Bilişsel yapılar, öğrenenlerin özel bir bilgi alanında ne bildiklerini değerlendirme fırsatı sunmaktadırlar. Bu yüzden, yeni bilginin yapılandırılmasını etkileyebilecek bilişsel yapıların tanımlanması ve öğretim ile bunların nasıl değiştiğinin incelenmesi önemlidir. Bu çalışmada 11. sınıf öğrencilerinin (15-16 yaş) kimyasal denge ünitesinin temel kavramlarına ilişkin bilişsel yapılarını ortaya çıkarmak ve bunların öğretim sonrası nasıl değiştiğini ortaya koymak amacıyla kelime ilişkilendirme testi kullanılmıştır. Bu amaç doğrultusunda, İzmir il merkezindeki bir ortaöğretim kurumundaki 11. sınıflardaki 30 öğrenci ile bir çalışma yürütülmüştür. Çalışmada veri toplama aracı olarak, 10 uyarıcı kelimeyi içeren kelime ilişkilendirme testi öğretim öncesi ve sonrası uygulanmıştır. Testte kullanılan uyarıcı kelimeler: "denge", "katalizör", "endotermik tepkime", "egzotermik tepkime", "basınç", "molar derişim", "tersinir tepkime", "maksimum düzensizlik", "ileri tepkime hızı", "geri tepkime hızı" dır. Verilerin analizinde, her bir uyarıcı kelimeye verilen cevaplar sayılmış, frekans tablosu hazırlanmış ve farklı kesme noktalarındaki zihin haritaları çizilmiştir. Çalışmanın sonuçları, öğrencilerin öğretim öncesi zihin haritalarında çoğunlukla denge kavramını terazi ve eşitlik gibi cevaplar ile fiziksel denge ile ilişkilendirme eğiliminde olduklarını göstermektedir. Aynı zamanda, öğretim öncesinde "maksimum düzensizlik" ve " tersinir tepkime" uyarıcı kelimelerinin zihin haritalarında yer almadığı, diğer uyarıcı kelimeler arasında da çok az bağlantının kurulabildiği saptanmıştır. Buna karşın öğretim sonrasında ise, öğrenciler denge kavramını kimyasal denge ile ilişkilendirebilmişler, tüm uyarıcı kelimler zihin haritalarında saptanabilmiş ve öğrencilerin uyarıcı kelimeler arasında daha fazla ilişki kurabildikleri saptanmıştır. Bu bulgular, 11. sınıf öğrencilerinin "kimyasal dengeye" yönelik bilişsel yapılarının öğretim sonrası olumlu yönde değiştiğini göstermektedir.

Cognitive structures offer an opportunity to assess what learners know with respect to a particular area of knowledge. It is therefore important to identify the cognitive structures that may also influence the structuring of new knowledge and examine how these change with instruction. This study used the word association test to reveal the cognitive structures of 11th grade students in the context of the basic concepts taught in the unit on chemical equilibrium and to understand how these changed after the instruction. In line with this goal, a study was conducted with 30 students enrolled in the 11th grade of a secondary school in the city of Izmir. In collecting data for the study, an association test consisting of ten stimulus words was implemented before and after the instruction. The stimulus words used in the test were, "equilibrium", "catalyzer", "endothermic reaction", "exothermic reaction", "pressure", "molar concentration", "reversible reaction", "maximum disorder", "rate of forward reaction" and "rate of reverse reaction". In the analysis, responses for each stimulus word is counted, a frequencies table is prepared, and mind maps with different cut-off points were drawn up. The results of the study indicated that students were most likely to associate the concept of equilibrium with physical equilibrium in their mind maps before the instruction, responding with words such as "weighing scale" or "balance". At the same time, it was found that the stimulus words "maximum disorder" and "reverse reaction" did not appear in their mind maps and that the responses given to the other concept stimuli revealed very few associations between them before the instruction. Following the instruction however, the students were able to associate the concept of equilibrium with chemical equilibrium; all the stimulus words on the mental map were defined and it was seen that the students were able to form substantially moreassociations between the stimulus words. These findings show that the cognitive structures of the 11th grade students with respect to "chemical equilibrium" changed positively after the instruction. STRUCTURED ABSTRACT Introduction Learners’ cognitive structures has important role in the field of science and chemistry education with the effects of the constructivist learning approach. According to constructivist approach, it is important to know what students know when they come into the classroom to design effective learning environments (Siegler, 1998). For this reason, identifing leaners’ cognitive structures has great importance in the learning process. Thus, Nakiboğlu (2008) stated that cognive structures help educators to understand how the learners’ knowledge change during the learning process. There are many techniques have been used to identify