(Polar molecules, Non-polar molecules, etc.)
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The shape of a molecule directly influences the strength of interactions by attractive/repulsive forces. Dr. Lavelle used the rod-shaped vs. spherical shape example in lecture, where the rod-shaped molecules have a stronger bond/higher boiling point because the dipole-dipole attractions were closer to each other. Since the molecule shape affects the strength of interactions, this means boiling point is also related to the molecule shape.
A good thing to think about are organic molecules (hydrocarbons, more specifically, alkanes). Van Der Waals forces are a strong contributor to the boiling point of molecules. Longer, more linear alkanes have a stronger Van Der Waals forces and therefore it requires more energy to break this attraction (meaning a higher boiling point). However, when adding side chains, it can interrupt Van Der Waals forces (some branching does contribute to a spherical shape as talked in the previous post), and therefore it requires less energy to break these bonds, meaning a lower boiling point.
The relative strength of the intermolecular forces helps determine the boiling points. Stronger intermolecular bonds require more energy to break, so substances with stronger bonds will have a higher boiling point.(vice versa) Furthermore, more branched particles have LESS surface area compared to a straight chain molecule, hence experience less Van der Walls forces, lowering their boiling points. (Van der Waals dispersion force is proportional to the surface area).
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