COLLOID SYSTEM

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CHAPTER10


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When a substance is stirred with anothersubstance, it will disperse into anothersubstance and its called as dispersed

system. Based on the particle size,dispersed systems divided into three

those are Solution, Colloid, and

Suspension


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Differences between Solution, Colloid, &Suspension

No Solution Colloid Suspension

1 Homogeneous,cant bedistinguished

although usingultra microscope.

Homogeneous if weobserve itmacroscopically &

Heterogeneous if weobserve it using ultramicroscope

Heterogeneous,can be separatedby filtering

2 All particle size is

less than 1nm

Particle size is

between 1nm-100nm

Particle size is

more than 100nm

3 Stable Generally stable Unstable


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No Solution Colloid Suspension

4 One phase Two phase, dispersedphase the dispersedsubstance, dispersionmedium the mediumused to dispersed

Two phase

5 Cant be filtered Cant be filtered unlessusing ultra filter

Can be filtered

6 Ex. Mixture ofsugar & water

Ex. Milk, coconut milk,soap, jelly

Ex. Mixture ofwater & sand


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Kinds of Colloid system based on the dispersed phase &

dispersion medium

Dispersed

phase

Dispersion

medium

Name Example

Solid Solid Solid sol Coloured glass

Solid Liquid Sol Ink, Jam

Solid Gas Solid Aerosol Smoke & Dust

Liquid Gas Liquid aerosol Fog, Cloud

Liquid Solid Solidemulsion/Gel

Jelly, Butter,Cheese

Liquid Liquid Emulsion Mayonnaise

Gas Solid Solid foam Pumice

Gas Liquid Foam Shake cream


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There are two kinds of emulsion :

Oil in Water O/W milk, coconut milk

Water in Oil W/O fish oil & crude oil

To form colloid system in the 2 substances that cantbe mixed should be added with emulsifier soap

that can emulsify oil into water.


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The Use of Colloid in Industry :

By make their product in a colloid system, industries

can present a mixture of substances which are notmixed into a homogeneous (macroscopically) &stable mixture. For example : Medicines in the formof syrup are also made in the colloid system so that

all ingredients can mix homogeneously.


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COLLOID CHARACTERISTICS

Tyndall effect* John Tyndall, British physicist (1820-1893)

* Tyndall effect is a light scattering by colloid particles

* Observed by drop a beam of light into an object its a

^Solution if the light will passed (looks transparent)

^Colloid if the light will be scattered

^Suspension if the dispersed particles are also seen

* Example : light of car lamp at foggy night & light that passes

our house.


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TYNDALL EFFECT


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Brownian Movement

* Robert Brown a British biologist (1773-

1858)* General : Brownian movement is a shaking& fast movement from the flying smallparticles in the liquid causes by collision of theparticles with the liquid molecules.

its a continous zig-zag movement ofcolloid particles

* It only can be observed using an ultramicroscope


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Electrical Charge on Colloid Particle

Colloid particles are electrically charge because

have ability to absorb ions on its surface & calledas adsorption. Adsorption process can be used forsugar whitening, nuritmedicine making, & waterpurification.

*Electrophoresis

The movement of Colloid particles in the electricalfield because they are electrically charged called

electrophoresis & it used to determine the colloidparticle charge. The + charge of colloid particle willmove to cathode ( - charge of electrode) and the charge of colloid particle will move to anode ( +charge of electrode)


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* Colloid Coagulation

The removal or reduction of colloidparticle charges causes coagulation, it mayhappen in electrophoresis cell or colloidsystem which added with electrolyte solutionor when the electrophoresis cell is flowelectric current. When coagulation, (-)particle charge will coagulate to the anodeand the ones with (+) charge will coagulateto the cathode. For example in rubberprocessing, rubber particles in latex is addedwith acetic acid so that they coagulate and

can be separated from the latex.


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* Water Purification Process

Colloid characteristic used to purify water is coagulation &

adsorption. Substances which are usually used to purify waterinclude :

^Alum is useful for deposing colloidal mud so it can befiltered, but when the water too turbid we need to addactive carbon & alum together

^Sand is useful for filtering deposit / sediment

^Chlorine to disinfectant

^Slaked lime for neutralizing pH, its base so willneutralize alum which is acid


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* Colloid Stability

To maintain the colloid stability, we can remove the colloid

charges & adding colloid stabilizer. The removal of colloidcharges is aimed at preventing from coagulation. It can dowhen we entering charged colloid into semi permeablemembrane (dialysis) the example of dialysis usage is

haemodialysis.

The addition of a substance in a colloid system mayincrease the colloid stability such as emulsifier and protectorcolloid. For example, the addition of gelatine in the making ofice cream in order that the ice cream will not separate so it will

be tough.


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Lyophilic and Lyophobic ColloidsLyophilic colloid is a colloid with big affinity between

dispersed phase and dispersion medium.

Lyophobic colloid is a colloid with weak affinity between

dispersed phase and dispersion medium.When the dispersion medium is water, the two colloids are

called as Hydrophilic ( like: soap, agar, starch, gelatine &detergen) and Hydrophobic ( like: sulphur sol, sulphide sol,metal sol).


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Differences between lyophilic sol and Lyophobic sol

No Lyophilic/Hydrophilic sol Lyophobic/Hydrophobic sol

1 Adsorb its medium Dont adsorb its medium

2 Stable at anyconcentration

Stable at low concentration

3 Hard to be deposited withthe addition of littleelectrolyte

Easy to be deposited withthe addition of littleelectrolyte

4 Viscosity is bigger thanits medium

Viscosity is the same at itsmedium

5 Reversible Irreversible


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THE MAKING OF COLLOID

Dispersion Method

The making of colloids by dispersion is conducted bybreaking the coarse particles into colloidal particles

* Mechanical Method

The making of colloids using mechanical method is bycrush coarse particles into a mortar or colloid driller so wecan have a certain refinery level. Then the grains arestirred in the dispersion medium

* Peptization Method

The making of colloid by peptization is conducted bybreak coarse grains from a deposit by Theassistance of a peptizer substances { peptonization }

* HomogenizationFor example the making of colloid by homogenization isconducted using a special machine. Instant milk is madeby mix skim milk powder into water in homogenizationmachine, so it will change into colloid-sized particles.


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* Bredig Arch MethodIts used to make metal sol. Metal that is going to be madeas electrode is sub merged into the dispersion medium andgiven electric current between the electrodes. Because itselectrically charged , the metal atoms will be thrown intothe dispersion medium. After that, the atoms will becondensed until the colloid is made.

Condensation Method

The making of colloid by condensation is conducted by join

the particles of solution into the ones in colloid-size.

*Redox ReactionThe example is the making of sulphur sol and gold sol.Sulphur sol is resulted from a reaction between Sulphideand Sulphur dioxide that is conducted by flow H2S gas intoSO2 solution.


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BREDIG ARCH METHOD


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* Hydrolysis ReactionIts a reaction of a substance with water. For example themaking of Fe(OH)3 sol conducted by entering FeCl3solution into boiling water

*Double Decomposition

The example is the making of AgCl. AgCl sol can be made

by reacting dilute silver nitrat solution with dilute HClsolution.

*Solvent Substitution

The example of colloid making by substitution solvent is

the saturated calcium acetate solution mix with alcohol willform a colloid in the form of gel.


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Type of Colloid that pollutes theEnvironment

Colloid is very beneficial for life. However, thereare also colloids that give disadvantages becausethey pollute environment. The example of colloidthat pollute the environment are smoke, fog, anddetergent


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COLLOID SYSTEM

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