An Analysis of the Visual Representation of Redox Reactions in Secondary Chemistry Textbooks from Different Chinese Communities

This study provides an analysis of selected aspects of the intended curriculum related to redox reactions as represented in secondary chemistry textbooks from the People’s Republic of China, with a special view also on Hong Kong, Shanghai, Taiwan, and the Chinese minority in Malaysia. This study reveals how chemistry textbooks deal with visual representations related to redox reactions and whether or not the visualizations provide any indication for the orientation of the intended curriculum, characterized by contexts suggested for chemistry learning. Specific criteria were derived from a literature review of the discussion on different levels of chemical representations and from a total of 346 visual representations related to redox reactions identified and analyzed from the textbooks. Based on the frequencies and levels of visual representations in the textbooks, this study showed that representations in textbooks from the People’s Republic of China mostly focus on the macro and macro-symbolic levels and indicate some aspects of everyday life as well as orientations towards industry and technology. The findings show that the textbook from Taiwan uses multiple macroscopic, submicroscopic, and symbolic representations to illustrate the redox reactions. The textbook from Hong Kong has a strong orientation along the content structure of chemistry, with mostly macro level representations. The textbook from the Chinese minority in Malaysia follows a strong structure-of-discipline orientation with limited visual support.


Introduction
A central concept of understanding common difficulties in teaching and learning chemistry suggested in 1991 by Johnstone [1] concerns the chemical thinking needed between three representational levels, namely, the macroscopic, submicroscopic, and symbolic levels. This central concept has been used for analysis of chemistry textbooks [2]. Macroscopically, students are required to observe, for example, combustion. In parallel, they are expected to imagine electron movements to provide an explanation at the particulate submicroscopic level. At the symbolic level, students are asked to represent the reaction by writing an equation of the chemical reaction by interrelating the symbolic level with both the macroscopic substances and submicroscopic chemical entities. Indeed, this is not an easy task and many students tend to most frequently focus their thinking at the macroscopic level because they live in a macroscopic world and can make experiences and observations at this level [3]. The concept of Johnstone's triangle of representational levels is not without critics and does need careful reflection, especially when planning assessment decisions on the use of the different consideration should be given to aiding students' interpretation of images [26]. In this respect, unfortunately, sometimes teachers confuse the different models in their instruction [27].
Modern chemistry education should embed the learning of abstract content into meaningful and relevant contexts [28][29][30]. In doing so, chemistry education should combine learning about submicroscopic entities and processes with the relevant macroscopic phenomena [1]. Both representational levels can benefit from visual support because a lot of the concepts in science, technology, engineering and mathematics (STEM) are visual-spatial in nature [31]. Visual representation can significantly improve learning when learners interact with the representation appropriately [32]. Many students, however, also have difficulties in understanding and making sense of certain visual representations especially when there is more than one representation [33].
Different curriculum structures and orientations [34] enable different views on the relevance of science education [28] to be transferred to chemistry textbooks. Textbooks are influenced by the authors' writing and explanation styles and transmit the authors' interpretation of the national curriculum. However, if textbooks are approved officially by educational authorities, such as the given ministries of education, they then represent an intended official curriculum [35]. Textbooks, however, are also influenced by commonly used practices when written by experienced teachers. In this way, Devetak and Vogrinc [36] suggest that textbooks also provide indicators of common classroom practices.
Textbooks have an important place in education; they provide a particular resource for teachers and students. Textbooks define a subject to the students and help to represent a school subject as students experience it [36]. Textbooks present both the content and the orientation of the curriculum [37] by forming a bridge for the translation of the official standards or syllabi into the implemented chemistry curriculum [38]. Textbooks offer both text content and visual representation to students. It is hard to say how the individual teacher will use a certain textbook but the teachers´usage of chemistry textbooks in many countries, e.g., in the People's Republic of China, is generally quite high [39]. Nothing, however, guarantees that teachers will follow the suggested path and activities [40]. Nevertheless, the textbook represents a kind of ideal and formal curriculum [41] that the teachers are expected to implement.
Since chemistry textbooks are the medium between chemistry and the learner [42], textbook analysis is gaining increasing interest in chemistry education in general (e.g., [2,25,43]), and in this journal in particular (e.g., [44,45]). Textbook analysis of visual representations can help to ensure that they are better used in future textbooks. The purpose of the current study is to analyze how grade 10 chemistry textbooks from different Chinese communities represent content related to redox reactions. The focus of this study is not to indicate conceptual errors but rather to characterize how the textbooks adapt visual representations related to redox reactions. This paper explores the visual representations of redox reactions and related content at the macroscopic, microscopic and symbolic levels as provided in grade 10 Chinese textbooks from the People's Republic of China, with a special view on Hong Kong, Shanghai, Taiwan and the Chinese minority in Malaysia to inform editors, authors or evaluators of chemistry textbooks about differences among the textbooks from this sample in order to identify areas for improvement. Analysis also focusses on whether the visual representations provide indications of the intended curriculum orientation [43]. Consequently, we investigated the following research questions:

