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The Chemical Educator

ISSN: 1430-4171 (electronic version)

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Abstract Volume 17 (2012) pp 149-151
DOI 10.1007/s00897122432

Bottoms Up to the Scientific Method

Marc Hill and Eugene T. Smith*

Harriet L. Wilkes Honors College, Florida Atlantic University, Jupiter, FL 33458
Received April 27, 2012. Accepted July 14, 2012.

Published: 10 August 2012

Abstract. A laser refractometry experiment, which is appropriate for a general chemistry course, is described for use on the first day of class to introduce the scientific method. A common laser pointer is used to analyze the composition of ethanol/water solutions contained in a martini glass. A hypothesis, a tentative but clear and compelling explanation, is presented by the instructor regarding refraction of light. Students observe that alcohol content in water influences the position of a laser beam after being projected through a glass onto a white board. Students are asked to propose a law based on the observed differences in refraction of light by pure water and pure ethanol, and then the instructor tests this law using a cocktail. The inaccurate prediction of their law leads to a critical analysis of the problem and suggestions for additional experiments, which is followed up with a discussion on theory.

Key Words: Laboratories and Demonstrations; general chemistry; laser

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