Ngoh Khang Goh

Bio: Ngoh Khang Goh is an academic researcher from National Institute of Education. The author has contributed to research in topics: Chemistry education & Creativity. The author has an hindex of 10, co-authored 34 publications receiving 557 citations. Previous affiliations of Ngoh Khang Goh include Nanyang Technological University.

Development and application of a two-tier multiple choice diagnostic instrument to assess high school students' understanding of inorganic chemistry qualitative analysis

Abstract: This article describes the development and application of a two-tier multiple choice diagnostic instrument to assess high school students' understanding of inorganic chemistry qualitative analysis. The development of the diagnostic instrument was guided by the framework outlined by Treagust. The instrument was administered to 915 Grade 10 students (15 to 17 years old) from 11 schools after they had learned the theory involved in qualitative analysis and after a series of qualitative analysis practical sessions. The Cronbach alpha reliability of the instrument was .68, the facility indices ranged from .17 to .48, and the discrimination indices ranged from .20 to .53. The study showed that the Grade 10 students had difficulty understanding the reactions involved in the identification of cations and anions, for example, double decomposition reactions, the formation and reaction of complex salts, and thermal decomposition. The findings of the study and literature on practical work were used to develop a qualitative analysis teaching package. © 2002 Wiley Periodicals Inc. J Res Sci Teach 39: 283–301, 2002

The synthesis, structural characterization and biocidal properties of some triorganotin(IV) esters of N-arylidene-ω-amino acids

Abstract: The methods of synthesis, elemental analysis, IR and NMR spectroscopic data and fungicidal activity against Ceratocystis ulmi are reported for a series of triorganotin esters of N-arylidene-ω-amino acids of general formula R 3 SnO-CO(CH 2 ) n N = CHAr (R = Ph, n-Bu; Ar = 2-HOC 6 H 4 , 2-HOC 10 H 6 ; n = 1, 2, 3 and 5). The crystal structures for two of the compounds, tributyltin N-2-hydroxynaphthalidene glycinate (1) and tributyltin N-2-hydroxynaphthalidene-β-alaninate (2), have been determined. Although both of these compounds have a trans-R 3 SnO 2 structure, in compound 1 the carboxylate group is monodentate and the fifth coordination position around the tin atom is taken up by a coordinated phenolic group, whereas in 2 the carboxylate group is bridging. These two examples thus correspond to the two different structures reported for trans-R 3 SnO 2 complexes. Both compounds were found to be active against Ceratocystis ulmi, but there was no significant difference in their levels of biological activity against this particular fungus. Apart from compound 1, the other tributyltin compounds reported are believed to adopt the carboxylate bridging mode shown by compound (2). Crystal data: for 1, crystals monoclinic, space group P2 1 /c, a = 12.9435(11) A, b = 13.5769(10) A, c = 15.7715(12) A, β = 108.919(6)°, Z = 4, R f = 0.046 and R w = 0.058 for 1448 significant reflections; for 2, crystals monoclinic, space group C 2/c, a = 24.588(14) A, b = 9.733(3) A, c = 27.611(12) A, β = 113.49(4)°, Z = 8, R f = 0.053 and R w = 0.069 for 3822 significant reflections.

Linking the Macroscopic, Sub-microscopic and Symbolic Levels: The Case of Inorganic Qualitative Analysis

Abstract: Basic Grade 10 inorganic qualitative analysis in Singapore requires students to carry out procedures using chemicals, apparatus and appropriate techniques for which they record their observations and make inferences based on the observations. As students are assessed mainly on their written observations, they focus on getting the correct results and writing ‘standard’ observations. Thus, many students merely follow instructions given in the worksheet and seldom think about or understand the reactions involved especially in terms of what is occurring in these reactions at the sub-microscopic level. To respond to this situation, the authors first designed the Qualitative Analysis Diagnostic Instrument to identify students’ understanding of the reactions involved in qualitative analysis. Secondly, the authors developed the Qualitative Analysis Teaching Package to help students learn qualitative analysis by facilitating their understanding of the sub-microscopic and symbolic level explanations of the macroscopic level experiences of the procedures and reactions involved, as well as the manipulative, observational and inferential skills and thinking processes required. The diagnostic instrument and teaching package are especially important with the imminent change from the current one-off national practical examination to school-based assessment in 2008 with the focus on manipulative, observational, analytical and planning skills.

