The concept of logarithms is considered as one of the great moments in mathematics (Eves, 1980) and regarded as an important mathematical concept that are useful for modeling and understanding population growth, radioactive decay, and compound interest (Smith & Confrey, 1994). It is also one of the core concepts for many mathematical courses such as calculus, differential equations, complex analysis. Despite its’ importance, students have many difficulties in learning the concept of logarithm. For example, Weber (2002) noted that students often forget many properties of logarithms shortly after they learn them and can seldom explain why these properties are true. Brezovski & Zazkis (2006) denoted that students often perform operations in logarithmic expression successfully when the meaning is overlooked. Moreover, Kastberg (2002) found that students characterize the logarithmic function as a symbol or a notation and understand logarithms as “problem to do”, and they have great difficulty to recognize non-standard problems based on logarithms without mentioning logarithmic function. Several researchers argued that approaches for teaching logarithm have a great role in students’ limited understanding of logarithm (Confrey, 1991; Confrey & Smith, 1995).  While students are encountering such difficulties, the instructional methods and strategies that we used to teach logarithms to students are considered important.
The secondary school mathematics curriculum of Turkey has been changed dramatically in recent years. In old curriculum, logarithm concept was taught mainly using procedural approaches and with routine problems.  Exponential and logarithmic functions were typically presented as formulas and students were assumed to associate the rules for exponents and logarithms with routine algorithms as a formal algebraic way. On the contrary, in the new curriculum, approaches such as mathematical modelling, problem solving, and reasoning have become primary components of mathematics teaching. The logarithm concept in the new curriculum is based on these approaches. Including several real life situation, new curriculums creates several opportunities for students to explore logarithm concept while connecting between numerical and algebraic experiences. On the other hand, we don’t know yet whether implementation of reformed mathematics curricula has a positive influence on students’ conceptions of logarithm. Therefore the purpose of this study is to investigate 11.th grade secondary school students’ conceptions of logarithm concept.

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