A fixed mass of gas in a thermally insulated container is compressed. After compression, the temperature of the gas will have:
Correct answer: D. risen, since doing work on the gas increases the kinetic energy of the molecules
- A. fallen, since more molecules bombarded the container and so they must be moving slower
- B. fallen, since more molecules collide more frequently with one another and so their average speed is lower
- C. remained constant if the compression is very slow
- D. risen, since doing work on the gas increases the kinetic energy of the molecules
- E. risen, since there are more intermolecular collisions and so more heat is produced by them
Explanation
When a gas in a thermally insulated container is compressed, work is done on the gas, and no heat is lost to the surroundings. This increases the internal energy of the gas, which is directly proportional to the temperature. The increased kinetic energy of the molecules results in a rise in temperature.
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About First Law of Thermodynamics
The first law relates heat supplied, work done and the change in internal energy through energy conservation. Problems use sign conventions and apply the law to isothermal, adiabatic, isobaric and isochoric processes. Internal energy is a state function, while heat and work depend on the path followed.
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