chenistry: How to Separate Mixtures (by Bev)

-basis: different components & properties

-come up with a process that differentiates between components with different properties

ex. high density/low density

TECHNIQUE	HOW IT WORKS
Mixture	-a substance comprised of more than one substance that is not chemically bonded
Separation	-the mixture’s components keep their identities -the more different the properties are, the easier it is to separate them -filtration: chooses components by particle size -flotation: chooses components by density -crystallization & extraction: chooses components by solubility -distillation: chooses components by boiling point -chromatography: chooses & absorbs components at different rates in a fluid mixture
Hand separation	-for solids -mechanical/heterogeneous mixture can be separated with magnet/sieve -evaporation: a solid dissolved in a liquid solution -liquid evaporates (from boiling) & the solid is left
Filtration	-for solids that are not dissolved in liquids -using a permeable filter, pass a mixture with solid particles through -the solid particles stay on top of the filter because they are bigger than the pores -the filtrate permeates but the residue remains in the filter
Crystallization	-a solid in a liquid -precipitation: from physical/chemical change, a solute (dissolved substance) is converted into a solid -flotation/filtration separate the solids -the desired solid becomes a saturated solution, containing the maximum amount of solute (which the liquid can no longer dissolve -evaporate/cool: solid becomes pure crystals, which are filtered Link: http://www.reciprocalnet.org/edumodules/crystallization/index.html
Gravity separation	-for solids based on density -centrifuge rapidly spins a test tube & separates substances of different densities, forcing the denser materials to the bottom -works best with small quantities
Solvent extraction	-a component moves to a solvent shaken with a mixture -works best with solvents that dissolve only one component -mechanical mixture (2 solids): only one solid dissolves in the liquid & the desired solid is left behind -solution: the solvent is insoluble because it is already present. It dissolves at least 2 substances & the unwanted substances remain -if shaken in the separatory funnel, the liquids from layers
Distillation	-for a solution of 2 liquids -heating the mixture triggers the low-boiling components to volatize (vapourize) -evaporated components collect & condense -the liquid with the lowest boiling point boils first, the vapour ascends to distillation flask & enters condenser, gas cools to a liquid, & distillate (condensed liquid formed from boiling) is dropped as a purified liquid
Chromatography	-a mixture is passed over a material that absorb some components more than others -different components pass over the material at different speeds -mobile phase: sweeps the sample over the stationary phase (ex. Wind sweeping swarm of bees over flower bed) -can separate extremely complex mixtures Ex. Drugs, plastics, flavourings, foods, pesticides -using very small sample sizes, the analysis can be highly accurate & precies -the separated components can be collected individually
Sheet/paper chromatography	-stationary phase is a liquid soaked into sheet of paper & mobile phase is a liquid solvent -some components spend more time in the stationary phase than others -components appear as separate spots spread out on the paper after drying/”developing”
Thin layer chromatography	-the stationary phase is a thin layer of absorbent (often SiO2 or Al2O3) coating a sheet of plastic/glass -some components bond to the absorbent strongly; others, more weakly -components appear as spots on sheet