1. exothermic
   1. energy transferred to surroundings
   2. magnesium ribbon in hydrochloric acid
   3. combustion of fuels
      1. calorimetric technique
         1. rise in temp of water = measure of energy transfer
         2. energy transfered to surrounding air
            1. not accurate
2. endothermic
   1. energy absorbed from surroundings
   2. sodium hydrogen carbonate in hydrochloric acid
3. enthalpy change
   1. heat energy in chemical reaction = enthalpy
   2. delta H : J or kJ
   3. mass : g or Kg
      1. 1cm3 water = 1g
   4. C= specific heat capacity of water = 4.2 J g-1 C-1 or 4.2 kJ Kg-1 C-1
   5. delta T : degrees C
   6. conservation of energy
      1. energy can not be created or destroyed
      2. enthalpy rise from chemical reaction
4. Energy Profiles and deltaH
   1. energy level diagrams
      1. enthalpy difference between reactants and products
   2. C3H8(g) + 5O2(g) ---> 3CO2 (g) + H2O (l)
   3. Stage 1
      1. Ea : Activation energy
         1. minimum energy for reaction to occur
      2. endothermic
         1. energy needed to break bonds
      3. covalent bonds broken
   4. stage 2
      1. atoms combine
      2. new covalent bonds formed
      3. exothermic
   5. larger alkane
      1. more energy released
      2. more bonds broken
      3. more bonds formed
      4. increase between alkanes
         1. almost constant
         2. extra CH2 unit
         3. energy kJ mol-1
            1. methane : CH4 : 882
            2. ethane : C2H6 : 1542
            3. propane : C3H8 : 2202
            4. butane : C4H10 : 2877
            5. penatne : C5H12 : 3487
            6. hexane : C6H14 : 4141
5. Bond Energy Calculations
   1. covalent bond
      1. particular amount of energy needed to break it
      2. particular energy given out when made
   2. Bond Energy (kJ mol-1)
      1. C-C : 348
      2. C-H : 413
      3. O=O : 498
      4. H-H : 436
      5. H-O : 464
      6. C=O : 745
      7. Cl-Cl : 242
      8. H-Cl : 431
      9. H2 + Cl2 ---> 2HCl Endothermic H-H : 436 Cl-Cl : 242 Exothermic 2 x HCl : -(2 x 431) delta H : -184kJmol-1 exothermic is -ve!