Measuring the density of cubes of Aluminium and Brass

Method of measuring volume:

1. Fill up a measuring cylinder to 150 ml.
2. Gently place the aluminium cube in the cylinder (do not drop it).
3. Measure the displacement increase.
4. Find the displacement of the cube( initial volume – final volume)
5. Repeat steps 1-4 for brass cube.
6. Measure the length of the aluminium cube with a rule and calliper.
7. Record length.
8. Repeat for brass cube.

Results

Volume:

Ruler and calliper:

Aluminium: 2cm±0.05cm per side

Percentage uncertainty =0.05/2=2.5%     2.5 X 3= 7.5%

Absolute uncertainty= 7.5% x 2= 0.15cm

Volume= 2^3=8cm^3 ± 0.15cm^3

Brass: 2cm±0.05cm per side

Percentage uncertainty =0.05/2=2.5%     2.5 X 3= 7.5%

Absolute uncertainty= 7.5% x 2= 0.15cm

Volume= 2^3=8cm^3 ± 0.15cm^3

Cylinder:

Aluminium: 158ml-150ml=8ml ± 2ml

Brass:  158ml-150ml=8ml±2ml

2ml is the same as 2cm^3

Percentage uncertainty for Aluminium and brass is 2/8= 25%

Mass:

Electronic and triple beam

Aluminium: 58.6g ± 0.05g

Brass: 53.7g ± 0.05g

Density:

Using density function: p= mass/volume

Since both the volume from measuring the sides of the cube and the volume calculated from the displacement, we can use the same equation.

Percentage uncertainty for Aluminium = 25%+8.53x10^-4=25.0008%

Aluminium: density= 58.6/ 8 = 7.2500±25.0008%= 7.25±1.81 g/cm^3

Percentage uncertainty for Brass= 25%+9.31x10^-4=25.0009

Brass: density=53.7/8 = 6.7125±25.0009%= 6.7125±1.67 g/cm^3

Conclusion

Through this experiment we can conclude that the density of the Aluminium cube is 7.25±1.81 g/cm^3 and the density of the Brass cube is 6.7125±1.67 g/cm^3. Our experiment is not very accurate as the measuring as there is approximately 25% uncertainty; this was due to the imprecise measuring of the cylinder cause by human error.

Evaluation

In this experiment our results were not very accurate because of the 25% uncertainty, we could improve our precision and accuracy of our results by:

• Used different people to measure the cube in order to get a more precise result.
• Used better equipment to improve accuracy.
• Repeat the water displacement test to increase accuracy by using an average.
• Keep constant room temperature in order to keep the metal density constant.
• Try different metals to obtain a variety of results to compare.