Colloids

Chapter 8 Solutions Colloids and Suspensions Osmosis and Dialysis

LecturePLUS Timberlake

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

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Colloids  Have medium size particles  Cannot be filtered  Separated with semipermeable membranes  Scatter light (Tyndall effect)

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Examples of Colloids 

Fog

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Whipped cream

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Milk

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Cheese

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Blood plasma

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Pearls LecturePLUS Timberlake

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Suspensions  Have very large particles  Settle out  Can be filtered  Must stir to stay suspended

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Examples of Suspensions  Blood platelets  Muddy water  Calamine lotion

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Osmosis In osmosis, the solvent water moves through a semipermeable membrane Water flows from the side with the lower solute concentration into the side with the higher solute concentration

Eventually, the concentrations of the two solutions become equal. LecturePLUS Timberlake

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Osmosis

4% starch

10% starch

H 2O

semipermeable membrane LecturePLUS Timberlake

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Equilibrium is reached.

7% starch 7% starch H2OO

water flow becomes equal LecturePLUS Timberlake

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Osmotic Pressure Produced by the number of solute particles dissolved in a solution Equal to the pressure that would prevent the flow of additional water into the more concentrated solution Increases as the number of dissolved particles increase LecturePLUS Timberlake

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Osmotic Pressure of the Blood  Cell walls are semipermeable membranes  The osmotic pressure of blood cells cannot change or damage occurs.  The flow of water between a red blood cell and its surrounding environment must be equal LecturePLUS Timberlake

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Isotonic solutions •

Exert the same osmotic pressure as red blood cells.

•

Medically 5% glucose and 0.9% NaCl are used their solute concentrations provide an osmotic pressure equal to that of red blood cells H2O LecturePLUS Timberlake

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Hypotonic Solutions Lower osmotic pressure than red blood cells Lower concentration of particles than RBCs In a hypotonic solution, water flows into the RBC The RBC undergoes hemolysis; it swells and may burst.

H 2O LecturePLUS Timberlake

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Hypertonic Solutions Has higher osmotic pressure than RBC Has a higher particle concentration In hypertonic solutions, water flows out of the RBC The RBC shrinks in size (crenation)

H2O LecturePLUS Timberlake

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Dialysis Occurs when solvent and small solute particles pass through a semipermeable membrane Large particles retained inside Hemodialysis is used medically (artificial kidney) to remove waste particles such as urea from bloodLecturePLUS Timberlake

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