Penelitian ini merupakan penelitian pengembangan dengan menggunakan model pengembangan Borg dan Gall modifikasi Sugiyono. Tahap pengembangan terdiri dari 10 tahap yaitu identifikasi masalah, pengumpulan informasi, desain produk, validasi desain, revisi desain, uji coba produk awal, revisi produk, uji coba pemakaian, revisi produk tahap akhir, dan produksi massal. Namun pada penelitian ini dibatasi sampai langkah ke 7 yaitu revisi produk. Penelitian ini meliputi: 1) Uji kelayakan bahan ajar melalui validasi ahli dan validasi guru IPA; dan 2) Uji coba keterbacaan bahan ajar oleh siswa kelas VII SMP. Hasil penelitian disimpulkan bahwa bahan ajar hasil pengembangan dikategorikan sangat layak digunakan dengan persentase kelayakan gabungan dari validasi ahli dan validasi guru IPA sebesar 82.66 %. Tingkat keterbacaan bahan ajar menunjukkan mayoritas siswa memberikan penilaian positif dengan persentase yaitu (1) ketertarikan terhadap isi buku ajar dengan persentase 100 %, (2) ketertarikan terhadap tampilan buku ajar dengan persentase 100 %, (3) penjelasan dalam buku ajar ini terlalu sulit dengan persentase ada sedikit yang sulit 100 %, (4) kesulitan kata maupun kalimat dengan persentase 100 %, dan (5) gambar buku dengan persentase mudah dipahami 80 % dan sulit dipahami 20 %.

This research is development research used Borg and Gall’s model development modificated by Sugiyono. The development step consists of 10 steps, they are problem identification, information collection, product design, design validation, design revision, preliminary product testing, product revision, trial usage, final product revision, and mass production. But this research is limited in the seventh’s step, it is product revision. This research includes: 1) Expedience test of learning material through expert validation and science teacher validation; and 2) Readability test of learning material by grade VII students of junior hight school. The result of this research concluded that learning material that has been developed was categorized very expediency to be used with the combination expedience percentage from expert and science teacher validation was 82.66 %. Readability test showed that the majority of students gave positive ratings by percentage (1) The percentage of interest in textbook content was 100 % (2) The percentage of interest in textbook appearance was 100 % (3) Explanation in this textbook is too difficult with percentage was a bit difficult 100 % (4) Words or sentences difficulty with percentage 100 %, and (5) The pictures of textbook with 80 % was easy to understand and 20 % was difficult to understand.

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