1.
Concerning visual representations (macroscopic, microscopic and symbolic) a. Are these present in Chinese chemistry textbooks related to redox reactions? b.
How are they used? c.
How are the different representational levels represented and related to one another?

2.
Are there any indicators in the visual representations in the textbooks of a modern chemistry curriculum that use everyday life and societal illustrations to contextualize chemistry learning?

Materials and Methods
Chinese people account for one of the largest ethnic groups in the world. Aside from the People's Republic of China with about 1.4 billion citizens, there are Chinese communities in many countries or regions. In some environments, Chinese people form the majority, such as in Taiwan or Hong Kong. There are also many minorities of Chinese people in different countries of the world. In most countries, the Chinese minorities are integrated into the national educational systems. This is not the case for Malaysia, where the Chinese community forms 23.2% out of 32.0 million Malaysian citizens [46]. Independent Chinese Secondary Schools (ICSSs) use the Chinese language as the main medium of instruction in Malaysia and operate a self-standing school system to provide mother-tongue education with the intention to preserve cultural identity. The educational systems in the People's Republic of China, Hong Kong, Taiwan and the Chinese minority in Malaysia do have some commonalities in their structures in that grade 10 forms the first year of upper secondary education. Chemistry is a compulsory subject and redox reactions are a common topic, mainly starting in grade 10.
In the People's Republic of China, different textbook series are launched in the market. The books are approved by the national school textbook authorized committee's review. Currently, three versions of chemistry textbooks for upper secondary school have passed the review. They are compiled by the People's Education Press, Shangdong Science and Technology Press, and Jiangsu Education Press (see Table 1; CN1-CN3). Fundamental redox reactions knowledge is explained in all these editions in the grade 10 textbooks. These three sets of textbooks form the first sub-sample in this study. In 1985, Shanghai was allowed to abstain from the Chinese National College Entrance Examination (NCEE) and apply an independent proposition [47]. The textbooks analyzed in the present study are edited and reviewed by the Shanghai Primary and Secondary School Curriculum Reform Committee and Shanghai Primary and Secondary School Textbook Review Committee. One corresponding textbook is the Shanghai Edition (CN4).
Hong Kong, as a special administrative region of the People's Republic of China, has been deeply influenced by western countries, mainly during the colonial time under the United Kingdom. The Hong Kong Education Bureau recommends textbooks for senior secondary school students [48]. We chose the textbook from Jing Kung Educational Press, that is one of the popular textbook publishers in Hong Kong (HK).
Nine years of compulsory education were implemented in Taiwan in 1968. In 2014, a new policy of 12 years Basic Education Curricula was introduced and is intended to be fully implemented in the 2019 academic year [49]. We chose the textbook from LungTeng Cultural (later called TW1), which is one of the textbooks that passed the official review by the National Academy for Educational Research (NAER). Basic Chemistry 1, Basic Chemistry 2 and Selective Chemistry 1 (see Table 1) were chosen as they contain redox reactions content. Table 1 references the textbooks where most of the redox reactions content is covered in the textbooks from the four different Chinese communities.
In the context of Malaysia, Dong Jiao Zong is an allied organization of the United Chinese School Committees' Association of Malaysia, named as UCSCA or Dong Zong, and the United Chinese School Teachers' Association of Malaysia, named as UCSTA or Jiao Zong, which is responsible for the Chinese-community-run education that organizes Chinese Education in Malaysia and provides an unified curriculum and examination to ICSSs [50]. In our study, as our sample (MY), we chose the Chinese chemistry textbook used among ICSS students published by the United Chinese School Committees' Association of Malaysia (see Table 1), the Upper Secondary School Chemistry (volume 1) and Upper Secondary School Chemistry (volume 2), that contain the main redox reactions section. This study focuses on visual representations related to redox reactions in Chinese textbooks which may be considered as a model of analysis from the chemistry curriculum. A glimpse at other topics from the chemistry curriculum did not provide any indications that other content is visually represented in different ways.
Basic tenets of qualitative content analysis were employed to analyze visual representations from the textbooks. In order to develop criteria for the analysis of the representational levels of the redox reactions, we adopted a scheme using criteria developed by Gkitzia et al. [25]. The criteria were employed to our three level representational framework and revised accordingly after several readings of the textbooks. The criteria looked at all levels of visual representations including figures, photos, and diagrams. Tables and straightforward chemical equations were not considered as being visual representations. Chemical reaction equations only became part of the analysis as part of figures, not when they were used as part of the text. In an iterative process, the criteria were applied to the sample in each round to a sub-sample of illustrations by three raters (first, second and forth author) until a fit of the coding scheme ( Table 2) was achieved. The reliability of the data analysis was checked by independent rating (first and fourth author), and in the case of disagreement, re-rating was performed. The agreement rates were generally high in all three rounds from the beginning (above 90%) and rose to 97% due to joint re-rating of disagreed interpretations of the visual representations shown in Table 2. Table 2. Criteria for evaluation on visual representation characteristics (adapted from Gkitzia et al. [25]). In the first round, we mainly focused on three different categories (see Table 2). First, levels of representation according to the Johnstone [1] triangle, i.e., macroscopic, submicroscopic, symbolic, and multilevel representations were selected as the initial data. The textbooks were coded and analyzed using the criteria described in Table 2. Second, we examined the degree of the multiple correlations between representations to see if the multiple levels were sufficiently linked, insufficiently linked, or unlinked. Third, the relation between visual representations to the main text was also evaluated.

