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Modifications are presented for the iodine clock reaction to introduce the concept of activity and to help students better appreciate molecular aspects of chemical equilibrium. The addition of an unreactive salt affects the activity of the reactants in the iodine clock reaction. The difference in activity affects how long the iodine clock reaction takes to show the color change, even though the concentration of reactants has not changed. Resources and suggestions are provided to use the modified iodine clock reaction in both introductory/general chemistry courses and more advanced analytical and physical chemistry courses to expose students to the concept of activity and its role in chemical reactions and equilibrium.

A mixture of salt water and isopropyl alcohol is immiscible, forming two separate liquids with the organic layer on top and aqueous layer on bottom. When universal indicator is added to such a mixture, all of the indicator compounds in the universal indicator preferentially dissolve in the alcohol--except for phenolphthalein at high pH. Mixtures of alcohol, salt water, and universal indicator in a bottle can be made to display a variety of layered color effects within the bottle by adjusting the pH. The various phenomena observed can be tied to an assortment of chemical topics including density, the classification of matter, solubility, intermolecular forces, and acid-base chemistry.

The focus of the present study is the learning processes of concepts related to hydrogen bonds, which were developed using a didactic sequence (DS). Based on the perspective of Imre Lakatos, it was observed whether the explanatory models created by upper-secondary students form progressive transition sequences, which are similar to what Lakatos, in his text The History of Science, calls a "problem" that increases the explanatory/heuristic power of the model. To evaluate the evolution of these models, which generally consist of progressive transitions, four phases were developed: (1) the categorization of answers obtained in the DS in Realist, Empiricist or Rationalist zones, as well as an attribution of scores; (2) the determination of a score range for said zones; (3) hierarchical cluster analysis (HCA) and (4) an analysis of the progressive transition of the explanatory models. A continuous review of the ideas expressed by the students during their learning of the subject revealed that a significant share of students progressed conceptually. In a general way, it can be said that the activities developed in the DS contributed substantially to the progressive transition of the explanatory models made by most students. Furthermore, the approach of the DS toward the subject of hydrogen bonds allowed the students to interpret the phenomena studied using their knowledge of Chemistry.

Being able to move between different representations levels (macroscopic, submicroscopic, and symbolic) is important to understand a chemical phenomenon meaningfully. The current study investigated how pre-service science teachers moved from symbolic representation to sub-microscopic representation. A total of 205 pre-service science teachers, first, balanced the three chemical reactions and then drew the reactions' sub-microscopic views if they were able to observe them. The findings revealed that pre-service science teachers are most successful at the symbolic level. Yet, this is not a valid conclusion for the sub-microscopic representation level. The drawings were analyzed concerning atomic size and molecular geometry and found that pre-service science teachers have common alternative concepts. Furthermore, they mostly have a superficial knowledge of the molecular geometry of chemical compounds. In conclusion, because preservice science teachers will teach in their future careers, it is important to encourage them to comprehend chemical phenomena at each representation level and shift between them to prevent alternative concepts they may have.

Students perceive molecular bonding as an abstract concept; therefore, learning this concept seems uninteresting and difficult. A strategically designed learning object (LO), such as in the form of a simulation, can be used to help students acquire accurate mental images and build appropriate schema in addition to providing a concrete learning experience and encouraging knowledge construction. This paper presents an evaluation of the design and development of the "Making Molecules" simulation through students' perceptions of the previous version and recommendations for improving a future version. Data were collected from two online chemistry courses (N = 159) through an anonymous online survey. Results suggest that students responded positively to the use of the simulation. They reported gaining a better understanding of molecular bonding through an interactive learning experience. One of their recommendations was to include more learning tasks related to complex molecules, expressing an interest in learning more about chemistry. This paper provides insights for educators and instructional designers regarding selection and/or design of an LO for optimizing student learning of complex topics.

The free volume fraction of a macromolecular structure can be assessed theoretically by using a suitable model; however, it can also be evaluated from experimental data obtained from dilatometry and positron annihilation lifetime spectra. In this second case, a regular geometry of the sub-nanometric cavities forming the free volume has to be assumed, although in fact they are irregularly shaped. The most popular approach is to guess spherical holes, which implies an isotropic growth of these last with temperature. In this work, we compared the free volume fraction, as obtained from experiments in a set of polybutadiene and polyisoprene cured rubbers and their blends, with the analogous quantity expected by using the lattice-hole model. The results allowed us to obtain insights on the approximate shape of the holes. Indeed, a cylindrical flattened geometry of the cavities produced a better agreement with the theory than the spherical shape. Furthermore, the best fit was obtained for holes that expanded preferentially in the radial direction, with a consequent decrease of the aspect ratio with temperature.

This critical appraisal is intended for users of the dimolybdenum method, well-established in electronic circular dichroism (ECD) to determine the absolute configuration of vic -diols and, in particular, for experimental researchers not being experts in chiroptical methods. The main goal is to demonstrate how to avoid misleading and ambiguous conclusions resulting from the rigorous application of the helicity rule by limiting the analysis to the vic -diol unit alone. We particularly focused on multichromophoric systems, especially those that may interfere with the absorption of an in situ formed dimolybdenum tetraacetate-diol complex. In this context, examples are presented of vic -diols for which stereochemical assignment based solely on the helicity rule is ambiguous and does not necessarily lead to correct results. The motivation for choosing these examples was to demonstrate the impact of the structure of the substrate on the complexation process with the metal core and its selectivity. For each selected case, results obtained are analyzed in detail together with a discussion of existing restrictions and choice of a support method to increase the credibility of the conclusion. Based on seven both educational and challenging examples, it was shown that the dimolybdenum methodology can also be effectively applied to complex chromophoric systems, provided that other chiroptical methods and/or computational support verify obtained results.

