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  Home > JCE Print > Journal of Chemical Education > Issues > 1998  > November  >
In the Laboratory
Do New Pennies Lose Their Shells? Hypothesis Testing in the Sophomore Analytical Chemistry Laboratory
Richard J. Stolzberg
Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK 99775-6160
Cover
November 1998
Vol. 75 No. 11
p. 1453
Abstract
Post-1982 pennies have a varying copper content that can be investigated in the introductory analytical chemistry lab. Groups of four students analyzed ten pennies sampled from the entire minting period to test the hypothesis that the copper shell wears out with time. The results of the flame atomic absorption spectrometry measurements disproved the hypothesis. Four groups observed an increase of 2 mg of copper per year of circulation, the opposite of the behavior expected if the hypothesis were true. Two groups reported a strong positive correlation between copper content and original penny mass. Only one group observed random variations in copper content. Copper-clad copper pennies have a dynamically changing copper content that could be the result of minting variability or changes accompanying the storage of pennies. Student reactions to these results are noted. Future experiments are suggested.
More Information
*  Citation
 Stolzberg, Richard J. J. Chem. Educ. 1998 75 1453.
*  Keywords
 laboratory instruction, copper, quant analysis, gravimetry, titrimetry, analytical chem
*  History
 Created:
Last Updated:		 June 18, 1999
June 24, 2005
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