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### Work equation

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

### Re: Work equation

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 $\Delta$V you need to account for the loss in work by putting a negative sign in front of the equation.

### Re: Work 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.