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  Home > JCE Print > Journal of Chemical Education > Issues > 2001  > March  >
In the Classroom
The Floating Needle
F. E. Condon
Department of Chemistry, The City College of the CUNY, New York, NY 10031

F. E. Condon Jr.
Palm Beach County Water Utilities, Florida

Cover
March 2001
Vol. 78 No. 3
p. 334
Abstract
A mathematico-physical treatment of the floating (on water) needle system is presented. Gravitational potential energy, buoyancy, surface energy, and interfacial energy are taken into account. The floating is regarded as a metastable state resulting from a minimum in the curve relating the energy to the distance of descent. It is shown that such an energy minimum arises naturally out of the mathematics needed to evaluate the factors mentioned above. The calculations are supplemented with simple experiments with paper clips and an aluminum nail ("pseudo-needles"), which lead to approximate upper limits to the diameters of cylindrical metal rods of different densities that can be floated on water.
More Information
*  Citation
 Condon, F. E.; Condon, F. E., Jr. J. Chem. Educ. 2001 78 334.
*  Keywords
 Flotation; Interfacial Energy; Interfacial Tension; Intermolecular Forces; Liquids; Physical Chemistry; Surface Energy; Surface Science; Surface Tension; Teaching / Learning Aids; Water / Water Chemistry
*  History
 Created:
Last Updated:		 February 6, 2001
August 31, 2005
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