Physics - Fluid Question with Solution | TestHub
Which of the following is NOT TRUE?
a. When soluble substance is dissolved in water, the surface tension of water increases.
b. When sparingly soluble substance is mixed with water, surface tension of water increases.
c. When insoluble impurity is added into the water, surface tension of water decreases.
d. In case of molten copper or molten cadmium, the surface tension increases with increase in its temperature.
Options:
Answer:
Solution:
When a highly soluble substance (like sodium chloride or sugar) is dissolved in water, the surface tension of water increases.
When a sparingly soluble substance (like phenol, soap, or camphor) is mixed with water, the surface tension of water decreases. Therefore, the statement that surface tension increases is incorrect.
When an insoluble impurity (like oil or grease) is added to water, the surface tension of water decreases.
For most liquids, surface tension decreases with an increase in temperature. However, molten copper and molten cadmium are exceptions where the surface tension increases with an increase in temperature.
Answer: b
