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Any student is expected to know that correct prediction is a necessary, but not a sufficient, condition any theory must meet to be acceptable. However, an eventual weakening of reflective and critical attitudes when dealing with “whats” and “whys” in science learning can easily lead to an identification of the predictive success of a given theoretical model, albeit useful as an intermediate state of reasoning, with the fundamental explanatory power of such a model. This is not always taken into proper consideration by teachers and textbooks. Examples from chemistry teaching are discussed in this paper.

The question of solubility of salts in water, besides being a field of interest in itself, provides good examples for the illustration of basic thermodynamics applied to chemistry. In this paper two pairs of salts, NaCl and CaCO3, and MgCO3 and MgSO4, are discussed to illustrate the interpretation of the different behavior of salts in water in terms of the fundamental concept of entropy (entropy of an isolated system or total entropy of a closed system plus its surroundings). As part of this discussion we also show how computer simulations can help improve students' understanding of these chemistry concepts.

A numerical problem was devised to improve the understanding of chemical equilibrium. It draws critical attention to the reference states when Kc and Kp are being used.

Software that illustrates Le Chatelier's principle; found on the Advanced Chemistry Collection CD-ROM, 3rd Edition.

An experiment and a computer simulation are presented to address a counterintuitive situation often encountered when teaching chemical equilibria. This is prompted by the question "How can the subdivision of a solid reactant affect the reaction rate and not the composition of the equilibrium state?"

Encouraging students to appreciate the approximations involved in using the rotational isomeric state approximation and the conditions under which they can be acceptable.

In this paper, the authors recall and systemize the restrictions to the application of Job's method, illustrate its use associated to proton magnetic resonance spectral intensities, and present some results of a computer program they developed for the case of multiple equilibria.

An equation sum can be used safely by itself in stoichiometric and equilibrium calculations only if the intermediates produced in separate reactions are at low steady-state concentrations and if there are no other equilibria involving those species.