The physical state of a substance under standard conditions of 100 kPa and a stated temperature (usually 298 K).
Surroundings
Everything that is not the chemical system.
System
Everything - the atoms, molecules, or ions - making up the chemical compounds being studied.
Activation energy E
The minimum energy required to start a reaction by the breaking of bonds
Endothermic reaction
A reaction in which the enthalpy of the products is greater than the enthalpy of the reactants, resulting in heat being taken in from the surroundings (ΔH is positive)
Enthalpy
The heat content that is stored in a chemical system
Enthalpy change, ΔH
Difference in enthalpy between reactants and products in a reaction
Enthalpy profile diagram
A diagram for a reaction to compare the enthalpy of the reactants with the enthalpy of the products
Exothermic reaction
A reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants, resulting in heat loss to the surroundings (ΔH is negative)
Endothermic reaction
A reaction in which the enthalpy of the products is greater than the enthalpy of the reactants, resulting in heat being taken in from the surroundings (ΔH is positive)
bond enthalpy = bond breaking - bond making
ΔH = H(products) - H(reactants)
Law of conservation of energy states energy cannot be created or destroyed
