which of the following are colloids ?

Options

A. Sulphur sol
B. starch
C. Gold sol
D. soap solution

Answer

To determine which of the given substances are colloids, we need to understand the definition and characteristics of colloids. Colloids are mixtures where the particle size is between 1 nanometer (nm) and 1000 nanometers (1 micrometer). Particles smaller than 1 nm form true solutions, while those larger than 1000 nm are classified as suspensions.

### Step-by-Step Solution:

1. **Understanding Colloids**:
- Colloids are defined by their particle size, which ranges from 1 nm to 1000 nm.
- They can be classified into different types based on their properties.

2. **Identifying the Substances**:
- We will analyze each substance mentioned to see if they fall into the colloid category.

3. **Sulfur Sol**:
- Sulfur sol is an example of a multi-molecular colloid.
- It consists of aggregates of sulfur particles that are within the colloidal size range.
- **Conclusion**: Sulfur sol is a colloid.

4. **Gold Sol**:
- Gold sol is also a multi-molecular colloid.
- It is formed by the aggregation of gold particles, which again fall within the colloidal size range.
- **Conclusion**: Gold sol is a colloid.

5. **Soap Solution**:
- Soap solution is an associated colloid.
- It contains micelles formed when soap molecules aggregate in water, which also fits the colloidal size range.
- **Conclusion**: Soap solution is a colloid.

6. **Final Conclusion**:
- All the substances mentioned (sulfur sol, gold sol, and soap solution) are colloids.

### Summary of Colloids Identified:
- Sulfur sol: Colloid
- Gold sol: Colloid
- Soap solution: Colloid