<![CDATA[This research were aimed to describe validity and effectiveness of students worksheet based-on guided inquiry at pressure topic, to improve students critical thinking skill. This research used Borg and Gall research and development model which is consisted of the preliminary studies, the development of the products, and testing products. The developing of students worksheet were tested by using the matching only pretest-posttest with control group design which was done in VIIIth grade at MTs Islamiyah Sukoharjo. This research used the instrument of validations expert, students response instrument, and students critical thinking skill test instrument. This research used descriptive analysis. Based-on the result of this research,it can be concluded that the product that has been developed has higly validated and effective in increasing students critical thinking skill.Penelitian ini bertujuan untuk mendeskripsikan kevalidan dan keefektifan LKS berbasis inkuiri terbimbing pada materi tekanan untuk meningkatkan keterampilan berpikir kritis siswa.Penelitian ini menggunakan model penelitian dan pengembangan Borg and Gall yang meliputi: studi pendahuluan, pengembangan produk, dan pengujian produk.LKS hasil pengembangan diujicobakan menggunakan the matching only pretest postest control group design yang dilakukan di kelas VIII MTs Islamiyah Sukoharjo. Penelitian ini menggunakan instrumen validasi ahli, angket respon siswa, dan instrumen tes keterampilan berpikir kritis siswa. Analisis data menggunakan analisis deskriptif. Hasil penelitian disimpulkan bahwa LKS yang dikembangkan memiliki kevalidan yang sangat tinggi dan efektif dalam meningkatkan keterampilan berpikir kritis siswa.Kata kunci: LKS, inkuiri terbimbing, keterampilan berpikir kritis]]>