The range of abstract concepts encountered when learning chemistry and the inability of students to make connections between the macroscopic, sub-microscopic, and symbolic representations, used in chemistry teaching, are believed to be the main reasons for students' difficulty when learning chemistry. Prediction and determination of molecular geometry using the theory of valence shell electron pair repulsion (VSEPR) is a sample of the abstract concept that is hard to understand by students who learn chemistry. Students may comprehend these ideas better if the learning process is supplemented with cutting-edge, interactive learning aids. To address the conceptual difficulties that students encounter when learning how to predict the shapes of molecules, a card game (MGCards) has been developed which is supported by simple molecular model building (MMB). The card game allows students to work through the steps required to predict the shape of a molecule in an engaging format. The student learning process is supported by feedback at all stages (if students make a mistake, they receive hints that will help them in the next step of the game). Action research with qualitative methods has been used to design, develop, and evaluate the MGCards. The MGCards and MMB were piloted at the University of Leicester with year one Natural Sciences students and modified based on the feedback received. Both MGCards and MMB were then used as part of the first-year chemistry education programme at Tanjungpura University in Indonesia. The findings of students' answer analysis (pre- and post-test) in both cycles showed that students had a better understanding after learning with MGCards and MMB. The positive feedback for MGCards and MMB confirmed that these resources were effective in delivering an engaging learning experience. The results suggest that MGCards and MMB play a significant role in enhancing students' understanding while also keeping them engaged.

Representations in chemistry are the tools by which students, instructors, and chemists reason with chemical concepts that are abstract. Although representations are regularly used within the chemistry classroom, there is more to uncover regarding the ways students interact with representations when given chemistry tasks. This study aimed to address this gap in knowledge. In this study, eighteen students enrolled in second semester general chemistry were recruited for data collection. Semi-structured interviews were utilized to observe how students approached a similar set of dipole-dipole interaction tasks when given four distinct representations. Analysis of the data revealed that students' approaches to these tasks were affected by the newly explicit features present within each representation. Additionally, the ordering in which the representations were presented to the students influenced the specific features students took notice of and implemented into their approaches to the tasks. These findings can better inform instruction and future research involving chemical representations such that students will form a solid foundation in working with and pulling relevant information from various representations when solving chemistry tasks.

Central to conceptual understanding of STEM disciplines is visuospatial processing. Despite its acknowledged role in assuring learners' success, less is known about the underlying reasoning students must employ when solving 3-D problems and the ways in which gaining an understanding of this can inform formative assessment and learning in STEM education. Chemists must utilise their spatial understanding when visualising 3-D structures and processes from 2-D representations and so this exploratory practitioner-researcher study sought to identify the ways in which secondary school chemistry students reason when explaining their predictions about molecular geometry, and how the use of certain modalities was linked to assessed accuracy. Coding of students' verbal and written responses to the research task revealed that students employed multiple reasoning strategies and conceptual resources to facilitate use of analytical heuristics and imagistic reasoning. Analysis of students' verbal responses and spontaneous gestures provided insight into the extent of imagistic vs. analytical reasoning and the finergrained conditions which promoted their use. Importantly, it was observed that despite being instructed on the use of VSEPR theory to find analytical solutions, some students exhibited preference for alternative reasoning strategies drawing upon imagistic reasoning; showing more nuanced and varying degrees of accuracy through their verbal responses and representations gestured in 3D space. This work has pedagogical implications as use of specific reasoning strategies and the identification of key conceptual resources is not readily promoted as classroom practice for learning or assessment. This study therefore raises questions and contributes to the evidence base for attending to learners' visuospatial thinking, as revealed through the multiple modalities they may use to assist and communicate their understanding, and highlights the significance of this to formative assessment in Chemistry and STEM Education.

The study diagnosed chemistry teacher trainees' difficulties in naming and writing structures of spiro and bicyclic compounds. The case study design was conducted in a constructivist environment to enhance chemistry teacher trainees' ability to construct, represent, and interpret the structural formulae of spiro and bicyclic compounds. Purposive sampling technique was employed to select 126 1st-year chemistry teacher trainees from University of Education, Winneba for the study. The results revealed that chemistry teacher trainees had difficulties in naming and writing structural formulae of spiro and bicyclic compounds. However, through the effective use of molecular model kits in teaching naming and writing structures of spiro and bicyclic compounds, these chemistry teacher trainees became conscious of IUPAC rules for naming and writing spiro and other cyclic compounds. At-test conducted indicated that a statistical significance difference existed between students' performance before the implementation of the intervention and after the intervention. It is recommended that chemistry teachers should adopt the use of molecular model kits in teaching concepts of organic nomenclature.

The concept of hybridisation is one of the most difficult concepts for chemistry students to grasp at all levels of learning. Research showed the students conceptual difficulty ranged from their lack of the prerequisite knowledge for grasping the topic hybridisation to chemical bond formation and orientations of atomic orbitals. This study investigated the difficulties Senior High School Students face in learning hybridisation. The study adopted a mixed-method approach using the sequential exploratory design. Purposive sampling was used to select six schools that offer elective chemistry subject. Simple random sampling was then used to select 120 Senior High School form 1 students to take part in the study. Convenient sampling was used to interview 24 students from the sample. Hybridisation Achievement Test (HAT) and Semi-structured interviews were self-constructed and used to collect data. Descriptive statistics and Content analysis were used to analyse the data. Results showed that, majority of students had difficulties in explaining the concept of hybrid orbitals, writing the electron configuration of [subscript 6]C, explaining the effect of hybridisation on formation of chemical bonds in [subscript 6]C, and type of hybridisation and shapes of compounds such as NH[subscript 3], OF[subscript 2], BCl[subscript 3], CO[subscript 2], SiO[subscript 2], C[subscript 2]H[subscript 2], BeF[subscript 2] and C[subscript 2]H[subscript 4]. The study also showed that students had difficulties in explaining and demonstrating the formation of C = C double bond in ethene and other compounds. Equally students were challenged in demonstrating the differences between the formation of sigma and pi bonds in compounds. Students had difficulties in using electron orbital diagrams to explain the shape of CO[subscript 2] as linear. The study concluded that Senior High School form 1 chemistry students in the Upper West Region of Ghana lacked the most basic and fundamental concept of hybridisation. Teachers need to use conceptual change instructional approaches to teach hybridisation in order to foster students' understanding and reduce misconceptions.

