Abstract:

In the everyday discourse inferring can be treated as the act of thought by which we pass from one set of propositions or statements to another. Inferring, from a pupils’ point of view, has been studied, initially, by Piaget and nowadays is examined in cognitive science. The formation of concepts is related with induction and deduction. Moreover, inferring is related to the construction and evolution of mental models. Children’s reasoning in science lessons has also been studied and their reasoning patterns are compared with the relevant ones in scientific disciplines and with the analogues in the history of science. The suggestions of such studies in teaching and learning processes have been tested through curricula addressed to different grades of education or different subjects. Scaffolding students’ inferring can occur either by modeling, by structuring activity, or by coaching—supporting and guiding students’ work.

In this study we present the framework and the choices aiming to facilitate students’ inferring to a scientifically acceptable conclusion about the pH indicators coloring agents of acids/bases solutions, starting from macroscopic observations. Students had already known that when dissolved in water, the strong acid hydrogen chloride forms hydrogen and chloride ions and similarly the strong base sodium hydroxide decomposes into hydroxide and sodium ions, according to Arrhenius theory. They had also learned that acids and bases solutions change the color of pH indicators.

In accordance with this previous knowledge, we designed stages of syllogism aiming to drive students to discern the agents responsible for color change of pH indicators from other possible ones. Students were guided to carry out an experiment in order to reach the scientifically accepted conclusion according to school chemistry framework that refers to the microscopic characteristics of acids and bases: the properties of acids and bases were correspondingly attributed to the hydrogen cations and the hydroxyl anions.

Moreover, through these stages we aimed to facilitate the transfer of knowledge and skills form the chapter of electricity (current, conductivity of solids or liquids, etc) which is taught at the same time of teaching pH indicators.
Students recorded their observations in the worksheet as well as they answered to the guided questions. After scaffolding students’ inferring at the micro level of acids and bases solutions, the constructed knowledge connected with real world phenomena. The procedure was completed with the necessary review and the evaluation of the students’ performance. This teaching plan was applied to 47 Greek students of 9th grade of secondary education. The first good impression promises positive results in a future application with a large sample of students.

References
Kinraide, T. B., and Denison, R. F. Strong Inference: The Way of Science, American Biology Teacher, 2003, 65, 19-424.
Polman, J., and Pea, D. R. Scaffolding Science Inquiry through transformative Communication, NARST Annual Meeting Oak Brook, IL, March 1997.
Romero, G., and Fernando, M. Epistemological Understanding and Inductive Inference: A Study of Physics in Early Childhood Education, Electronic Journal of Research in Educational Psychology, 2004, 2, 63-80.
Vlachos, G., and Kokkotas, P. Inferring as a process in teaching Science at the Primary School Level, ESERA, Rome, 1998.

Keywords:

Students' inferring, acids-bases.