separation techniques

• what does filtration do?


  separates insoluble solids from liquids
• when can filtration be used?


  can be used if your product is an insoluble solid that needs to be separated from a liquid reaction mixture
• when also can filtration be used?


  in purification for example solid impurities in the reaction mixture can be separated out using filtration
• what are the two ways to separate soluble solids from solutions?


  evaporation and crystallisation
• what us the process if evaporation?


  1. pour the solution into an evaporating dish
  2. slowly heat the solution. the solvent will evaporate and the solution will get more concentrated. eventually, crystals will start to form.
  3. keep heating the evaporating dish until all you have left are dry crystals
• what stops the process of evaporation being able to take place?


  the salt decomposing when heated
• what is the process of crystallisation?


  1. pour the solution into an evaporating dish and heat the solution. some of the solvent will evaporate and the solution will get more concentrated
  2. once some of the solvent has evaporated, or when you see crystals start to form, remove the dish from the heat and leave the solution to cool
  3. the salt should start to form crystals as it becomes insoluble in the cold, highly concentrated solution
  4. filter the crystals out of the solution, and leave them in a warm place to dry. you could also use a drying oven
• what can filtration and crystallisation be used to separate?


  rock salt
• what is the process of separating rock salt?


  1. grind the mixture to make sure that the crystals are small, so will dissolve easily
  2. put the mixture in water and stir. the salt will dissolve, but the sand wont
  3. filter the mixture. the grains of sand wont fit through the tiny holes in the filter paper, so they collect on the paper instead. the salt passes through the filter paper as its part of the solution.
  4. evaporate the water from the salt so that it forms dry crystals
• what is rock salt?


  rock salt is simply a mixture of salt and sand
• what are salt and sand?


  compounds - but salt dissolves in water and sand doesn't, this allows a great way to be able to separate them