Change in Internal Energy

The change in internal energy of a system can be calculated using the first law of thermodynamics, which states that the change in internal energy (ΔU) is equal to the heat added to the system (Q) minus the work done by the system (W). Mathematically, it can be represented as:

ΔU = Q - W

Given:
- Work done (W) = 104 KJ (positive value, indicating work done by the system)
- Heat released (Q) = 125 KJ (positive value, indicating heat released by the system)

Calculating the Change in Internal Energy:
To find the change in internal energy, we need to substitute the given values of work done and heat released into the equation.

ΔU = Q - W
ΔU = 125 KJ - 104 KJ
ΔU = 21 KJ

Therefore, the change in internal energy of the gas is 21 KJ.

Explanation:
- The equation ΔU = Q - W represents the first law of thermodynamics, which is a basic principle in thermodynamics that relates the change in internal energy of a system to the heat added to the system and the work done by the system.
- In this case, the gas releases 125 KJ of heat, indicating that heat is being transferred out of the system. Therefore, the heat released is a positive value.
- The gas also does 104 KJ of work, indicating that work is being done by the system. Therefore, the work done is a positive value.
- By substituting the given values into the equation, we can find the change in internal energy, which is equal to the heat released minus the work done. In this case, the change in internal energy is 21 KJ.

-21KJ