| thermochemistry | the study of the transfers of energy as heat that accompany chemical reactions and physical changes |
| calorimeter | something that measures the energy absorbed or released as heat in a chemical or physical change |
| temperature | a measure of the average kinetic energy of the particles in a sample of matter |
| joule | SI unit of heat as well as all other forms of energy |
| heat | energy transferred between samples of matter because of a difference in their temperatures |
| specific heat | amount of energy required to raise the temperature of one gram of a substance by one Celsius degree or one kelvin |
| enthalpy change | amount of energy absorbed by a system as heat during a process at constant pressure |
| enthalpy of reaction | quantity of energy transferred as heat during a chemical reaction |
| thermochemical equation | an equation that includes the quantity of energy released or absorbed as heat during the reaction as written |
| molar enthalpy of formation | the enthalpy change that occurs when one mole of a compound is formed from its elements in their standard state at 25⁰C and 1 atm |
| enthalpy of combustion | the enthalpy change that occurs during the complete combustion of one mole of a substance |
| Hess's law | the overall enthalpy change in a reaction is equal to the sum of enthalpy changes for the individual steps in the process |
| entropy | a measure of the degree of randomness of the particles, such as molecules, in a system |
| free energy | combined enthalpy-entropy function |
| free-energy change | (constant pressure and temperature) defined as the difference between the change in enthalpy, and the product of the Kelvin temperature and the entropy change |