Quasi-Adiabatic Evaporation of Liquids on a Glass Surface As Observed by Optical Interference

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 8 Issue 4 (2003) pp 244-247

Quasi-Adiabatic Evaporation of Liquids on a Glass Surface As Observed by Optical Interference

Daniel L. Arnold, R. Tristan Gingerich, Christopher D. Emerson, Taylor P. Ludwick, Andrew D. Ribbens, Jerome A. Santos, Joseph D. Taylor, Aaron S. Nudelman, and Allan M. Nishimura*

Department of Chemistry, Westmont College, Santa Barbara, CA 93108, nishimu@westmont.edu
Received December 18, 2002. Accepted April 21, 2003.

Published online: 9 July 2003

Abstract. Evaporation of volatile liquids is a fascinating process that easily draws student interest because of its apparent simplicity. Concepts that are introduced in general chemistry, such as molecular geometries, dispersion forces, and hydrogen bonding, can be used to explain why certain liquids evaporate faster than others. Measurements of the vaporation rates of liquids from ordinary glass surfaces are accomplished by a simple method based on optical interference. As the liquid evaporates, the vaporization occurs not only at the air/liquid interface, but also at the liquid/glass interface, and it is this latter process that serves to thermally insulate the film. These volatile liquids have comparatively low heat capacities; therefore, the temperature of this insulated film decreases because the energy for vaporization comes primarily from the liquid itself. The degree to which the vaporization occurs adiabatically depends upon the volatility of the liquid at room temperature.

Key Words: Laboratories and Demonstrations; physical chemistry; thermodynamics

(*) Corresponding author. (E-mail: nishimu@westmont.edu)

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