This paper describes the implementation of an open-ended inquiry experiment for high-school students, based on gas chromatography (GC). The research focuses on identifying the level of questions that students ask during the GC open inquiry laboratory, and it examines whether implementing the advanced inquiry laboratory opens up new directions for students' questions. We found correlations between students' achievements and the level of their inquiry questions, and showed that the GC open-ended inquiry laboratory engaged students with different abilities and helped them deepen their understanding in various ways, according to their different levels. (Contains 4 tables and 1 figure.)