The present article discusses research that uses the perspective of the construction of citizenship and the education of the citizen. This standpoint is supported by Edgar Morin and by UNESCO's report on education in the 21st century. To accomplish this task, the importance of a new practice in school in which the student is the centre of the classroom activities is discussed. In the present study the chosen perspective is STS (Science, Technology and Society), which has some significant points in common with Brazilian National Curriculum Standards and ECL (Event Centered Learning). Along with other theories this embraces the contextual discussion of scientific knowledge as a main strategy. In conclusion, a Physics teaching unit for the Fundamental School (8th grade) classroom has been developed, applied and evaluated. It deals with the historical background of the Manhattan Project (1941 - 1945) and includes the topics of nuclear fission, radiation, energy, chemical and biological weapons research and utilization. The approach to these issues is through the use of a problem-situation as suggested by the RPG (Role-Playing Game) therapeutic technique.
didactical unit; Modern Physics and STS (Science, Technology and Society)