A fluid in an insulated, flexible bottle is heated by a high resistance wire and expands. If $9.0 \mathrm {~kJ}$ of heat is applied to the system and it does $5.0 \mathrm {~kJ}$ of work, how much does the internal (thermal) energy of the fluid change?
A) 4.0 kJ
B) 14 kJ
C) -4.0 kJ
D) 45 kJ

Question

Quizplus · Accepted Answer

The change in internal energy ($\Delta U$) can be calculated using 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, $Q = 9.0 \mathrm {~kJ}$ and $W = 5.0 \mathrm {~kJ}$, so $\Delta U = 9.0 \mathrm {~kJ} - 5.0 \mathrm {~kJ} = 4.0 \mathrm {~kJ}$.

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