PPT Slide

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• Dispersion forces are weak forces caused by momentary  oscillations of electron density causing a momentary dipole in a  neighboring molecule.

• When particles collide, electron clouds are repelled,  and electron density is momentarily greater in one  region of the particle than in another.

• Transitory dipoles are induced in both  particles, which, in turn, induce  instantaneous dipoles in adjacent particles.

• Dispersion forces generally increase with molar mass.

• Greater contact allows the dispersion forces to act at more points,  so n-pentane has a higher boiling point than neopentane (same  molar mass).

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