What causes Brownian motion in colloidal dispersion?

Explanation

### Step-by-Step Solution:

1. **Understanding Brownian Motion**:
- Brownian motion refers to the random, zigzag movement of particles suspended in a fluid (liquid or gas). This motion is typically observed in colloidal dispersions.

2. **Identifying the Cause of Brownian Motion**:
- The primary cause of Brownian motion is the collision of the colloidal particles with the molecules of the dispersion medium.

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