Hello students like we’ve been discussing in the previous module about mixtures being classified as homogeneous mixture and heterogeneous mixture we already discussed about homogeneous mixture in detail now let’s start with heterogeneous mixture heterogeneous mixture is the mixture in which the constituents are not uniformly mixed throughout the mixture and more point  we’re going to note here the properties and composition of a heterogeneous mixture are not the same throughout the mixture now what does   mean to understand this let me take one example in the example i am taking muddy water that means in a jar  I have taken a mixture of mud and water if I support this muddy water into two  different  Jars the mixture is divided into two different jars what do you think is happening here can you see the difference yes the composition of muddy water is not the same because in heterogeneous mixture the constituents are not uniformly mixed so muddy water  it becomes an example of heterogeneous mixture now let us see how heterogeneous mixture is further classified as it is further classified as suspension and colloid we are going to learn everything in detail so let’s first start with suspension .suspension is a heterogeneous mixture in which the solute particles do not dissolve but they remain suspended in it and these particles are also visible to the naked eye particle size your students when I say it’s visible to the naked eye the size is greater than a hundred nanometers in diameter know what is NM Stands for nanometer . and one nanometer is 1 upon 10 raise to nine Meters let’s see different examples of suspension here the first one chalk Water  suspension can you see in the picture the chalk water suspension next One muddy water which you already discussed before milk of magnesia is also a suspension sand particles that Suspended in  water can you see the sand particles being suspended yes and the next one is flour  in water is also an example of suspension talking about these example students let’s talk about chalk water mixture now this chalk  water mixture if the suspension of chalk and water is kept under stopped for some time the Chalk  particles will start settling down at the bottom of the beaker can you see in the picture in the first picture we have kept as it is after some time the chalk has settle it down at the bottom of the beaker now what will happen if I filter the suspension if I filter  the chalk  particles are left behind as residue  you on the filter paper and a clear water is obtained as a filtrate isn’t it and if the same thing i apply for the muddy Water same thing is going to happen here also so if I keep it for some time the solute particles which are visible to the naked eye had settled at the Bottom the second type of heterogeneous mixture is a colloid let us define what is colloid .colloid is a mixture where the size of the particle is less than that of the particle in case of suspension Here  the particle sizes between one nanometer  and a hundred nanometers it diameter these particles are students uniformly spread throughout the solution due to relatively smaller size of the particles as compared to that of the Suspension this mixture might appear homogeneous to us but it’s not homogeneous it is a heterogeneous mixture as you can see in the picture one is of suspension other one is off colloid as a collided solution is a heterogeneous mixture isn’t it the two components of colloid are dispersed phase and dispersion medium dispersed phase  means students the particles which are spread uniformly and dispersion medium means the medium in which the particles that spread to understand this will take help of examples the examples of colloids are soap solution milk blood as you know blood is visible to us right but what is present in blood WBC RBC platelets can you see them necked eye   know but are the constraints present yes that why it also becomes an example of colloid start solution Ink and the last one is jelly these are the examples of the colloids so with this we have discussed the definitions of suspension and collide now let’s see the size and movement of particles in suspension and then colloid first we are going to start with suspension here i have taken a beaker sand in water it forms up suspension the particle size is greater than hundred nanometers and if you keep it under stop what will happen the particles will settle at the bottom sand at the bottom becomes disposed face and the top path becomes at dispersion medium likewise let’s talk about colloid in colloid i am taking the example of ink in water forms a colloidal solution particle sizes between one nanometer to 100 nanometers and the particles remain suspended throughout the solution can you see there the dispersed phase and dispersion medium so with this we understand the size and movement of particles now students let us see why milk is called as a colloid with the help of a small experiment I take one drop off milk it is examined under the microscope we can see small particles are floating in the liquid but under the microscope let’s see the picture can you see the slider in the small  particles yes if there are particles present that means it’s a heterogeneous mixture and colloid this observation clearly shows that collides are heterogeneous in nature through  they appeared  to be homogeneous to us let’s study now the most important property of heterogeneous mixture what can you see you two different glasses and one beam of light yes the first mixture is a salt solution and the second one is milk in water I have to take a two different classes now let’s pass a beam of light through both the glasses can you see some difference in both the glasses here milk is a colloidal Solution where  that particle size is so small that this scattered the beam of light I think you can clearly see the difference in the salt solution the light is not scattered whereas in a milk the light has been scattered and this scattering off beam of light is called as in tyndall effect so let us discuss about to tyndall effect in detail in tyndall effect is caused by scattering of light which we observe in both the solutions how is it affecting how is it scattering by very small particles in the colloidal solution in a transparent medium you see a picture was in the picture sunrays is coming can you see the ray of light clearly yes this is also because of tyndal effect it is often observed from the dust present in the air when sunlight comes in through the window all comes down to the hold of the cloud out so these are examples of tyndal effect one more example of tyndal effect when headlight beams are visible on foggy nights can see you here yes this is also an example of tyndal effect