A fluid in an insulated, flexible bottle is heated by a high resistance wire and expands. If 9 kJ of heat is
applied to the system and it does 5 kJ of work, how much does the internal energy change?
To determine the change in internal energy, we can use the first law of thermodynamics, which states that the change in internal energy (∆U) of a system is equal to the heat added to the system (Q) minus the work done by the system (W):
∆U = Q - W
In this case, we know that 9 kJ of heat (Q) is applied to the system, and the system does 5 kJ of work (W).
∆U = 9 kJ - 5 kJ
To find the change in internal energy, we can subtract 5 kJ from 9 kJ:
∆U = 4 kJ
Therefore, the change in internal energy is 4 kJ.