Techniques to Separate Solids from Liquids

Key Terminology

• Insoluble Solid: A solid that does not dissolve in a liquid, e.g., sand in water.
• Soluble Solid: A solid that dissolves in a liquid, forming a solution, e.g., sodium chloride in water.
  • Solution: Combination of solute (e.g., sodium chloride) and solvent (e.g., water).

Separation Techniques

Filtration

• Used for separating insoluble solids from liquids.
• Process:
  • Filter paper with tiny holes is used to allow liquid to pass through but retain solid particles.
  • Often used with a filter funnel for ease of use.
• Analogy: Similar to using a sieve in cooking.

Evaporation

• Used for separating soluble solids from liquid by removing the solvent through heating.
• Process:
  • Place solution in an evaporating dish or a crucible.
  • Heat gently using a tripod and Bunsen burner.
  • Solvent evaporates, causing the solution to become more concentrated.
  • Crystals form and eventually, only dry crystals remain.
• Advantages:
  • Quick and easy.
• Disadvantages:
  • Can lead to thermal decomposition of some solids if heated too intensely.

Crystallization

• Alternative for separating soluble solids that may decompose upon heating.
• Process:
  • Solution is gently heated, often using a water bath.
  • Stop heating when early crystals form; allow to cool.
  • More crystals form as the solution cools due to decreased solubility at lower temperatures.
  • Filter out crystals using filter paper and funnel.
  • Dry crystals by leaving them in a warm place or using an oven.
• Advantages:
  • Avoids decomposition due to gentle heating.

Conclusion

• Filtration is ideal for insoluble solids.
• Evaporation is quick but not suitable for heat-sensitive solids.
• Crystallization is slower but better for heat-sensitive solids.

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