Question

If T and \(\eta\) are the surface tension and coefficient of viscosity of a liquid, then with the increase of temperature

• A. both T and \(\eta\) increase
• B. both T and \(\eta\) decrease
• C. both T and \(\eta\) remain constant
• D. T increases but \(\eta\) decreases
• E. T decreases but \(\eta\) increases

Hint:

Hot water has lower surface tension (better for cleaning) and lower viscosity (flows more easily) than cold water.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Surface tension and viscosity are both properties of liquids that depend on intermolecular forces.

Step 2: Detailed Explanation:
As temperature increases:
• Surface tension (T) decreases because the increased thermal energy overcomes the cohesive forces between molecules at the surface.
• Coefficient of viscosity (\(\eta\)) decreases because the increased thermal energy reduces the intermolecular friction, allowing molecules to move more freely. Both properties decrease with an increase in temperature.

Step 3: Final Answer:
With an increase in temperature, both surface tension and viscosity decrease.