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Colloids

Colloids. Solutions. Have small particles (ions or molecules) Are transparent Do not separate Cannot be filtered Do not scatter light. Colloids. Have medium size particles Cannot be filtered Separated with semipermeable membranes Scatter light (Tyndall effect). Colloids.

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Colloids

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  1. Colloids

  2. Solutions • Have small particles (ions or molecules) • Are transparent • Do not separate • Cannot be filtered • Do not scatter light. LecturePLUS Timberlake

  3. Colloids • Have medium size particles • Cannot be filtered • Separated with semipermeable membranes • Scatter light (Tyndall effect) LecturePLUS Timberlake

  4. Colloids • In a solution, dispersed particles are molecule-sized (roughly 0.1 nm). • In a colloid the dispersed particles are 1 – 1000 nm.

  5. The Tyndall Effect Light scattered by the (larger) colloidal particles makes the beam visible.

  6. Examples of Colloids • Fog • Whipped cream • Milk • Cheese • Blood plasma • Pearls LecturePLUS Timberlake

  7. Suspensions • Have very large particles • Settle out • Can be filtered • Must stir to stay suspended LecturePLUS Timberlake

  8. Examples of Suspensions • Blood platelets • Muddy water • Calamine lotion LecturePLUS Timberlake

  9. A Suspension and a Colloid Suspended particles (sand) are far too large to show on this scale.

  10. Formation and Coagulation of a Colloid When a strong electrolyte is added to colloidal iron oxide, the layer of charge on the surface of each particle is partially neutralized… …and the colloidal particles coalesce into a suspension that settles quickly.

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