The purpose of this study is to produce a science learning tool with a valid, practical, and effective guided inquiry model. The subjects of the study were 8th grade students at SMPN 1 Martapura Timur. The development model used is the Tessmer model, which includes: 1) self-evaluation, 2) expert test, 3) individual test, 4) small group test and 5) field test. Descriptive quantitative research methods. The research subjects consisted of three individual student trial subjects, 12 small group test subjects. Subjects of the field test students were 30 students. Determination of research subjects in a purposive manner, namely students who have high, medium, and low academic ability. The results showed that the science learning tools were valid, practical and effective. Validation is shown from the results of the validation of 3 experts categorized as very valid and the test readability of teaching materials and worksheets by students who are categorized very well. Practically used because partner teachers are able to carry out learning activities. Effectively used based on the observed parameters namely 1) learning achievement test with 77% completeness, 2) students' critical thinking skills (analysis and drawing conclusions) are very good, while (interpretation, evaluation, explanation and independence) are good, 3) participant psychomotor skills very good students, 4) the behavior of students' characteristics (thorough and responsibility) on average is very good, 5) the social skills of students (working together and contributing ideas) on average are very good and the results of spiritual attitudes towards gratitude are very good categorized . The conclusion is that the learning tools developed meet the valid, practical and effective criteria.