Figure 1. The team of faculty and students from Yale Chemistry Department involved in the 2020 ‘Wonderful World of Chemistry: Magic Show.’

Demonstrations have long been important components in many chemistry classrooms, because they can both assist students in visualizing a concept that may seem abstract or intangible, and simultaneously create excitement and capture attention.¹ In fact, as early as 1662, Robert Hooke was appointed to curate demonstrations for Fellows of the Royal Society.²

In modern times, this emphasis has continued. For example, The Journal of Chemical Education has published 32 different procedures for flame tests of metal ions between 1928 and 2015 alone,³ a fact that may speak to the value of this demonstration in helping students to understand the structure of the atom.

Given the value of chemistry demonstrations to learning, in 2019 the Yale Chemistry Department developed an event called, “The Wonderful World of Chemistry: A Magic Show.” This hour-long lecture, given by Yale Chemistry Department faculty and students, was intended to introduce chemistry to students in local upper-elementary and middle school through a series of demonstrations, although many high school students and adults (typically the parents of students attending the show) also found it enlightening. Our primary educational goal was to provide the approximately 250 audience members a brief and exciting explanation of basic chemistry concepts like elements, molecules, chemical reactions, and catalysis.

In this article, we provide teachers with information that will help them perform our most successful demonstrations in their own classrooms and potentially create their own “Chemistry Magic Show.” Alternatively, teachers can pick and choose specific demonstrations that fit into their teaching plans around specific chemistry topics. We also explain how we combined all our demonstrations to create one free-flowing educational lecture, and discuss the pedagogical value of each individual demonstration. In addition, we provide links to each demonstration’s procedures, and highlight how we modified the procedures to improve safety and connect more effectively with our audience.

Safety

Safety is of paramount importance when performing any demonstration. Teachers should always be cautious and aware of any hazards related to materials used, so as to avoid unnecessary risks. It is also important to consider all of the products that will be formed (including gaseous products), and how best to dispose of chemical waste following the demonstration.

For both safety reasons and as an educational opportunity, it is valuable to make students aware of the hazards related to any demonstrations that are conducted. When performing demonstrations in the classroom, teachers and students alike should wear personal protective equipment (PPE), including lab coat/apron and safety goggles. Whenever appropriate, a safety shield and/or a fume hood should be used during the demonstration. We used an alternative approach when we were preparing our show, choosing to perform only demonstrations that did not require a fume hood. Based on our experience, we recommend that teachers practice beforehand any demonstration that will be used in the classroom. Specific safety information for each demonstration is available in the detailed procedures provided in the linked resource documents.

Overview of the demonstrations

Figure 2. A metal solution is ignited during the flame test demonstration.

In our Magic Show, we introduced audience members to chemistry starting from the simple (atoms and molecules) to the more complex (polymers and catalysis). Throughout the presentation, we tried to provide relatable examples for the audience, such as Taylor Swift’s choice to wear a T-shirt displaying the periodic table in one of her music videos (see the 2:35 minute mark). Table 1 summarizes the demonstrations we performed, as well as the chemical concepts to which we were exposing the audience. Below we describe how the demonstrations we performed fitted into our overall narrative, as well as how we related them to pedagogical concepts. Complete procedures and safety considerations for all of the demonstrations can be found in the linked AACT resource or in the linked external resource.

