Chemistry Reference
In-Depth Information
Presenting misconceptions first and teaching the scientific concept afterwards can
enable students to compare and investigate by themselves what is wrong with
statements like “some things are going away” or “combustion destroys matter, mass
is going to be less than before.” Integrating preconcepts in lessons in this way will
improve sustainable understanding of chemistry, and by comparing misconceptions
with the scientific concept students will internalize the concept of combustion. More
results in line with these hypotheses will be published in the future.
Barke and Doerfler [
23
] planned lectures concerning the subject acids, bases,
and neutralization. Because of the known misconceptions (see concept cartoons at
the end of this chapter) experiments and structural models are involved to avoid
most misconceptions. Instead of taking the usual equation “HCl + NaOH
!
NaCl + H
2
O” for the reaction, H
+
(aq) ions for acidic solutions and OH
(aq) ions
for basic solutions were introduced, the ionic equation for the
formation of water
molecules
was explained: “H
+
(aq) ions + OH
(aq) ions
H
2
O(l) molecules.”
Later students were told that some students are thinking of “HCl molecules” in
hydrochloric acid - the students rejected this statement and corrected it by pointing
out the ions. With regard to the neutralization other students are thinking of a
“
formation of salt
” because “NaCl is a product of this neutralization.” Students
discussed this idea with the result that no solid salt is formed in the neutralization.
Na
+
(aq) ions and Cl
(aq) ions do not react, but are left behind by the neutralization
reaction. Ions like these are usually called “spectator ions.”
So students were taught the scientific idea of the new topic first, and afterwards
confronted with well-known misconceptions. By comparing the scientific idea and
the presented misconceptions the students could intensify the recently gained
scientific concept. Preliminary data show that the consideration of misconceptions
in class is successful in understanding chemistry and preventing misconceptions.
More empirical research investigating whether this method is the most sustainable
strategy for teaching and learning will be forthcoming.
Teaching structure of matter
. With regard to teaching ions and ionic bonding,
Barke, Strehle, and Roelleke [
24
] evaluated lectures for the introduction of “atoms
and ions as basic particles of matter” on the basis of Dalton's atomic model (see
Fig. 10.4): scientific ideas concerning chemical structures of metal and salt crystals
are discussed. Following this way of instruction all questions regarding chemical
bonding are reduced to nondirectional electrical forces surrounding every atom or
ion - no electrons or electron clouds are involved at this time. However, the
structure of elements and compounds can be discussed because 3D models or
model drawings are possible on the base of Dalton's atomic model (see Fig.
1.11
).
In the first 2 years of teaching chemistry only the structure of matter should be
regarded (see Chap. 10) - the detailed questions according to chemical bonding
should be answered later after the introduction of the nucleus-shell model of the
atom or the ion. By combining ions to salts students learn the scientific idea about
their composition: cations and anions, their electrical attraction or repulsion, their
arrangement in ionic structures. Through this strategy of combining ions and using
ion symbols most of the related misconceptions, which can be found worldwide,
can be prevented [
21
]!
!