Levels of representation
A second round of the analysis focused on the function of images in relation to the text related to redox reactions. We evaluated how much of the visual representation is connected to the text for providing support to better understand the content, aside from just having a decorative function. Subsequently, we categorized the evaluation of image representation into decorative, organizational, or interpretational (see Table 3), which is an adaptation from Carney and Levin [51], and this was also interpreted by Nyachwaya et al. [52]. Table 3. Criteria for the evaluation of the function of the images (adapted from Carney and Levin [51]).

Category Subcategory Description
Function of images It is widely known that textbooks provide orientations of the curriculum and mirror the emphases behind them [53]. The third step of the analysis focused on the curriculum orientation transmitted by visualizations which were related to redox reactions obtained from the different textbooks. The scheme to analyze the curriculum orientations was adapted from the six categories related to curriculum orientation explicated by Eilks et al. [34] in the interpretation of Khaddoor, Al-Amoush and Eilks [43] (see Table 4). We analyzed the visual representation to see if the images represented the structure of the discipline orientation, history of science orientation, everyday life orientation, environmental orientation, or industry and technology orientation. The issue of socio-scientific orientation was also checked in relation to the text. Table 4. Criteria for the evaluation of curriculum orientation (adapted from Eilks et al. [34]).

Category Subcategory Description
Curriculum

Results
A total of 346 visual representations related to redox reactions were identified in the textbooks from Mainland China, Hong Kong, Taiwan, and Malaysia. In terms of the general content organization and structure, the differences in the textbooks between different Chinese communities are larger than the differences within the communities. From Figure 1, we can see that representations of the macroscopic (maximum 68%), symbolic (maximum 45%), and macro-symbolic (maximum 50%) levels are more prominent than other levels of representation. represented the structure of the discipline orientation, history of science orientation, everyday life orientation, environmental orientation, or industry and technology orientation. The issue of socioscientific orientation was also checked in relation to the text. Table 4. Criteria for the evaluation of curriculum orientation (adapted from Eilks et al. [34]).