• Flame Test: We first introduced chemistry by describing atoms, elements, and the periodic table. The different properties of elements were demonstrated through the flame tests of metal ions demonstration, which we connected to fireworks on the 4^th of July (Figure 2). Safety note: In this demonstration, teachers should be cautious when using an open flame, and a working fire extinguisher should be in the classroom.
• Decomposition of Potassium Permanganate: Next, to assist with learning, we asked the audience to identify which alkali ion was produced during the decomposition of KMnO₄ with glycerol. Audience members were expected to identify the potassium ion as being present, because the color of the flame that was produced upon decomposition of KMnO₄ matched the flame test color produced when potassium was used as an additive. Most audience members were able to successfully identify potassium as the ion. Teachers can use this type of questioning in the classroom to challenge students to identify unknown substances, and also to demonstrate how fundamental concepts provide the basis of solving practical challenges. Safety note: We performed this demonstration using a down-draft fume hood due to the gaseous products released, and should only be performed in a fume hood or outside.
• Boiling Water and Liquid Nitrogen: Next, we discussed the different phases of matter, using nitrogen and water as examples. As part of our presentation, we explained that we observe water in all three phases, solid (ice), liquid (water), and gas (steam) in our everyday lives. The phases were visualized by performing a demonstration involving mixing hot water and liquid N₂. In this experiment, the liquid nitrogen is converted to gaseous nitrogen, which results in a white billowing cloud containing a mixture of water vapor and gaseous nitrogen. This demonstration gives a spectacular effect and leaves a lasting impression on students. Safety note: Cold gloves should be used when handling containers with liquid nitrogen.

After using the first three demonstrations to familiarize the audience with basic chemistry, we moved onto demonstrations that focused on chemical reactions, which we explained are among the most important aspects of chemistry in society.

• Iodine Radical Clock: We introduced chemical reactions by showing the audience the visually-appealing iodine radical clock, which demonstrates how one can use indicators to provide an observer with information about the chemicals that are present in a solution. Specifically, we explained that the color changes in the reaction were occurring because the concentration of iodine (which is the chemical being detected) first increased and then decreased. For more advanced students, this demonstration could be connected to the concept of chemical equilibrium. Safety note: Some of the chemicals used in this demonstration are toxic and should only be handled with appropriate PPE.
• Methane Bubbles: Subsequently, we discussed the changes in chemical bonding that occur in a chemical reaction by describing the combustion of methane, which we demonstrated by burning methane bubbles. To explain the reaction, we noted that atoms can be combined in different ways to form different molecules, and made an analogy to how the same letters can be rearraged to form different words. Combustion reactions are an important component in our current energy infrastructure, and we used methane combustion to introduce the concept of fossil fuels. Safety notes: The combustion of methane in soap bubbles involves an open flame, and as a result should be performed in classroom with a fire extinguisher. We also recommend that the bubbles be burned on a heat-resistant surface (such as a watch glass) or above the demonstrator’s head using a candle taped to a ruler. In our Magic Show, we combusted the methane bubbles on our bare hands that had been soaked with water, but this is not appropriate for a classroom setting.

Figure 3. The luminol demonstration is used to highlight the concept of chemiluminescence.

• Luminol Demonstration: We also explained that although some chemical reactions, such as methane combustion, release heat, others release light, and we performed an experiment using luminol to highlight this concept. In this demonstration, we poured two solutions simultaneously into a coiled piece of glassware in the dark. One solution contained luminol, a copper catalyst and a base, and the other solution contained hydrogen peroxide. When the two solutions mixed, they immediately generated a fluorescent solution (Figure 3). We explained to the audience that luminol was commonly used in forensic investigations, because the iron in blood triggers its reaction with hydrogen peroxide to create a fluorescent stain. We increased the aesthetic appeal of this demonstration by running the luminescent solution through a glass coil from a rotary evaporator, but the chemiluminescence is still clearly visible even when the experiment is performed in a standard beaker or flask. Safety note: Some of the reagents in this demonstration are toxic and should be handled and disposed with care.
  
• Isopropanol Combustion in a Bottle: We concluded this section by discussing how light or heat are required to initiate some chemical reactions (such as in cooking) and demonstrated this concept by initiating the combustion of isopropanol vapor in a bottle. This reaction, which produces a spectacular ‘whoosh’ sound, can again be connected to the combustion of fossil fuels. Additionally, it can be related to the states of matter, as it is isopropanol vapor that is burning, as opposed to liquid isopropanol. For advanced students, this can lead to a discussion about why some compounds are more volatile than others. Safety note: This demonstration involves an open flame and should not be performed in a room with a low ceiling. It can, however, be easily performed outside.

We ended the show with a discussion of polymers and the catalysts that are used in their synthesis. We chose to talk about polymers because they are ubiquitous in consumer products and biology, and are one of the most important classes of molecules made using chemical reactions.

