Question

Statement (A): When the temperature increases the viscosity of gases increases and the viscosity of liquids decreases.
Statement (B): Water does not wet an oily glass because cohesive force of oil is less than that of water.
Statement (C): A liquid will wet a surface of a solid if the angle of contact is greater than \(90^\circ\).
Choose the correct option.

• A. A, B and C are false
• B. A and B false, C is true
• C. B and C false, A is true
• D. A and C false, B is true

Hint:

Liquids wet a surface when adhesive force between liquid and solid is greater than the cohesive force within the liquid. In such cases, the angle of contact is less than \(90^\circ\).

Answer 1

The Correct Option is C

Step 1: Analyze Statement (A).
For gases, viscosity increases with increase in temperature because molecular motion becomes more vigorous and momentum transfer between layers increases.
For liquids, viscosity decreases with increase in temperature because intermolecular forces become weaker and the liquid flows more easily.
Hence, Statement (A) is

true.

Step 2: Analyze Statement (B).
Water does not wet an oily glass because the adhesive force between water and oil-coated glass is smaller than the cohesive force within water molecules.
The statement says cohesive force of oil is less than that of water, which is not the correct reason.
Hence, Statement (B) is

false.

Step 3: Analyze Statement (C).
A liquid wets a solid surface when the angle of contact is less than \(90^\circ\).
If the angle of contact is greater than \(90^\circ\), the liquid does not wet the surface.
Therefore, Statement (C) is

false.

Step 4: Final conclusion.
Only Statement (A) is true, while Statements (B) and (C) are false.
Hence, the correct option is
\[ \boxed{\text{B and C false, A is true}} \]