Separation of Solids from Liquids

Types of Mixtures

• Insoluble Solid in Liquid: Mixture where the solid does not dissolve, e.g., sand in water.
• Soluble Solid in Liquid: Mixture where the solid dissolves forming a solution, e.g., sodium chloride in water.
  • Solute: The substance that dissolves (e.g., sodium chloride).
  • Solvent: The liquid in which the solute dissolves (e.g., water).

Techniques for Separation

1. Filtration

• Purpose: Separates insoluble solids from liquids.
• Method:
  • Use filter paper with tiny holes, placed in a filter funnel.
  • Pour the mixture through; liquid passes through, solid remains.

2. Evaporation

• Purpose: Separates soluble solids from liquids by removing the solvent.
• Method:
  • Place solution in an evaporating dish or crucible.
  • Heat with a Bunsen burner on a tripod.
  • Solvent evaporates, leaving behind dry crystals of solid.
• Pros: Quick and easy.
• Cons: Thermal decomposition risk for some solids when heated.

3. Crystallization

• Purpose: Separates soluble solids, avoiding thermal decomposition.
• Method:
  • Place solution in an evaporation dish.
  • Heat gently, often using a water bath.
  • Stop heating when crystals begin to form, and allow to cool.
  • Filter out crystals using filter paper and funnel.
  • Dry the crystals by either warming them in an oven or leaving them in a warm place.

Conclusion

• Crystallization is preferred over evaporation for heat-sensitive solids to avoid decomposition.
• These methods allow for the separation and recovery of solids from liquid mixtures effectively.

Note: Remember to consider the properties of the solid when choosing between evaporation and crystallization.