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The purpose of this study is to develop a performance assessment instrument with a valid, reliable, effective, and feasible scientific approach on the bomb calorimeter practicum. This research used Research and Development (R & D) method. Data collection in this research used observation method, questionnaire and documentation. The data of the research were analyzed using the quantitative descriptive analysis method. The result of research instrument of performance with scientific approach consisted of using tool, observing, writing observation data and analyzing observation data were valid with the mean of validation score of instrument design equals to 71,67% and instrument evaluation equals to 87,5%. The result of the performance assessment instrument is also reliable with reliability rating of each rater is 0.93. The performance appraisal instrument was declared effective with the percentage of assessment difference of 1.11%. Based on the result of the research, the performance appraisal instrument was also declared very feasible with the user response percentage of 86.93%. Iit can be concluded that the performance appraisal instrument is valid, reliable, effective and very feasible so that it can be used to measure student performance ability in bomb calorimeter practicum.