For heat, q:
▪ + q → if the system gains, takes in, or absorbs heat or energy
▪ – q → if the system loses, evolves, gives off, or releases heat or energy
For work, w:
▪ + w → work is done on the system by the surroundings (volume: compresses)
▪ – w → work is done by the system on the surroundings (volume: expands)
The air bags that provide protection in autos in the event of an accident expand because of a rapid chemical reaction. The air bags give off heat when they expand.
From the viewpoint of the chemical reactants as the system, what do you expect for the signs of q and w in this process?
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