Science / Biology / Entropy: The degree of disorder in a system. As energy is transferred from one form to another, some is lost as heat; as the energy decreases, the disorder in the system&emdash;and thus the entropy&emdash;increases.

Standard Molar Entropy

Science / Chemistry / Standard Molar Entropy: The entropy of one mole of a substance in its standard state. MORE

Standard Entropy Of Reaction

Science / Chemistry / Standard Entropy Of Reaction: A change in entropy associated with a reaction involving substances in their standard states. A superscript circle (°) distinguishes standard enthalpy changes from enthalpy changes which involve reac MORE

Second Law Of Thermodynamics (Entropy)

Science / Biology / Second Law Of Thermodynamics (Entropy): The energy available after a chemical reaction is less than that at the beginning of a reaction; energy conversions are not 100% efficient. MORE

Third Law

Science / Chemistry / Third Law: The entropy of a perfect crystal is zero at absolute zero. MORE

Second Law

Science / Chemistry / Second Law: The second law states that every spontaneous process causes a net increase in the entropy of the universe. Many alternative statements are possible, including: Heat cannot be converted to work via an MORE

Boltzmann Equation

Science / Chemistry / Boltzmann Equation: A statistical definition of entropy, given by S = k ln W, where S and k are the entropy and Boltzmann's constant, respectively, and W is the probability of finding the system in a particular state. MORE