Separation Techniques Flashcards
what technique can be used to retrieve solids from a solid-liquid mixture?
filtration
what techniques can be used to retrieve dissolved solids?
evaporation to dryness and crystallisation
how are solids collected through filtration?
when solid particles are too large to pass through the filter paper
how are solids collected through evaporation to dryness?
- solution is heated until all the liquid evaporates away, leaving behind the solid (sodium chloride crystals)
- for substances soluble and dissolve in water to form an aqueous solution
how are solids collected through crystallisation?
- Heat until saturated
- leave to cool so crystals can form,
- Filter to collect crystals as residue,
- Wash the crystals with a little distilled water - dry between filter paper.
what separation techniques are used to separate liquids?
simple distillation and fractional distillation
what do both simple distillation and fractional distillation do?
separate substances due to difference in boiling point
what is the purpose of simple distillation?
separate liquid from solid-liquid mixture
what does fractional distillation do?
separate miscible liquids. Liquids with lower boiling point will be collected as distillate first.
why are some dissolved solids unsuitable to be retrieved by evaporation to dryness?
some substances may decompose easily upon heating
which separation technique requires heating, filtering, washing and drying?
crystallisation
what is the purpose of using chromatography?
it is often used to check for illegal substances in food products or medicine
what causes separation in chromatography to occur?
it occurs due to difference in solubility
how soluble is the substance if it has travelled the furthest distance from the starting line in chromatography?
the substance would be the most soluble
What are pure substances?
- elements and compounds
- have a fixed m.p. and b.p.
