Les modèles et la modélisation de la réaction acide-base dans le ...

their own experience from everyday life situations: natural process is PP and a mancaused
process is CP (1).
Understanding quantity of matter appeared as another difficulty. Studies carried out
by Laugier (9) and Eils, Moellering & Valanides (15) showed that students were not
able to construct macroscopic phenomenology and to build the correct relationship
between the particle level and the macroscopic level, which is indispensable to gain
understanding of the CR. Most of them didn’t take into account proportionality (7,
13) and those who perceived the need for the proportionality rate in a CR, used and
considered only a ratio equal to 1 (14).
In addition Gauchon and Meheut (15) indicated that the students’ conception that
“both reactants are totally converted’’ was quite strong in problems where reactants
were totally converted, when the reactants were in different physical states.
Students still find it difficult problem to make connection between CP and CR.
Indeed, according to the study done by (1) a significant portion of Greek students did
not always make the connection between CP and CR. They considered the CR
intuitively as a simple process which can be represented by means of chemical
equations (2). Finally, although students studied and discussed CP on the
phenomenological as well as on the particle level, including chemical changes where
more than one substance was formed from one initial substance, CR were
consistently and exclusively categorized as reactions starting with two initial
substances and leading to one product. Also, they considered CR to be exothermic,
although they learned and differentiated between endothermic and exothermic
reactions (12).
1.2. The position of the problem and Research questions
This research concerns Congolese students from ten high schools located in Bukavu
region (East of Democratic Republic of Congo, DRC). DRC is an undeveloped country
in turmoil since 1996. There are some industries and manufacture: brewery, soap
factory, oil mill, mining companies…
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