This study was conducted to determine the differences in the conceptual understanding of 52 Turkish students who were taught with a scientific argumentation approach in grade 12 chemistry. The concept test was administered to the participants as a pre-test and post-test, and it contained two questions. The first had two sub-questions had two steps. The second had six sub-questions. The researcher of the current study, who was well-versed in chemistry education, and a chemistry teacher, expressed their views regarding the content validity of the concept test. The criteria scales and scoring rubrics were prepared by the researcher to evaluate the test in terms of a conceptual understanding of hydrogen bonding. This study, which thoroughly aims at learning the effects of scaffolding with argumentation, applied mixed-methods research to reveal students' understanding of hydrogen forces and to determine schemas by drawing. In quantitative analysis, the mean, median, and standard deviation values of the data collected from the students were considered. In qualitative analysis, the drawings and explanations of the students on the concept tests applied before and after the education were discussed. According to the results of the concept tests, improvement in the conceptual understanding of the students before and after the argumentation-based teaching could be observed; however, half of the students still evidently had a rote understanding. In conclusion, the scientific-argumentation-based teaching approach was effective in developing their conceptual understanding. Recommendations are made as a result of this study.

In recent years, chemistry educators are increasingly adopting immersive virtual reality (IVR) technology to help learners visualise molecular interactions. However, educational studies on IVR mostly investigated its usability and user perceptions leaving out its impact on improving conceptual understanding. If they evaluated students' knowledge gains, they tended to use information recall tests to assess knowledge gains. Employing interviews and diagram-drawing tasks, this study explored how students' conceptual understanding of the nature of hydrogen bonds and the shape of snowflakes changed through a collaborative IVR experience on snowflakes. Participants were 68 undergraduate chemistry students. Videos of pre-/post-interviews and student-generated diagrams were analysed. The results indicated a marked improvement in students' conceptual understanding of the nature of hydrogen bonds among water molecules in snowflakes. After IVR, 57 students provided scientifically acceptable explanations of the nature of hydrogen bonds. Improvements in students' understanding were related to the intermolecular nature of hydrogen bonds, the role of lone pairs of electrons in forming hydrogen bonds, and molecular interactions in 3D space. This study suggests that collaborative IVR could be a powerful way for students to visualise molecular interactions, examine their alternative conceptions, and build more coherent understanding. Implications for the design and implementation of IVR activities for science learning are discussed.

The present investigation aims to analyze the knowledge levels and chemical representation levels of pre-service primary school teachers (PPSTs) on the experiment of distillation. For this purpose, the cross-sectional survey technique, one of the quantitative research designs was employed. The study was carried out at a Faculty of Education in the Aegean Region of Turkey with 79 freshman pre-service teachers enrolled in the Department of Primary Education. This group is of particular interest as they are the last class who had taken the General Chemistry course since this course was removed from the curriculum in 2018. A Distillation Experiment Worksheet (DEW), which consisted of 9 open-ended questions involving the macroscopic, sub-microscopic, and symbolic representations was used as data collection instrument in the study. The worksheets were analyzed with the document analysis method according to the categories created within the scope of the chemical representation levels, and these categories were established in line with direct statements of the PPSTs. Results indicated that PPSTs confused the heterogeneous and homogeneous mixtures, physical properties such as volatility and density, and they were unable to differentiate between boiling and evaporation. The most crucial result of the study was that the PPSTs had difficulties in establishing a relationship between macroscopic and sub-microscopic representations. For this reason, they could not demonstrate the interactions between solvent and solute molecules at the submicroscopic level during molecular dissolution and they could not predict how the intermolecular interaction changes during the condensation and the distance between the particles. Based on the results of this analysis, our study provides several recommendations for lecturers in the last part of this paper.

Collaboration is regarded as one of the core competences of the 21st century when it comes to complex problem solving. In response to high dropout rates among STEM students, we developed a digital-collaborative intervention on a difficult topic, MO theory, for first-year chemistry students. First, students work independently in a Digital Learning Environment (DLE). Afterwards, they collaborate in small groups and create Concept Maps on MO theory. We evaluate this intervention through knowledge tests, tests of attractiveness, cognitive load, and usability during the DLE and concept mapping process, as well as audio and screen recordings during the collaborative group processes. This paper presents the detailed study design together with results from a first study in January 2021, focusing on the practicability of the intervention and students' feedback. Overall, each small group succeeded in creating a Concept Map. Students rated all phases of the intervention as attractive, with high usability and low cognitive load, although the interactive videos scored better for attractiveness and usability than the concept mapping process. On that basis, first adjustments for a second cycle of the intervention, which will be conducted in January 2022, were derived.

Understanding chemical models can be challenging for many university students studying chemistry. This study analysed students' understanding of molecular structures using the Lewis structure as a model, and examined what hinders their understanding. We conducted pre- and post-tests to analyse students' conceptions and changes in them. The measures contained multiple-choice questions and drawing tasks testing their understanding of concepts, such as polarity, geometry, charge or formal charge and expanded octet. The pre-test revealed a lack of knowledge and several misconceptions in students' prior knowledge. For example, the concept of polarity was well-known, but the combination of polarity and geometry appeared to be difficult. For some students, the representation of molecules was intuitive and lacking a systematic approach. Certain students used mnemonics and draw ball-and-stick models connected to surficial representations. After the chemistry courses, the conceptions and drawings had generally changed, and the level of the students' knowledge increased markedly. Although, fewer ball-and-stick models were drawn in the post-test, some students still used them. The main result was that students who drew ball-and-stick models in the pre-test were less capable of drawing the correct Lewis structures with electrons in the post-test. In addition, heuristics seem to hinder learning and some concepts, such as resonance, remained difficult. This is probably due to the fact that understanding molecular structures requires systemic understanding, where several matters must be understood at the same time. Our study highlights that the understanding of molecular structures requires conceptual change related to several sub-concepts.

