Iselin Grav Aakre

This paper shows how students’ preferred model of covalent bonding, exemplified by the hydrogen molecule, changes during their first two years of university studies. It analyzes some differences between first-year, second-year, and third-year students and between students who prefer different models. Chemistry students are introduced to several models and theories about chemical bonding and expected to integrate these models into a scientifically appropriate understanding of the topic, use them in constructive ways, and choose the most suitable model for the problem at hand. Research shows that students struggle with this and that even advanced students of chemistry tend to use simple models of chemical bonding, despite having learned more sophisticated models. This study analyzes first-year (N = 321), second-year (N = 221) and third-year (N = 199) chemistry students’ responses to a survey about students’ perceptions of chemical bonding and models of chemical bonding. Most first-year students chose either an octet model or a Lewis structure as their preferred model, while other models, such as a molecular orbital diagram, were popular among second- and third-year students. The study found a link between students’ preferred model and how students explain chemical bonding: Students who preferred different models used different concepts when describing chemical bonding and justified their choice of preferred model differently.

Distrust of science is a societal concern that could be linked to a limited understanding about the nature of science. Scientific models have an essential role as both tools for doing science and for describing and communicating science. This work investigates first-, second- and third-year Norwegian science students’ (N = 757) thoughts about what it means that a model is scientific, and their rating of how scientific different models of chemical bonding are. A review of Norwegian secondary school textbooks (N = 14) shows agreement between the models first-year students claim as familiar, and the models included in textbooks, but models known from school are not rated by first-year students as more scientific than unfamiliar models. Abstract models, such as an MO diagram or a potential energy graph, are rated as highly scientific by all students, regardless of level of familiarity with the model. A thematic analysis of students’ written explanations of what it means that a model is scientific was conducted and resulted in two main themes. The theme “the Truth” describes how students have a high degree of trust in science and what they perceive as scientific models. For the other main theme, “Research”, students more often describe scientific models as a product of science than as a tool for doing science and scientific research. In science education, focusing on scientific models’ role in the process of science could increase students’ understanding of scientific models and the nature of science.

First-year university students’ knowledge and conceptual understanding of general chemistry has been investigated using a multiple-choice concept inventory (Chemical Concept Inventory 3.0/CCI 3.0) as a pre-test (n = 221) and a post-test (n = 90) in two first-semester chemistry courses. This paper discusses the students’ answers to two questions about bond energy. Student interviews (n = 7) were performed for further insight in the students’ thought processes and validation of the CCI questions. Although many students appeared to recall that breaking a chemical bond demands energy, most were not able to use this fact to reason about the heat released in a chemical reaction, and the alternative conception that bond breaking releases energy seemed deeply ingrained and prevalent among the students. For one of the questions, more students gave the correct answer on the pre-test than on the post-test. Student interviews indicated that some students’ failure to pick the correct alternative for this question might be influenced by use of the word “always” in the correct answer, which discouraged those students that find chemistry to be a subject full of exceptions.