The biological activities, chemical stability, metabolism and delivery systems of quercetin: A review

Abstract: Background Quercetin, one of the most well-known flavonoids, has been included in human diet for a long history. The use of quercetin has been widely associated with a great number of health benefits, including antioxidant, anti-inflammatory, antiviral and anticancer as well as the function to ease some cardiovascular diseases (i.e., heart disease, hypertension, and high blood cholesterol). However, poor water solubility, chemical instability and low bioavailability of quercetin greatly limit its applications. Utilization of delivery systems can improve its stability, efficacy and bioavailability. Scope and approach In this review, biological activities, chemical stability, metabolism and toxicity of quercetin and different delivery systems for quercetin were discussed. Key findings and conclusions Quercetin digested in human body (e.g., mouth, small intestine, liver, kidneys) undergoes glucuronidation, sulfation or methylation. During the food processing and storage, many factors such as heat, pH, metal ions, could affect the chemical stability (including oxidation and degradation) of quercetin. Utilization of delivery systems including lipid-based carriers, nanoparticles, inclusion complexes, micelles and conjugates-based encapsulation has the potential to improve both the stability and bioavailability and thus health benefits of quercetin. Each delivery system has its unique advantages and shortcomings, and the specific selection should be based on the application domains. Moreover, the exploration of natural food-grade ingredients as main compositions of delivery systems for quercetin might be required in the future.

Chemical education: towards research-based practice

Abstract: Acknowledgements. General Preface J.K. Gilbert, O. de Jong, R. Justi, D.F. Treagust. J.H. van Driel. Foreword D. Gabel. A: Chemistry and Chemical Education. Preface to Section A J.K. Gilbert. 1. The Nature of Chemical Knowledge and Chemical Education S. Erduran, E. Scerri. 2. The History of Chemistry: Potential and Actual Contributions to Chemical Education J.H. Wandersee, P.B. Griffard. 3. Models and Modelling in Chemical Education R. Justi, J.K. Gilbert. 4. Learning Chemistry in a Laboratory Environment M.B. Nakhleh, J. Polles, E. Malina. B: The Curriculum for Chemical Education. Preface to Section B. 5. Chemical Curricula for General Education: Analysis and Elements of a Design W. de Vos, A.M.W. Bulte, A. Pilot. 6. The Roles of Chemistry in Vocational Education D. Corrigan, P. Fensham. 7. Informal Chemical Education S. Stocklmayer, J.K. Gilbert. 8. Context-based Approaches to the Teaching of Chemistry: What are They and What are Their Effects? J. Bennett, J. Holman. C: Teaching and Learning about Chemical Compounds. Preface to Section C D.F. Treagust. 9. The Particulate Nature of Matter: Challenges in Understanding in the Submicroscopic World A.G. Harrison, D.F. Treagust. 10. Bonding K.S. Taber, R.K. Coll. 11. Prblem-Solving in Chemistry G.M. Bodner, J.D. Heron. D: Teaching and Learning about Chemical Change. Preface to Section D R. Justi. 12. The Teaching and Learning of Chemical Equilibrium J.H. van Driel, W. Graber. 13. Teaching and Learning Chemical Kinetics R. Justi. 14. The Teaching and Learning of Electrochemistry O. de Jong, D.F. Treagust. 15. From Chemical Energetics to Chemical Thermodynamics M.J. Goedhart, W. Kaper. E: Developing Teachers and Chemical Education. Preface to Section E O. de Jong. 16. Exploring Chemistry Teacher's Knowledge Base O. de Jong, W.R. Veal, J.H. van Driel. 17. Research and Development for the Future of Chemical Education J.K. Gilbert, O. de Jong, R. Justi, D.F. Treagust, J.H. van Driel. Notes about the Contributors. Index.