Colloids can be prepared by two main methods: dispersion methods and condensation methods. Here’s a explanation:
1. Dispersion Method
- Idea: Break down larger particles into tiny colloidal particles.
- How: Use mechanical or chemical means to reduce particle size.
- Example methods:
- Grinding solids into fine powder and mixing in liquid (e.g., sugar solution → colloid)
- Dispersion of insoluble substances in water (e.g., finely divided metals in water)
2. Condensation Method
- Idea: Combine smaller molecules to form colloidal particles.
- How: Use chemical reactions to make particles grow to colloid size.
- Example methods:
- Chemical precipitation: Mixing two solutions to form insoluble colloidal particles (e.g., silver chloride sol)
- Oxidation/reduction reactions: Gold or silver sols prepared by reducing metal salts
Simple tip:
- Dispersion: Break big → small
- Condensation: Build small → bigger