Intermolecular forces performance comparison

The second component of analysis for determining the cognitive load effects of nanoscience and materials science contexts on exam items for the two different chemistiy courses, involved a paired item analysis. Two nanoscience items in the sub-categories of spectroscopy and band theory, as well as two materials items in the sub-categories of intermolecular forces (IMF) and Lewis stmctures, were inserted into the practice exam to serve as paired items in these same sub-categories. The first comparison we analyzed was both groups of students differential performance on non-nanoscience and materials exam items versus nanoscience and materials items (Figures 4 5). 

In Figure 4, the performance comparison on non-nanoscience and materials nanoscience and materials items for pre-engineering chemistry students, it can be seen that in both the areas of spectroscopy and Lewis structure, the engineering stndents have a higher performance when the format of the item inclndes reference to either nanoscience or special materials. This observation is very interesting, becanse nnlike the areas of intermolecular forces and band theory, neither of these concepts were known to be taught in the context of... 

In the interior of a colloidal particle, the interactions between molecules act in a symmetric manner. By contrast, an imbalance in the intermolecular forces exists at the particle surface since the local environment changes significantly. This then results in a surface tension that tends to minimize the particle surface area. In addition, the fraction of molecules residing at the particle surface increases rapidly with decreasing particle size. It is no wonder, therefore, that many colloidal particles with a dimension in the nanometer range show quite unique performance properties in comparison with the bulk materials. 

The heat of sublimation is connected with intermolecular forces in the crystal and with the lattice energy. This last quantity can fairly easily be calculated for crystals even by simple models (Section 8.7), so that a comparison between calculated lattice energies and measured heats of sublimation is a common way of checking the performance of intermolecular potential energy schemes. Unfortunately, heat of sublimation measurements for organic compounds are also hampered by many experimental problems and are often scarcely reliable [8]. Three main methods for their determination are available ... 

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