Question

At which of the following temperatures, the value of surface tension of water is minimum?

• A. $ 4{}^\circ C $
• B. $ 25{}^\circ C $
• C. $ 50{}^\circ C $
• D. $ 75{}^\circ C $

Answer 1

Answer: (D)

The surface tension of water is $72$ dyne $/ cm$ at $25^{\circ} C$. It would take a force of $72$ dyne to break a surface film of water $1\, cm$ long. The surface tension of water decreases significantly with temperature as shown in the graph below.

Out of the given four options $75^{\circ} C$ is the highest temperature, at which surface tension is lowest.