In the lab it comes out in a variety of ways. It comes out most commonly when the student gets to actually start doing their calculations and you ask them to relate that back to what they’ve actually physically measured. And when they start doing those sorts of things you realise there’s a bit of a misplaced idea here or a misconception that you can deal with there.
In the lab you can get students to weigh out quantities and react them and then do calculations for the yield, so they’re applying it. That’s the way in which they come to terms with what they’re actually doing and the molar basis for that. It’s about representing what’s going on, on a molecular basis. We handle things on a molar basis because they’re the amounts we can weigh, and it’s representative of what’s going on on the molecular scale. It’s just scaled up by 6 x 1023.
Choose practicals that align closely with important topics. For Example, three ways of experimentally determining a rate law - all three ways should be used in the lab.
You can get the students to physically feel that liquids are not compressible by giving them three closed syringes: one contains water, say 50 mL, that’s been put in the freezer to become ice; another syringe contains 50 mL of liquid water, and the other one is gas. Ask them to push the syringes and see what happens. They find they cannot push the syringes containing liquid or solid, even though they think there would be some space in the liquid one. The misconception is that liquids fall somewhere between solid and gas and so should be “a bit” compressible.
Do a demonstration, for example, a little explosion where you get a fluorescent gas coming off. It’s in a way related to the material, but it’s more about keeping them awake and engaged. It’s just a little bit of fun. That helps. They obviously enjoy it. Keep the didactic, formal teaching very, very short, and just mix it up quite a bit.
