V. Careaga, Astrid Blanco Guerrero, Gabriela Siracusano, M. Maier
Abstract This article describes two of the most common natural sources of red anthraquinones that have been used since antiquity for textile dyeing and as lake pigments, namely cochineal insect and the roots of Rubia and Relbunium plants. Carminic acid is the main component of carmine, the red colorant obtained from cochineal. Alizarin and purpurin are found in the extracts of Rubia roots, but Relbunium roots contain only purpurin. These red anthraquinones have been identified in a variety of cultural heritage objects. High performance liquid chromatography with diode array detection (HPLC-DAD) is described as the most suitable analytical technique for the identification of these dyestuffs, particularly in micro-samples from textiles or pigment layers in paintings and polychrome sculptures. Finally, application of HPLC-DAD analysis to the identification of lake pigments in micro-samples of mural paintings of two eighteenth century Andean churches in Peru is described.
{"title":"High performance liquid chromatography as a micro-destructive technique for the identification of anthraquinone red dyestuffs in cultural heritage objects","authors":"V. Careaga, Astrid Blanco Guerrero, Gabriela Siracusano, M. Maier","doi":"10.1515/cti-2022-0018","DOIUrl":"https://doi.org/10.1515/cti-2022-0018","url":null,"abstract":"Abstract This article describes two of the most common natural sources of red anthraquinones that have been used since antiquity for textile dyeing and as lake pigments, namely cochineal insect and the roots of Rubia and Relbunium plants. Carminic acid is the main component of carmine, the red colorant obtained from cochineal. Alizarin and purpurin are found in the extracts of Rubia roots, but Relbunium roots contain only purpurin. These red anthraquinones have been identified in a variety of cultural heritage objects. High performance liquid chromatography with diode array detection (HPLC-DAD) is described as the most suitable analytical technique for the identification of these dyestuffs, particularly in micro-samples from textiles or pigment layers in paintings and polychrome sculptures. Finally, application of HPLC-DAD analysis to the identification of lake pigments in micro-samples of mural paintings of two eighteenth century Andean churches in Peru is described.","PeriodicalId":93272,"journal":{"name":"Chemistry Teacher International : best practices in chemistry education","volume":"5 1","pages":"1 - 9"},"PeriodicalIF":0.0,"publicationDate":"2023-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46277177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract In this paper we describe an intervention study on the application of the octet rule. This study was conducted at a German University with students in their first- and second undergraduate year. As repeatedly observed by us before, the evaluation of the study confirmed that the students have difficulties with the application of the octet rule in general, but above all for charged molecules. After an intervention, which consisted of a detailed checklist for the application of the octet rule and training opportunities, the students’ competences increased, especially for the tasks which included charged molecules. Students’ explanations were not as good as expected; the linguistic quality did not increase significantly from pre-to post-test. This is not surprising, because the training of argumentation skills was not part of the intervention. The intended goal, training the application of the octet rule, has been achieved.
{"title":"How do students apply the octet rule and how do they justify this application?","authors":"David Keller, J. Hermanns","doi":"10.1515/cti-2022-0023","DOIUrl":"https://doi.org/10.1515/cti-2022-0023","url":null,"abstract":"Abstract In this paper we describe an intervention study on the application of the octet rule. This study was conducted at a German University with students in their first- and second undergraduate year. As repeatedly observed by us before, the evaluation of the study confirmed that the students have difficulties with the application of the octet rule in general, but above all for charged molecules. After an intervention, which consisted of a detailed checklist for the application of the octet rule and training opportunities, the students’ competences increased, especially for the tasks which included charged molecules. Students’ explanations were not as good as expected; the linguistic quality did not increase significantly from pre-to post-test. This is not surprising, because the training of argumentation skills was not part of the intervention. The intended goal, training the application of the octet rule, has been achieved.","PeriodicalId":93272,"journal":{"name":"Chemistry Teacher International : best practices in chemistry education","volume":"5 1","pages":"61 - 74"},"PeriodicalIF":0.0,"publicationDate":"2023-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49553913","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Brouwer, G. Fleerackers, I. Maciejowska, Claire McDonnell, M. Mocerino
Abstract This study contributes to the understanding of online professional development of university STEM (Science, Technology, Engineering and Mathematics) lecturers. An active learning massive open online course (MOOC) to develop best practice in teaching in university science laboratories was developed using the ADDIE (Analysis, Design, Development, Implementation, Evaluation) model in three cycles. The teaching beliefs and intentions of the participants were determined before and after they completed the MOOC and their level of satisfaction with this professional development opportunity was examined using a survey. The results showed high completion rates and an appreciation of the online course design. Participants who completed the course evaluation were satisfied and they identified the usefulness of the active learning components that required them to discuss and reflect, develop plans and peer-assess. A large majority developed new ideas to help them to improve their teaching. The participation in the course increased participants’ understanding of the multidimensional aspects of laboratory teaching and the challenges related to it. The majority of participants changed their teaching beliefs to become more student-centred.
