Guidelines for Precise Language

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The Representational Triplet

Chemical Educators have long been using the Representational Triplet to describe the three types of representation in Chemistry.[1] Below is the triplet set forth by the editors of Multiple Representations in Chemical Education:[2]

  1. macro: empirical properties of solids, liquids, colloids, gases, etc. Evidenced by everyday life, able to be measured. Some examples include density, concentration, pH, pressure, color change.
  2. submicro: aspects of chemistry which cannot be seen with an optical microscope directly. These include plotting electron density, atoms, molecules, rotatable models, shapes of orbitals, graphs or diagrams.
  3. symbolic: representations of the macroscopic or microscopic representations. Using symbols to represent atoms, or (s), (l), (g) to represent macro representations of solids, liquids and gases. Other examples of this are Lewis Structures, chemical equations, representing charges by + or -.

These three representations make up a triangle and nearly all of our descriptions in chemistry lie somewhere in the middle of the triangle - with aspects of all three types of representation. Some others argue for the existence of a 4th representation: analytical or quantitative. This can be argued to be part of the symbolic representation of the macro representation. If this is taken to be a fourth dimension, then these four are described as a tetrahedron, whereupon we use a mixture of the four representations when discussing chemical concepts or experiences.

The reason this is discussed is that it is known that students have trouble to distinguish between these three (or four) representations and it is critically important to use precise language in describing things. Here, we quote Bob Bucat and Mauro Mocerino discussing considerations regarding precise language use to avoid confusion:

Our very first recommendation concerns the careful use of language to distinguish between these two levels [submicro and macro]... To be precise, benzene doees not have a plane of symmetry (although its molecules do), water is not composed of the elements (as substances) hydrogen and oxygen, C8H18 is not octane (although octane's composition can be represented as C8H18), nylon is not a long molecule (although its molecules are long), polyethylene is not an enormous alkane, liquid limonene is not chiral (although it is optically active), a reaction energy profile diagram does not plot the energies of the reactants and products during reaction (although it may plot the combined energies of a small group of atoms before, during and after a single fruitful collisional event between reactant molecules, ions or atoms), and the substance concentrated sulphuric acid is a powerful oxidising agent (not the S atom in the +6 oxidation state). That members of the chemistry community know precisely what they mean by such loose statements does not mitigate the lack of awareness of students about the distinction between chemistry's levels. Should we take the trouble to be more careful and precise, even if to do so means being more wordy?[3]

To be honest, some of those precise language statements are too wordy to be understood clearly and one would argue that their verbosity undermines the desire to be more precise for student learning. As a rule, then, we advise that authors use these considerations when writing exemplars or editing exemplars. Avoid mixing the macro representational level with the submicro, especially, as this may confuse the reader who has not fully grasped the conceptual delineation between the two.


  1. Johnstone, A. H. (1991) Why is science difficult to learn? Things are seldom what they seem. Journal of Computer Assisted Learning. 7, 75-83
  2. Gilbert, J. K., D. F. Treagust (eds), Introduction: Macro, Submicro and Symbolic Representations and the Relationship Between Them: Key Models in Chemical Edcuation. Multiple Representations in Chemical Education Models and Modeling in Science Education 4, DOI 10.1007/978-1-4020-8872-8_1, Springer Science+Business Media B.V. 2009
  3. Bucat, B. and M. Mocerino. (2009) Chapter 1 Learning at the Sub-micro Level: Structural Representations. Multiple Representations in Chemical Education, Models and Modeling in Science Education 4, pp 11-29.
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