### Work equation

Posted:

**Sat Jan 16, 2016 9:15 pm**Why is there a negative in the work equation w=-PΔV?

Created by Dr. Laurence Lavelle

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

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=129&t=9845

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Posted: **Sat Jan 16, 2016 9:15 pm**

Why is there a negative in the work equation w=-PΔV?

Posted: **Sat Jan 16, 2016 9:22 pm**

If you are expanding a gas by a constant external pressure to match the positive difference in V you need to account for the loss in work by putting a negative sign in front of the equation.

Posted: **Sat Jan 16, 2016 10:39 pm**

When a gas expands, it does work against the lid that contains it - the gas is "pushing" against the lid and is ultimately losing energy. Therefore, the negative sign is incorporated into the equation to show that its expansion represents a loss of energy.