Pebble Demonstration for Moles

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. We want to show also that when we’re dealing with the same number of particles the overall mass is different for different types of particles or objects.