Surface Chemistry part 5

Added: 2026-05-12

[00:00:01]now coming to the next part there is your part five we have already covered till now that is your adsorption the different types of adsorption we have seen it physical absorption chemical absorption the friendly absorption isotherm we have seen it we have seen the equations we have also seen the uh uses or the applications of adsorption in our day-to-day life or in industries or whatever it is we can say that now we are going to the next one that is your dispersed system rather i should say in one word in simple word we are going to start the colloidal system that is a colloidal state of matter we are going to start got it we are going to start the next one the next part we can say that in this particular chapter so uh it is called dispersed system what is dispersed system the term dispersed system refers to a system you can see it on the screen in each one substance the dispersed phase is distributed in discrete units discrete means which is not visible throughout a second substance the continuous phase or a vehicle vehicle what is said because as the vehicle is moving so continuous means is also moving now each phase can exist in solid liquid or gaseous state yeah the phase can be whether the dispersed phase got it or the continuous phase which is also called as a dispersant medium you can write it down there all right this person medium clear so ah it's present that is dispersed phase and the dispersant medium can be solid can be liquid or can be gaseous now in simple words let me tell you what is dispersed phase means it is known as salute and what is dispersant medium means it is on a solvent together it forms what solution what solution colloidal solution just now i said colloidal solution got it in simple words disperse phase but you have to use this term here see for to make you understand i am saying you now don't use a solute and the solvent here no you can't solute and the solvent is used for true solutions but here you need to use for the solute dispersed phase and for the solvent it's a dispersant but you can say medium clear here you need to need to use that dispersed phase and the dispersion medium you have to use got it clear that you remember it you cannot use any other term apart from that we can say that so ah here in case of crystalloids or let's see we are having different types of solutions we will come to it now that is different types of solutions we are having true solution we are having colloidal solutions and we are having that is nothing but on a suspension all right which is also called heterogeneous dispersion we can say that suspension clear fine now true solution are formed from crystalloids what do you mean by crystallites which is completely soluble in water for example when sugar and salt is dissolved in water sugar and salt they're called as crystalloids they are known as crystallites they completely dissolve in water remember it they completely dissolve in water here water is a dispersant medium and sugar or salt is the dispersed phase just for example but we launched a dispersed phase and dispersion medium just i am giving an example just i am giving an examples children listen carefully here you will say water as a solvent and sugar is salute just to make you understand what is dispersed phrase and disperse and medium giving you but here the term will be solute and the solvent only because it's a true solution it's a crystalline it's a true solution it's a crystalline so don't get confused got it in terms of colloidal solution again and again i'm saying you that is salute will be known as dispersed phase and solvent will be known as dispersant medium mind it got it in case of colloidal solution which is known as this person just now i said you know you can see that is dispersed systems clear so in this way now that is a true solution now what i said you that if you take sodium chloride that is salt or sugar and if you dissolve in water it behaves where sugar behaves as a crystalloid and water is a solvent simply that is sugar is nothing but a solute and the water is a solvent fine but listen carefully now but the same substance that is sodium chloride or sugar when you add in benzene it does not dissolve sodium chloride sugar does not dissolve in benzene completely partially dissolves partially i don't say that it does not dissolve at all partially dissolves so hence it behaves as a colloidal solution so what you can say the sodium chloride when dissolved in water behaves as a crystalloid but same sodium chloride when dissolved in benzene behaves as a colloid we can say that it behaves as a colloidal solution now colloid means what colloid has come from the greek word which means glue glue glue means gum gum sticky got it colloid has come from the greek word which means sticky glue gum like substances they are called as colloids we can say that clear now substances like common salts sugar urea etc which is um obtained in the crystalline form and hence they are called as crystalloids they pass through what you can say parchment paper or the dissolve rapidly diffuse rapidly and they pass through the parchment parchment membrane you know the animal membrane or the parchment semi-permeable membrane so do say other weights we can say that they pass rapidly because the substance the particle size is so small now that can easily pass through any kind of filter paper any kind of filter paper any kind remember it but substances like starch gum glue gelatin albumin etc which are non-crystalline listen lon crystalline previously i was saying crystalline substance non-crystalline nature in the dissolved state do not diffuse what you can say rapidly they diffuse rather slowly at a very slow rate through the parchment membrane through a semi-permeable membrane through an animal membrane so those substances are known as colloids we can see that they are called as colloids or colloidal solution as a result it forms but if the particles settle down like suppose you have taken some chalk powder you have taken some cold dust you have taken some uh what you can say like clay or muddy have taken it you have mixed with water what you'll find that settle down they are not called colloids or crystallites they are called as suspended particles and such a system is called suspension you can say that such a system is known as suspension you can see it here i have written their heterogeneous dispersion where the particle size is greater than thousand nanometer which are those blood milk and all those things heterogeneous systems audit they undergo coagulation of flocculation later on you learnt it when i will go to the properties of the colloids got it clear and the true solution