I'm studying from a Kaplan book and it states "Work is done by a gas on its surroundings (positive work) increases the volume of a gas. Work done on a gas (negative work) decreases the volume of the gas". They also give the equation for pressure volume work as: W = P deltaV Heres my question. Isn't all that I stated above old convention? When a system does work on its surroundings, shouldn't the sign of the work be negative (the same way it would be if we were talking about heat)? In physical chemistry we always said: W = -PdeltaV This would seem to make more sense when considering: deltaE(sys) = q + w If anyone could give me a clear explanation of this, that would be much appreciated. Also, if anyone knows which is the convention used on the MCAT, that would be helpful information as well.