Compulsory Secondary Education students explanations regarding phenomena related to the volume of liquid moved by a immersed solid, to the density and to the buoyancy

Abstract

This paper presents a diagnosis of the explanations that the students give regarding the volume of fluid that moves an immersed solid and regarding the relationship between buoyancy of objects and its density. The study sets out with students from fourth year of Compulsory Secondary Education (ESO) at the beginning of the school year. In this respect, the knowledge of concepts displaced liquid volume and density are a pre-requisite for understanding phenomena studied during the school year (value of thrust and balance between weight and thrust forces to justify the buoyancy of objects). Results indicate that students reach this level with conceptions of the variables that influence the volume of displaced liquid that are similar to those of primary school children ones. The context-sensitive explanations show that students do not always apply the densities comparison criterion to explain the buoyancy of a solid in a liquid. These difficulties are all the greater in the case of buoyancy-immersion of a submarine, as a solid that is able to vary its average density.