Crystallisation and Separation Techniques

 Crystallisation  

- Used to obtain pure crystals of a solid from its solution.  

Process: The solution is first heated and then cooled, allowing the solid to crystallise out.  

Comparison with Evaporation:  

Evaporation: Quick method; heating leaves behind a solid, but often impure.  

Crystallisation: Slow method; solution left at room temperature becomes saturated, forming pure crystals.  

Fractional Crystallisation  

- Separates two or more salt solutes present in a solution.  

Principle: Different salts have different solubility at different temperatures, allowing selective crystallisation.  

Floatation  

- Separates two insoluble solids by mixing them in water.  

- One solid floats, while the other sinks.  

Example: Separation of sawdust from sand.  

Separating Funnel  

- Used to separate two or more immiscible liquids (liquids that do not mix).  

Principle: Liquids of different densities separate into layers.  

  - The denser liquid sinks to the bottom.  

  - The lighter liquid floats on top.  

Example: Separation of kerosene and water.  

Method: Open the tap to allow the denser liquid to flow out, leaving the lighter liquid behind.