Answer: A system that is giving off 65.0 kJ of heat and is performing 855 J of work on the surroundings has a change in the internal energy of -65.9 kJ.
Explanation: The system is giving off 65.0 kJ of heat (Q). By convention, when a system is releasing heat, Q < 0. Then, Q = -65.0 kJ.
The system is also performing 855 J of work (W) on the surroundings. By convention, when a system performs work on the surroundings, W < 0. Then, W = -855 J (-0.855 kJ)
According to the First Law of Thermodynamics, we can calculate the change in the internal energy (ΔE) of the system using the following expression.
A system that is giving off 65.0 kJ of heat and is performing 855 J of work on the surroundings has a change in the internal energy of -65.9 kJ.