The average density of four separate pieces of polypropolene was determined to be 0.867g/cm3. Given the average densities of six different known plastics, we were able to identify the unknown plastic as PVC by its density.
All materials for this experiment were provided by the preproom.
- Gather all equipment, known plastics, and unknown plastics
- Mass all known and unknown plastics, record mass
- For displacement, fill a graduated cylinder with water and record the initial volume
- Add one of the plastics to the cylinder and record the final volume.
- For linear measurement, measure the length, width, and height of each plastic with a Vernier caliber
- Calculate densities
Conclusions and Discussion
From the information obtained in this lab, it can be determined that the unknown sample is PVC. Density is an intrinsic characteristic; therefore it can be used to identify different samples. Density is found by using the formula:
By finding the mass and volume of an object, it is possible to calculate the density of that object.
In the Mass, Volume, and Density of Polypropolene Samples table, the data needed to calculate the density of the samples is shown. The mass was obtained from the use of a scale, and the volume was determined by measuring the length, width, and height of each sample. When trying to determine the volume of these samples, linear measurement was used instead of a displacement method because the plastic’s density is lower than that of water, causing it to float. Once the individual densities of all four samples is calculated, an average density is taken. The average density of polypropolene is 0.867g/cm3.
Because density is an intrinsic characteristic, it can be used to identify unknown samples. In the Mass, Volume, and Density of Unknown Sample table, the data needed to calculate the density of the unknown sample is shown. The mass was obtained from the use of a scale, and the volume as determined by displacement. It was determined that the density of the unknown sample was 1.5g/mL. With this information, we can identify the unknown as PVC. While PVC has a known density of 1.37g/mL, it has the closest known density to that of the unknown.