Which of the following properties cannot be used to distinguish between a solid and a liquid?

Options

A. Solubility
B. Compressibility
C. Change of state
D. Conductivity

Answer

To solve the question "Which of the following properties cannot be used to distinguish between a solid and a liquid?", we will analyze each option provided and determine if it can be used to differentiate between solids and liquids.

### Step-by-Step Solution:

1. **Understanding the Properties**:
- We need to evaluate the properties given in the options to see if they can distinguish solids from liquids.

2. **Option 1: Solubility**:
- Solids and liquids have different solubility characteristics. Generally, solids are less soluble than liquids, and some solids can dissolve in liquids. Therefore, this property can be used to distinguish between solids and liquids.

3. **Option 2: Compressibility**:
- Solids are generally less compressible than liquids. This means that when pressure is applied, solids do not change their volume as much as liquids do. Thus, compressibility can also be used to distinguish between solids and liquids.

4. **Option 3: Change of State**:
- When a solid is heated, it can change into a liquid (melting), and we can have both solids and liquids at the same time. This means that the change of state does not provide a clear distinction between solids and liquids because both can exist in different states. Therefore, this property cannot be used to distinguish between solids and liquids.

5. **Option 4: Conductivity**:
- Conductivity can vary between solids and liquids. Generally, solids (especially metals) conduct electricity better than liquids. This property can also be used to distinguish between solids and liquids.

6. **Conclusion**:
- After evaluating all the options, we find that the property that cannot be used to distinguish between a solid and a liquid is **Option 3: Change of State**.

### Final Answer:
**Option 3: Change of State**