In the context of reduced variables, how is a reduced variable defined?

The concept of reduced variables is fundamental in the study of thermodynamics, particularly when analyzing the behavior of substances near their critical points. A reduced variable is defined as the ratio of an actual variable (such as pressure, volume, or temperature) to its corresponding critical constant for that substance. This approach allows for the comparison of the properties of different substances in a dimensionless manner.

In this case, the correct answer states that a reduced variable is determined by dividing the actual variable by its corresponding critical constant. For instance, the reduced pressure is calculated by taking the actual pressure of a substance and dividing it by its critical pressure. This normalization allows for the establishment of trends and relationships that are applicable across a range of substances, especially near their critical points where traditional state variables can behave unpredictably.

By using reduced variables, one can easily interpret data and understand the universal behavior of fluids, helping to establish generalized equations of state and making thermodynamic predictions more manageable across different systems.