This study aims to produce an acid-base modulebased on a scientific approach with prompting and probing techniquesdetermine the level of validity, practicality and effectiveness of the module.This research includes development research withusing the Plomp development model which has threestages, namely the preliminary research phase,prototyping phase and stageassessment (assessment phase). At the prototype stageconducted self evaluation (self evaluation), expert judgment (expertreview), individual evaluation (one-to-one evaluation), evaluationsmall group (small group evaluation), while the assessment stageconducted through a field test (field test) in schools, namely SMAN1Painan. The research instrument used was a deep questionnairevalidity and practicality sheet form, objective form questions anda matter of critical thinking. The results of the module validitytest conducted bysix validators with a mean of 0.89, practicality by the teacheran average of 0.94 and practicality by students in small groupswith an average of 0.90 with a very high level of validity. ResultHypothesis test showed a significant difference between the resultslearning experimental and control classes at school does not existsignificant differences in school with student abilitiesThe low one. Hypothesis test results show the differencesignificant between the critical thinking skills of the experimental class andcontrol.

Keywords : Module, Acid-Base, Scientific Approach, Engineering, Probing Prompting, Critical Thinking, Modeling, Plomp Development.