Will a mixture of different substance separate into layers because of their different masses?

Question

I am doing a lab in school where the teacher gives us a pile of who knows what and we have to identify each substance in it. I was wondering if i take some liquid from the "sludge" will it contain all liquids, or will other liquids with a greater mass be sitting on the bottom?

Answer 1

the mixture should contain all of the substances. if you have the resources, i would suggest using thin layer chromatography to decipher the different substances.

Answer 2

I assume that you teacher is not going to give you a mixture of things that will blend together, such as sugar in water, or alcohol and water. Assuming that they will not mix:

Most liquid and solids sludges can be separated with a centrifuge. The solids generally will separate out in the bottom. Same can be true of different liquids if their density (not mass) is different, such as oil and water.

I would centrifuge the mixture first, and pour off the liquid(s). Then proceed with methods that you have been taught to identify the liquid component(s) and solid component(s).

After identifying the liquids, you might even boil them off to make sure that the teacher hasn't hidden any soluble/dissolved solids in it - if pure liquid, there will not be any (or very little) residue after boiling off.

You can also use a sieve (screens of different meshes) to separate out chunks from powders on the solid side.

If you receive all solids and are having trouble separating them, you might try stirring some of it into water to see if anything dissolves. Centrifuge out the undissolved solids and try alcohol for additional soluble substances. As above, boil off the water and alcohol and see if anything was separated by these substances.

Answer 3

You didn't say whether the mixture is organic or inorganic or completely unknown which would be very unusual in a classroom.

Centrifugation, dissolution, steam distillation, and chromatography are all good approaches [don't forget the possibility of magnetic separation for strange inorganic mixtures].

Advanced techniques like IR, UV, and NMR are very useful if available and you don't want to do all the derivative work.

However, your approach should be systematic for best results.

For inorganic mixtures, a standard qualitative analysis scheme can be found at http://wulfenite.fandm.edu/labtech/qualanal.htm

{{don't forget that H2S gas [for precipitation] is very toxic and should be used with adequate ventilation and under adequate supervision}}

For organic mixtures, a standard qualitative analysis scheme can be found at http://wwwchem.uwimona.edu.jm:1104/lab_manuals/c10expt25.html

Hopefully, your class will not give you extremely toxic, flammable, or carcinogenic materials to separate and determine (although in the old days my qual organic class did give out such things).

Answer 4

Mixtures phase separate into different layers if they are immiscible, independant of their mass.

Now if you are asking if in time will the liquids distribute themselves so that the lightest one will float on the heaviest one and they are all still miscible - the answer would be yes - except you would not be able to see anything until you disturbed the mixture.

Answer 5

The density of the different substances will play a part in whether or not they separate out.
If mercury is present, it will sit on the bottom.
Water and substances miscible with water will sit on top of the mercury and, oils and oil miscible substances will float on top of the water. Mercury separation will be noticable, the rest should look pretty gooey..

Answer 6

Different liquids will seperate because of their densities and also if they cannot be mixed together like oil and water.
For example that's how we separate water and organic substances in organic chemistry.

Answer 7

Well that is what happens to gas . If the room is near air tight with little or no currents u will find CO2 on the bottom and hydrogen would be at the top.

Answer 8

If it is a "pile" and a "sludge," you cannot depend upon it.