Spattering and Crackle of Hot Cooking Oil with Water
A Classroom Demonstration and Discussion
Gabriel Pinto
Grupo de Innovación Educativa de Didáctica de la Química, E.T.S. de Ingenieros Industriales, Universidad Politécnica de Madrid, Madrid 28006, Spain
Carmen V. Gauthier
Department of Chemistry and Physics, Florida Southern College, Lakeland, FL 33801
Any student that has spent time in the kitchen knows that hot vegetable oil will pop and spatter violently after coming into contact with water such as that on the surface of foods (meat, fish, potatoes, etc.). This well-known effect can be used as an instructional resource to promote cooperative, active, and inquiry-based learning about central concepts of chemistry including boiling point, miscibility, and density of liquids. The starting point of the learning activity is a demonstration of (i) the effect of adding a drop of water to hot (as for cooking) vegetable oil and (ii) the effect of adding a drop of vegetable oil to hot water (near its boiling point). Intermolecular interactions, properties of vegetable oils, and a variety of other topics, such as the importance of other heat points (smoke, flash, and fire) for oils, the fundamental of the crackle test for checking the presence of water in oil, and why an oil fire (for example in a kitchen) never should be put out with water, can also be addressed using this approach. Students have expressed keen interest in this type of everyday chemistry.
Supplement
Procedure if the activity is done as a lab exercise
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