Penelitian ini bertujuan mengetahui keterampilan berpikir kritis siswa melalui penerapan model pembelajaran Guided Inquiry dengan pendekatan Nested pada materi laju reaksi. Penelitian dilakukan di SMA Negeri 19 Surabaya. Instrumen yang digunakan dalam penelitian ini adalah lembar observasi keterlaksanaan model pembelajaran, observasi  aktivitas siswa, pretest dan posttest keterampilan berpikir kritis maupun hasi belajar, dan angket respon siswa. Dapat disimpulkan bahwa (1) Penerapan Keterlaksanaan model pembelajaran Guided Inquiry selama 4 kali pertemuan, memiliki persentase sebesar 96,42% ; 97,62%  ; 98,81% ; 100% yang berarti berada dalam kategori sangat baik. (2) Keterampilan berpikir kritis siswa meningkat dari pretest ke posttest ditunjukan dengan sebanyak 94,28% siswa tuntas pada komponen interpretasi, 94,28% pada komponen analisis, 97,14% pada komponen inferensi, dan sebanyak  97,14%.  (3) Hasil belajar siswa meningkat dari pretest ke posttest  ditunjukkan dengan rata-rata nilai posttest 89,71 dan secara klasikal 31 siswa tuntas atau 88,57. (4) Respon siswa diperoleh 98,73% untuk penerapan model pembelajaran Guided Inquiry dengan pendekatan  Nested.

Kata kunci : Guided Inquiry, Nested, Laju Reaksi, Keterampilan Berpikir Kritis, Hasil Belajar.

This study aims to determine students' critical thinking skills through the application of Guided Inquiry learning models with a Nested approach to material reaction rates. The study was conducted at Surabaya State High School 19 with one group pretest-poesttest design. The instruments used in this study were the observation sheet of the implementation of the learning model, observation of student activities, pretest and posttest of critical thinking skills and learning outcomes, and student response questionnaires. It can be concluded that (1) Implementation of Implementation Guided Inquiry learning model for 4 meetings has a percentage of 96.42%; 97.62%; 98.81%; 100% which means it is in a very good category. (2) The students' critical thinking skills increased from pretest to posttest indicated by 94.28% of students completed the interpretation component, 94.28% in the analysis component, 97.14% in the inference component, and 97.14%. (3) Student learning outcomes increase from pretest to posttest indicated by the average posttest value 89.71 and classically 31 students complete or 88.57. (4) Student responses obtained 98.73% for the application of the Guided Inquiry learning model with the Nested approach.

Keywords: Guided Inquiry, Nested, Reaction Rate, Critical Thinking Skills, Learning Outcomes.