Chemistry Reference
In-Depth Information
repetition. Many textbooks [
8
] provide excursions on matters of everyday life and
of environmental problems that can be studied concomitantly with the classical
topics of instruction in the classroom or by students studying at home.
For some issues there is the possibility to leave the scientific way of instruction
and to consistently use material from everyday life - in such cases the conditions for
motivational chemistry lessons are optimal. Wanjek [
9
] showed with a scientific
evaluation of the teaching unit “acids and bases” that food and cleaning substances
as examples for acids and bases increase motivation and interest in chemistry.
Particularly girls, who reported much less interest in chemistry than boys in a
questionnaire prior to these lessons, increased their interest to the level of the
boys following this instruction [
9
].
It will not always be possible to move everyday materials and references to life
into the foreground, so that the structure of discipline can be developed itself.
Harsch and Heimann [
10
] show many examples in their PIN concept how to
integrate everyday life topics into a genetically growing subject classification: detec-
tion of basic organic substances in food and well-known products, relationships
between test tube synthesis and biochemical metabolic processes, model experiments
to understand chemical recycling including energy balances [
10
].
Generation of cognitive conflict.
The classic way to develop intrinsic motivation
according to Piaget is through “generation of a cognitive conflict and equilibra-
tion.” Lind [
11
] formulated the same connection with the incongruity theory: the
difference between a perceived stimulus and the stimulus expected by an individual
is called incongruity. This mismatch may be the reason for motivation because
students are determined to eliminate those anomalies, to close the gap between the
expectation and actual observation.
In the preparation of lessons, the teacher has to
- Know or estimate the prior knowledge of students
- Select a presenting event, which is incongruent with student expectations
- Determine the presentation mode of the anomaly
- Set type and strength of the incongruence or anomaly [
11
]
In chemistry class, it is then possible to create mismatches by observation of
some natural phenomena or laboratory experiments and to motivate students to
solve the problem. It is left to the creativity of each teacher to select a topic
appropriate for phenomena or experiments - some examples are outlined below.
Melting temperature of ice.
Young students think that heating substances always
leads to an increase of their temperature - that is not true, however, for substances at
their melting or boiling temperature. So a mixture of ice and water is heated, stirred
and the thermometer observed: the temperature remains at a constant value of 0
C
(see E2.1). The observation that the temperature remains at an unexpected 0
C
motivates students to think about it. With the help of the teacher they learn that the
added energy is needed to first melt the ice, and only after all ice is melted the
temperature will increase with the amount of added energy. This experiment is very
suitable to differentiate between the idea of energy and measured temperatures.
