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This study was part of a 6-year integrated project designed
to build up a databank for students' science conceptions in Taiwan.
This study was based on our previous findings of the characteristic
and sources of students' mental models about acids and bases.
In this paper we discuss the link between these mental models
and the teacher's pedagogical content knowledge. The authors adopted
the naturalistic observation methods to observe a teacher's pedagogical
content knowledge in a ninth grader classroom. The findings showed
that the teacher's instruction nearly followed the teacher's guide,
but used a "spiral" method of teaching and emphasized
rote learning. In addition, in teaching propositions, the teacher
spent the most time supplementing the calculation of pH values,
which was covered in previous edition of the textbook. Furthermore,
the teacher overemphasized the specific properties of special
strong acids, rather than general properties. In teaching representations,
the teacher spent most time on elaborating textbook, giving examples
and calculating pH values. Everyday experiences, TV media and
teaching experiments were important sources of teacher's examples.
However, these sources were not based on students' preconceptions
of acid and base, therefore her teaching reinforced students'
incorrect understanding.
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CEJ Vol. 9, No. 2, Contents