Combined with Explains almost all Solution behaviors Fourth example of Colligative Properties: Osmosis – the movement of solvent through a semi- permeable membrane from a region of high solute concentration to low solute concentration.

pasta marshmallow nut light source Semi- Permeable Membrane bag 5% sugar solution This is the system at equilibrium This is what creates the dis-equilibrium In the beaker

pasta marshmallow nut light source The system is disturbed away from equilibrium X H 2 O (outside) ≠ X H 2 O (inside) 100% H 2 O (outside) ≠ 95% H 2 O (inside) The system will respond by shifting equilibrium H 2 O (outside)  H 2 O (inside) How???

Only water molecules can move thorough membrane The membrane is invisible to water

pasta marshmallow nut light source When the system responds by shifting equilibrium: If diluted to 1% sugar: mol/ L = M Using:  = c R T  = M x atm/M K x 298 K  = atm or 544 mm Hg The diluted sugar solution under pressure rises up the tube, like a manometer. The height represents the Osmotic Pressure

light source Water fills beaker corn syrup pipet fits tightly into hole core of carrot removed and filled with corn syrup Carrot As a membrane

pasta marshmallow nut light source

 = c R T  in: atm mol/L kelvin .0820 L/atm K Combined with Explains almost all Solution behaviors Osmosis – the movement of solvent through a semi- permeable membrane from a region of high solute concentration to low solute concentration. Osmotic Pressure – the pressure created after the system attains equilibrium, calculated by:

Combined with Explains almost all Solution behaviors Semi-permeable membrane: now this is a very special device: selective for molecular size  Size exclusion What is an important example that uses a Semi-permeable membrane? Living cells: have many ways of selecting which molecules get inside or stay outside

What is a Colloid? Intermediate between a true solution and a suspension High molecular weight Aggregate into large particles, ~micron Finely divided (“isolated”) dispersions

What is a Colloid? What is Cool Whip? Whipped toppings are essentially an emulsion of oil (usually around 35%) and sweetened water (around 60%) with an emulsifier, like phosphatidyl choline (lecithin), to maintain the suspension. The oil used for whipped toppings, like Cool Whip™, is hydrogenated vegetable oil, and after hydrogenation (saturation with hydrogen), all vegetable oils are the same (saturated), regardless of where they come from. So hydrogenated olive oil could easily be used to make whipped toppings.

What is Cool Whip? Oils (and fats) are fatty acids— phospholipids—have two parts (as their name suggests): a phosphate "head", and a long hydrocarbon "tail" (the fatty part). “head” “tail”

What is Cool Whip? An emulsion of oil and water is really just water with microscopic oil droplets floating in it (this is called a colloidal suspension). To get the oil to form these droplets, called micelles, the molecules of fatty acid have to pack together as closely as possible to minimize the volume of the micelle. To form a micelle, the heads of the molecules, which are soluble, form the outside of the drop, while the tails fill the inside. micelle Lots of micelles suspended in water No water wants to be here!

What is Cool Whip? The defining characteristic of unsaturated fats is that their tails have kinks in them. These kinks prevent the molecules from packing close together, so they tend to disrupt the micelles - the more unsaturated fats, the fewer and larger the micelles. Without good micelles, the emulsion will separate into its two phases (oil and water), and without a good emulsion, you can't whip the suspension into a dessert topping. kinks

What is Cool Whip? The unsaturated fats have tails have kinks that prevent the molecules from packing close together, so they tend to disrupt the micelles - the more unsaturated fats, the fewer and larger the micelles. Compare to a saturated— hydrogenated— fat

Micelles in Medicine Example 1. self-forming micelles by an eczema drug

Designer Micelles – Block Co-Polymer Note use of weight% “On the basis of examples already found in literature, one unifying rule for generating polymersomes predicts that f (the weight percent of the hydrophilic block) must be equal to 35±10%. Molecules with f >45% are expected to form spherical micelles, whereas molecules with f <25% are expected to form inverted nanostructures. When the weight percent of the hydrophilic block f ~ 35 % : vesicles (polymersomes) form When the weight percent of the hydrophilic block f >45 % : micelles form

S. Lecommandoux, M. F. Achard, J. F. Langenwalter, H.-A. Klok Macromolecules 34(26), (2001)

Different realm of colloid investigation: Dynamics of micelle monomers