seperating methods (9-11) (paper 1)

Question 1

when is filtration used

Answer 1

to seperate an insoluble solid from a liquid

Question 2

what is the name of the substance left in the filter paper

Answer 2

residue

Question 3

what is the name of the substance in the beaker after filtration

Answer 3

filtrate

Question 4

what apparatus is needed to preform filtration

Answer 4

• filter paper
• funnel
• beaker

Question 5

when is crystalisation used

Answer 5

to seperate a soluble solid from a solution

Question 6

describe a cyrstalisation

Answer 6

• heat solution in evaporating dish gently to crystalisation point
• filter out crystals and wash with distilled water
• leave to dry in a warm oven

Question 7

when is chramotography used

Answer 7

the seperate mixtures

Question 8

how does chromatography seperate mixtures

Answer 8

the dyes move up the filter paper at different rates

Question 9

describe the method of a chromatography

Answer 9

• draw a pencil line near the bottom of the filter paper
• add spots of ink on line in regualr intivals
• place in beaker of solvent ~ lower level than the line
• place a lid on top
• when solvent has nearly reached the top take out to dry

Question 10

why is a lid put ontop of chromatography

Answer 10

to stop the solvent from evapourating

Question 11

why is the base line of a chromatograph in pencil

Answer 11

pencil marks are insoluble and will not effect the result

Question 12

why does the solvent level have to be lower than the base line

Answer 12

else the inks will dissolve into the solvent rather than up the paper

Question 13

what is the end result of a chromatography called

Answer 13

a chromatogram

Question 14

what is an Rf value

Answer 14

the ratio between the distance travelled by the dissolved substance (solute) and the distance travelled by the solvent

Question 15

what is the formula used to calcualte the Rf value

Answer 15

Rf = distance travelled by solute / distance travelled by solvent

Question 16

what are the two differenet types of distilation

Answer 16

• simple
• fractional

Question 17

when is simple distilation used

Answer 17

seperating out a liquid from a solution

Question 18

when is fractional distilation used

Answer 18

seperating out a mixture of liquids with different boiling points

Question 19

how does simple distilation work

Answer 19

• as the solution is heated the solution with lowest boiling point evaporates
• the vapour is cooled and condensed and collected in a beaker

Question 20

how does fractional distilation work

Answer 20

• different liquids all have different boiling points ~ evaporate at different temperatures
• as the thermometer reaches the lowest bioling point the first liquid evaporates and condenses
• continues with the rest

Question 21

if the solutions with higher boiling points begin to evaporate while the lower one is in fractional distilation

Answer 21

the top of the fractionating column is coolest so the vapours of the higher boiling point liquids condense earlier and run back down the column