Penelitian ini bertujuan untuk menganalisis keterlaksanaan model pembelajaran guided discovery berbantuan media simulasi PhET untuk meningkatkan hasil belajar siswa pada materi gas ideal kelas XI MIPA di SMA Negeri 2 Nganjuk, menganalisis peningkatan hasil belajarnya, serta menganalisis respon siswa setelah mengikuti pembelajaran tersebut. Penelitian yang dilakukan ialah penelitian pre experimental dengan rancangan one grup pretest-posttest design. Pemilihan sampel menggunakan random sampling dengan cara diundi, sehingga didapatkan sampel kelas XI MIPA 4, XI MIPA 5, serta XI MIPA 7. Metode pengumpulan data menggunakan metode observasi, metode tes, dan metode angket respon siswa. Teknik analisis data menggunakan analisis keterlaksanaan pembelajaran, analisis peningkatan hasil belajar, serta analisis respon siswa. Berdasarkan analisis data disimpulkan: 1) Pembelajaran guided discovery berbantuan media simulasi PhET pada materi gas ideal kelas XI MIPA di SMA Negeri 2 Nganjuk terlaksana dengan sangat baik di ketiga kelas, aktivitas dominan yang dilakukan siswa per 5 menit selama 90 menit di ketiga kelas ialah aktivitas 7 yaitu mengisi LKS sesuai dengan hasil percobaan yang dilakukan dan membuat poster terkait hasil percobaan, selanjutnya aktivitas 6 yaitu melakukan percobaan dengan PhET Gas Properties sesuai dengan panduan LKS, serta aktivitas 4 yaitu membaca LKS, 2) Hasil belajar siswa pada ketiga kelas mengalami peningkatan secara signifikan setelah diterapkan model pembelajaran guided discovery berbantuan media simulasi PhET, dengan nilai <g> pada kelas eksperimen sebesar 0,8095, replikasi 1 sebesar 0,7632, dan replikasi 2 sebesar 0,7451. Ketiga kelas menunjukkan nilai <g> ≥ 0,7, sehingga dapat digolongkan berkategori tinggi, 3) Respon siswa sangat baik pada ketiga kelas baik kelas eksperimen, replikasi 1, serta replikasi 2.

This research aims to analyze the implementation of guided discovery learning model using PhET simulations. More specifically, it aims to analyze student learning outcomes, especially in a lesson about ideal gas, and describe students’ response to the learning model. It is a pre experimental research with one group pretest-posttest design. Using random sampling, students of XI MIPA 4, XI MIPA 5, and XI MIPA 7 were involved. Methods of data collection were observation, test, and students response questionnaire. The data analysis  techique were analysis of implementation of learning, analysis of improvement in learning outcomes, and analysis of student responses. The data analysis reveals that the implementation of guided discovery using PhET simulations: 1) In class XI MIPA 4, 5, and 7 at State Senior High School 2 Nganjuk was successfully carried out. The dominant activities carried out by students per 5 minutes for 90 minutes in all three classes is activity 7 which is filling in the worksheets according to the results of experiments conducted and making posters related to the results of the experiment, then activity 6 which is experimenting with PhET in accordance with worksheets guidelines, as well as activities 4 namely reading worksheets. 2) Student learning outcomes in all the three classes experienced improvement significantly, with the value <g> in the experimental class at 0.8095, replication 1 at 0.7632, and replication 2 at 0.7451. The three classes showed a value of <g> ≥ 0.7, so that it can be classified as high category. 3) The implementation of guided discovery learning using PhET simulations received a very good response in all three classes; experimental class, replication 1, and replication 2.