This image shows tricky topic moles hierarchy. At the top is the tricky topic moles. Below and linked to the moles tricky topic are four stumbling blocks labelled ‘What is a mole?’, ‘Purpose of moles’, ‘Knowledge of atoms’ and ‘Working with equations’. Underneath these stumbling blocks, and linked to them, are five student problem examples, ‘Unable to visualize a mole and grasp concept’, ‘Choosing the correct equation’, ‘Molecules as bonded atoms’, and ‘manipulating equations’. Each student problem example is linked back up the hierarchy to one or more stumbling blocks. Each student problem examples has a line below it leading to one or more of the problem distiller reasons explaining why the students have these problems.