The Brownian motion is due to:

Options

A. Temperature fluctuation withing the liquid phase
B. Attraction and repulsion between charge on the colloidal particles
C. Impact of moleculars of the dispersion medium on the colloidal particles
D. Convective current

Explanation

To solve the question regarding the cause of Brownian motion, we can follow these steps:

### Step 1: Understand Brownian Motion
Brownian motion refers to the random movement of microscopic particles suspended in a fluid (liquid or gas). This motion is not directed or systematic; instead, it appears erratic and unpredictable.

### Step 2: Analyze the Causes of Brownian Motion
Brownian motion is primarily caused by the collisions between the suspended particles and the molecules of the surrounding fluid (the dispersion medium). These collisions result in the random movement of the particles.

### Step 3: Evaluate the Given Options
We have four options to consider:
1. Temperature fluctuation within the liquid phase
2. Attraction and repulsion between charges on the colloidal particles
3. Impact of molecules of the dispersion medium on the colloidal particles
4. Convective current

### Step 4: Identify the Correct Option
- **Option 1**: While temperature fluctuations can affect the energy of the particles, they do not directly cause the random motion.
- **Option 2**: Attraction and repulsion between charges can influence stability but are not the primary cause of the random motion.
- **Option 3**: This option correctly identifies that the impact of molecules of the dispersion medium on the colloidal particles is what causes Brownian motion.
- **Option 4**: Convective currents can cause movement but are not the primary reason for the random motion observed in Brownian motion.

### Conclusion
The correct answer is **Option 3: Impact of molecules of the dispersion medium on the colloidal particles**.

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