Students often have difficulty understanding abstract concepts in chemistry and a low spatial ability, especially in visualizing intermolecular interactions at the submicroscopic level. Therefore, this study aims to analyze the spatial ability of students by using a 3D virtual representation as they study the curriculum topic of molecular geometry. The research was conducted with 13 male and 23 female year 10 secondary students in Jakarta, Indonesia. A qualitative methodology was employed to analyze students' spatial abilities while they undertook learning activities using 3D virtual representation. Data collection included a spatial assessment, a quiz about prior knowledge, student worksheets, interviews, observation sheets, reflective journals, and a molecular geometry test. Learning was carried out in three stages; engage, explore, and explain. The results of the research show that students' ability in spatial orientation is low whereas their ability in spatial relationships that involve using mental manipulation and rotation of 2D or 3D objects is more developed. Students employ this approach to develop their understanding of molecular geometry.

Research has shown that spatial ability plays a key role in understanding STEM (Science, Technology, Engineering, and Mathematics) content, including chemistry. Conservation of Matter (CoM) is an essential but challenging topic for chemistry students of all ages to grasp; it is often taught in a way where students memorize it but do not learn what it means conceptually. This research explored the relationship between understanding spatial ability and conceptual understanding of CoM in middle school students. CoM was examined in two ways using the Conservation of Matter Assessment (CoMA): through questions on conservation of atoms and the conservation of mass. Spatial ability was measured using the Purdue Spatial Visual Test: Rotations (PSVT). Significant, moderate correlations were found between spatial ability and understanding of CoM prior to and after a chemistry unit including instruction on CoM; the correlation was stronger after instruction. Scores on the PSVT and CoMA significantly increased pre to post instruction. The data show spatial ability may impact students' understanding of CoM, which contributes to the literature on factors that impact students' understanding of chemistry. Additionally, it provides evidence that teachers should consider including spatially rich experiences in their chemistry classroom, such as making explicit connections between the areas of Johnstone's Triad.

Covering: 1877 to 2017The ancestors of present-day crinoids are thought to be some of the earliest echinoderms, with fossil records dating back to the early Paleozoic Era (Ordovician Period, 505-440 million years ago). Their bright colours have been noted for over 100 years, and are attributed to a series of polyketide-derived pigments. Some crinoid metabolites display a range of biological activities, including cytotoxicity and fish anti-feedant activity. This review is divided into two parts. Part 1 is encyclopedic in scope, collating information on the >50 known metabolites isolated from crinoids, including their taxonomic source, collection location, chemical structure and biological activities. During the compilation of this data, two distinct themes emerged. Firstly, there is little variation in the class of metabolites produced by crinoids, irrespective of their species or geographic origin. Secondly, the complete and unambiguous assignment of crinoid metabolite structures has been, in many cases, a difficult task. This has been due to a lack of spectroscopic technology available in the past, the presence of proton-poor chemical structures, or both. Thus, Part 2 provides a critical discussion of crinoid chemistry, including the biosynthetic origin of crinoid pigments, as well as the pitfalls and solutions experienced by ourselves and other chemists when elucidating the chemical structures of crinoid metabolites.

Are the ways of engaging with the world that students develop through higher education particular to bodies of knowledge they study? In this article, we examine how students' accounts of the discipline of chemistry in England and South Africa changed over the three years of their undergraduate degrees. Based on a longitudinal phenomenographic analysis of 105 interviews with 33 chemistry students over the course of their undergraduate degrees in four institutions, we constituted five qualitatively different ways of describing chemistry. These ranged from chemistry as something that happens when things are mixed in a laboratory to a more inclusive account that described chemistry as being able to explain molecular interactions in unfamiliar environments. Most students expressed more inclusive accounts of chemistry by the end of their degrees and the level of change appeared to be related to their educational experiences. In contrast to approaches that emphasise the generic student outcomes from higher education, these findings highlight the importance of recognising the distinctive outcomes that students gain from their engagement with particular bodies of disciplinary knowledge. It further highlights the importance of students understanding their degrees as an educational experience that requires them to commit to engaging with these bodies of knowledge.

Concept mapping remains widely used in education. However, little is known about how self-constructed concept maps and peer feedback can improve student learning outcomes in chemistry. We investigated the effects of peer feedback on concept mapping and how it improves students' learning performance in a large second-semester, introductory chemistry course. Three hundred and twenty students were randomly assigned to one of two concept mapping conditions: self-constructed concept map with peer feedback and self-constructed concept map without peer feedback. Each group constructed concept maps that depicted the relationship between concepts on the topic of intermolecular force. The results showed that students in the self-constructed concept map with peer feedback condition outperformed students in the no peer feedback condition in chemistry learning outcome. Overall, this study demonstrates that peer feedback enhances the effectiveness of learning with generative concept maps. The implications and future directions are discussed.

