Question

what is the change in internal energy in joules for a system that releases 154 j of heat and does 125 j of work on its surroundings?

Explanation:

Step1: Recall the first law of thermodynamics formula

The first law of thermodynamics is $\Delta U = Q - W$, where $\Delta U$ is the change in internal energy, $Q$ is the heat transfer, and $W$ is the work done by the system.

Step2: Determine the signs of $Q$ and $W$

Since the system releases heat, $Q=- 154\ J$ (negative because heat is leaving the system). The system does work on its surroundings, so $W = 125\ J$ (positive because work is done by the system).

Step3: Substitute values into the formula

$\Delta U=-154 - 125$.

Step4: Calculate the result

$\Delta U=-279\ J$.

Answer:

-279 J