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1 Osmosis & Dialysis Conventional solutions –Gases Air is mixture/solution of N 2, O 2, etc … –Liquids Ionic – Salt in Oceans Non-Ionic - Sugar in water.

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Presentation on theme: "1 Osmosis & Dialysis Conventional solutions –Gases Air is mixture/solution of N 2, O 2, etc … –Liquids Ionic – Salt in Oceans Non-Ionic - Sugar in water."— Presentation transcript:

1 1 Osmosis & Dialysis Conventional solutions –Gases Air is mixture/solution of N 2, O 2, etc … –Liquids Ionic – Salt in Oceans Non-Ionic - Sugar in water –Solids Solder, metal alloys (e.g. Stainless Steel) Inorganic oxides, magnetite Fe 3 O 4 –Fe 3 O 4 has impossible valence between 2 & 3 = 2.67 –Fe 3 O 4 is actually FeO “dissolved” in Fe 2 O 3, a “spinel” structure Solutions share similar properties –Homogeneous –Well mixed, evenly distributed

2 2 NaCl in an aqueous solution. CHAPTER 5: Solutions, Colloids, and Membranes NaCl IN AN AQUEOUS SOLUTION

3 3 CHAPTER 5: Solutions, Colloids, and Membranes MOLECULES IN SOLUTION

4 4 Colligative Properties Solute effects the Solvent –Example of salt on snow covered road Freeze temp. of salty water < than pure water (snow) Outside temperature the same, so snow melts Works best when temp close to zero celsius But salt is tough on cars … promotes corrosion –Boiling point is increased with solute in solvent Sea water boils at higher temperature –Boiling point decreased with altitude Less air pressure, 1 atmosphere < 1bar Vapor pressure of water goes to ambient at lower o C

5 5 The equilibrium vapor pressure of a solution with (a) a nonvolatile solute is always lower than that of (b) the pure solvent by an amount that depends on the mole fraction of the solvent.

6 6 Special Solutions Other kinds of “solutions” –Colloids Small particles, no separation, skim milk Particles approaching molecular dimensions, <500 nm Kinetic energy keeps in motion, no settling –“Brownian Motion” observed in microscope –Suspensions Larger particles, may coagulate –Emulsions Mixtures of materials insoluble in each other Butter and cream are the same, different organization Convert cream to butter with agitation, reverse the emulsion –Cream is blend of oil particles immersed water solvent –Butter is blend of water particles immersed in oil matrix



9 9

10 10 Osmosis Living tissues are porous –Sweat is example of water through skin –Pores big enough for water, too small for blood Concentration cell –Permeable barrier between two different concentrations –∆S favors mixing versus separation (more random) –Tendency to mix generates pressure (& voltage) –Solvent goes through barrier to solution side “Osmotic” pressure develops on solution (mixing) side Flow will continue until pressure equals mixing tendency

11 11 A membrane is a barrier between two environments. A semipermeable membrane allows certain molecules to cross. All cells and organelles within cells are surrounded by semipermeable membranes. SEMIPERMEABLE MEMBRANES

12 12 LeChatelier’s Principle If a system at equilibrium experiences a change in concentration, temperature, or pressure, the equilibrium will shift to counteract the imposed change, establishing a new equilibrium

13 13

14 14 CHAPTER 5: Solutions, olloids, and MembranesCHAPTER 5: Solutions, olloids, and Membranes OSMOTIC DIFFUSION … a probability issue. More solute molecules hit membrane from left, so gradual movement of solute to right. At equilibrium, both sides have equal solute molecules.

15 15 Osmosis Solvent molecules flow through openings in membrane in order to equalize concentrations of solutions. Note height of water column, pressure created by equalizing concentration

16 16 Reverse Osmosis A concentration cell, running backwards –Permeable barrier between two different fluids –Can apply mechanical pressure (e.g a pump) Pump pressure can force water through membrane Pressure must exceed osmotic pressure for any flow Leaves salt behind, which does not fit through pores –Preferred method today for making Deionized Water Less energy use than heat distillation Better screening than ion-exchange resins (particulates pass) Sea water to fresh water ? Age-old desire in arid places –Requires pump energy, rejected water is saltier Membranes sensitive to contamination blockage High pressures for high flow invite membrane failure Polymetrics (Santa Clara) was 1970’s pioneer in field

17 17 Reverse Osmosis apply enough pressure to overcome osmotic pressure … flow is reversed and solvent pushed out of solution

