Victoria Peak College, Hong Kong, China

Abstract: Chemistry education at the junior secondary level often faces the challenge that students struggle to connect macroscopic phenomena with microscopic explanations and symbolic representations, leading to rote memorization rather than conceptual understanding. This study proposes a Contextualized Triple-Representation (CTR) instructional design model that integrates Johnstone's three levels of chemical representation—macroscopic, submicroscopic, and symbolic—with authentic local contexts relevant to Hong Kong students' daily lives. The model was implemented in a Secondary 3 "Acids and Bases" unit at Victoria Peak College, with two intact classes (n=78) serving as experimental and control groups over an 8-week period. The experimental group received CTR-based instruction, while the control group followed traditional textbook-based teaching. Quantitative data from pre- and post-tests, conceptual understanding assessments, and attitude surveys were collected, supplemented by qualitative data from classroom observations and student interviews. Results indicate that the experimental group demonstrated significantly greater improvement in both academic achievement (t=4.23, p<.001) and conceptual understanding (t=5.17, p<.001), particularly in the ability to translate across the three representational levels. Students in the experimental group also showed more positive attitudes toward chemistry learning and greater ability to apply chemical knowledge to real-world situations. The study suggests that contextualizing triple-representation learning within familiar local contexts can effectively reduce the abstractness of chemistry concepts and promote deeper, more meaningful learning for junior secondary students. Practical implications for frontline chemistry teachers in Hong Kong are discussed, along with suggestions for future research incorporating emerging educational technologies.

Keywords: triple representation; contextualized learning; junior secondary chemistry; acids and bases; instructional design; Hong Kong