Consider an insulated cylinder containing nitrogen gas and sealed on top by a heavy metal piston, as drawn in figure 1. The piston is free to slide up and down the cylinder, with negligible friction.
Initially, the piston is 0.20 m above the bottom of the cylinder, and the gas is at room temperature, 300 K. But then, a student ignites a small flame under the cylinder. As a result, the metal piston slowly rises until reaching a height 0.30 m above the bottom of the cylinder, at which point the student extinguishes the flame.
FIGURE 1

1. | The air pressure outside the cylinder is 1 atm. Immediately before the flame gets ignited, the pressure of the nitrogen inside the cylinder is:

A. | greater than 1 atm

B. | equal to 1 atm

C. | less than 1 atm

D. | We cannot determine the answer without more information.

2. | When the piston reaches a height of 0.30 m, the temperature of the nitrogen inside the cylinder is most nearly:

A. | 200 K

B. | 300 K

C. | 450 K

D. | 900 K

3. | Let W denote the work done by the nitrogen on the piston as it rises from 0.20 m to 0.30 m. During that time interval, the net heat absorbed by the nitrogen is:

A. | Equal to W, because of conservation of energy.

B. | Equal to W, because with pistons, work equals heat by definition.

C. | Greater than W, because the entropy of the nitrogen increases.

D. | Greater than W, because the internal energy of the nitrogen increases.

4. | Which graph best expresses the relationship between the pressure and volume of the nitrogen, as the piston rises from 0.20 m to 0.30 m?

A. | A

B. | B

C. | C

D. | D

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