The following PowerPoint presentations on various topics of the new teaching concept were presented at different international conferences. The descriptions and in some cases also the videos to the numerous demonstration experiments can be found under “Experiments”. If you are interested in the original slides, the lecture manuscript and further information material, please send me an e-mail (firstname.lastname@example.org, keyword: PowerPoint).
Teaching Entropy with Fun
The lecture with demonstration experiments provides an introduction into the "world of entropy," accompanied by the mascot "black sheep." Also first applications such as the fire piston and the popular tiny toy "pop-pop boat" are presented.
Teaching Entropy with Fun (Workshop)
The presentation is based on a workshop held at several international conferences. It is focused on seven experiments that are particularly suitable to illustrate different aspects of entropy and that could be performed by the attendees at various stations according to the rotation model. Beside the fire piston and the “putt-putt boat” as examples, other fascinating experiments such as the “low temperature Stirling engine” or the “ice melting blocks” are presented. However, the original presentation was revised, expanded and supplemented with numerous examples of application.
Chemical Potential from the Beginning
The chemical potential is introduced in this experimental lecture by characterizing it by its typical and easily observable properties, i.e. by designing a kind of “wanted poster" for it. After this introduction, which does not require any special previous knowledge, one is already able to predict whether whether a considered reaction can occur spontaneously or not. In order to describe the influence of temperature and pressure on the behavior of substances, linear approximations are often sufficient. The concentration dependence of the chemical potential is the “gateway” to the deduction of the mass action law, the calculation of equilibrium constants, solubilities, and many other data, the construction of phase diagrams and so on.
Chemical Potential in Focus—Osmosis and more Oral
After a short repetition of the chemical potential as a basic concept, the main focus of the experimental lecture lies on the flow of substances and its consequences such as osmosis and freezing-point depression. Such types of transformations are omnipresent in households and in the environment as well as in nature and in engineering. For example, it is known from everyday life that juice is “drawn out” of sugared strawberries, while cherries swell up and burst after a long rain. Selected experiments such as demonstrating osmotic pressure by constructing an “osmometer” by use of a carrot help to improve the understanding of such processes. Subsequently, the significance of these phenomena for the water balance of living organisms is demonstrated. The lecture ends with the discussion of the freezing-point depression (a prime example from everyday life is the melting effect of road salt).
The “Secrets” of Mixtures
In chemistry but also in everyday life, we are very often confronted with mixtures be they homogeneous or heterogeneous. Think for example at hard liquor, basically a homogeneous mixture of ethanol and water but also at fog, a heterogeneous mixture of air and minuscule water droplets. For an adequate quantitative description, the concept of chemical potential has to be extended on substances in real solutions by introducing an extra potential . If one has the discussion of mixing processes in mind, it is useful to assign an average chemical potential to a mixture made up of two components A and B, as is done for pure substances. Depending on whether the resulting mixture is homogeneous or heterogeneous the concentration dependence of this average potential is different. On this basis, concepts such as miscibility gap and lever rule are discussed. The theoretical considerations are supplemented by selected demonstration experiments (illustrated with photos taken during the presentation at the ChemEd Conference 2019), which are intended to arouse the interest of the students and help to strengthen the understanding.
Genie of Catalysis
Everyday experience already demonstrates that the rate of chemical reactions depends on temperature. For example, food spoils on a hot day much faster outside a refrigerator than inside. The exhaust gas catalytic converter in gasoline-powered cars, an example for another possibility to influence the reaction rate, is also known to everyone. But what is the connection between these two phenomena? In this context, the experimental lecture deals with the quantity (besides temperature) that determines the reaction rate, the so-called “potential threshold,” determining quantity, the so-called “potential threshold”, the difference in the chemical potentials between the reactants and a “transient substance” (on the way to the final products). These “potential thresholds” also play a key role in the explanation of the mode of action of a catalyst, which is discussed on the basis of the catalytic decomposition of hydrogen peroxide.
The “Mysteries” of Surface Phenomena
It is well-known that the chemical and physical properties of substances at surfaces differ from those in the bulk. With the help of quantities such as surface tension and surface energy, phenomena known from everyday life like the lotus effect can be explained. But the theoretical considerations are not only linked to everyday experience but also the motivating power of fascinating but nevertheless easily and safely realizable demonstration experiments can be used. During the workshop, the attendees have the opportunity to perform seven experiments that are particularly suitable to illustrate different aspects of surface phenomena at various stations according to the rotation model. One of the experiments shows, for example, how a small boat can be “powered” by liquid detergent. But it is is also amazing to observe what happens when two soap bubbles of differing sizes are connected via a closed stopcock and the stopcock is then opened.
Electrochemistry―A Question of Potential
Electrochemistry has witnessed a renaissance in recent decades; just think of the ubiquituous batteries, but also of the increasing importance of electromobility. The interaction between the chemical potential of the electrons and the electrical potential results, for instance, in the galvanic potential difference of an electrochemical half cell (Nernst equation). This opens the door to a wide range of applications. The Daniell cell represents the first experimental step into the topic.