<![CDATA[ABSTRAK Penelitian ini memiliki tujuan untuk meningkatkan aktivitas belajar dan kemampuan berpikir kritis siswa kelas X dalam pembelajaran kimia melalui model problem based learning (PBL). Dilaksanakan pada Februari - Maret 2023 sebanyak tiga siklus dengan tahapan penelitian ini yaitu: 1) perencanaan, 2) pelaksanaan dan observasi, 3) refleksi. Jumlah sampel penelitian adalah 32 siswa. Metode pengumpulan data meliputi penggunaan lembar observasi untuk memperoleh informasi aktivitas belajar siswa dan tes essay untuk mengumpulkan data kemampuan berpikir kritis siswa. Teknik deskriptif kualitatif dan kuantitatif dijadikan teknik untuk analisis data. Berdasarkan hasil penelitian, aktivitas belajar siswa meningkat dengan rata-rata siklus I sebesar 69%, siklus II sebesar 75%, dan siklus III sebesar 82%. Setiap siklus diperoleh kemampuan berpikir kritis siswa yang mencapai 50,05% pada siklus I, 61,67% pada siklus II, dan 66,49% pada siklus III. Menurut temuan, penggunaan model PBL pada pembelajaran kimia mendorong peningkatan aktivitas siswa dan keterampilan berfikir kritis dalam kegiatan pembelajaran abad ke-21. Kata kunci: aktivitas belajar, keterampilan berfikir kritis, pembelajaran abad ke-21, problem based learning ABSTRACT The reasearch are aimed at recognizing increased learning activities and critical thought capabilities of high school x - school students on chemical learning using the problem based learning model. The study is conducted as many as three cycles with the stages of planning, execution, observation, and reflection. Research time was carried out in February - March 2023. There were 32 students in the study samples. Data gathering techniques through test instruments learn to pick up data of students' critical thinking skill sand observation sheets to pick up data of students' learning activities. Data analysis uses qualitative and quantitative descriptive techniques. Research shows that there is an increase in student learning activity with a 69% average percentage of the I cycles, 75% of the II and 82% of the cycle III. Whereas whereas the attainment of critical thinking skills of the students at 50.05% of the I cycles, 61.67% of the cycles, and the III's 66.49%. This data shows that there has been an improvement in critical thinking skills and student learning activities at 21st-century learning using problem based learning models in chemical subjects. Keywords: Learning activities, Chritical thinking skill, 21st century, problem based learning]]>