{"title":"The impact of a professional development MOOC on the teaching beliefs of University Science Laboratory Teachers","authors":"N. Brouwer, G. Fleerackers, I. Maciejowska, Claire McDonnell, M. Mocerino","doi":"10.1515/cti-2022-0030","DOIUrl":"https://doi.org/10.1515/cti-2022-0030","url":null,"abstract":"Abstract This study contributes to the understanding of online professional development of university STEM (Science, Technology, Engineering and Mathematics) lecturers. An active learning massive open online course (MOOC) to develop best practice in teaching in university science laboratories was developed using the ADDIE (Analysis, Design, Development, Implementation, Evaluation) model in three cycles. The teaching beliefs and intentions of the participants were determined before and after they completed the MOOC and their level of satisfaction with this professional development opportunity was examined using a survey. The results showed high completion rates and an appreciation of the online course design. Participants who completed the course evaluation were satisfied and they identified the usefulness of the active learning components that required them to discuss and reflect, develop plans and peer-assess. A large majority developed new ideas to help them to improve their teaching. The participation in the course increased participants’ understanding of the multidimensional aspects of laboratory teaching and the challenges related to it. The majority of participants changed their teaching beliefs to become more student-centred.","PeriodicalId":93272,"journal":{"name":"Chemistry Teacher International : best practices in chemistry education","volume":"4 1","pages":"355 - 376"},"PeriodicalIF":0.0,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42000388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Comprehension of molecular scale is an essential component of a chemistry student’s education. However, it is especially difficult for most to wrap their heads around just how small the nanometer scale is at which the molecules they are taught about exist. Using 3D printing techniques to aid in visualization, we can model spherical molecules, namely buckminsterfullerene (C60) and the cuboctahedral gold cluster Au55, and scale them up by eight orders of magnitude. The new size of these molecules is comparable to a globe 13 cm in diameter, a model of the Earth scaled down by eight orders of magnitude. Seeing and holding both of these objects resized to similar dimensions, students are able to get a sense of how the molecular scale compares to the handheld scale. The fact that the molecule is scaled up by a factor of 1024 in volume also nicely contextualizes the magnitude of Avogadro’s number (∼0.6 × 1024), the constant of proportionality that converts the molecular scale to the handheld scale.
