elements and principles of design
- 1. Types of Colloids and Examples<br />Introduction to types of colloids and examples<br />A solution is a mixture of two substances, a solute and a solvent. Depending upon the particle size of the solute, the solution is divided into three types, True solution: A very small solute particle sixze, suspension: Very large particle size of the solute and Colloids: A size of the solute inbetween the 2 size.<br />So, the colloidal solutions or colloidal dispersions are intermediate between a true solution and a suspension. When the diameter of the solute particles are in the range of 10 A to 2,000A, the solution is called Colloidal solution. There are many type of colloidal solutions, depending upon the states of matter of both solute and solvent particles. Let us look at the types of colloids and examples.<br /> <br />Types of colloids and Examples:<br /> <br />There are two phases in a colloidal system: Dispersed phase, the solute and dispersion medium, the Solvent. Various types of colloidal solutions, depending upon the dispersed phase and dispersion medium are:<br /> <br />Dispersed PhaseDispersed MediumType of ColloidExampleGasLiquidFoamWhipped cream, Soda water FrothGasSolidSolid FoamPumice stone, Foam RubberLiquidGasAerosolFog, MistLiquidLiquidEmulsionMilk, Cod-Liver oilLiquidSolidSolid Emulsion(gel)Butter, Cheese, JellySolidGasSmokeSoot in air, DustSolidLiquidSolStarch, Protein, Paint, SolidSolidSolid SolRuby glass, Alloys<br /> <br />More on Types of Colloids and Examples<br />Colloidal solutions are also classified based on their interaction of the dispersed phase with the dispersion medium. Types of colloids based on this classification are: Lyophilic colloids and Lyophobic colloids. Lyophillic colloids are those, in which the dispersed phase has a strong interaction with their dispersion medium. Examples are: Milk, Jellies, Paint, etc. Lyophobic colloids are those, in which the dispersed phase is sparingly soluble in dispersion medium. Examples are Gold sol, Ferric hydroxide sol, etc<br />1) Lyophilic colloidsIn this type of colloids sols, the dispersed phase has great attraction for the dispersion medium. In such colloids, the dispersed phase does not precipitate easily and the sols are quite stable. If the dispersion medium is separated from the dispersed phase, the sol can be reconstituted by simply remixing with the dispersion medium. Hence, these sols are called reversible sols. Examples of lyophilic sols include sols of gum, gelatine, starch, proteins and certain polymers in organic solvents.<br />2) Lyophobic colloids<br />In this type of colloidal sols, the dispersed phase has little affinity for the dispersion medium. These colloids are easily precipitated on the addition of small amounts of electrolytes, by heating or by shaking and therefore are not stable. Once precipitated, it is not easy to reconstitute the sol by simple mixing with the dispersion medium. Hence, these sols are called irreversible sols. Examples of lyophobic sols include sols of metals and their insoluble compounds like sulphides and oxides. Lyophobic sols need stabilizing agents to keep the dispersed phase from precipitating out.<br />Hydrophobic sols are often formed when rapid crystallization takes place. With rapid crystallization, many centres of crystallization called nuclei are formed at once. Ions are attracted to these nuclei and very small crystals are formed. These small crystals are prevented from settling out by the random thermal motion of the water molecules. <br />Classification of Colloids Based on Type of Particles of the Dispersed Phase<br />1) Multimolecular colloids<br />2) Macromolecular colloids <br />3) Associated colloids.<br />Multimolecular colloids<br />In this type of colloids the colloidal particles are aggregates of atoms or small molecules with molecular size less than one nanometer (1 nm). For e.g., gold sol consists of particles of various sizes which are clusters of several gold atoms. Similarly, sulphur sol consists of colloidal particles which are aggregates of S8 molecules. The molecules in the aggregates are held together by Van der Waal forces.<br />Macromolecular colloids<br />Macromolecular colloidal particles are formed when on dissolution in a suitable solvent, the macromolecules have sizes which are in the colloidal range. Naturally occurring macromolecules are starch, proteins and cellulose. Man made macromolecules are polymers such as polyethylene, nylon and polystyrene. These colloids are quite stable and resemble true solutions in many respects.<br />Associated colloids (Micelles)<br />Certain substances behave as strong electrolytes at low concentration but at higher concentrations these substances exhibit colloidal characteristics due to the formation of aggregated particles. These aggregated particles are called micelles. Micelles are called associated colloids. <br />Mr. Julius Mr. Andrew Mrs. Teresa Mr. Eric Ms .Chevie <br /> Mrs. Manalo <br />\" Every person is a new door to a different world.\" <br />\" Friends are the most important ingredient in this recipe of life.\" <br />Friendship is like a flower,Glowing in its glory,Each and every seed,Telling its own story.<br /> <br />Open the envelope<br /> <br /> <br />A Family is like a bookthe endings never clearbut through the pages of the booktheir love is always near<br />I like a teacher who gives you something to <br />take home to think about besides homework.<br />The dream begins with a teacher who believes in you,<br /> who tugs and pushes and leads you to the next plateau, <br />sometimes poking you with a sharp stick called \" truth.\" <br />