Many studies suggest that students have difficulties in learning acid-base concepts. This study presents some conflicts in the textbook descriptions of these concepts and proposes these to be the cause of the students' difficulties. This is especially true regarding the description of the relationship among the Arrhenius, Brønsted−Lowry, and Lewis concepts of acids and bases, which are represented schematically as a cumulatively developing figure. However, some reagents, such as NH 3 , dry HCl, and H 2 SO 4 , cannot be classified as acid or base according to these descriptions. A new relationship is suggested in this study based on the ontological category of scientific knowledge. Finally, it is suggested that all three concepts be taught for the purpose of understanding not only the concepts but also the developmental nature of scientific theories.

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The aim of the present study is to shed light on the conceptions that young students have of heat and temperature, concepts that are both important in school science curricula and closely related to daily life. The subjects of the study were students from a rural district in South Korea and they ranged in age from 4 to 11 years. Interviews were conducted with each student on the basis of questions on temperature, thermal insulation, and heat equilibrium. After calculating the frequency and percentage of student responses and analyzing the rationale for their answers, it was found that younger students tended to view temperature as ''size'' or a ''summation of numbers.'' This tendency gradually diminished in older students. Most students had alternative conceptions of thermal insulation regardless of age; however, reasoning differed according to age. Younger students displayed a greater tendency to view insulation as a material property, whereas older students showed a greater tendency toward rational heat and temperature conceptions. Most students did not have clear concepts of heat equilibrium regardless of age, but possessed numerous alternative conceptions. ß

We present a critical discussion of how chemistry textbooks treat the electrolysis of water and aqueous salt solutions, based on a survey of general chemistry textbooks in English and Korean at secondary and tertiary levels, also informed by the historical background of 19th-century debates. English-language textbooks present various and contradictory accounts of the electrolysis of water; a key point of disagreement is whether hydrogen and oxygen gases originate from pre-existing H⁺ and OH⁻ ions, or from the direct reduction and oxidation of H₂O molecules. School textbooks in South Korea all present the same account, with no indication of alternative views. A vast majority of all texts ignore the possibility that H₂ and O₂ may result from secondary reactions, which was a standard view in the late 19th century following the works of Daniell and Miller. Concerning the electrolysis of aqueous salt solutions, all texts give oversimplified views of competing reactions based on standard reduction/oxidation potentials. It is understandable that textbooks try to present sufficiently simple pictures that students at each level can handle; however, this should not be done in a way that shuts down questions. We recommend that students should be made aware that textbook accounts are only models, and encouraged to extend their learning beyond the models. The plausibility of our recommendations is shown in a pilot study we conducted with secondary school students in South Korea.