[this is a copy of my post to that group, just to round this thread off]
Regarding how we avoid students thinking, I got quite a nice answer during the workshop actually. The presenter pointed out that with forces, no-one thinks that forces really are arrows [now there’s an interesting research project in its own right…] so students should be encouraged to view this very much as an abstraction.
If that is the case, is this a situation where a computer screen (like a mobile phone battery symbol) actually provides a better representation than a beaker of coloured water?
Or perhaps even a worksheet with bits to colour in?