Recent progress in elucidating chemical reactions allows to explain chemistry by the potential energy of the involved chemical structures. Nevertheless, from an educational point of view, empirical results indicate that students often do not connect the core idea of energy with other chemical concepts. From a resource-oriented perspective, students do not draw on a coherent concept of chemistry to solve a problem but rather activate diverse cognitive resources, crucially depending on the context. It is thus of interest which resources high school students activate to reflect on energetic aspects of a chemical reaction. In this study, 38 German high school students in 16 focus groups were asked to explain kinetic and thermodynamic aspects of the reaction between hydrogen and chlorine. The unguided focus group phase and the following semistructured qualitative interview were analysed by qualitative content analysis. Results show that students have a diverse network of cognitive resources on energetic aspects. However, this network's structure seems to be dominated by terminology and a few prominent ideas such as activation energy. In contrast, students seldom drew connections between bond-making and energy release. Many students mainly argued on a macroscopic level and relied heavily on technical terms. If they argued on the sub-microscopic scale, however, they often focussed on the whole system rather than on specific molecules and their structure. Hence, students interpreted concepts like activation energy or reaction coordinate diagrams on the system level leading to unproductive reasoning. Overall, it seems that students seldom activate resources on molecular structures to argue about energetic changes in chemical reactions. Also, they rarely refer to the fundamental principle of energy minimisation to reason about the driving force of reactions. These results suggest that chemical reactions should be explained already in high schools on a molecular level providing a more explicit reference to energy as a function of chemical structures.

The purpose of this research was to develop a multi-representation based e-book on the concept of intermolecular forces that is valid and feasible for use. The form of research used was Research and Development (R&D), which refers to the ADDIE development model consisting of five stages, namely analysis, design, development, implementation and evaluation. Data collection tools at the analysis stage were broken down to interview guidelines and observation sheets. At the development stage, the data collection tools used were content validation sheets (Content Validity) and views (Face Validity). At the implementation stage, the data collection tool utilized was an test of understanding on the concept of intermolecular forces. The results of content validation indicated that the developed e-book was valid. The face validity results showed that the correspondents were in agreement that the e-book had writing style and fonts that were easy to read, material explanations and videos that were easy to understand and images that were corresponding to the contents of the material. Overall, the ebook was found to be easily utilised and the material related to daily life. The ebook obtained learning outcomes that were to be highly mastered by the students.

Most junior high school students considered chemistry as a complicated science subject with an abstract concept, symbols, and terms that must be memorized. The difficulty of learning chemistry made students had low positive perceptions of chemistry. It was needed the right ways to introduce chemistry to them. The purpose of the multiple case study was to explore chemistry multimedia could help students understood chemistry and created a good impression. The study was conducted in three 7th grade classes in different schools. Classroom observations were done in four meetings to collect students' responses toward this multimedia by ending students filling out a questionnaire of impression. Test of classification of matter and its change was given in the last meeting to investigate the level of students' understanding. In the way to gain more depth information, two students from each class were an interview about the application of multimedia. The chemistry multimedia made it easier for the teacher to introduce chemistry through a podcast, molymod-like, and digital simulation. This study documented that the appearance of this multimedia could make the students attracted and curious about chemistry.

In previous published articles, formulae-based mnemonics by counting the total number of s bonds with a lone pair of electrons (LP), a localized negative charge (LNC), or a localized lone pair of electrons (LLP) and subtracting one (01) from this total value (TSLP, TSLNC, or TSLLP) to predict the power of the hybridization state of simple molecules or ions and organic compounds, including heterocyclic compounds have been discussed. These are the innovative and time-efficient methods of enhancing student interest. Here, in this new article, the limitations of conventional formulae in comparison to the use of innovative formulae have been discussed along with the application of the hybridization state in different fields of chemical education. This article encourages students to solve multiple choice type questions (MCQs) at different competitive examinations in a time economic ground on the prediction of hybridization state of simple molecules or ions to know their normal and subnormal geometry and prediction of hybridization state of hetero atom in different heterocyclic compounds to know the planarity of the compounds, which is very essential factor for prediction of aromaticity of heterocyclic compounds. Educators can use this comparative study in their classroom lectures to make chemistry authentic and intriguing. Because the use of mnemonics in classroom lectures is an essential tool to become a distinguished educator.

During the last three decades, chemical education in Slovenia has developed mainly in two chemistry education research groups, one located at the University of Ljubljana and the other at the University of Maribor. The present study aims to identify research papers in the field of chemical education published between 1991 and 2019 through a database survey. From a total of 273 identified research papers in the field of chemical education, an analysis of the papers published in respected international and Slovenian journals and monographs revealed four main research fields: (1) Submicrorepresentations, Models and Animations, (2) Chemistry Teacher Education, (3) Experimental Work, and (4) Conceptions of Basic Chemical Concepts. For further analysis, only papers published in English in respected peer-reviewed international journals were used (N = 41). Based on citations in Web of Science or Scopus, it seems that papers published in the first field have the greatest impact on the international research community. Some research monographs published in Slovenian aim specifically at contributing to bridging the gap between chemical education research and classroom practice, but further actions are necessary to achieve this goal in the future.

This study reports the effectiveness of nanoscience activities in enhancing secondary school students' understanding of two chemistry concepts: structure of atom and acid and bases. For the purpose of this study, quasi experiment was employed to 163 Grade 10 students from the Northern Region of Malaysia. Sample from the experimental group was exposed to a series of nanoscience activities lasted for 10 weeks. Students' understanding on the two chemistry concepts was tested using Chemistry Achievement Test (CAT). The CAT consists of multiple-choice questions and openended questions. Data obtained from CAT was analysed using one-way ANCOVA to identify the effectiveness of nanoscience activity in enhancing students' understanding of chemistry concepts. The findings show that there were statistically significant differences between experimental and control groups' mean scores (F (1,160) = 167.82, p < 0.05 n[subscript p] [superscript 2] = 0.512) with the experimental group students reporting higher mean. The ANCOVA result indicated experimental group students' understanding of chemistry concepts significantly higher than the comparison group. The qualitative analysis of open-ended responses further supports findings obtained from the quantitative analysis. The study suggests that integrating nanoscience into the contemporary teaching of chemistry is relevant and appropriate.

