## + or - w

$\Delta U=q+w$

Jessica Chen 2C
Posts: 103
Joined: Thu Jul 11, 2019 12:17 am

### + or - w

While I was reviewing I watched a few videos that stated the first law as delta u= q - w, and they said that w is positive when work is being done on the surroundings. It threw me off because it’s different from how we’ve been thinking about it, and now I’m confused. How are we treating w on the test? Is it positive or negative when work is being done on the system?

Zoya Mulji 1K
Posts: 105
Joined: Thu Jul 11, 2019 12:15 am

### Re: + or - w

when work is done on the system it is + and when work is done BY the system it is -. I think in physics, they use the opposite equation where U=q-w which is why that might be opposite, but in chem we use U=q+w.

vpena_1I
Posts: 109
Joined: Sat Aug 24, 2019 12:15 am

### Re: + or - w

Work is positive when it is done on a system (at least in our course). Think the video might've been using a physics equation.