{"title":"A billion times smaller than us: helping students comprehend the molecular scale","authors":"Jaspreet Sidhu, J. McIndoe","doi":"10.1515/cti-2022-0009","DOIUrl":"https://doi.org/10.1515/cti-2022-0009","url":null,"abstract":"Abstract Comprehension of molecular scale is an essential component of a chemistry student’s education. However, it is especially difficult for most to wrap their heads around just how small the nanometer scale is at which the molecules they are taught about exist. Using 3D printing techniques to aid in visualization, we can model spherical molecules, namely buckminsterfullerene (C60) and the cuboctahedral gold cluster Au55, and scale them up by eight orders of magnitude. The new size of these molecules is comparable to a globe 13 cm in diameter, a model of the Earth scaled down by eight orders of magnitude. Seeing and holding both of these objects resized to similar dimensions, students are able to get a sense of how the molecular scale compares to the handheld scale. The fact that the molecule is scaled up by a factor of 1024 in volume also nicely contextualizes the magnitude of Avogadro’s number (∼0.6 × 1024), the constant of proportionality that converts the molecular scale to the handheld scale.","PeriodicalId":93272,"journal":{"name":"Chemistry Teacher International : best practices in chemistry education","volume":"4 1","pages":"339 - 342"},"PeriodicalIF":0.0,"publicationDate":"2022-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45686415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Laboratory practical is an essential component for effective learning of science. To provide laboratory experience can be a challenge to some rural schools with limited laboratory facilities. The situation was exacerbated when schools were close due to the COVID pandemic. This paper reports a laboratory kit designed based on the Standard Curriculum for Secondary Schools in Malaysia (KSSM). The kit was evaluated by students and experienced teachers from town and rural schools. Pre- and post-test was conducted with the students before and after using the kit. A questionnaire was disseminated to appraise the students’ perceptions on practical learning. There was a significant improvement (p < 0.05) in the overall score of the post-test comparing to the pre-test. Both rural and town schools demonstrated a marked increase in the overall mean scores in the post-test. There was also improvement in affection for chemistry among students after using the kit. The practical kit can be deployed in schools with laboratory constraints and to be used outside the school settings. It was designed to be affordable, safe and environmental-friendly, providing individualized hands-on exposure.
{"title":"A curriculum-based laboratory kit for flexible teaching and learning of practical chemistry","authors":"Hee Ting Wong, S. Sim","doi":"10.1515/cti-2022-0014","DOIUrl":"https://doi.org/10.1515/cti-2022-0014","url":null,"abstract":"Abstract Laboratory practical is an essential component for effective learning of science. To provide laboratory experience can be a challenge to some rural schools with limited laboratory facilities. The situation was exacerbated when schools were close due to the COVID pandemic. This paper reports a laboratory kit designed based on the Standard Curriculum for Secondary Schools in Malaysia (KSSM). The kit was evaluated by students and experienced teachers from town and rural schools. Pre- and post-test was conducted with the students before and after using the kit. A questionnaire was disseminated to appraise the students’ perceptions on practical learning. There was a significant improvement (p < 0.05) in the overall score of the post-test comparing to the pre-test. Both rural and town schools demonstrated a marked increase in the overall mean scores in the post-test. There was also improvement in affection for chemistry among students after using the kit. The practical kit can be deployed in schools with laboratory constraints and to be used outside the school settings. It was designed to be affordable, safe and environmental-friendly, providing individualized hands-on exposure.","PeriodicalId":93272,"journal":{"name":"Chemistry Teacher International : best practices in chemistry education","volume":"4 1","pages":"343 - 353"},"PeriodicalIF":0.0,"publicationDate":"2022-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42001587","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Organic chemistry often represents a key impasse for students during their third level science education. Both intrinsic and extrinsic factors contribute to perceived difficulties in learning the subject. Moreover, the teaching of multi-step organic synthesis at third level has well-documented challenges. At University College Cork (UCC), we have adopted a strategy to engage students at the mid to late degree stage using an innovative teaching hook, to inspire interest and engagement. The approach was taken to outline chronologically some of the seminal breakthroughs in synthesis, and organic chemistry more generally, from the 1950 s to a few of the current leaders of today. Importantly the focus is on the people, the circumstance and the stories surrounding them. As a relevance-based hooking strategy grounded in a storytelling pedagogy, the goal was to inform students of the potential in organic chemistry and thus spark their interest for the subsequent lectures. Over multiple interventions, feedback from students has been highly positive. We posit that the design framework behind the ‘The People and Personalities’ could be adapted to many disciplines in a similarly successful manner. Overall, this approach proved inspirational for students, and was a most timely intervention in their degree program.
