This article presents a study that involves related concepts to complexometric titration, an application method of inorganic analysis, using the framework of a pedagogical technique called Levels of Openness of Inquiry, based on a form of active learning that emphasizes questioning, data analysis, and critical thinking. The purpose of this study was to develop higher cognitive processes in which students do something fairly complex with what they are learning, from knowledge, understanding and application to the analysis, synthesis and evaluation of related information with processes of various types of analytical methods. The laboratory practice used was the complexometric determination of copper and zinc in a falsified sample practice (spiked) of brass. The use of falsified samples offers a good variant in the teaching of complexometric titration processes. Thus, this writing offers teachers a proposal of didactic intervention that combines Levels of Openness, cooperative learning and falsified samples designed to teach neglected topics in this area. It also offers students the opportunity to transform a signifier into signified. This study shows favorable results to the learning process in a group of in service teachers involved in a Master program in chemistry teaching at Pedagogica Nacional University in Bogota.