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  Home > JCE Print > Journal of Chemical Education > Issues > 2007  > September  >
In the Laboratory
The Penny Experiment Revisited: An Illustration of Significant Figures, Accuracy, Precision, and Data Analysis
Joseph Bularzik
Department of Chemistry and Physics, Purdue University Calumet, Hammond, IN 46323-2094
Cover
September 2007
Vol. 84 No. 9
p. 1456
Abstract
Measuring the mass of many pennies has been used as an easy way to generate data for exercises with statistical analysis. In this general chemistry laboratory the densities of pennies are measured by weighting the pennies and using two different methods to measure the volumes. There is much to be discovered by the students on the variability of the values measured by these simple techniques. The average and standard deviation calculated for the densities measured by the different methods demonstrate that one measurement method is more accurate while the other method is more precise. Some of the measurement techniques yield density values precise enough to separate the densities of old pennies from new pennies. Some of the techniques have too large of an inherent error. Also for this simple process the bias of the numbers caused by the way the students measure the pennies is dramatically demonstrated. The data collected from this procedure can be used for a more advanced analysis and used in advanced courses, such as physical chemistry. The generated data does not give a Gaussian distribution, and the reasons for this asymmetry can be explained. An ANOVA analysis can illustrate which students have similar techniques and which ones are statistically different.
Supplement
Instructions for the students including postlab questions and ANOVA analysis are available.
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Folder JCE2007p1456W containing JCE2007p1456W.doc (Microsoft Word) and JCE2007p1456W.xls (Microsoft Excel)
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Citation
Bularzik, Joseph. J. Chem. Educ. 2007, 84, 1456.
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Keywords
Analytical Chemistry; Chemometrics; First-Year Undergraduate / General; Hands-On Learning / Manipulatives; High School / Introductory Chemistry; Laboratory Instruction; Nomenclature / Units / Symbols; Nonmajor Courses; Physical Chemistry; Physical Properties
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History
Created:
Last Updated:
7/23/2007
8/16/2007
 Caution! 
Experiments, laboratory exercises, lecture demonstrations, and other descriptions of the use of chemicals, apparatus, instruments, computers, and computer interfaces are presented in the Journal of Chemical Education as illustrative of new or improved ideas or concepts in chemistry instruction and are directed at qualified teachers. Although every effort is made to assure and encourage safe practices and safe use of chemicals, the Journal of Chemical Education cannot assume responsibility for uses made of its published materials. Many chemicals are hazardous. Precautions for the safe use of hazardous chemicals and directions for their proper disposal are described in the Material Safety Data Sheets and on the labels. We strongly urge all those planning to use materials from our pages to make choices and to develop procedures for laboratory and classroom safety in accordance with local needs and situations.
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