Theoretical models, submicroscopic scale

Chemical bonding is a theoretical idea that is a key part of the way matter is modelled by chemists at submicroscopic scales (as composed of extremely tiny quanticles , as described in Chapter 1) and so is not likely to be familiar to students from their experiences outside the classroom. However, if particle models are introduced in the manner recommended in this book (Chapter 2), students will have been introduced to the idea that the particles of which substances are made have holding power of varying strengths, which tends to cause them to clump together unless they have sufficient movement to overcome this. 

The first activity related to two models of the nature of matter at the submicro-scopic level. A core issue in teaching chemistry is that phenomena that can be directly observed (dissolving, burning) are commonly conceptualised at two very distinct levels (Johnstone, 1982) by a formal description and categorisation at the macroscopic level and through explanation of observed behaviour based upon theoretical models of the structure of matter at a submicroscopic scale (Taber, 2013). 

One of the most important features of modern chemistry is that it is a science that provides explanations of the reactions seen in the world at observable scales (at the molar or macroscopic level) in terms of theoretical submicroscopic entities such as molecules and ions and electrons. As chemistry teachers we are constantly shifting back and forth between the macroscopic descriptions and submicroscopic models this shifting takes place in our thinking and is reflected in our classroom talk. To follow our arguments and explanations, our students need to be able to follow these shifts. 

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