For the following processes, is the work done by the system (defined as the expanding or contracting gas) on the environment positive or negative?

(a) expansion of the burned gasoline–air mixture in the cylinder of an automobile engine

(b) opening a bottle of champagne

(c) filling a scuba tank with compressed air

(d) partial crumpling of a sealed, empty water bottle as you drive from the mountains down to sea level.

When a particular system does the amount of work on its environment, then the work W <0 which means the total energy of the respective system decreases/lowers.

Work done by the system can be obtained when the resolved forces have a component in the same/ equal direction as that of the displacement.

The work is considered as positive as the given gas expands and thus, it does work on the environment/ surrounding and then it raises the given cylinder in the respective engine at the time of ignited.

The work done by the champagne bottle is positive, as it pushes on the cork as it loosens, which results in the familiar popping sound as the cork shoots out of the bottle.

The work done by the gas inside the scuba tank is negative the scuba tank itself compresses the gas as it pumped into the apparatus.

The work done by the gas inside the partially crumpled water bottle is negative, as a great amount of pressure is experienced by the bottle as we drive from the mountains down to sea level, which crumples the bottle even more.