Density Lab

DENSITY LAB

I.  GUIDING QUESTION: How does the density of various solids affect the way the sound waves travel from a tuning fork?

II. HYPOTHESIS
                         Hypothesis (Adrian): I think that increased density of the medium might cause the sound waves to travel faster, but be quieter.
                         Hypothesis (Jude): The density will cause the pitch to increase although the loudness will not change.
                             
III. EXPLORATION
                         A. Materials:

• Wood
• Plastic
• Ream of Paper
• Rock
• Sponge
• Cement/Concrete
• Tuning Fork (341.3F)

                         B. Procedure:

1. Find desired materials. Measure or research to find their density.
2. Set up a table in your notebook with three headings: Material, Density and Loudness/Pitch/Observation.
3. Tap the side of the tuning fork against each material. Remember to always stay the same distance away from the tuning fork and to keep your tests in a room with the same temperature.
4. Write down your observations in the Loudness/Pitch/Observation category.

IV.  RECORD & ANALYZE
                                          A.  Data Tables:
                       

Material	Density	Loudness/Pitch/ Observation
Wood	680 kg/m(3)	High at first but softens to a medium pitch. Very empty loudness.
Polycarbonate Plastic	1360 kg/m(3)	A low, soft pitch. Loud.
Ream of Paper	94 kg/m(3)	Very loud, low pitch.
Volcanic Pumice	641 kg/m(3)	A medium pitch with a soft, rumbling after-effect. Not very loud.
Sponge	100 kg/m(3)	Extremely soft, almost no volume. Normal pitch.
Cement	1100 kg/metres(3)	Starts low, but rises to a medium volume. Low pitch.

C.  Analysis of Data (Adrian): I found that most of the time, the denser the material was, the lower pitch it had. However, density had no significant effect on the loudness. I wasn’t here while my lab partner Jude was doing these test, so it is difficult to make as many observations.
                
Analysis of Data (Jude): The lower pitch in some of the materials comes from the sound waves traveling through dense material. The rumbling from the Volcanic Pumice is from the rock itself. The crumbly, rough top would produce a rumbling. The ream of paper is unique because it is thick, therefore has the properties of dense material. The less dense materials produced a medium to high pitched sound. The sponge produced almost no sound because it was so soft and had an extremely low density.
                                         
IV. CONCLUSION
                            Conclusion (Adrian): My hypothesis was “I think that increased density of the medium might cause the sound waves to travel faster, but be quieter.” I found out that denser mediums caused a lower pitch, but didn’t have an effect on the volume of the sound. My hypothesis was completely wrong. I learned that different properties of the medium can effect the sound in different way, so sound won’t necessarily travel the same way in two materials with the same density.
                          
                            Conclusion (Jude): My hypothesis: “The density will cause the pitch to increase although the loudness will not change,” was proved sort of correct. It really varies from material to material. From the data table we can see that the denser the material the lower and louder the sound. This is because the particles are more compact therefore when they vibrate together they produce a greater sound.

V. FURTHER INQUIRY
                                     Further Inquiry (Adrian): I realized that there was a fatal flaw in out experiment that made all of data mostly invalid. We were supposed to be testing how density of various mediums effected how sound travels. So the density of the medium was supposed to be the variable, and all other factors such as the elasticity of the medium were supposed to remain constant. However, in our experiment we changed the density and elasticity whenever we changed mediums, so we couldn't be sure if the patterns we noticed in our data were because of the change in density or the change in elasticity. To avoid this next time, we would need to find materials with exactly the same elasticity, but different densities. Although that would be difficult to find, it would be necessary for our experiment to be truly scientific.

                                     Further Inquiry (Jude): For a start, I could have definitely had Adrian and myself test, but he was away, so I had to rely on my own data. I would have maybe liked to have added a few more materials to the test just to make the testing more interesting. Well after the tests were conducted, Adrian found a flaw that, not ruined our tests, but did change the ideology. We were meant to only manipulate the density, but we ended up in the course of choosing different materials changing elasticity and partially changing the temperature. To avoid this next time we should find different materials with the same elasticity but different density (that would be hard).I would have definitely liked to have changed the frequency of the tuning fork and maybe change the order of testing the items, just to make things simpler. Otherwise I feel that the testing in a nutshell went very well. Another test we could have conducted is measuring the speed of the sound waves and changing the frequency of the tuning fork.