Students’ misconceptions chemical equations

Presenting the idea of the chemical equation as a very useful model that can help us summarise what is going on in reactions, and which does a good enough job for most reactions, will both enable students to see the value of the formalism and stop them making unfortunate generalisations about all reactions going to completion (which could then later act as a misconception when they meet reactions that do not fit the model). 

Many school-made misconceptions occur because there are problems with the specific terminology and the scientific language, specially involved substances, particles and chemical symbols are not clearly differentiated. If the neutralization is purely described through the usual equation, HC1 + NaOH —> NaCl + H20, then the students have no chance to develop an acceptable mental model that uses ions as smallest particles. 

There are ample self-made misconceptions regarding the formulation of reaction symbols. Mulford and Robinson [32] discovered the following situations regarding questions 5 and 6 (see Fig. 5.21) when evaluating the empirical studies Responses to question 5 suggest that students came to us with a very poor understanding of chemical formulas and equations. Only 11 % selected the correct answer d. When we consider the number of students who selected responses a, c and e, we see that 65% chose responses that do not conserve atoms. Combining responses a, b and e indicates that 74% appear not to understand the difference between the coefficient 2 and the subscript 3 in 2 S03 [32],... 

In 1992-1994, Kienast [7] carried out tests on chemical equilibrium with over 12,000 students in four test cycles. The following misconceptions, which were also described by the above-mentioned authors, were observed with particular regularity In equilibrium the sum of the amount of matter (concentration) of reactants is equal to the sum of the amount of matter (concentration) of the products (...) in equilibrium the amounts (concentrations) of all substances which are involved in equilibrium are the same (...) the sum of the amounts of matter (concentrations) remain the same during a reaction (...) data which has been supplied on the amount of matter (concentration data) should be multiplied with stoichiometric coefficients from the reaction equation, in order to find the true amount of matter concentration [7]. 

The misconceptions that are most often encountered are those relating to chemical reactions (Chapter 4) and writing equations (covered earlier in section 7.2). Work on the reactivity series provides an excellent opportunity for students to encounter a wide... 

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