Genre and technicality in analogical explanations: Hong Kong's English language textbooks for junior secondary science

•Popular textbooks differed in their use of image and text in a water flow analogy.•All the textbooks used both text and image but only one included an explanation.•Only one textbook modelled the construction of technicality in text.•Books without an explanation text were less able to convey sequence or cause.•Other genres and images presented a more static, component-oriented perspective.

This paper examines how a core topic from junior secondary science, the use of analogy to teach the electric circuit, is presented in three English-language textbooks commonly used in Hong Kong's schools. Tools from systemic functional linguistics and semiotics were used in consultation with a science education specialist to compare the books' treatment of the topic. The analysis considered four interlocking aspects: genre, the use of the analogy to introduce the target knowledge, the construction of scientific knowledge in language, and the relations between the language and associated images. Differences were found in all these areas, with textbooks varying in how much support they gave students in the construction of technical knowledge. A key difference was the use of explanation versus procedure and/or report genres, resulting in a focus on the workings versus the components of the electric circuit. The books also varied in the role of the analogy in the construction of technicality, and in the extent to which they relied on images to convey meaning. These differences suggest that in some cases the teacher may need to provide additional support to make the textbook material accessible to students.