Étude des conceptions alternatives et des processus de raisonnement des étudiants de chimie du niveau collégial sur la molécule, la polarité et les phénomènes macroscopiques

The difficulties found in learning Chemistry are mostly ascribed to the fact that it comprises many complex and counter-intuitive concepts. But beyond these epistemological challenges, learning chemistry can be in jeopardy when it relies on learners’ unstable foundations mixed with alternative conceptions. Alternative conceptions are tacit internal representations that students hold in disagreement with scientifically accepted theories. The presence of alternative conceptions in students’ minds might harm their conceptual understanding leading them to wrongly explain the behaviour of matter and to make incorrect predictions in chemistry. Alternative conceptions are recognised as widespread and difficult to identify in a traditional educational setting. Many alternative conceptions in chemistry have been identified by different groups of researchers in international settings, but such an operation has never been carried out with Quebec college students. As Quebec’s post-secondary education system represents a unique context, a study of the particular difficulties of students in this system was necessary to draw an accurate picture of the situation. Furthermore, researchers presently suggest not only to list such alternative conceptions, but also to explore by what processes they lead to wrong predictions or explanations. Researchers indeed argue that mere lists of alternative conceptions cannot be easily used by teachers, who should be the target audience for these results if they are to take into account alternative conceptions in their teaching. However, no satisfactory typology of reasoning processes and alternative conceptions in chemistry exists today in the research literature. Several researchers in chemistry education suggest that such a typology is needed and should render explicit the reasoning processes involving these alternative conceptions. Explicitation of the reasoning used by the students while performing a task in chemistry would be the way to identify the alternative conception on which this reasoning is based.  Reasoning is viewed as the process that proceeds from implicit ideas to explicit answers. Not all wrong answers in chemistry come from alternative conceptions: some come from a lack of knowledge, other from logical errors. Since all types of wrong answers from students are problematic during teaching, it is relevant to consider them all. Thus, these concerns have inspired the following research question:  What alternative conceptions and modes of reasoning lead students to make poor predictions in chemistry or to give wrong explanations of the behavior of matter?  This doctoral research was conducted to provide an answer to this question. In total, 2,413 students enrolled in Science programmes in Québec’s college (postsecondary pre-university) system were involved in this research, which was divided into three phases: preliminary phase, pilot phase and main phase. Clinical interviews were conducted in the preliminary phase to explore chemistry students’ alternative conceptions. During the pilot phase, multiple-choice questions with open-ended justification were used to delimit the chemistry topics to be studied and to highlight ways of reasoning that students use. The main phase, for its part, used the two-tier “Molecules, Polarity and Phenomena” questionnaire (MPP) developed specifically for this research. The questionnaire was distributed to students via an adaptation of the Consol Web platform, developed by the research group of the principal investigator of this doctoral study. The results show that Science students hold several alternative designs, some of which are quite widespread among the population. In particular, a high proportion of students believe that evaporation causes the breaking of covalent bonds of the molecules (61.1 %), that all atom groups are molecules (78.9 %) and that atoms have similar macroscopic properties as the element (66.0 %). On the other hand, not all bad answers in the MPP show alternative conceptions. Some of them are rather explained by a deficiency in prior knowledge (for example, when students show a lack of knowledge of common chemical elements, 21.8 %) or an incomplete logical reasoning (when they believe the mere possession of polar bonds necessarily makes a molecule polar, which is observed in 24.1% of them). Alternative conceptions and reasoning that lead to incorrect answers are found among first-year and second-year students in the Science program, in some cases with decreasing frequency between the two years, and in others, at the same frequency in both subpopulations. These results mitigate the statement generally found in the research literature, that alternative conceptions are resistant to traditional teaching: according to the results of this research, some of them seem to actually be resolved through such a teaching context. The fact remains, however, that several alternative conceptions, deficiencies in basic prior knowledge and reasoning errors have been highlighted by this research. These learning problems lead college students to make incorrect predictions about the behaviour of matter, or to explain this behaviour incorrectly. In view of these results, a reflection on the teaching of chemistry at the college level, placing a greater emphasis on conceptual thinking and the use of reasoning for the prediction and explanation of the studied phenomena, should be considered.

Keyphrases: Alternative conceptions, Reasoning in science, Chemistry education, Post-secondary education