The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
Philip Johnson - One of the best experts on this subject based on the ideXlab platform.
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A learning progression towards understanding Chemical Change
Educación Química, 2013Co-Authors: Philip JohnsonAbstract:Abstract This paper focuses on findings relating to Chemical Change that were part of a wider study exploring students’ understanding of the concept of a substance. Including pilot work, around 6000 students from 45 schools were involved in the project. An instrument using fixed-response items was developed with distracter options based on likely misconceptions reported in the research literature. The possibility of a learning progression was explored using Rasch modelling. Overall, the data show a good ft to the Rasch model and a learning progression towards understanding Chemical Change emerged. The progression is presented and significant implications for the chemistry curriculum are discussed. There is reason to suppose a curriculum better matched to students’ needs as learners could bring improvement in their progress.
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Children's understanding of substances, Part 2: Explaining Chemical Change
International Journal of Science Education, 2002Co-Authors: Philip JohnsonAbstract:Focuses on the idea of Chemical Change and reports data from a study exploring the development of the concept of substance in children aged 11-14. Examines the use of the idea of elements, compounds, and bonding between atoms to explain Chemical Change and the intersection of these ideas with "basic" particle ideas. (Contains 21 references.) (Author/YDS
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Children's understanding of substances, Part 2: Explaining Chemical Change
International Journal of Science Education, 2000Co-Authors: Philip JohnsonAbstract:This is the second part of a paper which focuses on the idea of Chemical Change (see Johnson 2000). The reported data comes from a study which explored the development of children's concept of a substance (ages 11-14). It examines the use of the ideas of elements, compounds and the bonding between atoms to explain Chemical Change and the intersection of these ideas with 'basic' particle ideas. Evidence is presented which suggests that the particle ideas were the means by which the pupils came to acknowledge the phenomenon of Chemical Change, having been unmoved by a macroscopic approach which identified substances by melting and boiling point. Furthermore, a basic particle model in which individual particles still retained the macroscopic properties of the substance was found to inhibit an understanding of Chemical Change. Findings with respect to a burning candle are reported in a separate section. Important implications for teaching are discussed.
Martine Méheut - One of the best experts on this subject based on the ideXlab platform.
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Grade 12 French students' use of a thermodynamic model for predicting the direction of incomplete Chemical Changes
International Journal of Science Education, 2010Co-Authors: Isabelle Kermen, Martine MéheutAbstract:The authors of the current chemistry curriculum -implemented in grade 12 in France- provided a criterion of Change allowing predictions of direction of Chemical Changes and pointed out the difference to be made between experimental facts and models. A study analysing part of the curriculum content and the effects of teaching this content on students' reasoning was conducted. The content analysis presents the functioning of the thermodynamic model which highlights the links to be made between the experimental situation and the model when predicting the direction of a Chemical Change. This functioning specifies the role of the Chemical equation and that of the criterion of Change (comparing the reaction quotient to the equilibrium constant) and stresses the crucial points that may lead to misunderstandings. Written tests were administered to students after teaching to determine how they predicted the direction of a Chemical Change, whether they made a relevant choice between using the Chemical equation and using the criterion of Change and a clear distinction between the experimental situation and the thermodynamic model. Few students had a good understanding of the respective roles of criterion and Chemical equation. A majority used the criterion to predict the direction of Chemical Changes relevantly but correct answers were not widespread. Two particular mistakes, the modification of the expression of the reaction quotient and the prediction of a Change despite a missing reactant revealed that students do not properly understand the difference and the relationships between the experimental situation and the thermodynamic model.
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Grade 12 French Students’ use of a Thermodynamic Model for Predicting the Direction of Incomplete Chemical Changes
International Journal of Science Education, 2010Co-Authors: Isabelle Kermen, Martine MéheutAbstract:The authors of the current chemistry curriculum—implemented in Grade 12 in France—provided a criterion of Change allowing prediction of direction of Chemical Changes and pointed out the difference to be made between experimental facts and models. A study analysing part of the curriculum content and the effects of teaching this content on students’ reasoning was conducted. The content analysis presents the functioning of the thermodynamic model, which highlights the links to be made between the experimental situation and the model when predicting the direction of a Chemical Change. This functioning specifies the role of the Chemical equation and that of the criterion of Change (comparing the reaction quotient to the equilibrium constant) and stresses the crucial points that may lead to misunderstandings. Written tests were administered to students after teaching them to determine how they predicted the direction of a Chemical Change, and whether they made a relevant choice between using the Chemical equati...
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Different models used to interpret Chemical Changes: analysis of a curriculum and its impact on French students' reasoning
Chem. Educ. Res. Pract., 2009Co-Authors: Isabelle Kermen, Martine MéheutAbstract:We present an analysis of the new French curriculum on Chemical Changes describing the underlying models and highlighting their relations to the empirical level. The authors of the curriculum introduced a distinction between the Chemical Change of a Chemical system and the Chemical reactions that account for it. We specify the different roles of the three identified models: a thermodynamic one based on the reaction quotient and the equilibrium constant, a kinetic macroscopic one based on the rates of the opposing reactions, and a kinetic microscopic one. According to our analysis, interpreting the end-point of an incomplete Chemical Change should offer an opportunity to use the three identified models. We have investigated the reason(s) the students (grade 12) gave to explain why a Chemical Change remains incomplete, and whether they used one explanatory model more than another. The two macroscopic models were not used by a majority of students, and no student referred to the microscopic kinetic model. A rather high proportion of students held static conceptions of the equilibrium state. These results are discussed.
Isabelle Kermen - One of the best experts on this subject based on the ideXlab platform.
