Understanding the idea of a ‘substance’ is central to making sense of the variety of materials in the world and the way in which they change. Research into students understanding of chemistry shows, that they find many fundamental ideas difficult which can lead to problems in their progression. The carefully constructed sequence of ideas and activities in the ‘Stuff and Substance’ materials show how these important concepts can be developed and provide a sound basis for further study. This booklet looks at how practical work can be used to support the development of critical concepts in chemistry for secondary school students. Also provided are links to the videos and animations in the Stuff and Substance CD-ROM, and how they can be used to develop the story.