Isotherm

An isotherm is a curve or line on a graph that shows how a substance, such as a gas or a liquid, behaves at a constant temperature. It illustrates the relationship between two variables, like pressure and volume, when temperature remains unchanged. For example, in a gas, an isotherm can depict how pressure decreases as volume increases, with temperature held steady. Isotherms are useful in understanding and predicting the behavior of substances under specific thermal conditions, and they are fundamental in thermodynamics and process engineering.