Self-Motion of Sodium Benzoate Flakes on a Water Surface: A Demonstration

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• 作者：Katherine V. DarveshEarl Martin
• 刊名：Journal of Chemical Education
• 出版年：2017
• 出版时间：February 14, 2017
• 年：2017
• 卷：94
• 期：2
• 页码：226-229
• 全文大小：193K
• ISSN：1938-1328

文摘

Light crystals and flat solid flakes of sodium benzoate, when placed on a water surface, provide a fascinating display of mobile surface phenomena that can initiate discussion of intermolecular and intramolecular forces, of enthalpy and entropy effects, of concentration and surface tension gradients, or of Marangoni-type current, or simply initiate a conversation about what shape of solid gives the most dramatic motion or the maximum time of action before disappearing into solution. The demonstration to be outlined involves time-dependent dissolution of sodium benzoate at the surface of water at room temperature, accompanied by rapid rotational and linear motion until the solid disappears. This demonstration is easy to prepare for school visits or for in-class demonstrations; it is quick, and only requires sodium benzoate flakes, which can be prepared beforehand, and water.