the particle size is less than one nanometer and in case of colloidal substances the particle size ranges between one nanometer to thousand nanometer it is micro heterogeneous system like plasma macro molecular solutions they come under it got it they come under it we can say that clear now in this way you can see it here the particle size in case of true solution already have discussed with you less than one nanometer in case of colloidal it is greater than one nanometer it lies between one and thousand nanometer and in case of suspension you can see the particle size i have shown you diagrammatically see the particle sign case of true solution so small colored a little bit bigger and in suspension is much bigger so this settle down so this settle down in case of suspension see i've shown you the three types of solution here now here also the three different colors i have shown you uh here the color is don't think the color of the solution collides and suspension as such no just to differentiate got it just to differentiate so that's to make you understand now in case of solutions true solution i mean so that is crystalloids it's it can be of single atoms small molecules or ions or polyatomic ions and in colloids it's like aggregate of atoms means when the same smaller atoms they come close closer to each other they they form a big mass that is aggregation of atoms molecules or ions or macromolecules like proteins bigger molecules like proteins they form colloids got it so remember it when the single atoms molecules are ions when they come closer when they aggregate got it they mix with one another they are not nothing but known as colloids what it they are called as colloids and in suspension it forms a lump it clumps got it it combines so that it forms a lump a big lump got it and which settles down like mineral minerals grains such as sand and all those things we can suggest i was told told you not chalk powder charcoal powder sand clay mud and all these things when they settle down for example now you can see in your house you are getting uh you might be getting that is a dirty water that which is being supplied got it you might be getting for it you might be so you you take that particular dirty water in a glass got it and you allowed to just uh keep it undisturbed for some time you will see that whatever the sediments are there the mud is there the dirt is there the sand is there the mineral grains are there that it settles down at the bottom you will see as a sediment it settles down what is that known as that is called a suspension that solution is called as a suspension got it but in collides you will find its floating now the example of collateral solution i can give it you that is suppose a start solution example of colloidal solution if you have not seen a start you will say i don't know what it starts ok fine you can see in the winter season the sunlight which penetrates into your house through the doors or through the windows or through the ventilators you can see the dust particles is floating there what is that known as that is called as a collateral solution that is known as a colloidal solution all right so uh that is when thomas graham gave the definition of collateral solution he said it is a gum like glue-like sticky but later on the definition of colloids changed the grams classification of substances into crystalloids and colloids were soon proved to be wrong it is changed the idea changed all right it was found that a crystallized also behaves as a colloid under different set of conditions i gave you an example that if you take salt and dissolve in water it is a crystalline where water is a solvent and salt is a solute but when you dissolve in benzene or toluene it does not dissolve completely it partially dissolves so there it acts as a dispersed phase and dispersing medium the salt is a dispersed phase and benzene is a dispersant medium got it so hence don't think all uh gum glue sticky substance are colloids might be or might not be also it is not necessary got it clear so the idea of colloids or the definition of colloids has changed what it was given by thomas graham got it it has been changed it has gone a large change we can say that now we compare it with the help of the particle size and all those things so colloidal state of matter is therefore a state in which the size of the particle is such that that is between one thousand one nanometer two thousand nanometer that they can pass through filter paper but not through but not through animal or vegetable membrane i said you know the parchment paper it cannot pass through through semi permeable but it can pass through the ordinary but you can say filter paper now here you can see the difference between true solution suspension and colladeral solution is given in terms of particle size which i have discussed in terms of sedimentation collateral solution do not settle true solution also does not settle suppose if you add sugar or salt to water will you find after some time the sugar and salt will settle no rather you cannot see through a powerful microscope also the particle size is so small so small it is less than one nanometer you cannot see it also so there is no question of any settling down so true solution does not settle but suspension settle down definitely sand clay mud the settle down diffusion true solution diffuses quickly just now makes i discuss with you but uh suspension they do not diffuse they settle down now they remain as a residue on the filter paper and colloidal solution it diffuses slowly if you see a true solution it forms a transparent so this uh what you can say particles for that reason it's invisible i said you just now the particle size is less than one nanometer how you will see it you cannot see it through a powerful microscope also so this particles are not visible it's invisible but particles are visible when the naked eye or under microscope in case of suspension definitely it can be visible sand clay are you not able to see it definitely you'll be able to see it but in case of colloidal solution listen careful the particles scatter light when it observed under a microscope it scatters the light in case of true solution the light passes simply for example you take a beaker containing sugar solution you allow the light to pass through it you will see the light passes thoroughly simply till passes through because it is transparent clear but in case of what you can say start solution in case of gelatin solution in case of sodium thiosulfate solution which is a colloidal solution you will see the light gets scattered the best example i gave you to now the light the sunlight would penetrate through the doors windows or ventilators what