Use large scale diagrams with many molecules to show the progression from initial to reacting to equilibrium, and extend that with changes to the system that influence the equilibrium. In these ensure that there are many molecules present rather than one.
Use several real life examples with different ways of causing the equilibrium to shift. Swimming pool chemistry:
HOCl can enter the cells of undesirable organisms to kill them, but OCl- can’t, hence if the equilibrium is too far to the right it won’t act effectively. If you add acid (say HCl) the position of the equilibrium shifts to the left, producing more OCl-. That’s partly why the pH of the pool is important.
Use demonstration or simulation of how both forward and reverse reactions occur up to and at equilibrium in several mixtures. The PhET simmulation below shows both reactions are happening, even though concentration of reactants and products isn't changing.
Use drugs as an example of the relationship between how much of a species is protonated and how much is non-protonated. This is an equilibrium process. For a carboxylic acid drug, if it’s protonated it’s not ionic, if it’s not protonated it’s anionic. And if it’s going from gut into blood for example, whether or not it goes through the membrane will depend upon the pH of the system.
Relate equilibrium to students’ own experience of strong versus weak acids. For example, you can put vinegar on your fish and chips but not HCl. From high school they might have an understanding that vinegar is a weak acid compared to hydrochloric acid, but they never knew why. And you could then show them that with equilibrium, this is why.
