Clearly defining and clarifying crosscutting concepts (CCCs) helps students to apply them as thinking tools or lenses to understand disciplinary core ideas and science and engineering practices. This study identified three characteristics of the sub-concepts of CCCs: conceptual, superordinate, and common across disciplines, and explored a way based on the 5E instructional model that supports making CCCs explicit. A targeted and coherent unit of "scale" (one of the CCCs) served as an example to introduce the design and implementation of the instructions to externalise CCCs to students. After defining the four sub-concepts of "scale" based on scientific research literature, supportive teaching activities were selected and organised according to the 5E instructional model. There were 65 students (35 boys and 30 girls; 59 students in Grade One and six in Grade Two), who participated for two rounds of a CCCs elective course that we offered. They were all East Asian, aged 15-17, and came from 22 different classes. Most of them had chosen science as the compulsory subject to take the future university entrance exam. Through quantitative and qualitative analyses of students' responses to the paper test, multiple group interviews, and group work, we determined their spontaneous uncertainty, pre-concepts, and prior foundational experiences before entering the unit; identified their process of activating, constructing, and clarifying thinking during the unit; and found their better understanding of the three characteristics of "scale" after the unit. The 5E-based instruction facilitated active learning, conceptual change, and transfer by actively constructing understanding, formalising knowledge, and interrelating disciplines.