Something you can do visually in the lecture theatre is to take in some things you wish to connect and make up an item. Or in PhET, for example, there’s a little activity you can do making sandwiches and you can work out how much you need of which one and whether you’ve got something that’s there in excess or something that’s limiting. It's based on the molar ratios or the stoichiometric coefficients, which in turn are based on the number of moles reacting.
Take something into the lecture theatre, like a bag of pebbles - a whole lot that are the same size and make sure that it is visibly a kilogram (or another specified mass). Also have chickpeas or some other smaller and lighter thing. When you have a kilogram it’s really easily recognisable that there’re a lot more particles in the chick pea bag that there are in the pebble bag. You can’t show them a mole of something because it’s too many, but just use this to begin to unpack the idea that we’ve got a whole lot of tiny, tiny particles, much smaller than the ones in the demonstration.
