Colloidal systems are

Options

A. homogeneous
B. heterogeneous
C. suspensions
D. transparent

Answer

### Step-by-Step Solution

1. **Understanding Colloidal Systems**:
- Colloidal systems consist of small particles dispersed in a continuous medium. These particles are larger than molecules but smaller than what can be seen with the naked eye.

2. **Classification of Mixtures**:
- Mixtures can be classified into two main categories: homogeneous and heterogeneous.
- Homogeneous mixtures have a uniform composition throughout, while heterogeneous mixtures have distinct phases or components.

3. **Nature of Colloidal Systems**:
- Colloidal systems are classified as heterogeneous mixtures. Although they may appear uniform to the naked eye, they consist of distinct particles that do not settle out upon standing.

4. **Particle Size**:
- The particles in colloidal systems are of intermediate size, which is larger than those in solutions but smaller than those in suspensions. This size range typically falls between 1 nm to 1000 nm.

5. **Tyndall Effect**:
- The Tyndall effect is a phenomenon that helps distinguish colloidal systems from true solutions. When light passes through a colloidal mixture, it scatters, making the path of the beam visible. This effect is not observed in true solutions, where the particles are too small to scatter light.

6. **Examples of Colloidal Systems**:
- Common examples of colloidal systems include milk, paint, and blood. These mixtures appear homogeneous but are, in fact, heterogeneous due to the presence of dispersed particles.

7. **Conclusion**:
- Based on the characteristics and behavior of colloidal systems, we conclude that they are heterogeneous mixtures.

### Final Answer:
Colloidal systems are **heterogeneous mixtures**.

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