The solution or true solution - this is a mixture of one ormore substances which are dispersed in solvent (e.g. water oranother 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 vs ColloidsSolution:

• Transparent to ordinary light• Stable unless solvent evaporated• May pass through dialytic, but not true

osmotic, membranesColloids:

• 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 SOLUTION – HETEROGENEOUS system - with particle size of 10-9-10-7 m in diameter (1 – 100 nm, up to 500 nm)

COLLOIDAL SOLUTIONS

10-9 m = 1 nm = 0.001 micron10-7 m = 100 nm = 0.1 micron10-6 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:

1. 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.

Types of solutions depending of size of disspersed phase in dispersive medium

TYPE OF SOLUTION DIAMETER OF PARTICLES OF DISPERSED PHASE

True solutionTrue solution (homogenieous)(homogenieous)

< < 1010-9 -9 mm (<1nm)(<1nm)

ColloidalColloidal (heterogeious)(heterogeious)

1010-9 -9 - - 1010--77 m (1-100 nm) m (1-100 nm)

SuspensionSuspension > > 1010--77 m m (>100 nm)(>100 nm)

All cells are some kinds of colloid system (proteins, peptydes, hydrocarbons)

Colloidal systems are wide spread in nature in form organic or inorganic

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.

Solutions vs Colloids

Colloidal mixture, e.g. milkTrue Solution e.g. water

The Tyndall EffectThe Tyndall Effect

CLASSIFICATION OF COLLOIDAL SYSTEMS DEPENDING ON : :

I. STATE OF DISPERSSING AND DISPERSSED PHASE Disperssed

phaseDisperssing

phaseCOLLOID EXAMPLE

GasLiquidSolid

GasGasGas

-Aerosol liquidAerosol solid

-Fog, clouds, vapors

Smoke, dustGas

Liquid

Solid

LiquidLiquid

Liquid

FoamEmulsion

Zol

Foam: soap, beerCreams, nail polish, milk,

mayonese, butterPolymer solutions

GasLiquidSolid

SolidSolidSolid

Foam Emulsion

solid Zol solid

Pumeks, styrofoamGels, opal

Glass rubin, colour cristals

CLASSIFICATION OF COLLOIDAL SYSTEM DEPENDING ON:

Size of colloidal particules: monodisspersive (particles of disspersed phase have the same dimensions) polidysperssive (particles of disspersed phase have the different dimensions) 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

II.

III.

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.

Head ( polar, hydrophilic)

Tail ( nonpolar, hydrophobic)Dirt

H2O

H2O

H2OH2O

H2O

Micell

How detergent works...

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.

  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 can be caused by:

Coagulation (2)

Peptization – process reverse to coagulation – breaking coagulate and return from coagulate to colloid.

   SOL coagulation

GEL peptization

 

  

A Membrane Bsolvent solvent

Na+ Pr- Na+ Cl-

c1 c1 c2 c2

At the begining

Donnan’s equlibrium (1)

During diffusion solvent solvent

Na+ Pr- Na+ Cl-

After established equilibrium

Cl- Na+ Pr- Na+ Cl-

solvent solvent

x c1 + x c1 c2 - x c2 – x

Donnan’s equlibrium (2)(2)After established equilibrium

Cl- Na+ Pr- Na+ Cl-

solvent solvent

x c1 + x c1 c2 - x c2 – x

Na+ + RT ln aNa+ +Cl- + RT ln aCl- = Na+ + RT ln aNa+ +Cl- + 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- ]

A Membrane B

Donnan’s equlibrium (3)

• 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.

[Na+ ]A [Cl-]A = [Na+ ]B[Cl-]B

in A [Cl- ] +[Pr- ] = [Na+] in B [Na+ ] = [Cl-]

Donnan’s equlibrium (4)(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

THE END