What type of experimental activities do first year Physical Science teachers carry out in the classroom and to what extent do they contribute to the construction of scientific knowledge? The work is framed in the identification of the didactic relations between the experimental activities proposed by Physical Science teachers and the construction of scientific knowledge, by means of the analysis of some experimental activities carried out by first year Physical Science teachers in a High School. It is also proposed to categorize these activities according to the typologies proposed by R. Porlán, to relate them to the reasons that lead to their approach and to determine to what extent they contribute to the construction of scientific knowledge. This is a qualitative case study; an ethnographic research, with a Historical-Hermeneutic Approach.