BCH 3120 Study Guide - Quiz Guide: Brownian Motion, Scattering, Electron Microscope
2 May 2021
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Document Summary
Results from random collisions of colloidal particles with the molecules of the dispersion medium. Stoke"s law of sedimentation: most colloidal dispersions show little or no sedimentation because the particles are too small and sedimentation is opposed by their active brownian motion: Colloid particles spontaneously di use from a high to low concentration region: critical particle size: 0. 3 - 0. 5 m. Proteins carboxylic acid and amine functional groups. Depending on ph can carry net +ve, -ve or no charge (isoelectric) Due to changes in surface composition - substitution of ions (replacement of al3+ by mg2+ in bentonite clay gives a net negative charge to clay lamellae. Surfactant molecules strongly adsorb to particle surfaces. Combination of ionic and hydrophobic e ects: di use double layer = gouy-chapman layer. 2x = distance between 2 particles: stern ( ) potential. Decreases exponentially through di use double layer: pushing 2 particles close. Can"t come closer than di use double layer (no overlap)
