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Double-Diffusive Convection: A Simple Demonstration

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Mario Markus

Max-Planck-Institut für Molekulare Physiologie, Postfach 500247, 44202 Dortmund, Germany

Richard W. Schaeffer

Department of Chemistry, Kutztown University, Kutztown, PA 19530

J. Chem. Educ., 2004, 81 (4), p 526

DOI: 10.1021/ed081p526

Publication Date (Web): April 1, 2004

Abstract

Double-diffusive convection can be demonstrated using a cup, a pipet, coffee-whitener, and (optionally) a microscope. At first, cells (0.1–1 mm each) are formed; then, hundreds of needlelike structures become visible to the naked eye. This observation is related to a large number of interesting phenomena, such as deposition of chemical sewage at the bottom of the sea, salt distribution in oceans, and pattern formation in alloys, stars, and magma. If the microscope can be connected to video equipment (preferably with image storage in a computer) then a quantitative analysis of the emergence time and the size of the cells can be performed and compared to existing predictions.

Keywords (Audience):

Upper-Division Undergraduate

Keywords (Domain):

Demonstrations

Keywords (Feature):

JCE DigiDemos: Tested Demonstrations

Keywords (Pedagogy):

Hands-On Learning / Manipulatives

Keywords (Subject):

Transport Properties

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This article has been cited by 1 ACS Journal articles (1 most recent appear below).

Sugar Fingers and Double-Diffusive Convection
Richard M. Heavers , Liza A. Colucci
Journal of Chemical Education2009 86 (11), 1326
- Sugar Fingers and Double-Diffusive Convection
  Richard M. Heavers , Liza A. Colucci
  Journal of Chemical Education2009 86 (11), 1326
  Vertical convection cells ("fingers") develop at the interface between a horizontal layer of sugar solution above a slightly denser solution of ordinary table salt. These fingers occur primarily because the molecular diffusivity of sugar is less than that ...
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