8.8.2 Dynamic Properties of colloids Out-class reading Levine pp 402-405 13.6 Colloids
8.8.2 Dynamic Properties of colloids Out-class reading: Levine pp. 402-405 13.6 Colloids
8.8.2 Dynamic properties of colloids (1) Brownian motion Robert Brown (1773-1858) Vitality? In 1827, the botanist Robert Brown published a study "a brief account on microscopic observation on the particles contained in the pollen of plant. He reported an irregular motion of pollen grains
(1) Brownian motion In 1827, the botanist Robert Brown published a study “A brief account on microscopic observation on the particles contained in the pollen of plant”. He reported an irregular motion of pollen grains. Vitality? 8.8.2 Dynamic properties of colloids
8.8.2 Dynamic properties of colloids (1)Brownian motion Wiener suggested that the brownian In 1903, Zsigmondy studied Brownian motion arose from molecular motion motion using ultramicroscopy and found T F∝ independent of the chemical nature of the Unbalanced particles collision from medum For particle with diameter> 5 um,no molecules Brownian motion can be observed Although motion of molecules can not be observed directly, the Brownian motion gave indirect evidence for it
In 1903, Zsigmondy studied Brownian motion using ultramicroscopy and found： For particle with diameter > 5 m, no Brownian motion can be observed. Wiener suggested that the Brownian motion arose from molecular motion. Unbalanced collision from medium molecules Although motion of molecules can not be observed directly, the Brownian motion gave indirect evidence for it. (1) Brownian motion 8.8.2 Dynamic properties of colloids r T 1 r independent of the chemical nature of the particles
8.8.2 Dynamic properties of colloids (2) Diffusion and osmotic pressure 1905 Einstein proposed that D kRT rT f=frictional coefficient For spheric colloidal particles, XX Concentration gradient f= tnr Stokes'law Fickian first law for diffusion RT Einstein first law for D L6丌 r diffu uSIon D
(2) Diffusion and osmotic pressure x Fickian first law for diffusion Concentration gradient = dn dc D dt dx = − 1905 Einstein proposed that: Lf RT f k T D = = B For spheric colloidal particles, f = 6r Stokes’ law f = frictional coefficient L r RT D 6 1 = Einstein first law for diffusion 8.8.2 Dynamic properties of colloids
8.8.2 Dynamic properties of colloids (2)Diffusion and osmotic pressure Atoms and molecules had long been theorized as the In 1908, Perrin found that, for gamboge constituents of matter. Albert Einstein published a sol with diameter of 0.212 um, n=0.0011 paper in 1905 that explained in precise detail how the motion that brown had observed was a result of the Pa.s. After 30s of diffusion the mean pollen being moved by individual water molecules diffusion distance is 7.09 cm s-I making one of his first big contributions to science This explanation of Brownian motion served as D、RT1 convincing evidence that atoms and molecules exist L tnr and moves constantly. which was further verified experimentally by Jean Perrin in 1908 He calculated Avgadro's constant from this equation Because of the Brownian motion osmotic pressure also originates L=6.5×10 Which confirms the validity of Einstein- RT Brownian motion equation
In 1908, Perrin found that, for gamboge sol with diameter of 0.212 m, = 0.0011 Pas. After 30 s of diffusion, the mean diffusion distance is 7.09 cm s -1 . L = 6.5 1023 Because of the Brownian motion, osmotic pressure also originates RT V n = Which confirms the validity of EinsteinBrownian motion equation (2) Diffusion and osmotic pressure 8.8.2 Dynamic properties of colloids Atoms and molecules had long been theorized as the constituents of matter. Albert Einstein published a paper in 1905 that explained in precise detail how the motion that Brown had observed was a result of the pollen being moved by individual water molecules, making one of his first big contributions to science. This explanation of Brownian motion served as convincing evidence that atoms and molecules exist and moves constantly, which was further verified experimentally by Jean Perrin in 1908. L r RT D 6 1 = He calculated Avgadro’s constant from this equation