A fluid in an insulated,flexible bottle is heated by a high resistance wire and expands.If $9.0 \mathrm {~kJ}$ of thermal energy is transferred through heating to the system and it - $5.0 \mathrm {~kJ}$ of work is done on it,how much does the internal (thermal)energy of the fluid change?

Question

Quizplus · Accepted Answer

The internal energy change ($\Delta U$) in a system is given by the first law of thermodynamics, $\Delta U = Q - W$, where $Q$ is the heat added to the system and $W$ is the work done by the system. Here, $Q = 9.0 \mathrm{kJ}$ (heat added to the system) and $W = -5.0 \mathrm{kJ}$ (work done on the system, hence negative). Thus, $\Delta U = 9.0 \mathrm{kJ} - (-5.0 \mathrm{kJ}) = 14.0 \mathrm{kJ}$. However, the correct calculation should result in a 14 kJ change, indicating a mistake in my initial selection. The correct choice should be B, reflecting a 14 kJ increase in internal energy.

A Fluid in an Insulated,flexible Bottle Is Heated by a High