{"title":"Some people and personalities of organic chemistry: a teaching hook for mid-level university students","authors":"Katrina Mackey, M. McHugh, G. McGlacken","doi":"10.1515/cti-2021-0037","DOIUrl":"https://doi.org/10.1515/cti-2021-0037","url":null,"abstract":"Abstract Organic chemistry often represents a key impasse for students during their third level science education. Both intrinsic and extrinsic factors contribute to perceived difficulties in learning the subject. Moreover, the teaching of multi-step organic synthesis at third level has well-documented challenges. At University College Cork (UCC), we have adopted a strategy to engage students at the mid to late degree stage using an innovative teaching hook, to inspire interest and engagement. The approach was taken to outline chronologically some of the seminal breakthroughs in synthesis, and organic chemistry more generally, from the 1950 s to a few of the current leaders of today. Importantly the focus is on the people, the circumstance and the stories surrounding them. As a relevance-based hooking strategy grounded in a storytelling pedagogy, the goal was to inform students of the potential in organic chemistry and thus spark their interest for the subsequent lectures. Over multiple interventions, feedback from students has been highly positive. We posit that the design framework behind the ‘The People and Personalities’ could be adapted to many disciplines in a similarly successful manner. Overall, this approach proved inspirational for students, and was a most timely intervention in their degree program.","PeriodicalId":93272,"journal":{"name":"Chemistry Teacher International : best practices in chemistry education","volume":"4 1","pages":"327 - 338"},"PeriodicalIF":0.0,"publicationDate":"2022-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43916176","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hairunnisa Ramli, N. Zainal, Michael Hess, C. Chan
Abstract We present a basic principle and good practices of the rheology of polymers, particularly for teachers or lecturers at colleges or universities for educational purposes, as well as for beginner researchers who may refer to this article as their self-learning resources. Basic consideration of the experimental methods using parallel-plate oscillatory rheometer and step-by-step guidelines for the estimation of the power law dependence of storage, G′ and loss, G″ modulus as well as the estimation of the relaxation time at f cross G ′ − G ′′ ${f}_{,mathrm{cross}}^{,{G}^{prime }-{G}^{prime prime }}$ at terminal zone using various approaches such as commercial graphical software, manual graphical approach and commercial rheometer software are highlighted. Good practices for data interpretation using different approaches are described and compared where the outcomes revealed the manual graphical approach or commercial graphical software yield comparable results with the commercial rheometer software. In order to have better insight, several examples and exercises which are applicable for teaching and self-learning activities are also provided.
{"title":"Basic principle and good practices of rheology for polymers for teachers and beginners","authors":"Hairunnisa Ramli, N. Zainal, Michael Hess, C. Chan","doi":"10.1515/cti-2022-0010","DOIUrl":"https://doi.org/10.1515/cti-2022-0010","url":null,"abstract":"Abstract We present a basic principle and good practices of the rheology of polymers, particularly for teachers or lecturers at colleges or universities for educational purposes, as well as for beginner researchers who may refer to this article as their self-learning resources. Basic consideration of the experimental methods using parallel-plate oscillatory rheometer and step-by-step guidelines for the estimation of the power law dependence of storage, G′ and loss, G″ modulus as well as the estimation of the relaxation time at f cross G ′ − G ′′ ${f}_{,mathrm{cross}}^{,{G}^{prime }-{G}^{prime prime }}$ at terminal zone using various approaches such as commercial graphical software, manual graphical approach and commercial rheometer software are highlighted. Good practices for data interpretation using different approaches are described and compared where the outcomes revealed the manual graphical approach or commercial graphical software yield comparable results with the commercial rheometer software. In order to have better insight, several examples and exercises which are applicable for teaching and self-learning activities are also provided.","PeriodicalId":93272,"journal":{"name":"Chemistry Teacher International : best practices in chemistry education","volume":"4 1","pages":"307 - 326"},"PeriodicalIF":0.0,"publicationDate":"2022-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42434477","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract In this paper, we investigated and classified the answers of college freshmen when asked about “the final concentration value of a mixture of solutions ”. Prior to the explanation of the topic in class, a diagnostic questionnaire on “solutions” was presented to 532 first year students in the chemistry course at the University of Buenos Aires. The questionnaire consisted of three questions assessing the same concept: the calculation of the final concentration of a solution obtained mixing a concentrated and a dilute solution of the same solute. The format of the three questions was multiple choice answer with justification, but they differed in their chemical language style: chemical formulas, verbal-procedural, and visual languages were used. It was noted a trend to apply mathematical calculations, when chemical problems are addressed, even when such calculations are not necessary. Thus, obtaining a numerical result would be considered appropriate by the students, with no analysis of the significance of the value obtained. Nevertheless, question which uses visual language was answered correctly by a greater number of students. This would allow inferring that the use of this language brings students closer to a better understanding of the situation.
