The aim with this essay is to analyze subject-specific concepts in three textbooks for chemistry for the chapter air. The study will examine how these subject-specific concepts are distributed and how they are represented. The representations used are analogy and metaphor, example, relation and nothing used. The following questions were studied and answered.

- Which subject specific concepts are used?

- In which frequency does the subject specific content appear?

- How are these subject specific concepts used and presented in the text (with analogies, metaphors, examples or relation)?

In order to answer the questions for the thesis and to fulfil the aim for this study, a quantitative analysis was done and used as a method. The gathered material was analyzed with Vygotskijs theory of development of concepts. Analysis was made in depth for the subject specific contents that were found in the chapter of air in all three textbooks; which were atmosphere, helium, nitrogen, air pressure, and oxygen.

The frequencies of subject specific concepts align with Lindbergs theory (the margin of the amount of unknown words in textbooks has to be 5%) but does not align with Hipkiss theory (2%). Textbook “Utkik” has highest frequency of 4,5%, “PULS” 3,8% and “Boken om Fysik och Kemi” 3,1%.

In textbook “Utkik” the most used representation of the common subject specific contents was “relation” with 35%. In textbooks “PULS” and “Boken om Fysik och Kemi”, the most occurring representation was “analogy and metaphor” with 100 % respectively 67%.

The results show that the subject specific concepts used in each book were mostly different. The textbooks differ in information and the students will miss out on some knowledge depending upon which book that is studied in the classroom. The essay shows that there is a correlation between earlier studies such as Lindberg (et al. 2007), that in order to improve knowledge of the subject specific concepts, it is crucial to use representations such as “analogy and metaphor”. It is also evident that the teacher has a responsibility to evaluate the textbooks and, in some cases, complement the subject specific concepts in order to increase the students’ knowledge ability in natural science such as chemistry.