The thermodynamic condition of a substance defined by two or more independent thermodynamic properties is called

• A. State of a Substance
• B. Change of State
• C. Phase
• D. Condition

Answer: (A)

In thermodynamics, the state of a substance is defined by a complete set of independent properties. Knowing two or more independent properties—such as pressure and temperature or temperature and specific volume—uniquely determines this state, because all other properties follow from the equation of state for that substance. A change of state refers to a transition between states, a phase is a form of matter, and the term “condition” isn’t the standard way to describe the thermodynamic state. Therefore, the correct term is the state of a substance.