Separating Mixtures Oct 16th

Separation:
-Basis for separation: Different components and properties-components in a mixture retain their identities
-the more similar the properties are, the more difficult it is to separate them.
-Strategy: use any possible way to discriminate between components with different properties.

Hand Separation & Evaporation:
-Hand separation (Solid+Solid) 
-Use a magnet or sieve
-Evaporation(Solid dissolved in liquids)      boil away the liquid and the solids remain

Filtration (Solids NOT dissolve in water)
-use porous filter to separate the solids out. (If the pores are smaller than the solids)
-use filter paper-residue left in filter paper, filtrate, filtrate goes through filter paper

Crystallization(Solid in liquid)
-precipitation is the conversion of a solution to solid form by chemical or physical change
-solids are then separated by filtration or floatation
-saturated solution of a desire solid
-evaporate or cool-solids come out as pure crystals. Then crystals are filtered from remaining solvent.

Gravity Separation
-solids based on density
-A centrifuge whirls the test tube around at high speed forcing the denser materials to the bottom. Work best for small volumes.

Solvent Extraction
-a component moves into a solvent shaken with the mixture
-works best with solvents that dissolve only one components
-mechanical mixture:(Solid & Solid)
2 solids use liquid, one dissolved, get another one.
-solution: solvent is insoluble with solvent already present.
solvent dissolved 1 or more desire solids and leaves unwanted solids behind.
(If shaken in a separator funnel, the liquids will form layers then drain the solvent to leave the wanted material)

Distillation(Liquid in liquid solution)
-heating a mixture can cause low-boiling components to volatilize（vaporize）
-distillation is collecting and condensing volatilized components
-liquids with lowest boiling temperature boil first---vapor ascents to distillation flask and enters condenser; gas cools and condenses back to liquid dropping the distillate as a purified liquid.

Chromatography
-flow the mixture over a material that retains some components more than others, so different components flow over the material at different speeds.
-a mobile phase sweeps the sample over a stationary phase
-can separate very complex mixtures
-very small sample sizes analyses----highly accurate & precise
-separated components can be collected individually

Paper Chromatography(PC):
-stationary phase is liquid soaked into a sheet or strip paper mobile phase is a liquid solvent some components spend more time in stationary phase than other components appear as separate spots spread out on the paper after drying or "developing".

Sheet Chromatography:Thin layer chromatography (TLC）:
-stationary phase is a thin layer of absorbent (Al202 or So2 usually) coating a sheet of plastic or glass some components bond to the absorbent strongly other more weakly as with paper chromatography, components appear as spots on the sheet.