{"title":"Difficulties of novice students in solving the final concentration value of a mixture of solutions","authors":"E. Vaccaro, C. Stella, M. Alonso","doi":"10.1515/cti-2021-0026","DOIUrl":"https://doi.org/10.1515/cti-2021-0026","url":null,"abstract":"Abstract In this paper, we investigated and classified the answers of college freshmen when asked about “the final concentration value of a mixture of solutions ”. Prior to the explanation of the topic in class, a diagnostic questionnaire on “solutions” was presented to 532 first year students in the chemistry course at the University of Buenos Aires. The questionnaire consisted of three questions assessing the same concept: the calculation of the final concentration of a solution obtained mixing a concentrated and a dilute solution of the same solute. The format of the three questions was multiple choice answer with justification, but they differed in their chemical language style: chemical formulas, verbal-procedural, and visual languages were used. It was noted a trend to apply mathematical calculations, when chemical problems are addressed, even when such calculations are not necessary. Thus, obtaining a numerical result would be considered appropriate by the students, with no analysis of the significance of the value obtained. Nevertheless, question which uses visual language was answered correctly by a greater number of students. This would allow inferring that the use of this language brings students closer to a better understanding of the situation.","PeriodicalId":93272,"journal":{"name":"Chemistry Teacher International : best practices in chemistry education","volume":"4 1","pages":"297 - 305"},"PeriodicalIF":0.0,"publicationDate":"2022-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46660361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The identification of undergraduate chemistry students’ conceptual difficulties and common mistakes with basic concepts and problems in chemical kinetics provided the aim for this study, which involved 2nd-year/4th semester students who had passed the chemical kinetics component of a physical chemistry course. The study involved the analysis, evaluation and interpretation of students’ answers to the final examination in chemical kinetics. Three achievement groups, for the various topics, were identified: Group A, high achievement (mean ≈ 85%): (a) the steps in a chain-reaction mechanism, (b) integrated 1st- and 2nd-order rate laws; and (c) the Lindemann–Hinshelwood mechanism. Group B, intermediate achievement (mean ≈ 74%): (a) half-life, (b) instantaneous rate and the extent of reaction variable (ξ), (c) the Michaelis–Menten mechanism, and (d) theoretical rate law not asking for a final formula. Group C, low achievement (mean ≈ 54%): (a) experimental rate law and the reaction rate constant on the basis of an experimental-data table, (b) extracting the theoretical rate law, and (c) the Arrhenius equation. Students’ errors and misconceptions have also been identified. Successful students tended to respond well to straightforward questions on the theory of the subject, but had difficulties when solving problems. It is essential that teachers understand the potential of their students, especially possible misconceptions they may hold, and the teaching approaches that may contribute to overcoming the student difficulties. Problems in chemical kinetics can be very demanding both in terms of algebraic manipulations and conceptually. Teaching should focus on problem solving, with the emphasis on students themselves trying to solve the problems.
