Work

[Rachel Yu 1G]

When is work positive or negative and why?

[Matthew ILG 1L]

"In chemistry, the convention is that anything going out of the system is negative and anything coming into the system is positive. If your system is a gas in a piston, work is being done on the system when it is being compressed, so the work done on the system is positive, and the work done by the system is negative" -Khan Academy

[005324438]

It all depends on what you set your system as. If you have a beaker and a piston and your system in just the piston, then the beaker would be losing energy and the piston is gaining energy, this means the beaker is putting positive work on the piston. If your system is the beaker AND the piston, then that system is losing energy and the surroundings are gaining energy, the beaker/piston is putting work into the surroundings. It's confusing, but you can basically make it anything you want as long as you keep track of it.

[Rodrigo2J]

This depends on what you define as the system and the surroundings. If work is done on the system it is positive. If work is done by the system it is negative.

[Nicholas_Gladkov_2J]

When is work positive or negative and why?

If something is doing work then w is negative, if something has having work done on it w is positive.

[Lauren Stack 1C]

Work can be positive or negative, depending on how you look at it. If you compress a piston, there is positive work being done on the system, as there was an input of work to move the piston. Conversely, the work done by the system is negative.

[Abigail_Hagen2G]

It all depends on the system and the surroundings, and what is doing work on what. Whatever is doing the work will have negative work and vise versa.