learners’ cognitive structures such as concept maps, flow maps, structured grids, mind maps, and word association test (Kinchin and Hay, 2005; Novak and Gowin, 1984; Anderson and Demetrius, 1993; Tsai, 2001; Tsai and Huang, 2002, Dhindsa, Kasim and Anderson, 2011). Within these techniques, word association test (WAT) has been used by many researchers over the years (Cachapuz and Maskill, 1987; Johnstone and Moynihan, 1985; Kaya and Akış, 2015) . According to these studies, WAT is very useful to identify concepts, and relationship between these concepts in learners’ minds (Bahar, Johnstone and Sutcliffe, 1999; Bahar and Özatlı, 2003) . In chemistry education, WAT was used in many studies, however, there is still a need for studies invesitigating how learners’ cognitive stuctures change with the effects of the instruction. The Purpose of The Study The purpose of this study is to understand students' cognitive structures regarding the topic of chemical equilibrium by using word association test, and to identify how students' cognitive structures are affected by the instruction. In the line of this purpose, these questions were answered in the study:  What concepts did the students have in their cognitive structures about the basic concepts related to the unit on chemical equilibrium before the instruction?  Has there been a change in the students' cognitive structure regarding the basic concepts in the unit on chemical equilibrium after the instruction? If so, what kind of changes have there been. Methodology This research was based on one-group pre-test/post-test study. In this design, before instruction, the Word Association Test (WAT) was applied as a pre-test in the group, after the topic of chemical equilibrium began to be taught. The same test was employed as a post-test one week after the instruction. Sample The study sample included 30, 11th grade students who were studying in a secondary school in Izmir, Turkey. All students had volunteered to participate in the study, and they had similar backgrounds. The ages of the students ranged from 15 to 16 years. Instrument The data of this study was collected through a Word Association Test (WAT). WAT was administered as a pre-test and post-test to all groups. To conduct the WAT, ten key terms selected as cornerstones of chemical equilibrium were selected by the researchers. These key terms acted as stimuli. These were “equilibrium", "rate of forward reaction", "rate of reverse reaction", "catalyzer", "pressure", "molar concentration", "maximum disorder", "endothermic reaction", "exothermic reaction", "reversible reaction" Analysis In the analysis of WAT, three steps were followed. These are: 1. Analyzing the response words for each stimulus word 2. Counting the response words for each stimulus word and preparing a frequency table. 3. Drawing of mind maps. In the first stage, the researchers independently examined the responses to each stimulus word/phrase to check whether they were meaningful or not. After that, the Miles and Huberman (1994) formula was used to calculate the percentage of agreement for the responses. These percentages were respectively: equilibrium (93%), rate of forward reaction (90%), rate of reverse reaction (91%), catalyzer (91%), pressure (92%), molar concentration (92%), maximum disorder (94%), endothermic reaction (95%), exothermic reaction (92%), and reversible reaction (94%). In the second stage of the analysis, the responses included in the analysis for each stimulus word were counted and frequency tables were prepared. The third stage of the analysis included of mind maps that were drawn with using the frequencies of the response words to each of the stimulus words. Findings First research question in the study aims to reveal students’ cognitive structures regarding the basic concepts of chemical equilibrium before the instruction. With this aim, firstly, a frequency table was prepared for the responses to the stimulus words in the pre-test. After that, mind map with different cut-off point were drawn based on frequency table. According to first mind map displaying a cut-off point of 20 and above, students mostly associated the concept of equilibrium with a weighing scale and equality was based on their experiences in daily life. This result is striking in that it reveals the possible alternative conceptions that the students may have had. At the same time, in this mind map, some meaningful connections were determined. For example, molar concentration - mole, endothermic reaction - heat, endothermic reaction- enthalpy, exothermic reaction - heat, exothermic reaction and enthalpy are scientifically and correctly associated. In the second mind map with a cut-off point at 15-19, it was determined that the stimulus words did not change but