This article sets out to consider what we might mean by "practical" work, and the different purposes we might have for laboratory activities, in teaching chemistry. One common aim for student practical work is to support the learning of chemical concepts, but both the nature of chemical ideas and the demands of undertaking laboratory work can act as barriers to effective learning. The article analyses one common chemistry practical to illustrate why learning from student laboratory work can be challenging for students. Suggestions are offered for the effective use of chemistry practical work.