By Nicolette Puskar, Chemistry
Teaching Effectiveness Award Essay, 2024
The reality that humans can only see the world at the milliscale level is an unfortunate tragedy for chemists who long to witness the nanoscale building blocks of matter they aim to study. Relegated to using theoretical models and molecule building sets, physical chemistry students have traditionally been expected to learn concepts in the nanoscopic regime on an abstract level. While these approaches are suitable for students who are primarily auditory or kinesthetic learners, for those who are predominantly visual learners it has been a challenge, logistically and technologically, to design experiments which provide direct visual stimuli. Within the last few decades, visualization technologies like microscopy have achieved nanoscale resolution (2014 Nobel Prize in Chemistry), which now allows chemists to observe nanochemistry firsthand. When I became the head GSI for Physical Chemistry Laboratory in Spring 2022, the lab had recently obtained a new, state-of-the-art scanning electron microscope (SEM) that had not yet been implemented into the course curriculum. With this new addition, I saw a prime opportunity to design a new lab experiment that could facilitate a deep dive into the nano regime, and let students explore physical chemistry on this scale visually.
The five key areas of the physical chemistry lab experiment design are the pre-lab, instrument manual, lab procedures, report structure, and rubric. The most important element I wanted to implement in my design was to create an authentic and realistic experiment with the SEM, while keeping the overall structure exploratory. Since sample characterization is the most common modern use for the SEM, I decided to have the students explore a pre-made sample of nanoscopic tin spheres and analyze the size distributions of the spheres. With this choice, the pre-lab and instrument manual introduced the students to microscopy basics, how the SEM works, and how it compares to other microscopy variants. To implement an exploratory structure within the lab procedures, I elected to describe only how to take a good image with the SEM. Specific choices like what image to take, where on the sample, at what point in time, and at what spatial resolution were up to the students. This design decision presented the students with choices which allowed them to apply volitional control over their own learning experience, which turned the lab into an active learning exercise. The students were amazed by the modern technology, with one student describing the process as “very rewarding once the specimen is visible in all its glory, like a scientific version of the game of I Spy”.
Assessing the success of this lab design came from the report structure and rubric elements. In addition to implementing some traditional elements for the scientific report and rubric requirements, I also requested they evaluate the lab’s successes, critiques, what they learned, and if they would recommend this lab to future students. Out of 15 students who performed this laboratory experiment, all 15 said they would recommend it. Some common successes were appreciating the complex nature of the SEM and the artistic component required to take a quality image, while a common critique suggested the student make their own unique samples for characterization in the future. One student said, “this was the first time I have seen an instrument that so directly elucidates the structure of these species. I think the tangibility of this experiment nicely complements the prior labs which dealt with more abstract ideas of energy levels and wave functions.” To me, this summarizes my key takeaway from designing this laboratory experiment: the direct visualization of nanoscale chemistry is a welcome and novel learning experience for students with any learning style. I am excited to see how this experiment continues to evolve and improve with the new generation of GSIs.