Physlet Illustration: Work Done at Constant Pressure

 

 

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A piston floats atop a cylinder filled with 0.02 moles of an ideal gas. The cylinder is surrounded by a constant temperature bath. A digital temperature probe, which reads the gas temperature in °C, is attached to the cylinder. A digital pressure sensor, which reads the pressure in kPa, is also attached. Play the animation to heat the temperature bath, and watch the volume and pressure on the accompanying PV plot and in the data table below it. The table also displays the total work done by the gas since the process began. What can you conclude?

Hints:

  1. What is the initial volume, Vi, of the gas at the beginning of the process (in m3)?
  2. At the end of the animation, what is the final volume, Vf?
  3. What is the (constant) gas pressure, P,  in Pa [N/m2]?
  4. How should the total work done in this process depend on P, Vf  and Vi?
  5. Why is the sign of the work in this particular process positive?

Reference

See Walker, Section 18-3

Illustration written by Steve Mellema