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When a block slips on a rough surface, the work done by the surface on block is negative, while the work done by block on surface is zero. While writing the first law of thermodynamics, I have considered the block as my system and surface as the surroundings.

By the first law of thermodynamics, $$\Delta U=Q-W$$

Where $W$ is zero.

Now here's the poblem: by the IUPAC convention of work done on the system being positive, we have$$\Delta U=Q+W$$ where $\Delta U$ and $Q$ are the same as the first equation, but $W$ is nonzero. Why aren't the two equations consistent?

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  • $\begingroup$ Possible duplicates: physics.stackexchange.com/q/37904/2451 , physics.stackexchange.com/q/91197/2451 and links therein. $\endgroup$
    – Qmechanic ♦
    Commented Sep 4, 2021 at 5:02
  • $\begingroup$ @Qmechanic no, they arent duplicates. I understand the conventions well. Please read my question properly, as there seems to be an inconsistency when the works done by either system are not negatives of each other. $\endgroup$
    – yukelid
    Commented Sep 4, 2021 at 5:21
  • $\begingroup$ The difference is in definition of work in physics we tend to study a gas so what we care is that the amount of work done by gas on the surrounding which PdV whereas in chemistry we tend to study the changes occuring in the gases when the surrounding(We) so changes to them so we care what work the surrounding does on the gas which is -PdV $\endgroup$
    – Soham Patil
    Commented Sep 4, 2021 at 6:17

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