Separation techniques (simple)
Technique | Use | Example |
Decanting | insoluble s from l | slightly larger particles |
Filtration | insoluble s from l/aq | smaller particles |
Evaporation to dryness | soluble s from l/aq | heat stable solids |
Crystallisation | soluble s from l/aq | heat sensitive solids |
Magnetic separation | magnetic materials | COINS - cobalt, iron, nickel, steel |
Sublimation | substances that sublimes | iodine, dry ice, naphthalene, NH4Cl |
Separating funnel | immiscible l | oil+ water, kerosene + water |
Simple Distillation
solvent boils - vapour rises - cooled by cold water in condenser - collect as distillate
Thermometer: measure temp of vapour
Boiling chips: to ensure smooth boiling
Condenser: cold water put in at the bottom to ensure maximum heat transfer + effective condensation
Fractional Distillation
vapour moves up fractionating column - temp decreases up the column - higher bp condenses back into flask (collect lowest bp first)
Fractionating column: glass beads provides a larger surface area for condensation
* rarely tested, guided question if needed
Paper Chromatography #1
Concept: dissolve better = travel further
Examples: colour dyes, drug/ food testing
Solvent front: furthest point reached by solvent from starting line
Starting line: in pencil (does not dissolve)
Solvent level: lower that starting line as sample spot may be soluble
Lid: volatile liquids may evaporate
https://www.researchgate.net/profile/Daniel-Omokpariola/publication/349466574/
Paper Chromatography #2
Retention factor (Rf)
Eg: (using diagram) Rf red = 0.2
How to separate same Rf value?
-change solvent, longer paper, longer time
Locating agent: react with colourless substances to make visible