Which one of the following does not represent a colloidal system?

Options

A. Smoke
B. Ink
C. Air
D. Blood

Answer

To determine which of the following does not represent a colloidal system, we need to understand the characteristics of a colloidal system. A colloidal system consists of two phases: the dispersed phase (the particles) and the dispersion medium (the substance in which the particles are dispersed). Colloids are heterogeneous mixtures, meaning they have distinct phases.

### Step-by-Step Solution:

1. **Understanding Colloidal Systems**:
- A colloidal system consists of two phases: the dispersed phase (solid, liquid, or gas) and the dispersion medium (liquid, solid, or gas).
- Colloids are heterogeneous mixtures, meaning they do not have a uniform composition throughout.

2. **Analyzing the Options**:
- **Smoke**: Smoke consists of solid particles dispersed in air (a gas). This is a colloidal system because it has a dispersed phase (solid particles) and a dispersion medium (air).
- **Ink**: Ink is a mixture where solid pigments are dispersed in a liquid medium (water or other solvents). This also qualifies as a colloidal system.
- **Blood**: Blood contains various solid components (like cells and proteins) dispersed in a liquid medium (plasma). Thus, blood is also a colloidal system.
- **Air**: Air is a mixture of gases and does not have a dispersed phase. It is a homogeneous mixture, meaning it has a uniform composition throughout.

3. **Conclusion**:
- Among the options provided, air does not represent a colloidal system because it lacks the two distinct phases required for a colloid. Therefore, the answer is air.

### Final Answer:
Air does not represent a colloidal system.