Visuo-semiotic models, such as Lewis structures and ball & stick models, are widely used to enhance students' learning. However, there is limited research about the impact of these models on specific visuo-semiotic reasoning skills. In the current research, we aimed to determine the extent to which physical molecular models could enhance specific visuo-semiotic reasoning skills among students. The research question that we explored was, "what is the impact of physical molecular models on Grade 11 students' visuo-semiotic reasoning skills related to Lewis structures and ball & stick models of ammonia?" In this mixed-methods research, we collected data from purposively selected Grade 11 chemistry students aged between 15 and 18 from an under-resourced school in South Africa. Through a quasi-experimental design, participants in the experimental group (n = 101) used physical molecular models to learn about Lewis structure and ball & stick models of ammonia while participants in the control group (n = 100) did not. We subsequently tested students' visuo-semiotic reasoning skills. Results show that using physical molecular models significantly improved students' visuo-semiotic reasoning skills and reduced associated learning difficulties. We, therefore, recommend that these models should be used as an instructional tool to enhance learning.

Spatial ability is an important tool in chemistry and this ability can be improved. Various technologies have been used to improve spatial ability. However, it is not clear if viewing technologies should take the place of the model kit; the traditional method of learning about molecular structures. Our research aims to address this gap. In our study, we aimed to take advantage of student affinity to technology to drive spatial ability improvements (in the context of chemistry) by having students experience molecules in virtual space using modern viewing technologies (WBVE, AR, and VR). Students were first engaged with the technologies then were assessed to see if their ability to solve problems relating to 3D-molecular structure improved. The mean spatial ability of students improved over the course of the semester (permutation test, p < 0.05) and students using model kits scored higher than those using the technologies (t-test, p < 0.05). The collection and assessment of anonymous, aggregated, student responses for this study was conducted with the approval of the University of Calgary ethics board (REB13-0724). [Articles in this journal were presented at the University of Calgary Conference on Postsecondary Learning and Teaching.]

This is a fundamental and pedagogical work in quantum physics/chemistry, where we try to illustrate the Mulliken's question, "What are the electrons really doing in molecules?". And we also briefly review the development of the most popular numerical approaches in computational chemistry. We examine in a novel approach, how we can overall describe the electronic interactions in atomic systems with the conceptual help of a space-time picture of quantum mechanics. This is not a research article initially looking for new numerical results, but for the imperative fundamental reinterpretation of the (non-classical and stabilizing) electronic exchange and correlation energies, from the point of view of space-time scattering events between electrons. Consistently, we introduce Feynman type diagrams as pictorial representation of the (abstract) enthalpic integrals, scattering mechanisms, in quantum chemistry. In atomic structures, it is almost impossible to fully understand, covalent bonding, electronic enthalpies, surface science, orbital magnetism, catalysis… without computational chemistry. How well do we know the physical meaning of the quantum mechanisms behind the numerical approaches? We give an educational hit to this question, following the philosophy of R.P. Feynman, "just recognizing old things from a new point of view". The possibility of interpreting Coulomb and Fermi holes with space-time diagrams goes deep into the quantum behaviour of electrons, because the Coulomb forces in atomic systems create interreference patterns and then electrons cannot fill the electrostatic potentials everywhere as in classical mechanics. Quantum mechanics also allows electrons in atoms to collide in scatting events, introducing (dynamic) space-time mechanisms that reduce their repulsion energy; and actual successful computational chemistry methods include an average approximation to these stabilization mechanisms.

This study investigated the effect of interactive computer simulation-supported inquiry on South African grade 8 learners' comprehension of atoms and molecular structures. Two sample groups of 34 learners per sample group were used, one acting as a control group who were exposed to a teacher-directed pedagogy while the experimental group used simulations in inquiry-based learning as an intervention to enhance their understanding of atomic and molecular structures. Data were collected by means of conceptual tests, a questionnaire survey, and individual interviews. A statistical analysis of quantitative data gleaned from the post-test showed that the learners in the experimental group performed better than the control group learners. This reflects that the interactive simulations using in an inquiry activity impacted more favorably on the conceptual understanding of learners compared to a teacher-directed approach. The results of the questionnaire survey indicated that learners in the experimental class had a positive experience of using the simulations. They recognized that the simulations enhanced their visualization of abstract concepts, and they reflected on their efficacy in manipulating the simulation.

Chemistry as a discipline in general incorporates abstract concepts, which should be visualized through experiment- and application-oriented methods. It is a well-known fact in Turkey that chemistry class offered by simple and traditional methods cannot be understood by students at a satisfactory level. Such chemical subjects as atoms, molecules, and compounds include abstract concepts of this kind. The visualization of these structures is as strenuous as their teaching. Among the most arduous subjects is the teaching of the mechanism by which atoms form molecules, compounds, and many other structures by means of chemical and physical bonds. Students cannot conceptualize and understand such aspects as atom, molecule, compound, and mixture. The data were collected in a case study, a qualitative research design, to investigate the metaphors that were produced by 169 students of associate degree and bachelor's degree programs to refer to the formation of molecules from atoms. 167 students produced acceptable metaphors, which were categorized into eight themes. All the created metaphors incorporate positive connotations. It can be proposed based on the metaphors that the subjects at stake can be metaphorized and thematized for the concretization thereof. Thus, learning becomes more permanent and effective.

The aim of this study was to determine the validity and reliability of the Nanotechnology Awareness Scale (NAI) in Turkish culture. The study group consists of 624 biology, physics and chemistry teachers working in secondary schools in Antalya, Denizli, Burdur and Ankara. Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA) were conducted in order to determine its structural validity. Cronbach-alpha and stratified-alpha coefficient values were calculated for the reliability of the sub-dimensions and the whole of the scale, respectively. In EFA, Kaiser-Meyer-Olkin (KMO) value was found to be 0.92 and the Bartlett Test result (912 91 = 6519.27, p <0.00) was found significant. In addition, in original scale, a two-factor structure was found. This two factors solution explains 59.192% of the total variance. In CFA, factor structure of the scale was tested for two-factor solution as it was designed. According to the findings, it was found that the scale, containing 14 items with two sub-dimensions, had sufficient goodness of fit indices such as X[superscript 2]/sd =1.344, RMSEA = 0.07, GFI = 0.97, CFI = 0.97, NFI = 0.90 and AGFI = 0.83. These goodness of fit indices shows that we have good model-data fit. The Stratified-alpha coefficient was found as 0.942 for the whole scale. Cronbach alpha coefficient was found as 0.935 and 0.805 for the awareness sub-dimension and exposure sub-dimension, respectively. As a result of the research, it was concluded that the Turkish version of the scale can be used as a valid and reliable measurement tool.

