Work done on a system vs. by a system in a chemistry sense?

I know that when a system expands, it does work. But is work ever done onto a system? Is work ever positive? Could I have a few examples?

Question

Work done on a system vs. by a system in a chemistry sense?

I know that when a system expands, it does work. But is work ever done onto a system? Is work ever positive? Could I have a few examples?

zpupster · Answer

short and to the point discussion http://physics.stackexchange.com/questions/72492/what-is-the-sign-of-the-work-done-on-the-system-and-by-the-system

anonymous · Answer

ahh.. yes,... make a cylinder / piston/ and a gas...

1. compress the gas in the cylinder by the piston.. (work don on a system)
2. the gas expands back to its place pushing the piston. (work done by the system)..

you can put your +/- anywhere you want.... i won't mind...