Category Subcategory Description
Curriculum orientation Illustrations provoke the learning allowing the students to develop general educational skills to prepare them to become responsible citizens in future

Results
A total of 346 visual representations related to redox reactions were identified in the textbooks from Mainland China, Hong Kong, Taiwan, and Malaysia. In terms of the general content organization and structure, the differences in the textbooks between different Chinese communities are larger than the differences within the communities. From Figure 1, we can see that representations of the macroscopic (maximum 68%), symbolic (maximum 45%), and macro-symbolic (maximum 50%) levels are more prominent than other levels of representation.  Among the mentioned textbooks, the Taiwanese textbook and two of the textbooks from the PR of China (CN1 and CN2) cover a broader variety of representational levels than the textbooks from Hong Kong, Malaysia and two of the Chinese textbooks (CN3 and CN4).
Initially, we considered the first research question: What visual representations (macroscopic, microscopic and symbolic) are present in Chinese chemistry textbooks related to redox reactions, how are they used, and how are the different representational levels represented and related to one another? The data show that the way the textbooks illustrate redox reactions are different.

Levels of Representation
The analysis indicates that all textbooks show a high use of macro representations, except the Shanghai and Malaysian textbooks (Figure 1). The Shanghai and Malaysian textbooks use more symbolic and macro-symbolic level representations than the other Chinese textbooks. The Taiwanese textbook and one of the books from the PR of China (CN3) show a higher degree of multiple visual representations with the combination of the macro, submicro, and symbolic levels compared to the rest of the textbooks. The Hong Kong textbook tends to employ mainly macro and symbolic representations to explain fundamental chemistry knowledge related to redox reactions and visual representations in the Hong Kong textbook, in terms of the macro level, mostly refer to experiments. The Malaysian textbook uses visual representations at the symbolic level to explain the oxidation/reduction number, gain/loss of electrons, higher/lower valence, and oxidation/reduction. In terms of electrochemistry, the Malaysian textbook uses many macro-symbolic visual representations to illustrate advanced knowledge related to redox reactions of different electrochemical cells.

Multiple Visual Representations and Degree of Correlation between Representations
In terms of multiple representations, the Taiwanese textbook contains more multiple visual representation levels than the other books ( Figure 1). A combination of macro-symbolic representations is notable in most of the mentioned textbooks, followed by macro-submicro-symbolic combinations. Most of the textbooks use arrows and lines to connect different representational levels when they contain more than one representation (e.g., Figures 2a and 3b). The correlation between the different levels is generally sufficiently linked (Figure 4), for example, Figure 2a is an image with multiple representations including the macro, submicro and symbolic levels (the reaction of hydrochloric acid and magnesium). The reaction at the macro level, which happens inside the test-tube, is connected to digital simulated atoms and ions by an arrow, and atoms and ions are connected to correspond to chemical symbolic representations by more arrows. Textbooks from Hong Kong, Taiwan and one from the PR of China have visual representations that are insufficiently linked, but these numbers are small (average 10%). Among the mentioned textbooks, the Taiwanese textbook and two of the textbooks from the PR of China (CN1 and CN2) cover a broader variety of representational levels than the textbooks from Hong Kong, Malaysia and two of the Chinese textbooks (CN3 and CN4).
Initially, we considered the first research question: What visual representations (macroscopic, microscopic and symbolic) are present in Chinese chemistry textbooks related to redox reactions, how are they used, and how are the different representational levels represented and related to one another? The data show that the way the textbooks illustrate redox reactions are different.

Levels of Representation
The analysis indicates that all textbooks show a high use of macro representations, except the Shanghai and Malaysian textbooks (Figure 1). The Shanghai and Malaysian textbooks use more symbolic and macro-symbolic level representations than the other Chinese textbooks. The Taiwanese textbook and one of the books from the PR of China (CN3) show a higher degree of multiple visual representations with the combination of the macro, submicro, and symbolic levels compared to the rest of the textbooks. The Hong Kong textbook tends to employ mainly macro and symbolic representations to explain fundamental chemistry knowledge related to redox reactions and visual representations in the Hong Kong textbook, in terms of the macro level, mostly refer to experiments. The Malaysian textbook uses visual representations at the symbolic level to explain the oxidation/reduction number, gain/loss of electrons, higher/lower valence, and oxidation/reduction. In terms of electrochemistry, the Malaysian textbook uses many macro-symbolic visual representations to illustrate advanced knowledge related to redox reactions of different electrochemical cells.

