 Title: Density, Alcohol Content and the Archimedes Principle (Performed 09/11/13)

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Purpose: Part I was to examine three different objects of the same material in order to identify the type of metal. We used the water displacement method and the buoyancy method according to Archimedes Principle. Part II was to find the density of ethanol by mass. We used a 25.0mL graduated cylinder and a 25.00mL volumetric flask to measure the volume. We used two different pieces of glassware to determine the most accurate density of ethanol by mass since the measurement of volume is variable. Procedure: As stated in lab manual pages 23-24.

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Data and results for part I: Density and identification of a solid:

Calculated Density Using the Water Displacement Method
Mass of object (g)Initial volume (mL)Final volume (mL)Volume of object (mL)Density (g/mL) Trial 117.63561.964.02.18.4
Trial 221.70771.976.04.15.3
Trial 316.75567.869.82.08.4

d=m / V
Trial 1: d= 17.635g/2.1mL = 8.4g/mL
The average of the calculated density: 7.4g/mL
The calculated standard deviation: 1.8
We identified the metal as Zinc (7.14g/mL). However we believe the calculated density of trial 2 seemed inconsistent with the other two trials. Therefore we believe that the metal is actually yellow brass (8.47g/mL). The percent error: – 13%

Calculated Density Using the Buoyancy Method
Mass of objectInitial mass in apparatusFinal mass in apparatusVolume of objectDensity Trial 117.6515.472.182.188.10
Trial 221.7219.172.552.568.48
Trial 316.7714.762.012.018.34

dcyl = ms/Vcyl VH2O = Vcyl = m/dH2O
Trial 1: dcyl= 17.65g/2.18mL = 8.10g/mL
The average of the calculated density: 8.31g/mL
The calculated standard deviation: 0.099
We identified the metal as yellow brass (8.47g/mL)
The percent error: -2%
Data and Results for part II: Density of a liquid
Calculated Density of Liquid #2 Using a Graduated Cylinder
Mass of Container (g)Mass of container plus liquid (g)Mass of liquid (g)Volume of liquid (ml)Density (g/mL) Trial 187.26111.023.7425.00.949
Trial 287.29110.923.6125.00.944
Trial 387.27110.923.6325.00.945

d = m/V
Trial 1:
d = 23.74g/25.0mL = 0.949
The average of the calculated density: 0.946g/mL
The calculated standard deviation: 0.003
Using a graduated cylinder we found that liquid #2 had 33% ethanol by mass.

Calculated density of liquid #2 using a Volumetric Flask
Mass of Container (g)Mass of container plus liquid (g)Mass of liquid (g)Volume of liquid (ml)Density (g/mL) Trial 119.3943.5724.1825.000.9672
Trial 219.5043.5824.0825.000.9632
Trial 319.5143.5724.0625.000.9624

d = m/V
Trial 1: 24.18g/25.00mL = 0.9672g/mL
The average of the calculated density: 0.9642g/mL
The calculated standard deviation: 0.0026
Using a volumetric flask we found that liquid #2 had 21% ethanol by mass Conclusion: In part one the buoyancy method gives more significant figures and the standard deviation is smaller. Based on the density, using the buoyancy method, we identify the metal to be yellow brass. Using the less precise measurement method (water displacement method) we don’t think we would have identified the same metal. We feel this way because using the displacement method we identified the metal to be Zinc. 