separation techniques

Question 1

filtration (4)

Answer 1

separates suspensions
separation of solids or groups of solids from liquid in mixture using a medium through which allows substances of certain size to pass through pores
solids must be insoluble
apparatus: filter paper, funnel

Question 2

evaporation (4)

Answer 2

solution in which solute has a very high melting point
solvent does not need to be collected as boiled off and escapes as vapor into the air
solute is left behind as residue in holding container
not suitable for solutes which decompose upon heating

Question 3

crystallisation (4)

Answer 3

used to separate dissolved heat-liable (will decompose upon heating and hence can sublime) solid from a solution
begin with a saturated solution by heating to evaporate off most of the solvent from a solution to make hot and nearly saturate solution to heat up slightly
allowed to cool as the solids appear as pure crystals
cold solution is pounded off to obtain the crystals need to be dried by pressing between two filter paper

Question 4

simple distillation

Answer 4

separate and collect solvent from a solution of solutes or in a mixture of different liquids with different boiling points at least more than 25 degree diff in boiling point with the use of heat
mixture is heated until thermometer reads the boiling point of the substance with the lower boiling point
this more volatile substance would convert into gas and move up the fractioning column as hot air rises
this vapor rises into the condenser which converts the vapor into liquid by going into the reverse direction and transferring this liquid into a separate container

Question 5

fractional distillation

Answer 5

used to separate miscible liquids where components of liquid where the boiling points are in close range with each other
the mixture is heated until thermometer reads the boiling point of the component with the lower boiling point
because both components have boiling points in close range they would both vaporize
as these vapors rise into the fractioning column, the glass beads cause repeated condensation as they provide more surface area of the less volatile component
as the vapors rise to the top the less volatile component cannot withstand the cooler temperatures at the top of the column so condenses back into a liquid and falls back down to the container
the more volatile component continues rising to the condenser which converts it back into a liquid by going in the reverse direction and emptying it into a separate container

Question 6

separating funnel

Answer 6

to separate immiscible liquids
shake and leave until becomes stable again
component with higher density goes to the bottom of the separating funnel
funnel is opened and denser component flows out leaving only the top component

Question 7

decantation

Answer 7

process that separates components of mixture based on difference in density
does not allow for perfect separation as small amount of one component can contaminate the other
step one - sedimentation which uses gravity/centrifuge to separate mixture components based on density
step two - decantation which pours or siphons off top component of mixture or draining bottom

Question 8

sublimation

Answer 8

separates mixture of solids containing one which sublimes and one which does not by heating mixture
cotton stoppered inverted funnel placed over mixture when heated heat liable solid will sublime and then turn into a gas
this gas travels to the top of inverted funnel
once hot gas touches cooler funnel and solidifies back into a solid
solid scrapped off and collected in another container from the funnel

Question 9

magnetism

Answer 9

method involves separation of magnetic substances from non-magnetic substances by means of a magnet

Question 10

paper chromatography

Answer 10

used to separate a mixture of solutes or liquids with a different solubility and degree of absorption
uses a porous or absorbent medium and a solvent which can move over material
commonly used to separate mixture of dyes or inks or different types of sugars
draw base line 1 or 2 cm away from edge of chromatography paper
place a sample ink/mixture on line and let sample dry before placing more sample on same spot
place other known components on line with a distance away from first ink sample for comparison