A liquid will not wet the surface of a solid if the angle of contact is

Options

A. `0^(@)`
B. `45^(@)`
C. `60^(@)`
D. `gt90^(@)`

Answer

To determine the condition under which a liquid will not wet the surface of a solid, we need to analyze the concept of the angle of contact (also known as the contact angle). Here’s a step-by-step solution:

### Step 1: Understand the Concept of Contact Angle
The contact angle is defined as the angle formed between the tangent to the liquid surface at the contact point and the solid surface. It indicates how well a liquid wets a solid surface.

### Step 2: Analyze the Cases of Wetting and Non-Wetting
- If the contact angle is **less than 90 degrees**, the liquid wets the surface. For example, water on glass has a contact angle of about 0 degrees, indicating good wetting.
- If the contact angle is **greater than 90 degrees**, the liquid does not wet the surface. An example is mercury on glass, which has a contact angle greater than 90 degrees.

### Step 3: Identify the Given Options
The options provided are:
- A) 0 degrees
- B) 45 degrees
- C) 60 degrees
- D) Greater than 90 degrees

### Step 4: Determine the Correct Option
Since we are looking for the condition under which a liquid will not wet the surface of a solid, we focus on the contact angle being greater than 90 degrees. This indicates that the liquid does not spread over the surface and forms a droplet instead.

### Conclusion
The correct answer is **D) Greater than 90 degrees**. This means that if the contact angle is greater than 90 degrees, the liquid will not wet the surface of the solid.

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