Task: Text Categorization
Input (English): The paper that introduced this concept extended the work of Morse and Frazer in measuring osmotic pressure. The activity of a species is equal to this value divided by a reference value, and one way of defining it takes the exponent of the chemical potential divided by Boltzman's constant times temperature. It is related to the mole fraction of a given species in solution by the Lewis-Randall rule. The phase with the lowest value of this quantity is the most favored, and this quantity is used to correct for non-ideality by correcting for intramolecular forces. Also defined as pressure multiplied by its namesake coefficient, for 10 points, name this quantity that describes the escaping tendency of a gas, symbolized f.
Output (English): Science