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Read the whole thing. I promise, it's really amusing at the end.



The goal to the Density of Pennies lab experiment was to find the density of groups of pennies, sorted by year. With the densities of pennies, the goal was then to find the changes in the metals that the pennies were made up of over time, and to ultimately find the year that the pennies changed from a structure of mostly the element copper to a structure containing another, unknown metal.
For the procedure, the pennies were weighed, and then their volumes were measured using 50 milliliter graduated cylinders. The densities were then calculated in groups in a chart. For accuracy, a collaborative chart of all densities calculated was then created, and the mean of all densities was found. Then each density was subtracted from the mean to find how far it was from the average. For precision, the standard deviation of the collaborated densities could have been found. Finally, since the degrees of both accuracy and precision were known, the uncertainty associated with the glassware and scales was then known. Therefore, more precise hypothesis could be made as to what the true value of the pennies’ volumes and masses would need to be in order to satisfy the requirements that the pennies changed in elemental composition between the years 1980-1984 and that the pennies were composed of 2.5% Copper and of 97.5% another, unknown metal. This set of years was known because all measurements of the pennies’ densities and masses showed similar fluctuation in that time frame: an average of 1.4 grams per milliliter, according to the average of two trials. Finally the equation (97.5%)x + (.2235)=y was used, where densities for the most likely metals, Tin and Zinc, were x, and y was the density of a penny in the case of the metal’s density substituted for the x variable. Using the given equation, Tin had the density closest to the required density.
However, according to the U.S. Mint, Zinc was the metal that replaced Copper as the most abundant metal in the penny (Mint). The original hypothesis was proven wrong, and so the entire experiment underwent a review process in order to more accurately determine the composition of the penny in a future experiment. The following conclusions were made in the process of review. First, more accurate instruments for measuring volumes of pennies would be used. Secondly, the number of pennies would be increased and decreased to find the number that best represented each time frame. Then the experiment could be done more accurately.
The goal of this experiment, in conclusion, was to determine the unknown metal in pennies and when the pennies changed in composition from mostly Copper to mostly the unknown metal. However, the faulty weighing and measuring procedures for the experiment were too imprecise and inaccurate for a knowledgeable conclusion to be reached. Therefore, the experiment was a failure.