Addressing barriers to understanding emission spectroscopy for novice chemistry students

Abstract

Spectroscopes are practical tools that show the quantization of emitted light from excited elements and compounds, as well as helping students understand modern models of the atom and appreciate the unique identifying power of spectroscopic signatures. Spectroscopic instruments are usually costly and complex, therefore a self-made and low-cost Mini Spec was an ideal way for first-year chemistry students to learn about emission lines and spectroscopy itself. Design-based research was used over five cycles to devise and refine a laboratory exercise that included the individual construction of a Mini Spec, the use of the Mini Spec to observe discrete and continuous spectra from readily available light sources, and guided interpretation of observations in a report sheet. In the first two cycles the Mini Spec construction time, conceptual multiple-choice items, and student performance were used to gauge barriers to student understanding. In cycles 3, 4 and 5 the data methods changed to gain deeper insights into student sense-making and the associated barriers: students’ report sheet explanations were coded according to defined learning outcomes and a recorded collaborative post-lab activity was analysed. Three primary barriers to students’ understanding of spectroscopy emerged over the five cycles: the demands of the task, conceptual difficulties inherent in spectroscopy and language. Cognitive Load Theory was used to interpret and address emerging barriers to student sense-making, and as such, informed all design-decisions made throughout the study. A variety of refinements to the laboratory exercise were implemented over the five cycles, including: providing students with construction templates, guided questions on the components of the Mini Spec, scaffolded reporting of observations, guided questions to help student interpret observational data, and pre- and post-lab activities. In addition, a rubric was developed to evaluate students’ levels of understanding. Refining the laboratory exercise led to a reduction in the demands of the task as evidenced by decreased construction times, improved performance and gains in understanding the components of the Mini Spec. The development of support for the conceptual barriers experienced by students remains an on-going process due to the nature of design-based research, however, progress was made in improving student understanding of spectral line formation and classification. Language appeared to be an underlying barrier that continued to emerge over the five cycles, be it in interpreting Mini Spec construction instructions, the nuances of non-technical terminologies used to describe electron transitions, or the technical terminologies of optics. For example, students interpreted “jumping” as electrons moving upwards only and they struggled to distinguish between refraction, reflection, and diffraction. Students also seemed to avoid unfamiliar and complex words such as discrete and quantized. Through flagging language as a barrier, this study sought to contribute new insights into novice student difficulties in spectroscopy, over and above addressing known conceptual difficulties. Additionally, the study confirmed the utility of Cognitive Load Theory and design-based research in interpreting and addressing barriers to understanding spectroscopy experienced by novice students.