The most prominent use of an<unk>  is to predict the<unk>  of gases and liquids. One of the simplest<unk>  for this purpose is the ideal gas law, which is roughly accurate for gases at low pressures and high temperatures. However, this<unk>  becomes increasingly inaccurate at higher pressures and lower temperatures, and fails to predict condensation from a gas to a liquid. Therefore, a number of much more accurate<unk>  have been developed for gases and liquids. At present, there is no single<unk>  that accurately predicts the properties of all substances under all conditions.
In addition to predicting the behavior of gases and liquids, there are also<unk>  for predicting the volume of solids, including the transition of solids from one crystalline<unk>  to another. There are<unk> s that model the interior of stars, including neutron stars. A related concept is the perfect fluid<unk>  used in cosmology.
Equation of state
Quantum yield
Extraction ratio
Potential energy
Reaction rate constant
Arrhenius equation
Greenhouse effect
Arithmetic mean