seperating methods (9-11) (paper 1)
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when is filtration used
to seperate an insoluble solid from a liquid
what is the name of the substance left in the filter paper
residue
what is the name of the substance in the beaker after filtration
filtrate
what apparatus is needed to preform filtration
• filter paper • funnel • beaker
when is crystalisation used
to seperate a soluble solid from a solution
describe a cyrstalisation
• heat solution in evaporating dish gently to crystalisation point • filter out crystals and wash with distilled water • leave to dry in a warm oven
when is chramotography used
the seperate mixtures
how does chromatography seperate mixtures
the dyes move up the filter paper at different rates
describe the method of a chromatography
• 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
why is a lid put ontop of chromatography
to stop the solvent from evapourating
why is the base line of a chromatograph in pencil
pencil marks are insoluble and will not effect the result
why does the solvent level have to be lower than the base line
else the inks will dissolve into the solvent rather than up the paper
what is the end result of a chromatography called
a chromatogram
what is an Rf value
the ratio between the distance travelled by the dissolved substance (solute) and the distance travelled by the solvent
what is the formula used to calcualte the Rf value
Rf = distance travelled by solute / distance travelled by solvent
what are the two differenet types of distilation
• simple • fractional
when is simple distilation used
seperating out a liquid from a solution
when is fractional distilation used
seperating out a mixture of liquids with different boiling points
how does simple distilation work
• as the solution is heated the solution with lowest boiling point evaporates • the vapour is cooled and condensed and collected in a beaker
how does fractional distilation work
• 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
if the solutions with higher boiling points begin to evaporate while the lower one is in fractional distilation
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