18 18 Reverse Osmosis 30 atm*14.7 psi/atm ≈ 450 psi ! (your tires have about 30 psi)

19 19 When excess pressure is applied to impure water, the backwards flow is called reverse osmosis. This can be used to purify water. CHAPTER 5: Solutions, Colloids, andMembrnesCHAPTER 5: Solutions, Colloids, andMembrnes REVERSE OSMOSIS

20 20 These are two ways by which molecules may cross semipermeable membranes. In osmosis, water may cross the membrane, but not other substances. Osmosis limited to SOLVENTS In dialysis, water or small solutes such as ions or sugars may cross the membrane, but not large molecules such as proteins or starch. In all cases, molecules move through simple diffusion to equalize solute concentrations. OSMOSIS AND DIALYSIS

21 21

22 22 These surround all cells and maintain different concentrations of ions and molecules inside and outside the cells. Ions and large molecules require special transport systems to carry them across the membrane as needed. CHAPTER 5: Solutions, Colloids, and Membranes CELL MEMBRANES

23 23 If RBCs are immersed in hypotonic or hypertonic solutions, water will cross the RBC membrane inappropriately, destroying its function. Eventually the cells in hypotonic solution will burst in what is called hemolysis; the cells in hypertonic solution shrivel during crenation. OSMOSIS IN RED BLOOD CELLS (RBCs)

24 24 Definitions


26 26 In dialysis, small solutes can cross a special membrane. They always cross from high to low concentration. Dialysis is used to separate solute molecules from colloidal particles. Kidneys carry out dialysis by removing urea and creatinine and retaining water and electrolytes Artificial dialysis can be used if kidneys are diseased. CHAPTER 5: Solutions, Colloids, and Membranes DIALYSIS

27 27 Creatinine is muscular waste product, removed by kidneys

28 28 Muscles release Creatinine, healthy kidneys release it in urine, diseased kidneys require filtration removal.


30 30 Dialysis Methodology

31 31 Small molecules move through pores to equalize solute concentration

32 32

33 33 In dialysis, small molecules and ions can flow from a solution of higher concentration to a lower concentration solution. DIALYSIS

34 34 Tubing Pump Eccentric wheel squeezes tubing, pushing liquid forward nothing touches fluid except the tubing, no contamination

35 35 Dialysis treatment center

36 36 Ethylene gas to Polyethylene Plastic most common plastic, “Poly” n ≥ 1000 ethylene units

37 37 Glucose & Fructose in sugars Both are C 6 H 12 O 6, but have different structures Glucose has 6 member ring, while Fructose has 5

38 38 Sucrose is Sucrose + Fructose Joined via oxygen bond between molecules, a simple natural table-sugar polymer we use every day

39 39 Starch polymer similar bonding structure as sucrose, but n≈600 note that simplified diagram does not show all hydrogen

40 40 Starch polymer similar bonding structure as sucrose, but n≈600 note that simplified diagram does not show all hydrogen

41 41 Starch polymer can also be branched, n can be>1000

42 42 Today’s Experiment We will observe osmosis –Solvent goes through the membrane –Inside pure water moves to salty outside –Inside salty water absorbs water from outside We will observe dialysis –Smaller molecules (sugar) go through bag –Large molecules (starch) cannot pass

43 43 Our experiment

44 44

45 45 Experiment basics Weigh bag before and after osmosis –Did water bags get heavier or lighter? If heavier, water moving into salty bag If lighter, water moving out of pure water bag Weigh bags before and after dialysis –Did honey filled bags get heavier? Which one gained the most? –Did sugar pass through the bag? Benedict test will detect sugar passage –Did starch pass through the bag? Iodine test will detect starch

46 46 Which was it? (maybe both) Chem. test to see of solute moved out –BOTH osmosis and dialysis can occur –Test for osmosis is weight gain –Test for dialysis is passage of sugar Test for sugar using reagent –Turns blue  orange if sugar present –Run 4 test tubes One blank, a water only control, expect no change One with sugar, test the test …make sure it works Water from outside 2 dialysis bags –If it turns color, sugar = dialysis (unless you’re sloppy)

47 47 Questions Google, text, or handbook for structures –Fructose, Glucose, Vitamin C, Starch –Computer available at desk, or your own Pore size based on formula weight –Little molecules pass, big ones don’t Benedict test for sugars –Change blue to yellow if sugar present

48 48 Los Alamos National Laboratory's Periodic Table

49 49 Variation on experiment

50 50 edudev/LabTutorials/Dialysis/Kidneys.html

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