Penelitian ini bertujuan untuk menghasilkan Lembar Kegiatan Siswa (LKS) berbasis pendekatan saintifik pada materi perubahan lingkungan untuk melatihkan kemampuan berpikir kritis siswa kelas X SMA yang valid, praktis dan efektif. Penelitian ini menggunakan metode pengembangan Four D Models (define, design, develop dan disseminate), tetapi pada tahap disseminate tidak dilakukan. Lembar Kegiatan Siswa yang dikembangkan diuji cobakan pada 15 siswa kelas X SMA Negeri 1 Gedeg, Mojokerto. Parameter yang diukur adalah kelayakan teoritis ditentukan berdasarkan validasi LKS dengan perolehan skor hasil validasi LKS, kepraktisan LKS ditentukan berdasarkan keterlaksanaan aktivitas siswa dan respon siswa serta keefektifan LKS ditentukan berdasarkan hasil belajar siswa. Data yang diperoleh dianalisis secara deskripstif kuantitatif. Hasil analisis menunjukkan bahwa LKS memperoleh skor validasi sebesar 3,76 dengan kategori sangat valid. Kepraktisan LKS yang ditinjau dari keterlaksanaan aktivitas siswa yang memperoleh persentase 97,16% dan respon siswa memperoleh persentase sebesar 99% dengan kategori sangat praktis. Keefektifan LKS yang ditinjau dari hasil belajar siswa memperoleh persentase 83%.

Kata Kunci : Lembar Kegiatan Siswa, Kemampuan Berpikir Kritis, Perubahan lingkungan, Pendekatan Saintifik

This study aims to product Students Worksheets (LKS) based on scientific approach on the environmental change to train tenth graders’ critical thinking that is valid, practical, and effective. This study used Four D Models (define, design, develop, and disseminate), but disseminate stage was not done. The developed Students Activity Sheet was tested among 15 students of tenth grade at SMA Negeri 1 Gedeg, Mojokerto. The Parameters measured are the Students Worksheets (LKS) validation was determined based on the validation score acquisition, the Students Activity Sheet practicality was determined based on the implementation and students’ response, and the effectiveness of Students Worksheets (LKS) was determined based on students’ learning outcomes. Data were analyzed descriptively quantitative. The analysis result showed that the score of Students Activity Sheet was 3.76 with the very valid category. The Students Activity Sheet practicality in term of its implementation was 97.16% and students’ response was 99% with the very practical category. The effectiveness of the Students Activity Sheet in terms of students’ learning outcomes is 83%.

Keywords : Students Activity Sheet, The Ability of Critical Thinking, The Environmental Change, Scientific Approach