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Grade 12 French students' use of a thermodynamic model for predicting the direction of incomplete Chemical Changes
International Journal of Science Education, 2010Co-Authors: Isabelle Kermen, Martine MéheutAbstract:The authors of the current chemistry curriculum -implemented in grade 12 in France- provided a criterion of Change allowing predictions of direction of Chemical Changes and pointed out the difference to be made between experimental facts and models. A study analysing part of the curriculum content and the effects of teaching this content on students' reasoning was conducted. The content analysis presents the functioning of the thermodynamic model which highlights the links to be made between the experimental situation and the model when predicting the direction of a Chemical Change. This functioning specifies the role of the Chemical equation and that of the criterion of Change (comparing the reaction quotient to the equilibrium constant) and stresses the crucial points that may lead to misunderstandings. Written tests were administered to students after teaching to determine how they predicted the direction of a Chemical Change, whether they made a relevant choice between using the Chemical equation and using the criterion of Change and a clear distinction between the experimental situation and the thermodynamic model. Few students had a good understanding of the respective roles of criterion and Chemical equation. A majority used the criterion to predict the direction of Chemical Changes relevantly but correct answers were not widespread. Two particular mistakes, the modification of the expression of the reaction quotient and the prediction of a Change despite a missing reactant revealed that students do not properly understand the difference and the relationships between the experimental situation and the thermodynamic model.
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Grade 12 French Students’ use of a Thermodynamic Model for Predicting the Direction of Incomplete Chemical Changes
International Journal of Science Education, 2010Co-Authors: Isabelle Kermen, Martine MéheutAbstract:The authors of the current chemistry curriculum—implemented in Grade 12 in France—provided a criterion of Change allowing prediction of direction of Chemical Changes and pointed out the difference to be made between experimental facts and models. A study analysing part of the curriculum content and the effects of teaching this content on students’ reasoning was conducted. The content analysis presents the functioning of the thermodynamic model, which highlights the links to be made between the experimental situation and the model when predicting the direction of a Chemical Change. This functioning specifies the role of the Chemical equation and that of the criterion of Change (comparing the reaction quotient to the equilibrium constant) and stresses the crucial points that may lead to misunderstandings. Written tests were administered to students after teaching them to determine how they predicted the direction of a Chemical Change, and whether they made a relevant choice between using the Chemical equati...
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Different models used to interpret Chemical Changes: analysis of a curriculum and its impact on French students' reasoning
Chem. Educ. Res. Pract., 2009Co-Authors: Isabelle Kermen, Martine MéheutAbstract:We present an analysis of the new French curriculum on Chemical Changes describing the underlying models and highlighting their relations to the empirical level. The authors of the curriculum introduced a distinction between the Chemical Change of a Chemical system and the Chemical reactions that account for it. We specify the different roles of the three identified models: a thermodynamic one based on the reaction quotient and the equilibrium constant, a kinetic macroscopic one based on the rates of the opposing reactions, and a kinetic microscopic one. According to our analysis, interpreting the end-point of an incomplete Chemical Change should offer an opportunity to use the three identified models. We have investigated the reason(s) the students (grade 12) gave to explain why a Chemical Change remains incomplete, and whether they used one explanatory model more than another. The two macroscopic models were not used by a majority of students, and no student referred to the microscopic kinetic model. A rather high proportion of students held static conceptions of the equilibrium state. These results are discussed.
Hiroshi Uchikawa - One of the best experts on this subject based on the ideXlab platform.
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Chemical Speciation of Trace Zinc in Ordinary Portland Cement Using X-ray Absorption Fine Structure Analysis
Journal of the American Ceramic Society, 2004Co-Authors: Isao Tsuyumoto, Hiroshi UchikawaAbstract:Chemical Change of trace zinc in ordinary portland cement (205.1 ppm) was investigated in hydration process using X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). Intensities of the peaks appearing at the same energy of ZnO in XANES spectra were decreased with cement hydration. The interatomic distances and the coordination numbers of the first and the second shells calculated from EXAFS spectra indicated that ZnO hydrolyzed to zincate ion [Zn(OH)4]2− with cement hydration keeping their fundamental structure of ZnO4 tetrahedra.
Charles W. Anderson - One of the best experts on this subject based on the ideXlab platform.
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Students' conceptions of Chemical Change
Journal of Research in Science Teaching, 1992Co-Authors: Joseph J. Hesse, Charles W. AndersonAbstract:One hundred high school chemistry students who had completed a unit on Chemical Change were given a written instrument in which they were shown three oxidation-reduction reactions and were asked to explain them. Eleven students representing a range of achievement levels were chosen for more intensive clinical interviews in which they explained their responses, evaluated the quality of their responses, and compared them to other hypothetical responses. Interview results revealed that students commonly experienced difficulties at three different epistemological levels: 1. Chemical knowledge. Most students failed to invoke atoms and molecules as explanatory constructs, even though they had been emphasized in their chemistry course. Some students also listed “substances” such as heat, cold, or decay as reactants or products. 2. Conservation reasoning. Many students could not predict or explain mass Changes in the Chemical reactions. Their most common problems included (a) a tendency to treat Chemical Changes such as rusting as physical Changes in form or state, and (b) failure to understand the role of invisible (in this case gaseous) reactants or products in the reactions. 3. Explanatory ideals. Many students demonstrated a preference for explanations based on superficial analogies with everyday events (e.g., rusting is like decay) over explanations based on Chemical theories. Only one of the 11 students interviewed demonstrated mastery of the unit's contents at all three levels. Results of this and other research indicate a need for substantial revision in chemistry teaching practice.