you have what you have seen it there you've seen it or not the light gets scattered for that reason only you're able to see the particles which is floating there the light is getting scattered there now in case of true solution it can pass through any animal membrane filter paper because particle size is very small so it can pass through but in suspension it will remain as a residue on the filter paper any type of and in colloidal solution it will pass through filter paper but not through animal membrane got it clear i've said you then transparent opaque and translucent we have discussed now that is the physical state of dispersed phase and dispersion medium i have already discussed with you the nature of interactions the types of particles i have discussed now based upon what you can say this classification of colloids when you come based upon the dispersed phase and disperse and medium the colloids are of different types you can see you can see this particular chart so here i am discussing based upon the physical state of dispersed phase and dispersion medium the classifying the colloids now i am classifying here but based upon dispersed phase and dispersion medium what is that we are having solid solid solid sole example is your colored glass gemstones the costly stone which you're using now in your that is ring we can say they are colloids ruby emerald they are colloids solid liquid that is known as simply soul soul means what collateral solution s o l listen to the spelling see the spelling not s o l e got it nor s o u l no not at all sol so pain self fluids in this way solid gas aerosols you can go through it this particular chart i'm not just have to read it out this particular one but it's very important very important here you will be getting the short questions here that if suppose the dispersion medium is liquid and the dispersed phase is a gas then what is the type of colloid known as it is form example your soap leather froth that is your shaving cream and all those things they come under it clear so hence you go through this particular chart is important because it is given the type of colloids in the basis of physical state of the dispersed phase and the dispersant medium so you will be getting the short questions upon it like solid gas dispersed phases solid and dispersed medium is a gas it is known as what aerosol so what is that example smoke dust and all those things so here one thing i remembered let me just tell you that if the dispersant medium is water listen carefully it is known as the type of soul is known as aqua solar hydrosol you may write it down if the dispersant medium is alcohol then the type of colloidal solution is called alkosol if the dispersion medium is benzene it is known as benzosol if the dispersion medium is gases like here you can see this was a medium is a gas that is called as aerosol example is smoke dust and all those things clear so this chart you go through it it's important now next coming to lyophilic and lyophobic collides lyophilic means what the word you break it up lyo means liquid got it philip means loving so liquid loving colloids are called as lyophilic liquid loving which loves the solvent which loves the liquid which loves the dispersant medium that is called lyophilic colloids substances like gum gelatin starch etc which are mixed with a suitable liquid as the dispersant medium directly from the colorado solution simply you are mixing it up for example you want to make a starch solution what you'll do you'll take water dispersion medium that's a liquid you add starch you will see it easily dissolves in it and dissolves something it easily forms a colorado solution in it easily nothing you have to do just to steer it little bit that's it easily directly we can make a collateral solution so that is called as lyophilic colloids reliabilic souls but they are also lyophobic phobic means what heating liquid hating when i say lyophobic lyo means liquid liquid hating colloids means they do not have any affinity for the solvent they do not love the solvent do not love the dispersion medium they are called as lyophobic colloids lyophobic souls the substances like metals their sulfides etc which do not simply mix with the dispersant medium got it and form collateral solution they have got some special methods of preparations all right to prepare these colloids we will learn some special method in the next we will see the special methods are there so such substances are called lyophobic colloids or lyophobic souls liquid loving lyophilic liquid hitting lyophobic liquid loving colloids can be prepared by simple methods order directly but liquid heating colloids cannot cannot be paired by simple methods they have got some special techniques some special methods of preparation we can say that all right clear so in this way uh we are having uh what you can say large phallic and live phobic colloids lyophilic collides is also known as intrinsic colloids lyophobic colloids is also called extrinsic colloids lyophilic colloids is reversible colloids it's a reversible soul all right but lyophobic is irreversible in nature reversible means that is what you find is that suppose when you mix it this particular suppose you are mixing uh that is your starch and water all right so what do you do just to simply shake it that is you can mix it so they are reversible in nature we can see that these are reversible so hence they known as because these soles are quite stable and cannot be easily precipitated so hence they are reversible for it but the other one the liphobic they are not easily precipitated all right they are irreversible in nature we can say clear and they cannot be prepared with simple methods i should say all right now next is the lipoic are easily hydrated they are highly hydrated but they are not much hydrated because they do not have affinity for the solvent so they are not hydrated at all got it then the nature of the substance is i told you the lyophilic colloids is starch gum proteins etc they generally form life folliculites but metals and the sulphides forms life of which alkaloids live folliculides have viscosity much higher than that of the medium but lyophobic colloids are viscosity same as that of the medium medium means the dispersant medium or the solvent then life will collide the surface tension is usually lower than that of the dispersant medium but in case of lyophobic colloids the surface tension is nearly the same as that of the dispersant medium okay so these are the difference between lyophilic and lyophobic we can say that now coming to the types of colloids that is another types on the basis of the types of particles basically the we have got multi molecular macromolecular