Crystallisation

• What is crystallisation?

  Crystallisation is used to separate a soluble salt from a solution (a liquid)

  
• How can soluble salts make solutions?

  • When a soluble solid (e.g. sodium chloride) is mixed with water , it dissolves 
  • This forms a solution (e.g. sodium chloride solution)
• Describe how to separate a soluble solid from a solution using crystallisation?

  • Gently heat the solution - this makes the crystallisation process faster
  • If we leave the solution for a few days, the water will evaporate 
  • This will leave behind salt crystals of the solid

  
• Why do we have to be careful when heating a solution to separate a soluble salt from it?

  • Certain chemicals will break down if we heat them  
  • So sometimes it is better to allow the water to evaporate on its own