Asia-Pacific Forum on Science Learning and Teaching, Volume 11, Issue 2, Article 2 (Dec., 2010)
Esin ŞAHİN PEKMEZ
Using analogies to prevent misconceptions about chemical equilibrium

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Introduction

Misconceptions are very important in the learning process and they have to be taken into account as these misconceptions can interfere with studentsí learning of scientific principles or concepts (Palmer, 2001; Taber, 2000). For this reason, the selection of teaching methods has an important factor in preventing studentsí misconceptions. Using analogies is one of the teaching methods. Analogies can help students build conceptual bridges between what is familiar and what is new (Glynn, 2007). They simplify visualization of the abstract concepts by the student.

Studies about analogies in science education have shown that analogies cause a significantly better acquisition of scientific concepts than the traditional instruction and help students integrate knowledge more effectively (Bilgin & Geban, 2001; Gadre, 1986; Piquette & Heikkinnen, 2005; Sarantopoulus &Tsaparlis, 2004; Stavy, 1991).

Using analogies is not new in chemistry education; they have been used through the ages by researchers to help students understand theoretical concepts (Huddle & White, 2000). For instance, Gadre (1986) used a seesaw analogy to teach the reading of manometers. At the end of the study, it was founded that using analogies effected learnersí achievement positively. In his research, Silverstein (1999) used the big dog-puppy dog analogy. In this analogy, puppy dogs are restricted to a specific dog run; they represent bond electron pairs. Big dogs represent delocalized bond electron pairs. In another study, Silverstein (2000) used a football analogy to explain weak and strong acid-bases. He said that partial ionization is a difficult concept for some to comprehend; the phrase may not evoke much in the mind of a visual learner. Visual analogies are often helpful when abstract concepts are explained. Hence, in his analogy he likens an acid, which is a proton donor, to a quarterback. The quarterback is a football ďdonor,Ē whose job is to deliver the ball by either passing it to a receiver or handing it off to a running back. Research was carried out by Chiu and Chen (2005) to determine the effects of dynamic computer analogy on 8th grade studentsí understanding of the behaviors of particles. The results of the study revealed that both static and dynamic computer analogies were significantly effective for learning the nature of particles.

Another chemistry topic with the most analogies is chemical equilibrium, since that topic includes the most abstract concepts such as its dynamic nature, the distinction between equilibrium and non-equilibrium situations, the mental manipulation of Le Chatelierís principle (Kousathana & Tsaparlis, 2002). Some of the analogies related to chemical equilibrium which were found in the literature are presented below:

Harrison and Buckly (2000) made a transparent simulation to explain dynamic equilibrium. They divided the students into two groups and gave them 24 small coins. Students in group A were given 24 coins, but students under B were not given any coins.

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   A (g) a  B (g)

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Students under A represented reactants, B represented products. While half of the reactants were converted to products, ľ of products were converted back to reactants. This analogy illustrated very few aspects of chemical equilibrium such as reversibility of the reaction and the dynamic aspect. Key aspects of chemical equilibrium, like calculation of the equilibrium constant and application of Le Chatelierís principle, were not explained with this analogy. Similarly, Wilson (1998) developed three analogies to teach chemical equilibrium. Wilson used 40 matches to explain how a system reached equilibrium in the first analogy. In the second analogy, he explained the dynamic equilibrium starting with a different number of matches. In the third analogy, he used different reaction rates and temperatures to explain Keg.

According to literature review, it was determined that there were many analogies which explained the dynamic aspect of chemical equilibrium such as dancing couples, two groups throwing the balls/apples back and forth, fish between two aquariums and bees in a beehive (Dickerson & Geis, 1981; Olney, 1988; Russel, 1988; Sarantopoulos & Tsaparlis, 2004). In addition to these analogies, some analogies in the literature explained only the application of Le Chatelierís principle like a see-saw and rubber band and gas flow between syringes (Balkwill, 1976; Russel, 1988; Thomson, 1976). Among these analogiesí most evident limitations are that (Raviolo & Garrtiz, 2009):

  • They show an equality of ďconcentrationsĒ of reactants and products in equilibrium (fish between two aquariums, bees in a beehive, gas flow between syringes).
  • They do not explain equilibrium at molecular level (dancing couples, fish between two aquariums).

In this paper, we present chemical equilibrium analogies, including dynamic equilibrium, reversibility, equality of rates, calculation of equilibrium constant and the application of Le Chatelierís principle, based on assumption that analogies may help students learn abstract concepts by visualization (Treagust & Chittleborough, 2001).

It is very important that studentsí prior knowledge and misconceptions are determined and a teaching method (or combination of different methods) that overcomes misconceptions is selected. According to «alik and Ayas (2005), in Turkey, most of the teachers do not know how to determine studentsí misconceptions in the learning process. On the other hand, from our teaching experiences in high schools and by informally talking with teachers, it was determined that many chemistry teachers prefer just lecturing with the chalk and talk method today. In this method, the teacher presents concepts to students who sit in the classroom, listen and write (Kara & Yesilyurt, 2007). Most of the time, teachersí focus on solving numerical problems rather than concept learning since students mainly need to solve numerical problems in the university entrance examination. Another reason why teachers prefer the chalk and talk method in chemistry lessons is that the high school chemistry curriculum consists of many topics, and teachers do not have enough time to design activities and materials (Nakipoglu, 2003). Therefore, this study can help chemistry teachers rethink their teaching methods and will inform them about using and importance of analogies in the teaching and learning process.

There are many studies that specifically investigate studentsí understanding of several chemical concepts such as a mole, atom, molecule, chemical equilibrium, chemical bonding and phase changing (Bar & Travis, 1991; Griffiths & Preston, 1992; Novick & Nussbaum, 1981; ÷zmen & Demircioglu, 2003; Wheeler & Kass, 1978). Among these topics, chemical equilibrium is one of the fundamental concepts in chemistry, like many other topics such as acid-base, electrochemistry, solubility, which are related to chemical equilibrium. Additionally, teaching chemical equilibrium takes up a large part of the chemistry curriculum in Turkey. As a result, the number of questions based on chemical equilibrium in university entrance examination is considerable. In this case, learning about chemical equilibrium correctly is vital to obtain high scores in the entrance examination. Results of the researches showed that subject of chemical equilibrium has been regarded as problematic for students (Banerjee & Power, 1991; Bergguist & Heikkinen, 1990; Gussarsky & Gorodetsky, 1990, Griffiths, 1994; ÷zmen, 2007). The most frequently encountered misconceptions according to the research are given below:

  • No reaction occurs at equilibrium.
  • The rate of the forward reaction is greater than the reverse reaction at equilibrium.
  • Concentrations of the reactants are equal to the concentrations of the products at equilibrium.
  • When one of the reactives is added, equilibrium always shifts to the productsí side.
  • When one of the reactives is added to the equilibrium mixture, only the concentration of products changes.
  • If the amount of a reactant is increased, its concentration remains the same.
  • When a solid substance is added to heterogeneous equilibrium systems, equilibrium is disturbed.
  • The numerical value of Keq changes with the amounts of reactants or products.
  • Concentration of the products or reactants change with the addition of a catalyzer.

Although these studies were conducted with subjects of different age levels, similar misconceptions were identified.

In this study, the aim was to investigate the effects of analogies related to chemical equilibrium in preventing studentsí misconceptions. Depending on this aim, these research questions were addressed:

  • Is there any significant difference in the achievement mean scores between pre-tests of experimental and control groups?
  • Is there any significant difference in the achievement mean scores between post-tests of experimental and control groups?
  • Is there any significant difference in constructing knowledge between experimental and control groups?

 


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