Solid-Liquid Mixtures

• Filtration


  • can be used to separate insoluble solid from liquid
  • insoluble solid is collected as residue
  • liquid is collected as filtrate

  
• Evaporation to dryness


  • used to obtain soluble solid from a solution by heating the solution until all the solvent boils off
  • the solvent which has a lower boiling point than the solute changes into gas first and evaporates
  • solute is left behind
  • suitable for obtaining solids that do not decompose on heating

  
• Crystallisation


  • used to obtain solid from a solution by allowing a hot saturated solution to cool
  • a saturated solution is a solution in which no more solute can be dissolved in the solvent
  • suitable for obtaining solids that decompose upon heating
  • many crystals require a fixed amount of water in its crystal lattice, this water is known as water of crystallisation
• Steps of Crystallisation

  
  

  1. heat the solution until it is saturated
  2. leave the hot saturated solution to cool until crytsallisation occurs
  3. filter to collect the crystals. Rinse crystals with cold distilled water and dry between sheets of filter paper
• Simple Distillation

  • used to separate a pure solvent(liquid) from a solution

  1. solution is heated, boiling chips are added for smooth boiling/ The solvent, which has a lower boiling point evaporates. The vapour rises and enters the condenser through the exit sidearm of the distillation flask
  2. The vapour cools in the condenser and condenses back into liquid form, and is collected in the conical flask as distillate
  3. as more solvent vapourises, the solution becomes more concentrated, eventually leaving a solid residue in the distillation flask