Thinking about energy as an orange liquid
Teaching Guidance for 11-14
Dealing with an abstract quantity
Strictly speaking energy is an abstract quantity with a calculated number and a unit of measurement. However, even with the brightest pupils of this age range, you will do few calculations, and even then only for a limited range of situations. Therefore, we have chosen the orange fluid to stand in place of the quantity. We hope this will engage the imagination. Although it does not have much predictive power, the model does have considerable value as a tool to think with. We think you'll need to use one like this, if not this one.
We have suggested that you concentrate on changes where comparatively few stores account for all of the energy changes. So no orange fluid can cross the boundaries of what you describe. The fluid may move around, and even become more spread out with time, but there is still the same quantity of fluid. Furthermore, this fluid behaviour is familiar, following the everyday behaviour of water.