Step 1: Understanding the Concept:
Segregation (also called demixing) is the undesirable separation of a previously uniform mixture into its components. This is a common problem in powder handling.
Step 2: Detailed Explanation:
1. Percolation Segregation: If there is a wide range of particle sizes, smaller particles can fall through the gaps between larger particles during movement or vibration.
2. Trajectory Segregation: Heavier or larger particles travel further when thrown or tumbled compared to smaller/lighter ones.
3. Density effects: Particles with different densities will respond differently to gravity and centrifugal forces during mixing.
4. Prevention: Using liquid binders (wet granulation) or having uniform particle sizes (Option A) prevents segregation.
Step 3: Final Answer:
Variance in size and density is the primary driver of segregation in dry powder mixtures.