Description:
For the phenomena of floating and sinking, although they are parts of everyday students’ experiences, it is not easy for them to construct spontaneously feasible explanatory schemes. The results of educational research show that students hold, regarding to these phenomena, explanatory schemes which are monocausal (floating and sinking are due to only one cause, frequently related to the weight or other property of the body), while scientific explanation is polycuasal (floating and sinking of bodies is due to the relationship between the intensities of two opposite forces: weight of the body and buoyant force of the liquid). In this article we report (1) explanatory schemes sustained by students regarding hydrostatic behavior of small bottle in simple situation (bottle floats in water and sinks in oil) and (2) predictive and explanatory schemes of its hydrostatic behavior in a complex situation (the same bottle in water and oil). Similarly as students of primary and junior-high school, high-school students use basically monocausal schemes and are not able to elaborate polycausal schemes, even in the complex situation. Nevertheless, after they have known the hydrostatic behavior of the bottle in the complex situation, it is possible to note favorable changes in students ideas. These changes, in more sophisticated didactic designs and with major time investment, might be a base for a development toward the schemes which are nearer to explanatory schemes accepted by scientists.