Evaporation and Crystallisation

• What is the term used to describe a solid that can be dissolved?

  Soluble
• What are the two methods to separate soluble salts from solutions?

  • Evaporation
  • Crystallisation
• What is the first step in the evaporation method to separate a soluble salt?


  Pour the solution into an evaporating dish
• What happens to the solution when it is slowly heated during evaporation?


  The solvent evaporates and the solution becomes more concentrated
• What should you do once crystals start to form during evaporation?


  Keep heating the evaporating dish until only dry crystals remain
• Why is evaporation a quick method for separating soluble salts?


  Because it rapidly removes the solvent from the solution
• When should you use crystallisation instead of evaporation?


  When the salt decomposes upon heating
• What is the first step in the crystallisation method?


  Pour the solution into an evaporating dish and gently heat it
• What occurs as some of the solvent evaporates during crystallisation?


  The solution becomes more concentrated
• What should you do when you see crystals starting to form during crystallisation?


  Remove the dish from the heat and leave it to cool
• Why do crystals start to form in the cold, highly concentrated solution?


  Because the salt becomes insoluble in the cold solution
• What is the final step in the crystallisation process?


  Filter the crystals out of the solution and leave them to dry
• Where can you leave the crystals to dry after filtering them out?


  In a warm place, a drying oven, or a desiccator
• What are the key differences between evaporation and crystallisation methods for separating soluble salts?


  • Evaporation is quicker but not suitable for salts that decompose.
  • Crystallisation is slower but allows for the formation of larger crystals.
• What is the purpose of evaporation and crystallization in chemistry?


  To separate soluble solids from a liquid mixture
• What is a mixture of liquid and insoluble solid called?

  A mixture
• Give an example of a mixture of liquid and insoluble solid.


  Sand and water
• What is a solution?


  A liquid containing a soluble solid
• Provide an example of a solution.


  Sodium chloride in water
• What happens during evaporation?


  The liquid turns into vapor, leaving behind any solid residue
• Why is it important to control the heating during evaporation?


  To prevent decomposition of some solids when heated
• What are the steps involved in crystallization?


  1. Heat gently using a water bath.
  2. Observe the formation of crystals.
  3. Stop heating when more crystals appear and allow to cool.
  4. Filter the crystals using filter paper and dry them.
• What is the first step in the crystallization process?


  Heat gently using a water bath
• What should you do once you start to see crystals forming during crystallization?


  Stop heating and allow the solution to cool
• How do you filter the crystals after crystallization?

  Using filter paper
• How should you dry the crystals after filtering?


  By leaving them somewhere warm or using an oven
• What is the significance of cooling the solution slowly during crystallization?


  It allows for larger and purer crystals to form