A water proofing agent chages the angle of contact from

Options

A. from acute to `90^(@)`
B. from obtuse to `90^(@)`
C. from an acute to obtuse value
D. from an obtuse to acute value

Explanation

To solve the question about how a waterproofing agent changes the angle of contact, we can follow these steps:

### Step 1: Understand the Concept of 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 a liquid wets a surface.

### Step 2: Identify the Two Scenarios
1. **Without Waterproofing Agent**: When there is no waterproofing agent, the surface is wet by the liquid (water in this case), and the angle of contact is acute (less than 90 degrees). This means that the liquid spreads out on the surface.

2. **With Waterproofing Agent**: When a waterproofing agent is applied, it alters the surface properties. The water drop does not spread out as much and instead forms a more spherical shape, resulting in an obtuse angle (greater than 90 degrees). This indicates that the liquid does not wet the surface effectively.

### Step 3: Visual Representation
To illustrate this, we can draw two diagrams:
- **Diagram 1**: A surface without a waterproofing agent showing a water droplet with an acute angle of contact.
- **Diagram 2**: A surface with a waterproofing agent showing a water droplet with an obtuse angle of contact.

### Step 4: Conclusion
The application of a waterproofing agent changes the angle of contact from acute to obtuse, indicating a decrease in the wettability of the surface.

### Final Answer
A waterproofing agent changes the angle of contact from acute angle to obtuse angle.

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