# 8: PT Behavior and Equations of State III

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Learning Objectives

• Module Goal: To introduce you to quantification in fluid phase behavior.
• Module Objective: To highlight the principle of corresponding states and its importance for thermodynamic correlations.

• 8.1: Principle of Corresponding States (PCS)
The principle of Corresponding States (PCS) was stated by van der Waals and reads: “Substances behave alike at the same reduced states. Substances at same reduced states are at corresponding states.” That is, “Substances at corresponding states behave alike.”
• 8.2: Acentric Factor and Corresponding States
It is important to point out that the PCS that we have just discussed was originally outlined by van der Waals. In reality, it is the simplest version of the principle of corresponding states, and it is referred to as the two-parameter PCS. This is because it relies on two parameters (reduced pressure and temperature) for defining a “corresponding state.”
• 8.3: Action Item

8: PT Behavior and Equations of State III is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Michael Adewumi (John A. Dutton: e-Education Institute) via source content that was edited to conform to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.