Abstract: The research objectives was to produce a Structured Assignment Sheet based on Three Scientific Questions (SAS-3SQ) in sub material factors affecting reaction rate, which was feasible to use. The feasibility were validity, practicality, effectiveness. The method used in this research was R&D. To determine whether SAS-3SQ was feasible to use on validity, practicality, and effectiveness criteria, a limited trial was conducted. SAS-3SQ tested in 15 students of 11th grade respondents at SMAN 2 Lamongan. The validation data obtained from 3 validators were analyzed by using expert judgment.