Work

[Nathan Mariano 2G]

How can we determine whether the work is performed by or on the system? What makes work positive or negative in terms of the system?

[armintaheri]

Work is positive (done on the system) if it adds energy to the system. For example, if you increase the pressure of a gas using a piston, you are doing work on the gas because you are adding energy to it. If you heat a gas, you are adding energy to it, therefore you are doing work on it.

[Phil Timoteo 1K]

So does that mean work can't be negative?

[ryanhon2H]

Work can be negative if it is done by the system, opposite of doing work on the system in that heat is released in contrast to adding heat, or energy.

[JT Wechsler 2B]

If work is done on the system it is positive. If work is done by the system it is negative. This is kind of like temperature changes in a system being endothermic and exothermic. If heat is being given into a system it’s positive and if heat is leaving the system it’s negative.

[AlyssaBei_1F]

I think of work like exothermic and endothermic. Doing work on a system is positive because you are adding energy. Work by a system is negative because energy is released.

[Kaylee Kang 1G]

If work is positive, then it is adds energy into the system. If it is negative, energy is released!