Compared to hands-on experiments, virtual laboratory work has the advantage of being both more cost- and time-effective, but also invokes questions about its explorative capacities. The aim of this chapter is to study how students' scientific reasoning was contingent on altered guiding structures within a virtual laboratory experiment. The virtual laboratory was developed through a design experiment involving three successive versions with altered guiding structures. Analysis of 12 dyads' reasoning about gas solubility in water revealed that the problem was not primarily for the students to realize how the volume of gas changed, but rather to understand the concept of solubility of gases. It was also observed how the guiding structures within each version influenced the students' reasoning about the studied phenomenon in certain trajectories.