How mnay colloidal systems exist in nature in which gas is dispersed phase?

Answer

To determine how many colloidal systems exist in nature where gas is the dispersed phase, we can analyze the combinations of phases involved in colloidal systems.

### Step-by-Step Solution:

1. **Understanding Colloidal Systems**:
- A colloidal system consists of a dispersed phase and a dispersion medium. The dispersed phase can be solid, liquid, or gas, and the dispersion medium can also be solid, liquid, or gas.

2. **Identifying the Dispersed Phase**:
- In this case, we are focusing on gas as the dispersed phase.

3. **Combining Gas with Other Phases**:
- **Gas as Dispersed Phase with Solid as Dispersion Medium**:
- When gas is dispersed in a solid, it forms a solid foam. An example of this is foam rubber. This is a valid colloidal system.
- **Gas as Dispersed Phase with Liquid as Dispersion Medium**:
- When gas is dispersed in a liquid, it forms a foam. An example of this is froth. This is also a valid colloidal system.
- **Gas as Dispersed Phase with Gas as Dispersion Medium**:
- When gas is dispersed in gas, it does not form a colloidal system; instead, it results in a homogeneous mixture. Therefore, this does not count as a colloidal system.

4. **Conclusion**:
- From the analysis, we find that there are two types of colloidal systems where gas is the dispersed phase:
1. Solid foam (e.g., foam rubber)
2. Foam (e.g., froth)
- Therefore, the total number of colloidal systems in which gas is the dispersed phase is **2**.

### Final Answer:
**2 colloidal systems exist in nature where gas is the dispersed phase.**