Examining Strategies Used by Pre-service Science Teachers in Stoichiometry Problems in Terms of Proportional Reasoning

Öz

Stoichiometry problems are one of the best examples of problem solving in chemistry education. Proportional reasoning supports correct answers in stoichiometry problems. It is needed to examine how these problems are solved as well as the accuracy of solutions because of the importance and benefits of conceptual problem solving. This study utilizes the embedded multiple case study design. The stoichiometry problem solutions of 37 pre-service science teachers (PSTs) were examined based on three units of analysis; (i) whether pre-service teachers balanced the equations correctly or not, (ii) the accuracy of solutions, and (iii) strategies used to solve problems. More than half of the PSTs balanced the equations correctly but most of them did not interpret the integers in the equations appropriately. Participants were inclined to use algorithmic approach more than proportional reasoning. The accuracy of solutions and the frequency of algorithmic approach increased while the complexity of problems decreased. PSTs had difficulties in making sense of integers of chemical reactions, using intensive units such as density, and converting units. It is thought that PSTs prefer to use strategies that they learnt in their prior learning experiences. Within the context of findings, we suggest that PSTs should be supported conceptually about the meanings of integers and should be introduced using proportional reasoning in problem solving prior to algorithms.

Anahtar Kelimeler

• Stoichiometry problems,proportional reasoning,pre-service science teachers

Fen Bilimleri Öğretmen Adaylarının Stokiyometri Problemlerinin Çözümünde Kullandıkları Stratejilerin Orantısal Akıl Yürütme Açısından İncelenmesi

Öz

Orantısal akıl yürütmenin doğru sonuca ulaşmayı sağladığı stokiyometri problemleri kimya eğitiminde problem çözmenin en iyi örneklerinden biridir. Kavramsal problem çözmenin önemi ve faydaları göz önüne alınarak, stokiyometri problemlerine ilişkin çözümlerin doğruluğunun yanı sıra nasıl bir yaklaşımla çözüldüğünün de incelenmesi gerekmektedir. Bu amaçla araştırmada nitel araştırma yöntemlerinden bütüncül çoklu durum kullanılmıştır. Çalışmada, 37 fen bilgisi öğretmen adayının stokiyometri problemlerine ilişkin çözümleri (i) tepkimeleri doğru denkleştirilip denkleştirilmediği, (ii) çözümlerin doğruluğu ve (iii) problem çözümünde kullanılan stratejiler olmak üzere üç adımda incelenmiştir. Öğretmen adaylarının yarısından fazlasının tepkimeleri doğru denkleştirdiği ancak denkleştirilmiş tepkimelerdeki katsayıları doğru yorumlayamadığı görülmüştür. Öğretmen adayları algoritmik yaklaşımı orantısal muhakeme stratejilerinden daha fazla kullanmayı tercih etmiştir.  Soruların karmaşıklık düzeyi arttıkça öğretmen adaylarının problemleri doğru çözme ve algoritmik yaklaşımı kullanma oranları azalmıştır. Öğretmen adaylarının stokiyometri problemlerini çözerken tepkimelerdeki katsayıların belirttiği molar oranı tam olarak anlamlandıramadığı, tepkimeye giren maddelerden biri yoğunluk gibi intensif bir birim cinsinden verildiğinde çözüme ulaşamadıkları ve birimleri doğru dönüştüremedikleri gözlemlenmiştir. Öğretmen adayları stokiyometri problemlerini daha önceki derslerinde nasıl çözmeyi öğrenmiş iseler yine aynı şekilde çözmeyi tercih ettikleri düşünülmektedir. Bulgular çerçevesinde, kimyasal tepkime problemlerinden önce katsayıların ne anlama geldiği ile ilgili kavramsal desteğin sağlanması, problem çözümüne orantısal akıl yürütme stratejileri ile başlanarak bu desteğin işlemsel süreç ile pekiştirilmesi önerilmiştir.

Anahtar Kelimeler

• Stokiyometri problemleri,orantısal akıl yürütme,fen bilimleri öğretmen adayları

Kaynakça

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