Question

In most liquids, with rise in temperature surface tension of liquid

• A. decreases
• B. increases
• C. remains unchanged
• D. first decreases and then increases

Hint:

Higher temperature weakens the cohesive forces between liquid molecules.

Answer 1

The Correct Option is A

Step 1: Empirical rule
Experiments show that surface tension falls almost linearly with temperature, as in Eotvos and Ramsay-Shields formulas.

Step 2: Molecular picture
Larger kinetic energy of the molecules reduces the effective attraction between neighbours at the surface.

Step 3: Limit
At the critical temperature the surface tension vanishes.

Step 4: Answer
For most liquids surface tension decreases with increase in temperature, option (A).

Final Answer:
Surface tension falls with temperature. This is option (A). \[ \boxed{\text{(A) }\text{Decreases}} \]