Papers by Shahidul Islam Khandaker
Chemistry Education Research and Practice, 2007
Novices often lack the descriptive knowledge of phenomena that is the basis for an expert's inter... more Novices often lack the descriptive knowledge of phenomena that is the basis for an expert's interpretation of scientific concepts. Such lack of knowledge may lead to poor conceptual understanding, and misinterpretation of these concepts. Lecture demonstrations can provide essential experiences that serve as a context for discussion of over-generalized or oversimplified concepts. The design of such demonstrations starts from surveying the limited knowledge base of the student, followed by exploration of the richness of relevant contexts of the expert, and identifying key instances that can serve as meaningful discussion topics. An example of the design of a demonstration set for teaching solvent miscibility and its relation to intermolecular interactions is given, followed by results of its application in two different presentation modes: confrontation (aims at generating a conflict with existing conceptions) and refinement (aims at promoting differentiation and contextualization of scientific concepts). The students' involvement in peer discussion, associated with these demonstrations, is evaluated by considering the distribution of students' predictions. [Chem.
Key Points Lecture demonstrations Refinement of concepts Solvent miscibility Lecture demonstr... more Key Points Lecture demonstrations Refinement of concepts Solvent miscibility Lecture demonstrations These over-generalization and over-simplification are the misconception.
Table 3.1. Weight of crude caffeine Weight of 5 tea bags 2.20g×5= 11g Weight of crude caffeine 0.... more Table 3.1. Weight of crude caffeine Weight of 5 tea bags 2.20g×5= 11g Weight of crude caffeine 0.35g Percentage of yield = Mass of crude caffeine / mass of tea bags x 100% = 0.35g / 11g × 100% = 3.2 % Low molecular weight of tannin is soluble in organic solvent and it makes isolation of caffeine more difficult. Tannin contains hydroxyl group that can form ester bond with gallic acid in which the ester bond can be easily cleaved. Initially, some sodium carbonate was
Dedicated To My parents ACKNOWLEDGEMENT All thanks and my deepest sense of gratitude is to The Al... more Dedicated To My parents ACKNOWLEDGEMENT All thanks and my deepest sense of gratitude is to The Almighty Allah who enables me to do this work properly. It is my privilege to be able to express my deepest sense of gratitude and sincere appreciation to my reverend teacher and supervisor Mr. Md. Azharul Arafath, Assistant Professor, Dept. of Chemistry, SUST, Sylhet, for his keen interest, constructive criticism, constant motivation and caring have been indispensable factors in the successful completion of my venture. I would like to acknowledge and express my obligation to Professor Dr. Syed Shamsul Alam , Ex-Head, Dept. of Chemistry, SUST, Sylhet, for providing the necessary infrastructure and all the facilities required to carry out this work. I would to extend my thanks to all of the teachers of the Dept. of Chemistry, SUST, Sylhet, for their hearty cooperation and suggestion during the working and submission period of this research project. I would like to give special and cordial thanks to my friends and senior research students who helped me throughout the research work and in the preparation of paper. I express my deepest sense of gratitude to my beloved parents, family members and relatives for their immeasurable sacrifice, blessing and longstanding encouragement that leads to all my success in study and other fields.
Caffeine has the chemical elements carbon, hydrogen, and oxygen and nitrogen in its structure. It... more Caffeine has the chemical elements carbon, hydrogen, and oxygen and nitrogen in its structure. It has a bitter taste and soluble in water and organic solvents. It is a white crystalline xanthine alkaloid and psychoactive stimulant.
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Papers by Shahidul Islam Khandaker