filtration & crystalisation

• what does filtration separate?

  insoluble solids from liquids
• what is filter paper?

  paper which has lots of tiny holes enough, the holes are small enough that water can pass through but solids can't
• how does filtration work?

  1. get filter paper and a funnel
  2. pour the mixture into the filter funnel
  3. this will leave the solid behind on the paper
• what is a solution?

  a soluble solid in the liquid that has dissolved
• how do you separate a solution?

  evaporation or crystallisation
• how does evaporation work?

  1. place our solution in an evaporating dish on top of a trip and slowly heat it with a bunsen burner
  2. this will cause the solvent to start evaporating and the remaining solution to get more concentrated
  3. after a while crystals will start to form because its so concentrated
  4. eventually all the solvent will disappear, leaving us with dry crystals of our solid
• what are the benefits of exportation?

  • quick and easy
• what are the issues with evaporation?

  some solids will decompose when heated (thermal decomposition)
• how does crystallisation work?

  1. place our solution into an evaporation dish and heat it but heat it more gently (e.g. in a water bath)
  2. once some of the solvent has evaporated and we start seeing crystals forming, we stop heating it and leave it to cool
  3. as the solution cools more crystals will begin to form because solids are less soluble at colder temperatures
  4. filter out the crystals using filtration
  5. dry our crystals by leaving them somewhere warm