To do positive work, you must push in the direction of motion. That requires an increase of volume as the walls of the balloon move out :)
It could be that the internal energy decreases at the same time but you might be putting heat in.
If an ideal gas does positive work on its surroundings, we may assume, with regard to the gas:
A. Volume increases
B. Internal energy decreases
C. Pressure decreases
D. Temperature increases
E. Pressure increases
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