The [4+2] cycloaddition remains one of the most intriguing transformations in synthetic and natural products chemistry. In nature, however, there are remarkably few enzymes known to have this activity. We herein report an unprecedented enzymatic [4+2] cyclization cascade that has a central role in the biosynthesis of pyrroindomycins, which are pentacyclic spirotetramate natural products. Beginning with a linear intermediate that contains two pairs of 1,3-diene and alkene groups, the dedicated cyclases PyrE3 and PyrI4 act in tandem to catalyze the formation of two cyclohexene rings in the dialkyldecalin system and the tetramate spiro-conjugate of the molecules. The two cyclizations are completely enzyme dependent and proceed in a regio- and stereoselective manner to establish the enantiomerically pure pentacyclic core. Analysis of a related spirotetronate pathway confirms that homologs are functionally exchangeable, establishing the generality of these findings and explaining how nature creates diverse active molecules with similar rigid scaffolds.

Chemotypes are a new approach for representing molecules, chemical substructures and patterns, reaction rules, and reactions. Chemotypes are capable of integrating types of information beyond what is possible using current representation methods (e.g., SMARTS patterns) or reaction transformations (e.g., SMIRKS, reaction SMILES). Chemotypes are expressed in the XML-based Chemical Subgraphs and Reactions Markup Language (CSRML), and can be encoded not only with connectivity and topology but also with properties of atoms, bonds, electronic systems, or molecules. CSRML has been developed in parallel with a public set of chemotypes, i.e., the ToxPrint chemotypes, which are designed to provide excellent coverage of environmental, regulatory, and commercial-use chemical space, as well as to represent chemical patterns and properties especially relevant to various toxicity concerns. A software application, ChemoTyper has also been developed and made publicly available in order to enable chemotype searching and fingerprinting against a target structure set. The public ChemoTyper houses the ToxPrint chemotype CSRML dictionary, as well as reference implementation so that the query specifications may be adopted by other chemical structure knowledge systems. The full specifications of the XML-based CSRML standard used to express chemotypes are publicly available to facilitate and encourage the exchange of structural knowledge.

An absorption line at 900 nm has been observed in Perspex. Samples of 1 and 2 cm thickness were used and the integrated absorption (line width times peak absorption) of the line was proportionate to the thickness. Facilities for lowering the sample temperature were not available and therefore both measurements were carried out at room temperature. A Red Tide spectrophotometer was used to measure this absorption. According to the Optics Group at National Institute of Standards and Technology, USA, the line can be assigned to the "3rd overtone CH stretch of the methyl and methylene group." The present result was compared with historic data for boron impurities in indium phosphide to demonstrate the versatility of this form of spectroscopy.

Many undergraduate chemistry students struggle to understand the concept of stereoisomers, molecules that have the same molecular formula and sequence of bonded atoms but are different in how their atoms are oriented in space. Our goal in this study is to improve stereoisomer instruction by getting participants actively involved in the lesson. Using a pretest-instruction-posttest design, we instructed participants to enact molecule rotation in three ways: (1) by imagining the molecules' movements, (2) by physically moving models of the molecules, or (3) by gesturing the molecules' movements. Because gender differences have been found in students' performance in chemistry (Moss-Racusin et al., 2018), we also disaggregated our effects by gender and examined how men and women responded to each of our 3 types of instruction. Undergraduate students took a pretest on stereoisomers, were randomly assigned to one of the 3 types of instruction in stereoisomers, and then took a posttest. We found that, controlling for pretest performance, both women and men participants made robust improvements after instruction. We end with a discussion of how these findings might inform stereoisomer instruction.

Attitudes towards learning chemistry have been little studied in secondary school students, especially regarding dimensions related to problem solving, the molecular atomic perspective of chemistry, and real-world connection of chemistry. In the present study, we first aimed to design and assess the psychometric properties of the attitude to learning Chemistry instrument (ALChI). A second aim of the study was to assess sex differences and the relation between achievement and attitudes. Participants were 503 secondary school students, from a central southern region of Chile, who answered a 23-item version of the ALChI. The results of the exploratory factor analysis (EFA) revealed that an 18-item scale was most appropriate grouped into four factors: real world connection (RWC), perceived difficulty in problem-solving (PDPS), confidence in problem solving (CPS), and atomic molecular perspective of chemistry (AMPCh). Confirmatory factor analysis (CFA) confirmed the four-factor structure of the model, with optimal fit indexes. Sex factorial invariance was also obtained for configural, metric, and scalar models, demonstrating that ALChI was invariant for sex. Reliability analysis showed moderate to good indices, which suggests good internal consistency of ALChI. On a descriptive level, the highest mean was for the CPS subscale, which entails that students showed a favourable disposition towards their ability to succeed in solving chemistry problems. A structural equation multiple indicators multiple causes (MIMIC) model was conducted to compare factor latent means for sex and assess the relationship between achievement and attitude latent variables. These analyses revealed that achievement was positively associated with all four latent factors. However, no difference by sex was observed across all four factor means. These findings are partially in line with the results from previous studies in more developed countries where attitudes towards chemistry have been consistently linked to academic performance and male students tend to have more positive attitudes than their female counterpart. Our findings are of relevance for researchers, school teachers, and secondary school students since attitudes towards learning chemistry play an important role in choosing a future career path.

