Physical Separation Techniques: Filtration & Crystallisation

Introduction

• Focus on describing physical separation techniques
• Techniques covered: Filtration, Crystallisation, Distillation, Chromatography
• Physical separation techniques separate mixtures, not elements in compounds
• Chemical reactions (reduction, electrolysis) separate elements in compounds

Filtration

• Used to separate an insoluble solid from a liquid.

Key Concepts

• Insoluble: A solid that will not dissolve in a liquid.
• State Symbols: Indicate the state of a chemical (solid, liquid, gas, dissolved in water).

Example

• Silver chloride (s for solid) and water (l for liquid).
• Silver chloride does not dissolve in water (insoluble).

Process

1. Use a filter funnel and filter paper.
2. Pour mixture (solid in liquid) into the filter paper.
3. Liquid passes through the filter paper.
4. Solid material is trapped in the filter paper.
5. Result: Liquid is separated from the solid.

Applications

• Widely used in chemistry to separate mixtures.

Crystallisation

• Used to separate a soluble solid from a liquid.

Key Concepts

• Soluble: A solid that will dissolve in a liquid.
• Aqueous Solution: A solution where a substance (solute) is dissolved in water (solvent).
• State symbols: aq (dissolved in water), s (solid).

Example

• Sodium chloride (aq for aqueous solution) and water.

Process

1. Start with a sodium chloride solution.
2. Leave the solution for a few days for water to evaporate.
3. Crystals of solid sodium chloride form.
4. Optionally heat the solution to speed up evaporation.
5. Be cautious as some chemicals can break down with heat.

Conclusion

• Filtration separates insoluble solids from liquids.
• Crystallisation separates soluble solids from liquids.
• Important techniques with specific applications in chemistry.