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ERIC Number: EJ918272
Record Type: Journal
Publication Date: 2010-Jun
Pages: 4
Abstractor: As Provided
ISSN: ISSN-0021-9584
Vapor Pressure Plus: An Experiment for Studying Phase Equilibria in Water, with Observation of Supercooling, Spontaneous Freezing, and the Triple Point
Tellinghuisen, Joel
Journal of Chemical Education, v87 n6 p619-622 Jun 2010
Liquid-vapor, solid-vapor, and solid-liquid-vapor equilibria are studied for the pure substance water, using modern equipment that includes specially fabricated glass cells. Samples are evaporatively frozen initially, during which they typically supercool to -5 to -10 [degrees]C before spontaneously freezing. Vacuum pumping lowers the temperature to [approximately]-20 [degrees]C, and temperature and pressure are recorded on warm-up, first for sublimation, then vaporization, with a pronounced halt at the triple point. Analysis of the data by the integrated Clausius-Clapeyron equation typically yields [delta][subscript sub]H[subscript m] and [delta][subscript vap]H[subscript m] values within [approximately]2% (1 kJ/mol) of literature, from which [delta][subscript fus]H[subscript m] can also be estimated with fair precision. The experiment is designed for the undergraduate physical chemistry teaching laboratory; aspects of it are also appropriate for demonstrations in general and physical chemistry courses. (Contains 5 figures.)
Division of Chemical Education, Inc and ACS Publications Division of the American Chemical Society. 1155 Sixteenth Street NW, Washington, DC 20036. Tel: 800-227-5558; Tel: 202-872-4600; e-mail:; Web site:
Publication Type: Journal Articles; Reports - Descriptive
Education Level: Higher Education
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A