Multiple Visual Representations and Degree of Correlation between Representations
In terms of multiple representations, the Taiwanese textbook contains more multiple visual representation levels than the other books ( Figure 1). A combination of macro-symbolic representations is notable in most of the mentioned textbooks, followed by macro-submicrosymbolic combinations. Most of the textbooks use arrows and lines to connect different representational levels when they contain more than one representation (e.g., Figure 2a, 3b). The correlation between the different levels is generally sufficiently linked (Figure 4), for example, Figure  2a is an image with multiple representations including the macro, submicro and symbolic levels (the reaction of hydrochloric acid and magnesium). The reaction at the macro level, which happens inside the test-tube, is connected to digital simulated atoms and ions by an arrow, and atoms and ions are connected to correspond to chemical symbolic representations by more arrows. Textbooks from Hong Kong, Taiwan and one from the PR of China have visual representations that are insufficiently linked, but these numbers are small (average 10%).

Relation to Text
In terms of the relationship between pictures and text, most of the textbooks show a high relation to the text ( Figure 5), with concrete references in the text and captions connecting the pictures with the text. Only the Taiwanese textbooks and one from the PR of China (CN1) contain a few pictures that are unrelated to the text. For example, Figure 2c is an unrelated representation in the Taiwanese textbook; the main text is about oxidation numbers but the picture is decorative, only providing visual enjoyment. It does not provide further help for deeper understanding. Figure 2a is an example of a visual representation that is completely related to the text and aids learners' understanding of redox reactions; the text is about the electron transfer of a reaction between magnesium and hydrochloric acid. The picture provides a comprehensive model that combines the macro, submicro, and symbolic levels. Figure 2b is an example of a visual representation that is partially related to the text. The text mentions that oxidizing agents can be used for sterilization and the picture illustrates this with a bottle of contact lens care solution. The caption of the picture refers to the main constituent (hydrogen peroxide).

Relation to Text
In terms of the relationship between pictures and text, most of the textbooks show a high relation to the text ( Figure 5), with concrete references in the text and captions connecting the pictures with the text. Only the Taiwanese textbooks and one from the PR of China (CN1) contain a few pictures that are unrelated to the text. For example, Figure 2c is an unrelated representation in the Taiwanese textbook; the main text is about oxidation numbers but the picture is decorative, only providing visual enjoyment. It does not provide further help for deeper understanding. Figure 2a is an example of a visual representation that is completely related to the text and aids learners' understanding of redox reactions; the text is about the electron transfer of a reaction between magnesium and hydrochloric acid. The picture provides a comprehensive model that combines the macro, submicro, and symbolic levels. Figure 2b is an example of a visual representation that is partially related to the text. The text mentions that oxidizing agents can be used for sterilization and the picture illustrates this with a bottle of contact lens care solution. The caption of the picture refers to the main constituent (hydrogen peroxide).

Relation to Text
In terms of the relationship between pictures and text, most of the textbooks show a high relation to the text ( Figure 5), with concrete references in the text and captions connecting the pictures with the text. Only the Taiwanese textbooks and one from the PR of China (CN1) contain a few pictures that are unrelated to the text. For example, Figure 2c is an unrelated representation in the Taiwanese textbook; the main text is about oxidation numbers but the picture is decorative, only providing visual enjoyment. It does not provide further help for deeper understanding. Figure 2a is an example of a visual representation that is completely related to the text and aids learners' understanding of redox reactions; the text is about the electron transfer of a reaction between magnesium and hydrochloric acid. The picture provides a comprehensive model that combines the macro, submicro, and symbolic levels. Figure 2b is an example of a visual representation that is partially related to the text. The text mentions that oxidizing agents can be used for sterilization and the picture illustrates this with a bottle of contact lens care solution. The caption of the picture refers to the main constituent (hydrogen peroxide).

Function of Images
In terms of the function of images, decorative, organizational, and interpretational images appear in all the textbooks ( Figure 6). The Shanghai textbook (CN4) has the highest use of images that focus on help for the learners to understand the text that are organizational. The Malaysian textbook has the highest rate of interpretational figures and the textbook from Hong Kong as well as one of the textbooks from the PR of China (CN2) have the highest degree of decorative pictures. Figure 3 shows examples of decorative, organizational, and interpretational representations from the different textbooks. Figure 3a shows an image of different iron-rich foods that plays a decorative role in enhancing the readers' imagination. Figure 3b aids the understanding of a hydrogen-oxygen fuel cell by showing the cell structure that reflects a redox reaction. Figure 3c is an example of an interpretational image that illustrates the reactions of copper wire and silver nitrate solution at the macroscopic, submicroscopic and symbolic levels, which aids in deeper comprehension for students.

