Helping learners make sense of 'stuff'

A Y9 student was telling me about the new topic she had started in science: 

'we were looking at the Periodic Table, and it had stuff like iron, and you had to know what the symbol for it was, and if it had certain ions you balanced them'. 

'Stuff' featured often in this student's reports of her science lessons, and indeed she was being taught about the nature of 'stuff'. This is chemistry - learning about different types of 'stuff', and how it reacts with other 'stuff'. However, chemists characterise 'stuff' as elements, compounds, mixtures and so forth which do not obviously relate to perceived properties of materials, and we explain much of the subject in terms of various particle models. These ideas provide the conceptual basis of our science,¹ but students often have difficulty making sense of such abstract notions.