RESEARCH www.rsc.org/cerp | Chemistry Education Research and Practice Student test performances on behavior of gas particles and mismatch of teacher predictions Jia-Chi Liang a , Chin-Cheng Chou b and Mei-Hung Chiu c* Received 4th November 2010, Accepted 12th March 2011 DOI: 10.1039/C1RP90029C The nature and behavior of gas particles are essential concepts in teaching and learning of school chemistry. However, findings about students’ understanding of gas particles  their composition, structure, and interactions involving movement and distribution — revealed that the difficulties students encounter in understanding gas particles vary with age. The purpose of this article is to examine how students responded to six two-tier items in a diagnostic test about the behavior of gas particles in two containers and how teachers predicted students’ test performance. The participants in this study were eighth graders (n = 102), ninth graders (n = 92), and physical science teachers (n = 31) in junior high schools in Taiwan. The results revealed that only a low percentage of students could answer the entire set of six questions correctly, and that the 9th graders outperformed the 8th graders. In addition, we found that students changed their models about gas behavior when the orientation of the apparatus changed, and that they had difficulty using a consistent model to answer all of the questions, especially those questions involving a change of pressure. The results also showed that the physical science teachers could not predict accurately the students’ understanding of the behavior of gas particles because they underestimated the effect of the pressure influencing students’ performance on test items. We conclude that the findings of this study suggested that science teachers could help students build a consistent view of gas particles by focusing on understanding why students would hold inconsistent models in different contexts. Educational implications for promoting students’ and teachers’ better use of models for learning and teaching the submicroscopic are discussed. Keywords: kinetic gas theory, gas particles, models, diagnostic test items, animation Introduction The particulate theory is the basic conceptual framework for the nature of matter in teaching and learning of school chemistry. However, many students of different ages and with different experiences of formal instruction still believe that matter is continuous, not particulate in nature. Not surprisingly, some misconceptions of the particulate nature of matter are deeply rooted and resistant to changesuch as, that molecules are not in constant motion, the particles in a gas are not uniformly distributed, molecules move in gases and liquids but not in solids, and so on (Novick and Nussbaum, 1981; Lee et al., 1993; Chiu, 2007). Generally speaking, students have much difficulty in understanding particulate models and distribution of gas particles. Johnstone (1993) has highlighted the three main components of chemistry teaching since the mid-1960s: the macro, the submicro and the symbolic modes. He further elaborated the three elements that can be thought of as corners of a triangle (Johnstone, 2000). However, “no one form is superior to another, but each one complements the others” (Johnstone, 2000, p.11). These forms of the subject are (a) the macro and tangible: what can be seen, touched and smelt; (b) the submicro: atoms, molecules, ions and structures; and (c) the representational: symbols, formulae, equations, molarity, mathematical manipulation and graphs. According to Johnstone (1993), students are often stuck in the macroscopic mode when they study chemistry; the main reasons for these views are: (1) most science learning and teaching materials are introduced and presented in a macroscopic manner; (2) dynamic representation is not introduced into appropriate topics. In addition, multi- modality of terminologies confuses students. For instance, Haidar and Abraham (1991) claimed that although teachers communicated with students using scientific language, students would not automatically respond to questions using the terminology of particles. Gilbert and Boulter (2000) stated the importance of models and modeling in learning chemistry. Constructing meaningful and runnable mental models is helpful for students to understand how particles function in a submicroscopic world. For more than two decades, studies in simulations or animations for representing the systems of molecules have played important roles in helping students’ visualization of the submicroscopic nature of molecules (i.e., Kozma et al., 2000), but, very few simulations or animations have been used in assessments. Therefore, in this study we intended to explore the possibility of the use of animations to diagnose students’ understanding of gas particles, because we considered that this type of assessment to be crucial in chemistry education. 238 | Chem. Educ. Res. Pract., 2011, 12, 238–250 This journal is © The Royal Society of Chemistry 2011 Downloaded on 27 April 2011 Published on 21 April 2011 on http://pubs.rsc.org | doi:10.1039/C1RP90029C View Online