Are Pennies Today Worth Less?

Background:

How many times have you heard your parents say that money just doesn’t buy today what it used to? Well they may in fact have a point. It would seem, if we use the penny as an indicator, that perhaps our money isn’t what it used to be. Most Americans are aware that the penny is considered to be made of copper. As you can tell by looking at a piece of pure copper wire, copper itself is quite soft and pliable. Like most metals, for example silver, in order for copper to be durable, it must be alloyed with another metal. Some people believe that today’s pennies feel different from those of earlier times.

The study of chemistry involves not only the observation of changes in matter, but also the measurement of these changes. In fact, most chemical principles cannot be fully understood without obtaining and analyzing some quantitative data. The techniques of data collection, data analysis and measurement are a very important part of chemistry. In this investigation, you will make a number of measurements and then use these measurements to determine a physical property: density.

Problem:

Determine the consistency of the properties of pennies throughout various decades.

Procedure:

1. Obtain 10 pennies minted in each decade 1960’s to 2000’s.

2. If you don’t know already, do some research and find out what other have been used in making our pennies.

3. Use simple lab procedures to examine the pennies’ density

  1. Using the water displacement method, determine the volume of the pennies for each decade. The volume is low enough that it is not possible to see a change in water level with one penny. Find the volume for all ten pennies for the decade, then divide to determine the volume of each penny. Be sure to record the most precise measurement you can read/estimate.
  2. Determine the mass of each of your pennies. If your 10 pennies for a decade include duplicates, say two pennies from the year 1973, you do not need to repeat the measurement.

Data:

Year / Volume / Mass

Analysis:

Calculate the density of the pennies for each year you have. Using a graph, determine if and when any change in the elemental make-up of pennies occurred.

Conclusion:

Did a change in composition occur? If so, when?

Compare the density of the pennies at different times to the densities of some common elements and determine which, if any, elements have been added to the pennies.
Density of Zn = 7.14 g/cm3
Density of Al = 2.70 g/cm3

Density of Pb = 11.34 g/cm3

Density of Ge = 5.323 g/cm3

Density of Cu = 8.96 g/cm3