and associated collides multi molecular understand the word when on dispersion of a substance in the dispersant medium a large number of atoms or smaller molecules of the substance whose diameter is less than one nanometer that means the crystalloids when they come together they aggregate together got it in the dispersant medium the smaller atoms the smaller molecules they come together they aggregate together got it to form a species having size in the colloidal range that means the particle size whose size is less than one nanometer you know they are crystalloids they come closer when they will come closer the particle size is going to increase it will become more than one nanometer so when they will reach the colloidal range then that particular kind of colloids is called multi-molecular colloids initially it is less than one nanometer they will aggregate they will collide they will come together but in the dispersion medium the smaller molecules forms a bigger molecules a larger molecules and hence when there is a colloidal range that particular collide is called multi molecular collides example is a gold soul got it having several atoms got it a sulfur sole having several atoms thousands of atoms are there when they come together they form but you can say nothing but gold soul gold atoms that is crystallites but when they come together got it in a given solvent they come together and they form a gold soul that is they form a multi color similarly sulfur atoms they come together and they form a sulfur soul we can say in a particular solvent now why they will come together because they are held together by weak van der waals forces when they come together they are held together by weak mandrels forces so in case of multimolecular collides that force which is responsible to hold the two or more atoms together to form a multi molecular collides is your van der waals forces i hope you understood this macromolecular collides when certain substances having big size molecules called micro molecules having larger molecular masses are dissolved in a suitable liquid they form a solution in which the molecules of the substance that is the dispersed particles of the size in the colloidal range so when they are dissolved in a solution when they are put in a solution then the molecules the macromolecules they break up got it they break up and they are having the size they are having the particular size uh in that of the colloidal range all right so that is nothing but known as macromolecular collides got it big size molecules they're already big in case of micro they combine multi molecular sorry they combine the smaller they combine and become bigger here already these big size molecules they are already macromolecules they are having large molecular masses they when they are dissolved in suitable liquid when they are put in a suitable liquid insulable solvent in a suitable dispersant medium they form a solution of the molecules of the substance if if it is needed to break up they break up also got it and they give rise to a colloidal range the particles comes in the colloidal range so that sort of colloids is called as macromolecular colloids example is polymers with high molecular masses like starch cellulose protein enzymes they are got it ah if you say some artificial polymers like your polythene nylon polystyrene synthetic rubber you'll be studying about it in the biomolecule chapter in the polymers and polymerization in details about it so these substances start cellulose or polythene nylon they are known as micro molecular colors because already the particle size is big already they are large molecules already the dimension is bigger already they have got high molecular masses they come in the colloidal range and they become stable all right so that particular colloid is called as macromolecular colloids we can say that then associated collides or micelles we can say the substances which are dissolved in medium at a low concentration behave as a normal or strong left light at low concentration when any substance is dissolved but at higher concentration it exhibits a colloidal properties so remember that associated colloids at a higher concentration behaves as a associated collides only at a higher concentration because they have the colloidal set up properties but at lower concentration there is it is a normal electrolyte it is a normal electrolyte we can say that for example sodium chloride in low concentration its a normal electrolyte dilutes nacl we cancel that but concentrated one in case of benzene in benzene solution in benzene solvent the waves as a colloidal particles because in case of benzene the sodium chloride molecules they come closer again they form an aggregated particles which is called as associated the name itself it says association means definitely association how it is formed a group of people when they come for a cause that is called association see also same thing when the uh somebody can say dispersed phase or the solute what you can say that they come closer in a given solvent at a higher concentration got it they form an associated colloids which is known as micelles aggregated particle thus formed are called as micelles it is known as my cells we can say that so here i've given you the difference between the multi-molecular micro molecular and associated colloids so to say now listen here in case of micelles the formation of micelle takes place only above a particular temperature and that particular temperature is called as craft temperature and only above a particular concentration which is called as critical micelle concentration remember these two terms graph temperature k r afd not c r f t k r a f t the scientist was there got it so which is represented letter t k capital t subscript is small k that is called craft temperature the formation of micelles or associated colloids takes place only above a particular temperature that is called craft temperature and above a particular concentration that is called critical micelle concentration or cmc we can say critical micelle concentration all right now you'll be studying about about the micelles later on also that is the form that is for the soaps you know the critical uh what you can say concentration is nothing but 10 to the power minus 3 4 to ten to the power minus three moles per liter cmcs for soaps so for the soap and the detergents where hundred molecules they come closer and it forms a associated collides or micelle formation takes place we can say that clear so micelle formation takes place of a particular temperature that is called as craft temperature and above a particular concentration that is called critical micelle concentration so to say so this is all about