This paper aims at exploring prospective physics teachers' reasoning associated with the concepts of reference frame, time and event which form the framework of the classical kinematics and that of the relativistic kinematics. About 100 prospective physics teachers were surveyed by means of a questionnaire involving classical kinematics situations and relativistic ones. The analysis of the answers shows a deep lack of understanding of both concepts of reference frame and event. Some students think that events may be simultaneous for an observer and not simultaneous for another one, even when both observers are located in the same reference frame. Most of the students surveyed cannot give an answer only depending on the location of the observer when his/her velocity is mentioned as if the movement contaminated the event. This lack of understanding is embodied in reasoning implemented by the population surveyed to address classical kinematics questions and seems to form a major obstacle to grasping relativistic kinematics.
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.
Learning chemistry includes learning the language of chemistry (names, formulae, symbols, and chemical equations) which has to be done in connection with the other areas of chemical knowledge. In this study we investigate how French students understand and use names (of chemical species and common mixtures) and chemical formulae. We set a paper and pencil test composed of open-ended and multiple choice questions (5 questions in total) to students (N= 603) who have been learning chemistry for 2 years (age 14) and others for up to 7 years (age 19, first year university). For all grade levels we found that the students have great difficulties understanding notions introduced right from the first two years of chemistry teaching. The scientific name opposed to a common name does not seem to be a relevant tool used by the students to classify chemical species and mixtures. They struggle to decode a chemical formula out of the context of a chemical equation and fail to decode them in that context. The students surveyed are not able to correctly associate with a name or a formula, both macroscopic (a pure substance or a mixture) and microscopic (an atom or a molecule) criteria. They seem to have mainly a microscopic reading of the names and the chemical formulae. Therefore we think that the language of chemistry could be a source of trouble for the learning of the notion of substance. These results confirm the need to offer teachers new didactical tools to develop the teaching of the language of chemistry.
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