Question

The gas is cooled and loses $65$J of heat. The gas contracts as it cools and works done on the system equal to $20$J is exchanged with the surroundings.

What is $\Delta E$ (in J)?

Answer 1

As the heat is released and the work is done on the system.

So, $q=-65J$ and $W=20J$

Now, using first law of thermodynamics,

$\Delta E=q+W$

$\Rightarrow \Delta E=-65+20=-45J$

Hence, the value of $\Delta E$ is $-45J$.