that the responses to these increased. For example, the stimulus word response "cerebellum" appeared in this mind map. That the students formed an association between the concept of "equilibrium" and "cerebellum" is significant in that this indicates meaningful associations that they had carried with them from their biology lessons. Also, molar concentrationion, molar concentration –volume, pressure- volume and pressure- piston were evidence of the meaningful associations that the students could make. When third mind map for the cut-off point 10-14 was examined, it can be seen that two new stimulus words (rate of forward reaction" and "catalyzer) have been added as compared to first and second mind map. This showed that the students were able to form a two-way association between these concepts. . According to fourth mind map for the cut-off point 4-9, map, 8 of the 10 stimulus words have a place on this map. Differing from the other mind maps, the stimulus phrase "rate of reverse reaction" took its place on the map for the first time. When the students' responses to this stimulus phrase are examined, it can be seen that, just as in the responses to "rate of forward reaction," the same responses of "reaction" and "catalyzer" were given. The aim of second research problem in the study is to determine changes in change in the students' cognitive structures regarding the basic concepts in the unit on chemical equilibrium after the instruction. Similary to before instruction, mind map with with different cut-off point were drawn based on frequency table. In the first mind map for cut-off point 20 and above after instudction, it was seen that 6 stimulus words have found their place on this map. According to this mind map, the responses given to the concept of equilibrium, that is, "reaction," "products" and "equilibrium constant," show that the students' cognitive structures have changed and that what was perceived as physical equilibrium has now been associated with chemical equilibrium. When the mind map for a cut-off point at 15-19 after instruction was examined, it was seen that the number of stimulus words did not change compared to the mind map for the cut-off point 20 and above but that the responses given to the stimulus words have increased. For example, the responses given to the stimulus word "equilibrium" such as Kp, reactants, mole is an indication that the students were able to form meaningful relationships. In the third mind map for cut-off point at 10-14 relating to postinstruction, it is observed that both the number of stimulus words and the responses to these have increased. In fact, the stimulus words "forward" and "reverse reaction rates" appear on this mind map for the first time. The last mind map relating to post-instruction shows that all of the stimulus words given to the students are present in this mind map. In particular, it is striking to see that the two sets of stimulus words representing the concepts of "maximum disorder" and "reversible reaction" have found their way to this mind map for the first time. Results and Discussion The main aim of this study is t determine determining how the cognitive structures of 11th-grade students changed with respect to the topic of chemical equilibrium. With this aim, word association test twice as a data collection tool, was applied once before and once following the instruction. According to the results of the analysis of the pre-instruction WAT, students regarded particularly the concept of equilibrium as a phenomenon referring to physical equilibrium. Thus, there are many studies in which it is reported that students have the tendency of conceptualizing chemical equilibrium in terms of a physical phenomenon, leading to the creation of alternative conceptions (Griffiths, 1994; Hackling and Garnett, 1985; Huddle and Pillay, 1996). On the other hand, after the instruction, the students offered responses that showed that their associations pertaining to the concept of equilibrium were no longer physical but chemical. The responses of "Kd", "reaction" and "products" for the concept of equilibrium indicate this. This mind map at the same time differs from the mind map belonging to before the instruction in that it has more stimulus words and more responses. This result showes that, with regard to the basic concepts of chemical equilibrium, compared to before the instruction, the students were able to form new connections that were associated with each other instead of offering isolated structures. These findings indicate that the cognitive structures of the 11th grade students with respect to "chemical equilibrium" changed positively after the instruction. Similar results were observed in other studies (Cachapuz and Maskill, 1987; Nakiboğlu, 2008).