The liquid that does not wet the solid surface has an ______ angle of contact.a)900b)acutec)obtused)600Correct answer is option 'C'. Can you explain this answer?

Question

Answer

The angle should be obtuse.... cuz at this angle, the liquid surface moves away from the solid surface and hence cannot wet the solid.

Answer

When liquid molecules are attracted strongly to themselves and weakly to those of solids, it costs lots of energy to create liquid-solid surface and liquid then does not wet the solid.

For Example:

Mercury molecules (which make an obtuse angle with glass) have a strong force of attraction between themselves and a weak force of attraction toward solids. Hence, they tend to form drops.

On the other hand, water molecules make acute angles with glass. They have a weak force of attraction between themselves and a strong force of attraction toward solids. Hence, they tend to spread out.

Answer

Explanation:

- Angle of Contact:
When a liquid droplet is in contact with a solid surface, the angle between the tangent to the liquid surface at the point of contact and the solid surface is known as the angle of contact.
- Types of Angle of Contact:
There are three types of angles of contact:
- Acute angle: When the liquid wets the solid surface, the angle of contact is acute.
- Obtuse angle: When the liquid does not wet the solid surface, the angle of contact is obtuse.
- Right angle: When the liquid neither wets nor spreads over the solid surface, the angle of contact is a right angle.
- Explanation of the Answer:
In this case, the liquid does not wet the solid surface, which means it forms a droplet on the surface and does not spread out. In such a scenario, the angle of contact is obtuse. This is because the liquid molecules have a stronger cohesive force between them compared to the adhesive force between the liquid and solid, leading to a higher angle of contact. Therefore, the correct answer is an obtuse angle of contact.

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