<![CDATA[Chemical bonding is frequently perceived as an abstract and challenging topic by high school students, often resulting in low chemical literacy and underdeveloped scientific writing skills. Conventional, teacher-centered instruction further exacerbates these issues by limiting opportunities for authentic inquiry and scientific communication. To address this gap, this study aimed to develop, validate, and evaluate the effectiveness of a STEAM-based (Science, Technology, Engineering, Arts, and Mathematics) learning module integrated with Project-Based Learning (PjBL) to enhance chemical literacy and scientific writing skills among senior high school students. The research employed a Research and Development (R&D) design using the 4D model (Define, Design, Develop, Disseminate). Participants included 64 students from two experimental classes (XI C1 and XI D1), 25 students from a control class (XI E1) at SMA Negeri 2 Gianyar, and 36 students from SMA Negeri 1 Jatinom for a limited trial. Data were collected through pretest–posttest assessments of chemical literacy, observation rubrics for scientific writing skills, and student and teacher response questionnaires. Expert validation yielded an average Aiken’s V index of 0.967, indicating high validity in content, language, presentation, and alignment with STEAM–PjBL principles. The limited trial demonstrated high practicality, with readability and usability rates of 92% and 91.23%, respectively. In the main implementation, the module proved highly effective: (1) students’ chemical literacy improved significantly, with a normalized gain (N-Gain) of 0.88 (high category), outperforming the control group (N-Gain = 0.69); and (2) scientific writing skills achieved a mastery level of 91.44% (very good category), with a mean score of 3.66 out of 4. Positive responses from students (90.08%) and teachers (96.87%) confirmed that the STEAM–PjBL module fostered an interactive, contextual, and meaningful learning experience. The findings indicate that the module meets the criteria of validity, practicality, and effectiveness, making it well-suited for implementation in chemistry classrooms particularly within Indonesia’s Merdeka Curriculum framework. This study offers a replicable model for integrating interdisciplinary, student-centered approaches to strengthen both conceptual understanding and scientific communication competencies.]]>
