Solution vs Colloids The solution or true solution - this is a mixture of one or more substances which are dispersed in solvent (e.g. water or another solvent). The true solution is one phase system because it has dispersed particles below 1nm. particles can not be detected by optical means, like microscopes, including an ultra microscope. solution is homogeneous, as one-phase liquid (e.g. one solvent or pure water). does not show the Brownian movement. may pass throug dialitic membrane

Solution vs Colloids Solution: Colloids: Transparent to ordinary light Stable unless solvent evaporated May pass through dialytic, but not true osmotic, membranes Colloids: Typically 1000 nm or more per particle Not totally transparent – Tyndall Effect May separate out Particles are too large to pass through most membranes

COLLOIDAL SOLUTIONS COLLOIDAL SOLUTION – HETEROGENEOUS system - with particle size of 10-9-10-7 m in diameter (1 – 100 nm, up to 500 nm) 10-9 m = 1 nm = 0.001 micron 10-7 m = 100 nm = 0.1 micron 10-6 m = 1000 nm = 1 micron

The colloidal system [synonyms: colloidal state, colloid, sol or colloid ] solution – are heterogeneous dispersive (mostly two phase ) configuration, in which we can distinguish two phases: continues - dispersing phase (solvent(s) or bulk material) which is relatively very small in size particles (e.g. water particles are about 0.1 by 0.2 nm) not continues - dispersed phase which particles diameter are relatively large, 1-100 nm (10-9 – 10–7 m), and in case of biopolymers – up to 500 nm.

Properties of colloids: They can be seen in ultra–microscope. Attention: the difference between an ultra-microscope and ordinary one is that in the former the light falls laterally on the liquid under study, instead of from below. The ordinary microscope with x400 magnifications has limitations for particles below 1 micron, but still is able to show “general structures of colloid system”. 2. They are not dialyzed –> Colloidal particles will not be separated by membranes (like bladder or parchment paper), because will not diffuse through a membrane. 3. They show permanent Brownian motions – mostly particles smaller than 100nm are able to make strong Brownian motion. 4. They show Tyndall effect – visible scattering light by the colloidal particles. 5. They may coagulate –> colloid particles become agglomerated.

DIAMETER OF PARTICLES OF DISPERSED PHASE Types of solutions depending of size of disspersed phase in dispersive medium TYPE OF SOLUTION DIAMETER OF PARTICLES OF DISPERSED PHASE True solution (homogenieous) < 10-9 m (<1nm) Colloidal (heterogeious) 10-9 - 10-7 m (1-100 nm) Suspension > 10-7 m (>100 nm)

Colloidal systems are wide spread in nature in form organic or inorganic All cells are some kinds of colloid system (proteins, peptydes, hydrocarbons) In nature collods are for example: fog, volcanic dust).

Tyndall Effect This is light scattering by coloidal solution (for example by dust, fog, milk,etc.). When light beam passes through the colloidal dispersion it is scatter and therefore it is visible. When light beam passes through the solution, like water, does not scatter and therefore it can not be seen.

Colloidal mixture, e.g. milk Solutions vs Colloids The Tyndall Effect True Solution e.g. water Colloidal mixture, e.g. milk

CLASSIFICATION OF COLLOIDAL SYSTEMS DEPENDING ON : I. STATE OF DISPERSSING AND DISPERSSED PHASE Disperssed phase Disperssing phase COLLOID EXAMPLE Gas Liquid Solid - Aerosol liquid Aerosol solid Fog, clouds, vapors Smoke, dust Foam Emulsion Zol Foam: soap, beer Creams, nail polish, milk, mayonese, butter Polymer solutions Emulsion solid Zol solid Pumeks, styrofoam Gels, opal Glass rubin, colour cristals

CLASSIFICATION OF COLLOIDAL SYSTEM DEPENDING ON: II. Size of colloidal particules: Ø monodisspersive (particles of disspersed phase have the same dimensions) Ø polidysperssive (particles of disspersed phase have the different dimensions) III. Ratio of disperssed phase to dispersing medium : liophilic colloids – they have large affinity to solvent particules; colloidal particulues are serrundes by solvents particules liophobic colloids – they have small affinity to solvent and absorb on the particules’ surface large quantities of one type of ions

CLASSIFICATION OF COLLOIDAL SYSTEM DEPENDING ON (cont.) IV. Quality of disperssive phase: Emulssions – the dispersed phase solutions of nonpolar substances (e.g. lipids) which do not have affinity with dispersing phase (e.g. water). Emulsions have hydrophobic character and are also called suspenssions or not-reverse colloids. In living organisms example of emulssions are lipids. Small particles of lipids can be dispersed in water thanks to the compounds called emulsifiers. Emulsifier – this is compund which can be „dissolved” in both liquids- dispersed and dispersing. For example consumed fats are emusified by bile acids included in bile. They have ability to decrease surface tension, like soap in water.

Micell How detergent works... Head ( polar, hydrophilic) Tail ( nonpolar, hydrophobic) Dirt H2O H2O H2O H2O H2O Micell

Coagulation (1) COAGULATION – it is ability of colloid particles to combine and form larger structures called agregates. After reaching appropriate size they loose ability „to flow” and they sediment on the bottom. Coagulation can be caused by:   1. radioactivity– beta ray 2. heating – coagulation of protein (egg) 3. evaporationor freezing of dispersive medium 4. dehydration , for example by using acetone, alcohol 5. addition of electrolite to colloid

Coagulation (2) Peptization – process reverse to coagulation – breaking coagulate and return from coagulate to colloid.   SOL coagulation GEL peptization

Donnan’s equlibrium (1) At the begining A Membrane B solvent solvent Na+ Pr- Na+ Cl- c1 c1 c2 c2 During diffusion solvent solvent Na+ Pr- Na+ Cl- After established equilibrium solvent solvent Cl- Na+ Pr- Na+ Cl- x c1 + x c1 c2 - x c2 – x

Donnan’s equlibrium (2) After established equilibrium A Membrane B solvent solvent Cl- Na+ Pr- Na+ Cl- x c1 + x c1 c2 - x c2 – x mNa+ + RT ln aNa+ +mCl- + RT ln aCl- = mNa+ + RT ln aNa+ +mCl- + RT ln aCl- aNa+A aCl-A = aNa+B a Cl-B dla f=1 c=a cNa+A cCl-A = cNa+B c C l-B [Na+ ]A [Cl- ]A = [Na+ ]B[Cl-]B in A [Cl- ] +[Pr- ] = [Na+ ] In B [Na+ ] = [Cl- ]

Donnan’s equlibrium (3) [Na+ ]A [Cl-]A = [Na+ ]B[Cl-]B in A [Cl- ] +[Pr- ] = [Na+] in B [Na+ ] = [Cl-] Product of diffuse ion concentration on one side of the semipermeable membrane is equal to the product of diffuse ions concentration on the other side of the membrane. On both sides of the membrane sum of cations and anions must be the same.

Donnan’s equlibrium (4) From the side where ions are not able to diffuse, diffusing ion’s concentration of the same charge as protein is always smaller and concentration of ions with oposite charge is always larger when compared to side with no-diffusing ion (protein).

Example 1 – protein with anionic character A Membrane B Na+ Pr - Na+ Cl – Cl- Na+A > Na+B Cl –A < Cl –B Amount of ions on let side is compensate by anions of protein

Example 2 – protein with cationic character A Membrane B Cl- Pr + Na+ Cl – Na+ Na+A < Na+B Cl –A > Cl –B

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