answers: triple point
context: potential (which is negative) for the liquid, pushing water molecules into the vapor (evaporation) and a chemical potential for the vapor, pushing vapor molecules into the liquid (condensation). Only when these "forces" equilibrate is equilibrium obtained. Conjugate variables (thermodynamics) In thermodynamics, the internal energy of a system is expressed in terms of pairs of conjugate variables such as temperature and entropy or pressure and volume. In fact, all thermodynamic potentials are expressed in terms of conjugate pairs. The product of two quantities that are conjugate has units of energy or sometimes power. For a mechanical system, a small increment of </s> SI unit cubic metre (m) and its divisions, in particular the cubic decimeter, more commonly called the litre (1 dm = 1 L = 0.001 m), and the cubic centimetre, also called millilitre (1 cm = 1 mL = 0.001 L = 10 m). The volume of a quantity of liquid is fixed by its temperature and pressure. Liquids generally expand when heated, and contract when cooled. Water between 0 °C and 4 °C is a notable exception. Liquids have little compressibility. Water, for example, will compress by only 46.4 parts per million for every unit increase in atmospheric pressure </s> point cells of hydrogen, neon, oxygen, argon, mercury, and water for delineating six of its defined temperature points. This table lists the gas–liquid–solid triple points of several substances. Unless otherwise noted, the data come from the U.S. National Bureau of Standards (now NIST, National Institute of Standards and Technology). Triple point In thermodynamics, the triple point of a substance is the temperature and pressure at which the three phases (gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium. For example, the triple point of mercury occurs at a temperature of −38.83440 °C and a pressure of 0.2 mPa.
question: the temperature and pressure at which a liquid and a gas are in equilibrium