QJEEM25Ph37ec: JEE Main 2025 Physics - Class 11 JEEM25Ph37ec Solution: Given below are two statements: Statement I: The hot water…
Given below are two statements:
Statement I: The hot water flows faster than cold water
Statement II: Soap water has higher surface tension as compared to fresh water. In the light above statements, choose the correct answer from the options given below
Multiple Choice Options
- A Both Statement I and Statement II are false
- B Both Statement I and Statement II are true
- C Statement I is false but Statement II is true
- D Statement I is true but Statement II is false
Step-by-Step Verified Solution
Let's analyze the statements one by one:
When water is heated, its viscosity decreases. In simple terms, hot water is "thinner" than cold water.
Lower viscosity means there is less internal friction in the fluid, which allows it to flow more easily and, consequently, faster under the same conditions.
Therefore, under identical pressure conditions, hot water indeed flows faster than cold water.
This makes Statement I true.
Soap is a surfactant. Surfactants reduce the surface tension of the liquid by interfering with the cohesive forces between the water molecules.
Fresh (pure) water has a relatively high surface tension (about 72.8 mN/m at room temperature), but when soap is added, the surface tension is decreased.
Therefore, soap water has lower, not higher, surface tension compared to pure water.
This makes Statement II false.
Based on this analysis, the correct answer is:
Option D: Statement I is true but Statement II is false.