{"title":"Chemistry students’ conceptual difficulties and problem solving behavior in chemical kinetics, as a component of an introductory physical chemistry course","authors":"Charalampia Stroumpouli, Georgios Tsaparlis","doi":"10.1515/cti-2022-0005","DOIUrl":"https://doi.org/10.1515/cti-2022-0005","url":null,"abstract":"Abstract The identification of undergraduate chemistry students’ conceptual difficulties and common mistakes with basic concepts and problems in chemical kinetics provided the aim for this study, which involved 2nd-year/4th semester students who had passed the chemical kinetics component of a physical chemistry course. The study involved the analysis, evaluation and interpretation of students’ answers to the final examination in chemical kinetics. Three achievement groups, for the various topics, were identified: Group A, high achievement (mean ≈ 85%): (a) the steps in a chain-reaction mechanism, (b) integrated 1st- and 2nd-order rate laws; and (c) the Lindemann–Hinshelwood mechanism. Group B, intermediate achievement (mean ≈ 74%): (a) half-life, (b) instantaneous rate and the extent of reaction variable (ξ), (c) the Michaelis–Menten mechanism, and (d) theoretical rate law not asking for a final formula. Group C, low achievement (mean ≈ 54%): (a) experimental rate law and the reaction rate constant on the basis of an experimental-data table, (b) extracting the theoretical rate law, and (c) the Arrhenius equation. Students’ errors and misconceptions have also been identified. Successful students tended to respond well to straightforward questions on the theory of the subject, but had difficulties when solving problems. It is essential that teachers understand the potential of their students, especially possible misconceptions they may hold, and the teaching approaches that may contribute to overcoming the student difficulties. Problems in chemical kinetics can be very demanding both in terms of algebraic manipulations and conceptually. Teaching should focus on problem solving, with the emphasis on students themselves trying to solve the problems.","PeriodicalId":93272,"journal":{"name":"Chemistry Teacher International : best practices in chemistry education","volume":"4 1","pages":"279 - 296"},"PeriodicalIF":0.0,"publicationDate":"2022-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42435803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hortensia Natalia Pérez-Vallejo, M. A. Contreras-Ruiz, J. G. Ibanez
Abstract As a result of social distancing measures in response to the Covid-Sars 2 pandemic, our school sent chemistry kits to the students’ homes for remote experimentation. This allowed the performance of ∼25 experiments per person in each of the Fall 2020 and Spring 2021 semesters in an elective chemistry course. Students were requested to design some experiments of their own and then have the entire group reproduce them. One such experiment consisted of the anodic indirect electrogeneration of colloidal sulfur by solution acidification to produce thiosulfate disproportionation. This was evidenced by the well-known Rayleigh scattering phenomenon. Here, the trajectory and polarization state of light are modified by its interaction with a medium containing particles of smaller diameter than the wavelengths of incident light. If white light interacts with this medium, the smaller wavelengths (e.g., blue, violet) are radially scattered while the longer wavelengths (e.g., orange, red) pass through the suspension. Such scattering is responsible for beautiful sunsets and blue skies and is produced here by an indirect electrochemical process that generates colloidal sulfur. Students evidence the scattering of light shone from simple cell phone flashlights. The entire procedure is performed in a 2-h class session. Key student outcomes are presented.
{"title":"Distance learning: an interdisciplinary experiment on Rayleigh scattering","authors":"Hortensia Natalia Pérez-Vallejo, M. A. Contreras-Ruiz, J. G. Ibanez","doi":"10.1515/cti-2022-0006","DOIUrl":"https://doi.org/10.1515/cti-2022-0006","url":null,"abstract":"Abstract As a result of social distancing measures in response to the Covid-Sars 2 pandemic, our school sent chemistry kits to the students’ homes for remote experimentation. This allowed the performance of ∼25 experiments per person in each of the Fall 2020 and Spring 2021 semesters in an elective chemistry course. Students were requested to design some experiments of their own and then have the entire group reproduce them. One such experiment consisted of the anodic indirect electrogeneration of colloidal sulfur by solution acidification to produce thiosulfate disproportionation. This was evidenced by the well-known Rayleigh scattering phenomenon. Here, the trajectory and polarization state of light are modified by its interaction with a medium containing particles of smaller diameter than the wavelengths of incident light. If white light interacts with this medium, the smaller wavelengths (e.g., blue, violet) are radially scattered while the longer wavelengths (e.g., orange, red) pass through the suspension. Such scattering is responsible for beautiful sunsets and blue skies and is produced here by an indirect electrochemical process that generates colloidal sulfur. Students evidence the scattering of light shone from simple cell phone flashlights. The entire procedure is performed in a 2-h class session. Key student outcomes are presented.","PeriodicalId":93272,"journal":{"name":"Chemistry Teacher International : best practices in chemistry education","volume":"4 1","pages":"185 - 190"},"PeriodicalIF":0.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42572614","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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