To find the heat lost by the system, we can use the first law of thermodynamics, which states that the change in internal energy of a system is equal to the heat added to the system minus the work done by the system. Mathematically, it can be expressed as:
ΔU = Q - W
Where: ΔU is the change in internal energy Q is the heat added to the system W is the work done by the system
In this case, the internal energy decreases by 300 J (ΔU = -300 J), and the work done by the system is 120 J (W = 120 J). We need to find the heat lost by the system (Q).
ΔU = Q - W -300 J = Q - 120 J
To isolate Q, we rearrange the equation:
Q = ΔU + W Q = -300 J + 120 J Q = -180 J
Therefore, the heat lost by the system is -180 J. The negative sign indicates that heat is lost from the system.