Given the task definition and input, reply with output. In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

This equation is used to determine slopes of a phase diagram, and can also be applied to solids as well as liquids. One form neglects the volume of the liquid and assumes the ideal gas law, while its more common form is derived from the first law of thermodynamics and assumes that the change in Gibbs Free Energy is zero. This form is expressed as the derivative of pressure with respect to temperature equals the heat absorbed divided by the temperature times the change in volume. FTP, name this equation that describes transitions from one phase to another, named for two scientists
Science