SC2b ~ Filtration & Crystallisation

• Crystallisation separates a solute from a solution
• A filtrate is placed in an evaporating basin and heat is applied from a bunsen burner 
• The heat will evaporate the filtrate and leave behind the solute 

• Filtration is used to separate an insoluble substance from a liquid 
• Filter paper is used to filter a solution, leaving behind the insoluble substance (in the filter paper) and the filtrate (in the beaker) 

1) A student decides to make pure, dry copper chloride crystals. She adds an excess of insoluble copper chloride solution to dilute hydrochloric acid. Copper chloride solution forms. 

    a) Name a suitable method to remove excess copper carbonate from the solution.  (1 mark)

    b) The student leaves her copper chloride solution on a windowsill.
         (i) Explain why crystals of copper chloride form after a few days.  (3 marks)
         (ii) Give a reason that explains why the student pours away the remaining solution, and then pats the crystals with filter paper.  (1 mark)

1a) Filtration.

1b) (i) Water evaporates (1) and the solution becomes saturated. (1) More water evaporates and crystals form. (1)

1b) (ii) It dries the crystals.