Power of Catalysts Coke and Mentos PDF

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EDCI 767 Science Demonstration: The Power of Catalysts by Felix Autenrieth Possible Curriculum Contexts:   

Science 8: Introduction to kinetic molecular theory – explain how particles move in different states Chemistry 12: Reaction kinetics – effect of a catalyst on a PE diagram; applications of catalysts Cross-curricular: Negative health effects such as the risk of obesity when drinking soda-pop drinks such as Coca-Cola on a regular basis

Materials needed:  

½ liter bottles of Coca-Cola or Pepsi regular (with sugar) or light (with artificial sweetener aspartame) One Mentos for each bottle as catalyst

Directions:   

Place the Coca-Cola bottles on a tray, which collects the overflowing liquid Throw into each bottle one Mentos Note if the height of the fountain is larger for regular Coca-Cola or Coca-Cola light

Questions: Write the two questions on the blackboard, one related to catalysts and one related to nutrition, and ask students to reflect critically on them, while observing the demonstration.  

Students with inter-cultural competence act as catalysts for positive social change. What do catalyst do literally and metaphorically? In previous classes, you learned that sugar is harmful for health. Why are soda-pop drinks even more harmful than sugar alone?

Explanation of effect: In a closed Coca-Cola bottle, carbon dioxide is under pressure and as such completely dissolved. When one opens the bottle some of it is released (the swoosh sound), but most of the carbon dioxide remains in solution due to an energy barrier to overcome for the phase transition from liquid to gas. A catalyst (the Mentos) lowers this energy barrier and the carbon dioxide can proceed readily to its favored phase, which is at room temperature and atmospheric pressure gaseous carbon dioxide. See below the diagram of an un-catalyzed and catalyzed energy pathway:

The energy barrier hindering the energetically favorable carbon dioxide release stems from a large amount of activation energy, which is required for the initial formation of gas bubbles. The Mentos catalyst lowers this activation energy, as the catalyst’s surface is porous and the little pores allow the formation of initial bubbles more readily. Therefore, the overall physical phase transition can proceed rapidly and all the dissolved carbon dioxide gas is pushed out of the bottle as soon as the Mentos is added to the Coca-Cola. Catalysts are never consumed in chemical reactions or phase transitions, therefore one needs only negligible amounts of any catalyst in order to promote large-scale chemical or physical changes (a phase transition is a physical change), which are energetically feasible but require activation energy. Literally, catalysts are helpers for chemical reactions and the metaphorical meaning is related to that as well. A few people can promote large social change when they successfully identify the obstacles for necessary social change and remove those roadblocks in the general thinking of a society. In this way, they can catalyze large movements, such as the civil rights movements, thereby transforming an entire society and promoting positive social change. Rationale of connecting science with social science This demonstration will promote students’ active engagement with BC’s curricular core competencies Critical Thinking, Personal Awareness and Responsibility and Social Responsibility. In think, this is in particular important for chemistry 12 students who enjoy learning high-level chemistry (they all elected the course), but often forget to think critically about their social responsibility as future scientists in society. They might do important research about obesity as well, but in order to have a meaningful and

fulfilling career as a scientist it is important to engage in deeper questions beyond just writing a lab report....