Question

In a closed container, a liquid is stirred with a paddle to increase the temperature, which of the following is true?

• A. $\Delta U=\Delta w\ne 0,q=0$
• B. $\Delta U=w=0,q\ne 0$
• C. $\Delta U=0,w=q\ne 0$
• D. $w=0,\Delta U=q\ne 0$

Answer 1

Answer: (A)

$\Delta U=\Delta w\ne 0,q=0$

The container is closed. Therefore, the heat transfer between the surroundings & the system is zero.

Therefore, $q=0$

Also, the temperature is increased $\Rightarrow \Delta T>0$

$\therefore \Delta U=n{C}_V\Delta T\ne 0$

$\therefore$ By first law of thermodynamics, $\Delta U=\Delta W+q$

$\therefore$ $\Delta U=\Delta W\ne 0\&q=0$