A comparison of a pennies mass to the year it was minted

A comparison of a pennies mass to the year it was minted
By Trevor Gustafson



Introduction:
This experiment was done to discover the relationship between a penny’s weight and the year it was minted. My hypothesis going into this experiment was that “The longer a penny is in circulation, the lighter it will become. See figure 1:“Predicted results of the comparison of a pennies mass to the year it was minted.”



Materials used:
· 1 penny from the 1960’s
· 2 pennies form different years in the 1970”s
· 3 pennies from different years in the 1980’s
· 3 pennies from different years in the 1990’s
· 1 penny from the 2000’s
· 1 scale
· a pencil
· a notebook
· a piece of graphing paper


Procedure:

· 1 Create a hypothesis
· 2 Graph predicted outcome
· 3 Weigh individual pennies and mark findings on a chart
· 4 Mark individual data along with class data on a second chart
· 5 Mark individual data along with class data on a graph


Results:
· See attached Figure 1. “Predicted results of the comparison of a pennies mass to the year it was minted.”
· See attached Table 1. “Personal data concerning the comparison of a pennies mass to the year it was minted.”
· See attached Figure 2. “Group data concerning the comparison of a pennies mass to the year it was minted
· See attached Table 2. “Group data concerning the relationship of a pennies mass to the year it was minted.”


Analysis

1 Plot both the class data and your individual data on the same graph. Show the mass of each penny in grams on the y-axis and the year the penny was minted on the x-axis. Highlight the points that correspond to your individual data.
· See Figure 2: “Group data concerning the comparison of a pennies mass to the year it was minted”

2 Are the experimental results consistent with your hypothesis? If not, propose a new hypothesis
· No.
· The older pennies were actually heavier than the newer pennies
· The change was not gradual, but happened suddenly during the year 1982 (during 1982, some of the pennies were lighter and some were heavier)
· My new hypothesis is
“Something besides wear must have played a part in the sudden weight change of the penny during 1982.”

3 What effect might aging have on the mass of a nickel, a dime, or a quarter?
· Those coins are made of different materials so we can’t know what affect aging would have on them from this experiment.

4 Would using a balance that was many times more sensitive have made a difference in your conclusion about the effect of aging on a penny?
· The greater sensitivity might possibly have yielded different results.

5 What improvements might you have expected in you graph if only one student had done all the weighing on a single balance.
· Taking out variables such as multiple students and balances might have yielded a more consistent graph.

6 Compare your individual graph to the graph of class data. Why might you expect better results with the entire class data set than with your individual data set?
· Because most of the dots up until 1982, including my own, fell on 3.1 and most of the dots after 1982, including my own, fell on 2.5, It’s possible that the few odd ball points on the graph may have been miss-calculations.

Conclusion
· A pennies weight does not decrease by more than one decimal point of a gram the longer it has been in circulation.
· The coins minted before 1982 were actually heaver than the ones minted after 1982.
· Something caused the pennies to suddenly become lighter during and after 1982.
· Something besides wear must have played a part in the sudden weight change