NEET UG PHYSICS MCQ: MECHANICAL PROPERTIES OF FLUIDS

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Understanding +4 | -1

With an increase in temperature, surface tension of liquid (except molten copper and cadmium)

View answer and explanation

Correct option: C

decreases

Option C (decreases) is correct because the surface tension of most liquids decreases as temperature increases due to increased molecular kinetic energy.

Solution approach

Correct Answer + Core Reason: decreases. Surface tension generally decreases with increasing temperature because the increased thermal energy reduces intermolecular forces.

Step-by-Step Solution:

Step 1: Understand the relationship between temperature and surface tension.

Step 2: Recall that surface tension is due to cohesive forces between liquid molecules.

Step 3: As temperature increases, the kinetic energy of molecules increases, weakening the cohesive forces.

Step 4: Weaker cohesive forces result in lower surface tension.

Why other options are wrong:
- Option A: increases - Incorrect. Increasing temperature generally weakens intermolecular forces, reducing surface tension.
- Option B: remain same - Incorrect. Surface tension is temperature-dependent and generally decreases with increasing temperature.
- Option D: first decrease and then increases - Incorrect. While some complex behaviors can occur in specific substances, the general trend is a decrease in surface tension with increasing temperature.

Key Concepts:
- Surface Tension
- Intermolecular Forces
- Temperature Dependence

Memory Aids:
- Higher temperature, lower surface tension (think of water becoming \

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