Question

what is the change in internal energy, \\( \delta u \\), in joules, for a system that absorbs 575 j of heat and does 415 j of work on its surroundings?

• 415 j

+ 160 j
+ 575 j

• 160 j

+ 990 j

Explanation:

Step1: Recall the first law of thermodynamics

The first law of thermodynamics is given by $\Delta U = Q+W$. Here, $Q$ is the heat added to the system and $W$ is the work done on the system.

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

Since the system absorbs heat, $Q = + 575\ J$. The system does work on the surroundings, so $W=-415\ J$ (work done by the system is negative as per the sign convention of the first law of thermodynamics).

Step3: Calculate $\Delta U$

Substitute the values of $Q$ and $W$ into the formula $\Delta U=Q + W$. So, $\Delta U=575\ J+( - 415\ J)$.

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Answer:

+ 160 J