Function of Images
In terms of the function of images, decorative, organizational, and interpretational images appear in all the textbooks ( Figure 6). The Shanghai textbook (CN4) has the highest use of images that focus on help for the learners to understand the text that are organizational. The Malaysian textbook has the highest rate of interpretational figures and the textbook from Hong Kong as well as one of the textbooks from the PR of China (CN2) have the highest degree of decorative pictures. Figure 3 shows examples of decorative, organizational, and interpretational representations from the different textbooks. Figure 3a shows an image of different iron-rich foods that plays a decorative role in enhancing the readers' imagination. Figure 3b aids the understanding of a hydrogen-oxygen fuel cell by showing the cell structure that reflects a redox reaction. Figure 3c is an example of an interpretational image that illustrates the reactions of copper wire and silver nitrate solution at the macroscopic, submicroscopic and symbolic levels, which aids in deeper comprehension for students.

Curriculum Orientation
Concerning the second research question, looked at as a whole, the results indicate that all the textbooks basically follow a structure of the discipline orientation (Figure 7), especially the textbooks from Shanghai and Malaysia. Everyday life orientation is covered by images in all textbooks to a certain extent, except in the Shanghai textbook. Industry and technology illustrations can be found in all textbooks. Environmental issues are addressed in the Hong Kong textbook and one of the textbooks from the PR of China (CN1) by pictures. History of science is represented only by visual representations in the Taiwanese textbook.

Curriculum Orientation
Concerning the second research question, looked at as a whole, the results indicate that all the textbooks basically follow a structure of the discipline orientation (Figure 7), especially the textbooks from Shanghai and Malaysia. Everyday life orientation is covered by images in all textbooks to a certain extent, except in the Shanghai textbook. Industry and technology illustrations can be found in all textbooks. Environmental issues are addressed in the Hong Kong textbook and one of the textbooks from the PR of China (CN1) by pictures. History of science is represented only by visual representations in the Taiwanese textbook.

Curriculum Orientation
Concerning the second research question, looked at as a whole, the results indicate that all the textbooks basically follow a structure of the discipline orientation (Figure 7), especially the textbooks from Shanghai and Malaysia. Everyday life orientation is covered by images in all textbooks to a certain extent, except in the Shanghai textbook. Industry and technology illustrations can be found in all textbooks. Environmental issues are addressed in the Hong Kong textbook and one of the textbooks from the PR of China (CN1) by pictures. History of science is represented only by visual representations in the Taiwanese textbook.

