Milk looks chalky andmilky as it does. But why? My teacher said suspension is a mixture with fine particles suspended in it. But every suspension will settle down as it‘s left undisturbed, why wouldn‘t the milk just settle down and become layer of water and one layer of milk sediment?
The raw milk would settle, but this that comes to shop is already partially de-fatted (the fat particles are the major big particles). But if you would centrifugate it, it'll settle. The reason why it doesn't happen without centrifugation is simple - settling happen because the particle has a lower energy in the bottom (like the rock, that will fall down). But if the particle is small enough, the thermal motion (remember that the temperature means the particles are moving) is rapid enough to prevent the particles from settling down.
I am not 100% sure but, yes, I believe milk is a suspension (of fat in water). To answer your question about why it doesn't settle. It does. The only difference is that fat is lighter than water so, instead of sinking to the bottom the fat (cream) rises to the top. You've never heard the saying? ;-) Of course, the fat particles are of different sizes and the larger ones will rise to the top quickly while the smaller ones may take a very long time, probably much longer than the drinkable life of the milk. This is probably why you've never witnessed it, you'd throw it out before you got to that stage. Also, you would usually use some each day which means it's getting mixed at least once a day. Why not do the experiment? Get a jar and put some milk in, cover it, and leave it undisturbed. See how long it takes before you can see through the jar (or the mould grows 3 feet high). My guess is a few weeks For both. Hope this helps. TV EDIT: Ah, yes. As the previous poster mentions, you may never get all of the particles to come out of suspension due to the heat energy in the milk. How cold does your fridge go? -273.15 degrees C? ;-) It would still be an interesting experiment though.
Milk is a colloid and not a suspension. It falls under the class of emulsion.It is a solution of colloid in water and it freezes and boils practically at the freezing and boiling point of pure water. A colloidal solution is a two phase system,one of which usually a solid,is dispersed in a finely divided state throughout the other phase,usually a liquid.