Molecular orbital diagrams are commonly taught and used for describing chemical bonding chemistry courses including courses at the college level. Misconceptions that occur when students construct and/or use these diagrams are difficult to anticipate, diminish the diagram utility, and limit student learning. In this exploratory study, a combination of think-aloud activities and written probes was used to identify misconceptions that persist into upper-level college chemistry courses. While the majority of students could properly construct molecular orbital diagrams, many struggled to use and interpret the resulting diagrams. Pronounced disconnects between the depiction of chemical bonds and how these depictions demonstrate molecular properties such as stability and reactivity were observed, informing strategic curricular interventions.

Students commonly develop alternative ideas about topics in science. According to constructivist view of learning, students' alternative conceptions and misconceptions about the process of developing new knowledge should be highlighted. Remedy can be undertaken through conceptual change approach. In order to understand what factors causes 9th grade students to make mistakes in various sub concepts of shape of molecule, qualitative research design was followed. Misconceptions of the students about shape of the molecule were identified and analyzed. Accordingly, plan of action was framed for tackling each of the hard spots found among students. Lack of content information, previous knowledge, instructional approaches, process of assessment, cognitive and meta-cognitive strategies were attributed towards the cause of misconceptions.

Recently there is an increasing need for experiments that can be conducted remotely. In this sense, this paper presents three experiments about materials science and an X-ray diffraction (XRD) technique that can be taught and performed entirely remotely. The first experiment is about the calculation of lattice parameters, atomic radii, and densities of metallic elements with a body-centered cubic (BCC) structure. The second experiment is about the calculation of lattice parameters, axial ratios, unit cell volumes, and densities of yttria-stabilized zirconia (YSZ) solid solutions. The third experiment is about applying the Rietveld refinement technique to distinguish the enantiomers of the pharmaceutical molecule naproxen and determine the hydration degree of commercial naproxen sodium pills. For the first two experiments, students worked with simulated data, whereas for the third one, they worked with experimental data collected and provided by the Instructor. Besides the materials science and XRD concepts, students were introduced to the operation of the free softwares Vesta and GSAS II and to the Crystallography Open Database, a free database for structural data of organic and inorganic compounds. The paper explains the background, goals, and results obtained by the students in each one of the experiments. Detailed information about the experimental procedures and their implementation is complemented by the Supporting Information file and Supporting Videos. Although the experiments were presented in an increasing level of difficulty, they are independent of each other, allowing the instructors to apply them according to their needs and learning objectives.

Atomic/molecular visualization for human sight is usually generated by a software that reproduces a 3D reality on a 2D screen. Although Virtual Reality (VR) software was originally developed for the gaming industry, now it is used in academia for chemistry teaching. This work reviews the scientific literature on 3D visualization in stereoscopic vision, the VR. VR has the capability to simulate reality since we do not observe these real particles, but it reproduces their shapes and movements digitally. The aim of this study is to present the applications of this technology and to show the function of VR in the field of chemistry and the potential for implementation of VR in research and educational settings. The review is based on 219 articles and meeting papers, between 2018 and 2020, obtained from Web of Science (WoS). A series of registers from the WoS repository was analyzed and assigned to three groups, an analysis of 2D support software, analysis of research on Virtual Reality (VR), and research on Virtual Laboratories (VL). The research on advanced atomic/molecular simulation reveals discrepancies regarding the VR effectiveness of Chemistry teaching. Novel Virtual Reality Laboratory (VRL) methodologies are emerging that have a high impact on educational and research scenarios. VL and VRL entail several advantages and drawbacks, such as the implementation of new methodologies, the increase in the students' motivation, the growth of new spaces for collaborative online interaction, and the interaction with physical structure of any impossible, dangerous, or not feasible elements. Finally, the article compares the main features and the learning outcomes of the VRL and the traditional laboratory.

General Chemistry serves virtually all STEM students. It has been accused of covering content in a "mile wide and inch deep" fashion. This has made it very difficult to assess, where chemistry educators have relied on assessments of specific topics. Assessing across all these different topics requires introducing many different chemical systems and contexts, which may pose a threat to validity in the measurement of students' knowledge of general chemistry concepts. With many different systems and contexts, it is possible that students will have varying familiarity, may resort to memorization, or rely on fragments of knowledge to answer. To account for challenges which may arise with different systems and contexts, we have developed an assessment instrument for measuring students' understanding of key concepts from a year-long sequence of general chemistry that relies on a single context: water. The Water Instrument was developed using exploratory sequential design to target eight of the ten anchoring concepts for general chemistry. Psychometric results will be presented from the final pilot administration, where an item response model was used to evaluate the assessment. Further evidence gathered through Response Process Validity interviews will be presented. The evidence gathered indicates this assessment offers a valid and reliable estimate of students' understanding of general chemistry concepts in the context of water, which makes this instrument promising for general chemistry assessment. The comprehensive nature of the assessment can provide rich information to instructors regarding their students' conceptual knowledge of the wide range of topics covered in a year-long sequence of general chemistry.

This perspective paper analyses the possibilities and challenges of using cheminformatics as a context for STEM education. The objective is to produce theoretical insights through a SWOT analysis of an authentic educational cheminformatics project where future chemistry teachers engineered a physical 3D model using cheminformatics software and a 3D printer. In this article, engineering is considered as the connective STEM component binding technology (cheminformatics software and databases), science (molecular visualizations), and mathematics (graph theory) together in a pedagogically meaningful whole. The main conclusion of the analysis is that cheminformatics offers great possibilities for STEM education. It is a solution-centered research field that produces concrete artifacts such as visualizations, software, and databases. This is well-suited to STEM education, enabling an engineering-based approach that ensures students' active and creative roles. The main challenge is a high content knowledge demand, derived from the multidisciplinary nature of cheminformatics. This challenge can be solved via training and collaborative learning environment design. Although the work with educational cheminformatics is still in its infancy, it seems a highly promising context for supporting chemistry learning via STEM education.