Discussion
The abstract nature of modern chemistry expects that learners' understanding of macroscopic phenomena be enhanced by submicroscopic and symbolic explanations [54]. Johnstone's triangle [1] approaches teaching and learning with a thorough combination of these three representational levels.
Although chemistry experts, persons with fluent and flexible performance [55], can easily switch between the different representational levels, studies on students show that learners regularly have difficulties in correctly relating representations from the different representational levels [56], because students generally have conceptual difficulties when dealing with visual representations [33].
As stated by Mahaffy [57], chemistry education differs from country to country, school to school, and culture to culture; there are no universal solutions when the level of the learner, the learning objective, and the teaching style are not in the same context. Inevitably, the intended, implemented and attained curricula have a mismatch between each other [58]. However, the data in this study provide some ideas about the ways in which different Chinese textbooks address representations of redox reactions. The representations might potentially be useful to teachers.
In terms of the distribution of the different levels of representation from this sample, macroscopic representation is dominant among other visual representations. This finding is very different from recently reported findings on chemistry textbooks from Africa, for example, Upahi and Ramnarain [2] reported a dominance of symbolic representations for the textbooks in Nigeria. To suggest reasons for this difference, however, would be highly speculative, but the reasons may lie in different curriculum traditions and lack of practical work, more than in the aspects of culture or socio-economic development [43]. However, the curriculum orientation [34] and the function of visual representations [51] concerned with redox reactions were not defined [2]. Treagust et al. [54] suggest that macroscopic representations are the basis of chemistry learning, but macroscopic understanding relies on an explanation at the submicroscopic level. Combined representations could be helpful. Combined visual representations are, however, limited in the sample of textbooks in this study. But the degree of correlation between the representational levels is high (above 89%). The high correlation between multiple representations might be helpful. Russell et al. [59] suggest that the simultaneous use of macroscopic, submicroscopic and symbolic representations can help to reduce students' alternative conceptions in learning chemistry.
The curriculum orientation in the different textbooks shows that the structure of discipline orientation is dominant in the textbooks from this sample. Decontextualized chemistry representations are still prominent in many countries around the world [6]. As Eilks and Hofstein [60] state, "science learning should start from contexts that are connected to the life of the students, their prior experiences, their interests [ . . . ] everyday lives of students and the society which they live in have the potential to offer meaningful contexts to the students" (p. 17). This claim is in line with the works of Holman [29], Stuckey et al. [28], and Sjöström et al. [6]. Our findings indicate that everyday life application and industry and technology orientation are already observable in the textbooks from this sample. It seems, however, that more everyday and societal life orientation is needed in the visual stimuli in the textbooks because the proportion is small (no more than 27%). Socio-scientific issues and environmental orientation remain scarce. Visual support for these perspectives might also be strengthened in the future to better support a broader contextualization of learning with textbooks in Chinese chemistry education.
Even though all the textbooks placed more emphasis on the structure of the discipline, in terms of the way that science knowledge is represented, the textbook from Taiwan and one textbook from China (CN3) use a more comprehensive way to illustrate the abstract concept of redox reactions via multiple macro-submicro-symbolic representations. The Malaysian and Shanghai textbooks tend to focus on pure science by visual representations. The other textbooks from the PR of China (CN1-3), Hong Kong and Malaysia embed everyday life issues, but mainly with a focus on pure science learning. The Hong Kong textbook provides a pleasurable visual experience with colorful macro pictures but still mostly focuses on fundamental knowledge learning.
This study has attempted to identify the use of visual representation in chemistry textbooks produced for and used in grade 10 classes from different Chinese communities. There are several limitations. It was not possible to analyze all textbooks available and changes in textbooks occur over time. Currently, new textbooks have been announced for chemistry education in Taiwan and Malaysia and further analysis might show whether or not they will be different from the current ones analyzed in this study. Another limitation is that the focus of this study was only on one topic in chemistry education, namely, redox reactions. This study also focused on selected aspects and cannot state anything about how and with what intensity the textbooks are used by the teachers, as well as to what extent teachers use other resources in chemistry classes.

Conclusions
To date, little is known about secondary chemistry textbooks from different Chinese communities. The present study shows the variety of chemistry textbooks from the selected regions although there is basically the same culture and language behind the four Chinese communities. The purpose of this study was not to evaluate whether the visual representations related to redox reactions and given in the textbooks are right or wrong, and was not intended to recommend one "best" textbook. The aim was to show how visual representations related to redox reactions are used and how textbooks might be improved by comparing them systematically to each other.
In this article, we examined visual representations related to redox reactions in secondary chemistry textbooks from different Chinese communities. This study has attempted to contribute to an understanding of the intended curriculum of secondary chemistry education in different Chinese communities based on the assumption that textbooks are important resources for teaching and learning [8,61].
Most Asian countries are making substantial efforts to improve the quality of science education and invest in corresponding research [62]. Specifically, since the late 1980s, Taiwan science education has developed substantially because of its economic boom. Since that time, Taiwan has built an active chain of researchers within East Asia [63] and western countries [64] for the development of science education. This might be a reason why the Taiwanese textbooks provide the richest representation content because it is based on research findings. These rich representations can provide ideas and directions for textbooks published in other Chinese communities. Specifically, one recommendation is to present rich illustrations of the redox content using visualizations that show a good balance between the relationships of the three representational levels of chemistry. Much research has shown that learners benefit when the relations of the different levels are clear and explicit, well connected to the text, and are related to meaningful contexts for the students. In most Asian countries, however, central examinations are still considered as the main component in educational assessment and promotion [65]. These central examinations mostly focus on the science content, with an emphasis on students being able to know information rather than understanding the relationships between concepts, and rarely refer to contexts and socio-scientific implications. Consequently, this might be the reason why most textbooks still tend to follow a structure of discipline approach. Perhaps there should be reflection on the central examinations to promote further development of the textbooks.