A liquid does not wet solid surface if angle of contact is

Options

A. equal to 45 deg
B. equal to 60
C. greater than 90
D. zero

Answer

To solve the question about the angle of contact for a liquid that does not wet a solid surface, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Wetting and Non-Wetting Liquids**:
- Wetting liquids are those that spread on a solid surface, forming a contact angle less than 90 degrees.
- Non-wetting liquids do not spread on the surface and form a contact angle greater than 90 degrees.

2. **Defining the Angle of Contact**:
- The angle of contact (or contact angle) is the angle formed between the tangent to the liquid surface and the solid surface at the point of contact.
- It indicates how well the liquid wets the surface.

3. **Analyzing the Conditions**:
- If the angle of contact is less than 90 degrees, the liquid is considered a wetting liquid (it adheres to the surface).
- If the angle of contact is greater than 90 degrees, the liquid is considered a non-wetting liquid (it does not adhere to the surface).

4. **Conclusion**:
- Therefore, for a liquid to not wet a solid surface, the angle of contact must be greater than 90 degrees.

### Final Answer:
A liquid does not wet a solid surface if the angle of contact is **greater than 90 degrees**.

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