Keterampilan berpikir kritis merupakan cara berpikir untuk mengevaluasi secara sistematis pendapat pribadi dengan pendapat orang lain yang digunakan untuk memecahkan sebuah masalah. Keterampilan berpikir kritis siswa disekolah ditingkatkan melalui penggunaan LKS berbasis Contextual Teaching and Learning. LKS berbasis Contextual Teaching and Learning dikembangkan bertujuan untuk memperoleh kelayakan lembar kerja siswa tentang (1) kriteria isi yang ditinjau dari kriteria isi, penyajian, dan bahasa, (2) Peningkatan keterampilan berpikir kritis setelah menggunakan LKS berbasis Contextual Teaching and Learning, dan (3) respon siswa terhadap LKS berbasis Contextual Teaching and Learning. Penelitian dilakukan dengan menggunakan metode penelitian 4-D yang merupakan singkatan dari define, design, develop, dan disseminate. Hasil penelitian menunjukkan bahwa kelayakan teoritis pada LKS berbasis Contextual Teaching and Learning mendapatkan persentase validitas isi sebesar 82,64% dan validitas konstruk sebesar 86,76% dan kelayakan empiris mendapatkan respon sangat positif oleh siswa pada saat menggunakan LKS berbasis Contextual Teaching and Learning. Peningkatan keterampilan berpikir kritis siswa pada materi laju reaksi sub bab faktor-faktor laju reaksi dengan kemampuan kognitif rendah, sedang dan tinggi berturut-turut sebesar 0,588, 0,384, dan 0,612.
Critical thinking skill is a way of thinking to systematically evaluate personal opinions with other opinions and is used to solve a problem. Students critical thinking skill in school was improved through the use of student worksheet based on Contextual Teaching and Learning. The aims of the developed student worksheet based on Contextual Teaching and Learning were to obtain the feasibility of student worksheet about (1) content criteria which consists of content, presentation, and language, (2) Increasing critical thinking skill after using student worksheet based on Contextual Teaching and Learning, and (3) student responses to student worksheet based on Contextual Teaching and Learning. This study used the 4-D research method which stands for define, design, develop, and disseminate. The results showed that the theoretical feasibility of student worksheet based on Contextual Teaching and Learning gained a percentage of content validity by 82.64% and construct validity by 86.76% and empirical feasibility received very positive responses from students for the student worksheet based on Contextual Teaching and Learning based worksheet. The increasing of students critical thinking skill on reaction rates matter sub-chapter of the reaction rate factors with low, medium and high cognitive abilities respectively by 0.588, 0.384, and 0.612.