In practical work focussing on conceptual development, students spend valuable in-class time on collecting data rather than making sense out of it. This provides a barrier to learning about the targeted concept. To address this problem, we developed an approach that we coin "collaborative data collection." Using a practical on the topic "density," we describe this approach and illustrate how the focus of practical work shifts away from mere data-collection towards meaning making. Although a single practical is described, the approach can be applied to other practicals as well.