Penelitian ini bertujuan untuk mendeskripsikan keterlaksanaan, aktivitas peserta didik, keterampilan berpikir kritis, hasil belajar, dan respon peserta didik pada materi laju reaksi. Jenis penelitian ini merupakan penelitian praeksperimen metode deskriptif kuantitatif dengan desain penelitian one group pretest posttest design. Sasaran penelitian ini adalah kelas XI MIA 3 MAN 1 Tuban. Instrumen yang digunakan adalah lembar observasi keterlaksanaan, lembar aktivitas peserta didik, lembar tes keterampilan berpikir kritis, lembar tes hasil belajar, dan angket respon peserta didik. Hasil penelitian menunjukkan (1) rata-rata keterlaksanaan pada pertemuan pertama, kedua dan ketiga sebesar 94,65%, 96,43%, dan 98,96% dengan kriteria sangat baik. (2) Aktivitas peserta didik yang relevan pada pertemuan pertama, kedua, dan ketiga sebesar 86,30%, 88,89% dan 94,46%, aktivitas peserta didik sangat baik karena aktivitas yang relevan lebih tinggi daripada aktivitas yang tidak relevan. (3) Keterampilan berpikir kritis dapat dilatihkan dibuktikan dengan persentase peningkatan N-gain score pada kategori tinggi sebanyak 100%. (4) Hasil belajar peserta didik dalam memahami konsep sangat baik dibuktikan dengan ketuntasan klasikal sebesar 88% dan persentase  peningkatan N-gain score pada ketegori sedang sebanyak 33% dan pada kategori tinggi sebanyak 67%. (5) Respon positif peserta didik sebesar 100% dengan kategori sangat baik.

Kata kunci: Guided Inquiry, Keterampilan Berpikir Kritis, Laju Reaksi

The purpose of this research is implementation, activities of students, critical thinking skills, learning outcomes, and responses of students to the material reaction rate. This type of research is a preexperimental research with quantitative descriptive method with one group pretest posttest design. The target of this research was the XI MIA 3 class MAN 1 Tuban. The instruments used were implementation observation sheets, student activity sheets,critical thinking skills test sheets, learning outcome test sheets, and students response. The results showed (1)the average implementation at the first, second, and third meetings was 94,65%, 96,43%, and 98,96% with very good criteria. (2) Activities of relevant students in the first, second, and third meetings were 86,30%, 88,89%, and 94,46% the activity students was very good because relevant activities were higher than irrelevant activities. (3) Critical thinking skills can be trained as evidenced the percentage of N-gain score increases at high criteria by 100%. (4) The learning result of students in understanding the concept are very well proven by clarity of 88% and the percentage of N-gain score increases in the medium category by 33% and in the high category by 67%. (5) Positive responses of students by 100% with very good categories.

Keywords: Guided Inquiry, Critical Thinking Skills, Reaction Rate