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Abstract | Acid | Dissociation (Chemistry)

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  ABSTRACT: This article summarizes an investigation into how Flash-based cartoon video tutorials featuring molecular visualizations a ff  ect students’ mental models of acetic acid and hydrochloric acid solutions and how the acids respond when tested for electrical conductance. Variation theory served as the theoretical framework for examining how students compared and contrasted their understanding of weak and strong acids to the tutorials. Specifically, students’ ability to recognize variation  between their mental models and the events portrayed in the videos was examined through picture construction exercises and semistructured interview questions focused on metacognitive monitoring. Interestingly, the items noticed as being in variance were items that were emphasized by still image representation in the tutorials prior to showing the visualizations. Mechanistic items, specifically  movement of ionic species toward electrodes, were replicated in students’  drawings only if they were explicitly conveyed, but students were not inclined to mention them as features in variance with their initial understanding. Overall, sca ff  olding animations in a cartoon context with explicit connections between experimental evidence and the submicroscopic level resulted in students being  proficient at replicating what they explicitly observed both structurally and  mechanistically. KEYWORDS:  First-Year Undergraduate/General, High-School/Introductory Chemistry, Chemical Education Research,   Computer-Based Learning, Misconceptions/Discrepant Events, Acids/Bases, Electrochemistry, Qualitative Analysis, Solutions/Solvents   INTRODUCTION   This study is part of a larger study, of which the first part was published in 2014. 1 In Part I, variation theory was used to examine how students detected di ff  erences  between their understanding and the information presented in 15 molecular visualizations of pure liquid water and solid and aqueous sodium chloride tested for  electrical conduction.1 The fi ndings of this study revealed that students made significant progress toward improving their mental models of the animated events after viewing the molecular visualizations as they tended to incorporate aspects of the visualizations in which they identified variance  from their mental model. Students often demonstrated imperfect understanding and had di ffi culty adapting their understanding to completely match what they saw. Meta- cognitive monitoring and mental model picture construction exercises revealed that students were most likely to correct their understanding to fit with basic structural features portrayed in the animations, but students tended to dismiss details of the animations that were too challenging to draw or would take too much e ff  ort to construct. The visualizations, in part I, were not part of a lesson, and lacked the guidance that comes from instruction. Tutorials Featuring Molecular Visualizations  In part II of this study, we turn our attention toward studying how students learn from visualizations that are introduced in the context of an animated video lesson, which we also refer to as a tutorial due to their intended use. They were designed to guide and assist students with making connections between macroscopic evidence and submicroscopic representations. Video tutoring has the advantage of o ff  ering valuable and convenient assistance at low cost and, more importantly, helps students, particularly average and low- achieving students, to master content and improve problem solving performance.3 In our study, tutorials were uniquely used to sca ff  old and introduce visualizations allowing key structural representations from the visualization to be emphasized. Many researchers have shown that molecular visualizations are useful tools that aid students in the conceptualization of the particulate nature of macroscopic events.5 − 15 Viewing anima- tions helps students to form a more detailed mental model of the event,1 and helps students connect to concrete models.16 However, even though students may try to adapt what they see in the animations, they  typically retain imperfect under- standing.1 For students to learn from external representations, they must have the cognitive ability to reason and think about the concepts being represented. In essence, students need cognitive skills that are necessary for understanding the purpose of the animation to help them become visually literate of the information portrayed.16 Studies have also shown that when an animation is complex it can lead to further di ffi culties as students may misinterpret what they view.17 Complex animations without sca ff  olding may overwhelm students and a ff  ect their ability to process the visuals. It is important for students to have guidance and instruction while viewing molecular visualizations as students may miss essential features if they are not made explicit through instruc- tion.5,18 Chang and Linn reported that guiding students to make connections to laboratory events, such as critiquing confounding experiments and conducting virtual experiments, while also considering the information presented in molecular visualizations related to the events, helped students make connections between macroscopic and atomic levels.19 Thus, the goal of this study was to examine how students adapted their mental models of a strong acid [aqueous hydrochloric acid] and a weak acid [aqueous acetic acid] tested for electrical conductivity, to fi t with features of the same events portrayed in video tutorials. Studies on Students’ Understanding of Acids  Understanding how students tend to make sense of the nature of acidic aqueous solutions is important as it allows us better insight into how the videos a ff  ect student understanding. Since the students in this study had very little instruction about acids,  prior knowledge was likely strongly influential, and these  ideas are often contrary to those of scientists.20,21A common introductory definition  of acidity is the Arrhenius definition, a concrete model that focuses on matter  21,22 and recognizes that acids  produce hydrogen ions in aqueous solution. The Brønsted-Lowry and Lewis theories are also commonly referenced definitions  that describe acids with bases in the context of reactions.22 These process models are less relevant to this study, as  reactions were not the focus of the videos. Instead the videos in this study portrayed a materialistic view of acids, consistent with the Arrhenius definition,  in which a strong acid dissociates readily into hydrogen ions and anions, while a weak acid dissociates much less.21,22 This definition, while  seemingly concrete, can be  problematic for students when they are asked to apply it to classify acidic solutions as strongly acidic or weakly acidic.23 Some students misunderstand the importance of holding the concentrations constant so that comparisons can be made as to how readily the acids dissociate into ions. In addition, students may think that a strong acid has a strong bond causing it to stay together, while a weak acid has a weak  bond that is easily broken.23,24 To summarize, it seems that many students struggle to understand the ionic nature of acids20,21 which could a ff  ect students’  ability to relate how acidic solutions would have the ability to conduct electricity. Understanding acids and acid strength continues to be challenging for students as they progress into advanced college chemistry courses. McClary and Talanquer reported that advanced college chemistry students’ mental models of acids were  often hybrid models that combined assumptions from one or more scientific models and were partnered with intuitive beliefs about chemical properties.25 In this paper, we examine how general chemistry students begin to construct their knowledge in the direction of their abilities and experiences and refine their understanding with the assistance of tutorials featuring molecular visualizations. METHODOLOGY   Theoretical Framework: Variation Theory  The primary purpose of the study was to determine how students made sense of the information presented in tutorials that focused on the particulate nature of strong and weak acids. Specifically, what features do students pay attention to when they  view tutorials and how does this a ff  ect their understanding. Variation theory, a theoretical extension of phenomenography, was the theoretical framework used to conceptualize the study and to examine the fi ndings. For a more detailed explanation of variation theory, we encourage the reader to review the paper associated with
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