Research into practice: Visualising the molecular world for a deep understanding of chemistry

Why is chemistry so difficult? A seminal paper by Johnstone (1982) offered an explanation for why science in general, and chemistry in particular, is so difficult to learn. He proposed that an expert in chemistry thinks at three levels; the macro (referred to as the observational level in this article), the sub-micro (referred to as the molecular level here), and representational (referred to as the symbolic level here). The observational level involves chemistry that is visible and tangible, incorporating what we can perceive with the senses. The molecular level of understanding consists of mental images that chemists use to imagine and explain observations in terms of atoms, ions and molecules. Observed phenomena and molecular-level processes are then represented in terms of mathematics and chemical notation at the symbolic level.