In the formula ∆U = q + w, work done by the system during expansion is (negative/positive), and heat (gained/lost) by the system is positive.
negative, gained
negative, lost
positive, gained
positive, lost
Correct option 1. negative, gained
Explanation:
The sign conventions for process functions (like work and heat) are such that a positive sign is attributed to the system if it gains energy (in the form of heat or work).