This paper reports the results of research in which the objective was to explore the preconceptions of slope in seventh-grade students. Preconceptions are understood as students' knowledge prior to the formal teaching of a certain concept. For data collection, task-based interviews composed of ten tasks applied to 21 Mexican students were used. The data analysis was carried out using the Thematic Analysis method. Results indicate that the students have several preconceptions in which they consider the slope as any of the following: an intersection with the X or Y-axis, an arithmetic operation, a length, an object, a height, and "something to do." These findings pose the challenge of achieving conceptual changes from these preconceptions. In this sense, science education has been the field most exploited in mathematics education; a collaboration between teachers and researchers from both fields could contribute to finding strategies to face this challenge.