Results & Analysis
1.) To determine the density and composition of a penny it must be first weighed on a scale. Find the average mass of multiple pennies from the same year. After weighing it find the volume by placing the pennies into a 50 ml beaker with 15 ml of water. Note the change in volume to obtain the volume of the pennies, obtain the average volume, and then calculate the density by dividing the mass of the penny by the volume.
2.) To keep measurements accurate and precise test multiple pennies from the same year and make sure to measure 10mls of water as precisely as possible. Keep human error to a minimum; always zero the scale before weighing.
Graph of Lab Sections Density of Pennies Overtime:
2.) Based on the data provided by the laboratory section, the density of the penny remained unchanged until 1982 when the overall average density dropped due to the composition of the penny changing. As clearly seen above there was a lot of human error or possibly calculation error. The year 1991 should be disregarded and years with 0 densities were due to not having that penny year tested.
1.) Avg Density of Pennies from 1975-79: 10.7 g/ml 1995-1999: 7.0 g/ml
8.94(.95) + x(.5) = 10.7 g/ml x(.975) + 8.94(.025) = 7.0
.5x = 2.207 g/ml .975x = 6.77 x = 4.414 g/ml x = 6.95 g/ml
Based off of the density calculation for the years 1995-1999 it is clear that the unknown metal that replaced most of the copper is zinc with a density of 7.14 g/ml. Human error is mostly to blame for the years 75-79 calculation.
The main goal of this experiment was to obtain the density of pennies throughout multiple decades and determine when the composition was changed by observing when the density of the penny changed. This was done by obtaining the mass of the penny using a scale and the volume of the penny using a graduated cylinder. By using D = M/V it was possible to obtain the density of a penny of a