Isobaric and Isochoric Processes

Ch 4, Lesson E, Page 2 - Isobaric and Isochoric Processes

• In an isobaric process, the pressure remains constant.
• As you can see, phase changes may occur, as in step 12 in the diagram on the left.
• Or no phase change may occur as in step 23.
• So you need to be careful.  It is often prudent to break the phase change out as a separate step as I have done here.
• If you have tables of thermodynamic data, this is not absolutely necessary, but if you are using heat capacities, then it is necessary.
• In either case, recognizing the significance of the phase change will help you better understand the process.
• The volume of the system remains constant in an isochoric process.
• Again, phase changes can occur and it is still smart to break this out as a separate step.
• Next, we’ll apply the 1st Law to an isobaric process and we’ll follow with a 1st Law analysis of an isochoric process.