# Process and State Variables (PSV)

### Process and State Variables

Describing and analyzing processes requires that you can understand, calculate, and manipulate both process data as well as state variables.

How would you calculate process variable values from measurements ?

• Manipulate process flow data
• Interconvert mass, volume, and moles(and their flows)
• Calculate mass(mole) fractions from mole(mass) fractions for a mixture
• Calculate pressures using a manometer(and explain the concept of gauge pressure)
• Interconvert between different temperature scales
• Explain the difference between intensive and extensive variables

Certain calculations require you to know quite a bit about the "state" of a material(i.e., its state of aggregation(phase), temperature, pressure, chemical composition, etc.).How can we quantify properties about a material 's state?

• Calculate State Variables $\hat U$ and $\hat H$
• Define "state variable"
• Explain why one must choose a reference point when calculating state variables
• Generate "fictitious paths" from your reference state to your desired state
• Use heat capacities and phase data to calculate $\hat H$ and $\hat U$ from fictitious paths
• Use tabular data to determine $\hat U$ and $\hat H$