

Granite

Vacuum

Amplitude

Frequency

Wavelength

Speed

Which wave properties changed? Based on your simulator results, state a general rule relating what you heard with the properties that changed.

7. We are now going to investigate the effect of temperature on the speed of sound further. Connect a microphone probe to DIN 1 and a temperature probe to DIN 2 on the ULI. Click on Logger Pro. Set up the cardboard tube with one end closed, the temperature probe in the middle and the microphone probe at the open end.

Procedure: Click on the Collect button and snap your fingers beside the microphone. Snap several times until the collection process is done. You may have to practice this to capture the snap since the collection time is very short. When you are successful, you should see your snap and the echo of your snap. Click on the graph to select it and Analyze à Examine from the top menu bar. Drag the analyze lines to read the time for the snap and the echo.

You will run this several times at two different temperatures. The first runs will be at room temperature. For the higher temperature, partially open the closed end and run hair dryers in the two ends until the tube is hot. Seal the closed end and run several trials, again saving to analyze later. When you are finished, fill in the data table below. Calculate speed by dividing distance by time.

Cold

Hot

Trial

Distance

Time

Speed

Temperature

Distance

Time

Speed

Temperature

1

2

3