### Work Equation

Posted:

**Tue Jan 19, 2016 11:11 pm**Could someone explain why the work equation is w=(NEGATIVE)P delta v? I understand where everything comes from but I'm still having trouble grasping why the entire equation is negative.

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=129&t=10120

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Posted: **Tue Jan 19, 2016 11:11 pm**

Could someone explain why the work equation is w=(NEGATIVE)P delta v? I understand where everything comes from but I'm still having trouble grasping why the entire equation is negative.

Posted: **Tue Jan 19, 2016 11:14 pm**

The sign is negative because as work is done by the system on its surrounding there is decrease in the internal energy of a system.

Posted: **Tue Jan 19, 2016 11:15 pm**

By convention, we make work "negative" PΔV because we are looking at the work done by a system. If it were work done on a system, then it would just be PΔV without the negative sign. This is because, from the standpoint of the system, when it expands, hence when ΔV is positive, the system loses energy by doing work on the surroundings. Energy lost is, by convention, given a negative sign, which is why the work done by a system equals -PΔV.