Density Labratory

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Accelerated Studies in Physics and Chemistry Laboratory

Author: Shannon K. Smith

Team Members: Grace Corley, Caroline Kerley, Bryson Thomas

Date of Experiment: April 8, 2011

Date Report Submitted: May 2, 2011

Class: Accelerated Studies in Physics and Chemistry, D block

Mr. Mays, Instructors

Purpose

The purpose of this experiment was to accurately measure the density of sections of PVC plastic and sections of aluminum metal and compare them to these values to the published values. The goal was to have the calculated values as close as possible to the published values.

Background

For this lab, the displacement method was used to determine the volume of the four sections of PVC plastic and aluminum metal. The displacement method was first used by Archimedes, a greek philosopher, who discovered the displacement method by sitting down into his bathtub and noticed how the water level rose when he got in and sunk back down when he got out. He then and used this method to determine the volume for the King’s crown to make sure it was made of real gold.

The equation used to solve for density was ρ = m/V, where ρ is the density expressed in g/cm³, m is the mass expresses in grams and V is volume in cm³. This equation can also be written as m=ρV so that mass varies directly with volume and density is the constant of proportionality and the slope of the line. This equation was discovered by Mendeleev in the 19th century when he predicted the density of germanium.

The team calculated the mass of the sections of PVC and Aluminum on the triple beam balance. Then the team filled the graduated cylinder with water depending on the height of the different sections. The sections were put into the water and the volume of the water was recorded before and after the section was inserted into the water. This procedure was repeated for each section of PVC and Aluminum.

The teams hypothesis was that the team could accurately predict the density of samples of PVC plastic and Aluminum.

Experimental Procedure

The following equipment was used in this experiment:

250-mL graduated cylinder

PVC plastic sections (4)

Aluminum metal sections (4)

triple-beam balance

The team first calculated the mass of each section of PVC plastic and Aluminum metal on the triple beam balance. These values were then recorded.

The team started with the PVC plastic sections and went from the shortest section to the tallest section. The team filled the graduated cylinder with water depending on the height of the sections of PVC plastic so that the water came slightly above the PVC plastic when the PVC was held up to the cylinder. This volume of the water was recorded. Then, the PVC plastic was carefully slid into the graduated cylinder and the new volume with the PVC section in the water was recorded. The final volume was subtracted from the initial volume to get the displacement. The density was calculated using the equation ρ = m/V. This procedure was repeated for the Aluminum metal sections.

Results

The values for the PVC plastic section are shown in Table 1.

Table 1.

Pipe:	mass,g	initial volume, mL	final volume, mL	displacement, mL	density, g/ cm³
1-1	37.5	156	181	25	1.5
1-2	31.1	129	150	21	1.48
1-3	24.5	110	127	17	1.44
1-4	18.6	90	103	13	1.43

The values for the Aluminum metal are shown in Table 2.

Table 2.

Aluminum:	mass, g	initial volume, mL	final volume, mL	displacement, mL	density, g/ cm³
1-1	34.6	118	131	13.0	2.66
1-2	41.7	150	166	16.0	2.61
1-3	48.2	169	186	17.0	2.83
1-4	56.6	204	225	21.0	2.70

The density was converted from g/mL to g/cm³ using the conversion 1mL/1cm³.

Discussion

Graph 1 represents the line of best fit for PVC plastic and Graph 2 represents the line of best fit for the Aluminum metal.

INSERT GRAPHS HERE

For the experimental error, the average of the PVC plastic and Aluminum densities were calculated. For PVC, the result was 1.46 g/cm³ and for Aluminum the result was 2.7 g/cm³. The experimental error was calculated using the equation:

experimental error = (|predicted value - experimental value|/ predicted value) x 100%

The PVC plastic error was 4.28 % and the Aluminum error was 0%.

The error was very low so our results were very close to the published results.

The teams hypothesis was that the team could accurately predict the density of the samples of PVC plastic and Aluminum. The results were definitive and the hypothesis was confirmed.

Conclusion

The team did accurately predict the densities of the sections of PVC plastic and Aluminum, so the hypothesis was confirmed. The results were very similar to the published values so the teams values were very accurate.