AIIMS 2019 Physics Surface Tension MCQ Question
Assertion : It is better to wash the clothes in hot soap solution.
Reason : The surface tension of cold solution is more than the surface tension of hot solution.
If both assertion and reason are true and reason is correct explanation of assertion.
If both assertion and reason are true and reason is not correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
Correct Answer
Detailed Explanation
The statement is false because while it is true that higher temperatures generally decrease the surface tension of liquids, the surface tension of soap solutions is not universally lower than that of ordinary water (H₂O). In fact, soap solutions can exhibit varying surface tensions depending on concentration and other factors, but they often have higher surface tension than pure water due to the presence of surfactants that disrupt cohesive forces. Therefore, the claim that soap solutions always have lower surface tension than water is misleading. Options (C) and (D) are irrelevant as the statement can be definitively evaluated as false.
Found an issue with this question?