chem vocab May 1

thermodynamics

the study of energy change

first law of thermodynamics

energy is neither created nor destroyed in ordinary chemical reactions and physical changes

enthalpy

change in energy of a chemical reaction (AH)

activated complex

a high energy transitional structure in a chemical reaction where old bonds are breaking and new bonds are forming

catalyst

a substance that speeds up a reaction, without itself being changed or reused, by lowering the required activation energy

heat of formation

heat energy released or gained when a compund is formed (Hf)

entropy

measure of disorder; degree of randomness (S)

second law of thermodynamics

the universe tends toward greater disorder spontaneously

third law of thermodynamics

the entropy of a hypothetical pure crystalline substance is zero

Gibbs free energy

thermodynamic state function that gives a criterion for spontaneous change. AG=AH-TAS

bond energy

amount of energy required to break one mole of bonds in the gas state