<![CDATA[Science process skills (SPS) are a key component of chemistry learning under the Kurikulum Merdeka, yet classroom assessment in chemistry still emphasizes knowledge over skills, and systematically designed SPS test instruments remain limited particularly for the reaction rate topic, which is closely tied to scientific inquiry activities. This gap is widened by the limited integration of expert validation with empirical Rasch Model analysis in developing SPS instruments for this topic, making the development of a valid, practical, and reliable instrument an important undertaking. This study is a development research project aimed at producing a valid, practical, and reliable Science Process Skills (SPS) test instrument covering the topic of reaction rates. The instrument was developed using the Plomp model, which comprises the preliminary investigation, design, realization/construction, test/evaluation/revision, and implementation phases. The developed instrument consists of multiple-choice questions with five answer options covering science process skill indicators. Field testing was conducted with students from class XI MK 1 at SMA Negeri 10 Gowa. Data were collected via expert validation sheets, teacher and student response questionnaires, and student test results. Data analysis was performed using descriptive methods and the Rasch Model. The results indicate that the developed SPS test instrument was confirmed valid based on expert judgment, reliable based on both theoretical and empirical consistency analyses, and practical based on highly positive teacher responses regarding its ease of use. Consequently, the developed SPS test instrument for the reaction rate topic satisfies the requirements for validity, reliability, and practicality, making it suitable for measuring students' science process skills. ABSTRAK Keterampilan proses sains (KPS) merupakan aspek penting dalam pembelajaran kimia pada Kurikulum Merdeka, namun penilaian pembelajaran kimia di sekolah masih lebih menitikberatkan pada aspek pengetahuan, sementara instrumen tes yang secara sistematis mengukur KPS masih terbatas, khususnya pada materi laju reaksi yang sarat aktivitas ilmiah. Kesenjangan ini diperbesar oleh belum terintegrasinya validasi ahli dengan analisis empiris berbasis Model Rasch pada pengembangan instrumen KPS materi tersebut, sehingga pengembangan instrumen yang valid, praktis, dan reliabel menjadi penting untuk dilakukan. Penelitian ini merupakan penelitian pengembangan yang bertujuan menghasilkan instrumen tes keterampilan proses sains (KPS) pada materi laju reaksi yang valid, praktis, dan reliabel. Pengembangan instrumen menggunakan model Plomp yang meliputi fase investigasi awal, fase desain, fase realisasi atau konstruksi, fase tes, evaluasi dan revisi, serta fase implementasi. Instrumen yang dikembangkan berupa butir soal pilihan ganda dengan lima alternatif jawaban yang meliputi indikator keterampilan proses sains. Uji coba dilakukan pada peserta didik kelas XI MK 1 SMA Negeri 10 Gowa. Data penelitian diperoleh melalui lembar validasi ahli, angket respons guru dan peserta didik, serta hasil tes peserta didik. Analisis data dilakukan secara deskriptif dan menggunakan Model Rasch. Hasil penelitian menunjukkan bahwa instrumen tes keterampilan proses sains yang dikembangkan dinyatakan valid berdasarkan penilaian ahli, reliabel berdasarkan analisis konsistensi teoretis maupun empiris, serta praktis berdasarkan respons guru yang sangat positif terhadap kemudahan penggunaannya. Dengan demikian, instrumen tes keterampilan proses sains pada materi laju reaksi yang telah dikembangkan telah memenuhi aspek kevalidan, reliabilitas, dan kepraktisan yang layak digunakan sebagai alat ukur keterampilan proses sains peserta didik.]]>