• Nylon Synthesis: We introduced the concept of polymers using simple monomers such as ethylene, and then completed a demonstration which involved the preparation of a thread of nylon several feet in length. We explained that nylon, which is made from amide monomers, was used in a wide variety of applications including food packaging, fishing lines, and brushes. For a classroom setting, we would also encourage a discussion of how polymer properties change depending on the monomer units that are present.
• Elephant Toothpaste: Our last demonstration involved the synthesis of elephant toothpaste, which highlights the use of catalysts to speed up chemical reactions. We linked this activity to polymers by explaining that polymers are often synthesized using catalysts. As a classroom exercise, it would be effective to use this demonstration as the basis for discussing applications of catalysts, which are ubiquitous. For example, catalysts are used to make fertilizer, pharmaceutical, and plastics. The Elephant Toothpaste demonstration makes a considerable mess, so performing it on spill pads or outside can be beneficial.

Finally, we note that some of the demonstrations performed in the videos are not featured in this article, either because of safety risks (for example, igniting balloons filled with hydrogen gas) or a lack of reproducibility and suitability for a large audience (for example, the chemical garden demonstration). These experiments should only be performed in specialized settings.

Potential modifications

While the demonstration-based format of our Magic Show necessitated that students were only observers, several of the demonstrations can be modified to be performed by individual students or in small groups as a laboratory activity. For example, flame tests and the Elephant Toothpaste demonstration are already commonly performed in high school classrooms; on the other hand, though they are suitable for this purpose, experiments involving luminol or the iodine radical clock are not often converted into laboratories. We did not explain chemical concepts in significant detail in our show, due to our desire to introduce a number of different concepts and the varying ages of our audience. However, the development of classroom-based laboratory activities based on our demonstrations would allow for a more focused, in-depth educational approach. Finally, it is likely possible to perform the demonstrations with accompanying explanations for a remote audience, although some of the excitement associated with the demonstrations will likely not translate as effectively over video.

Potential pitfalls

Even though we practiced the demonstrations extensively, there were occasions when our experiments did not work as expected (due to problems with reagents or experimental errors), which can be disappointing to students and presenters alike. However, when demonstrations do not work as planned, it provides an opportunity to educate students about why chemical reactions can “fail,” and to discuss the considerable resources that the chemical industry devotes to ensuring that reactions are reliable and reproducible. It can also be a method to introduce students to the idea of “failure” in science and how great scientific discoveries are often the result of initial experiments that did not work. Nevertheless, we have included in the linked resources the various best practices we learned to ensure that our demonstrations were “successes.”

Feedback

The feedback we received from students, parents, and teachers about the Magic Show has been overwhelmingly positive, with one audience member memorably describing it as ‘very perfect and amazing.’ After the shows, many students and parents asked us for more detailed information about chemical concepts that had been discussed, such as catalysis. Therefore, the demonstrations we performed would be particularly useful in a classroom setting, where more comprehensive explanations and discussions could ensue.

Our experience is that a lecture such as “The Wonderful World of Chemistry: A Magic Show” is a successful method to excite students about chemistry, and to introduce them to basic chemical concepts through demonstrations. We hope that this article will provide teachers with access to procedures if they desire to perform these demonstrations in their classroom, create new laboratory activities, or develop a “chemistry magic show” at their own school.

Acknowledgements

We are grateful to all of our co-workers who have been part of the Magic Show, as they were responsible for developing the experiments described in this article. We also thank Maria Parente and Claudia Merson at the Yale Office of New Haven Affairs for assistance with organizing the Magic Show.

References

1. Price, D. S.; Brooks, D. W. Extensiveness and perceptions of lecture demonstrations in the high school chemistry classroom. Chem. Educ. Res. Pract. 2012, 13, 420-427. 
   
2. Taylor, C.A. The Art and Science of Lecture Demonstration; CRC Press: Boca Raton, Louisiana, 1988.
3. Bretz, S. L.; Mayo, A. V. M. Development of the Flame Test Concept Inventory: Measuring Student Thinking about Atomic Emission. J. Chem. Educ. 2018, 95, 1, 17–27.
   

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