Thermochemistry
•Heat changes during chemical reactions
•Thermochemical equation. eg.               
•H2 (g) +  O2 (g) ---> 2H2O(l) DH =- 256  kJ;
•
•DH  is called the enthalpy of reaction.
•if DH is + reaction is called endothermic
•if DH is - reaction is called exothermic