C3.3 Energy Calculations

C3.3 Energy Calculations

1. Comparing the energy released by fuels

   • Calculating energy released
     • Energy = mass x specific heat capacity x temp rise
   • A calorimeter can compare energy released

2. Energy transfer in solutions

   • The equation works for any fluid

3. Energy level diagrams

   • Energy is measured in kilojoules per mole (kJ/mol)
   • Exothermic reactions
     • Surroundings get hot
   • Endothermic reactions
     • surroundings get cooler
   • Activation energy and catalysts
     • Activation energy is how much energy is needed to start a reaction
     • Catalysts create an alternate pathway to the products so lower the activation energy
   • Bond breaking and bond making
     • Endothermic is breaking bonds
     • Exothermic is making bonds

4. Calculations using bond energies

   • Bond energy
     • Energy needed to break a bond between two atoms
     • Used to work out the energy change
     • Work out energy to break each reactant then how to make product
       • We can then tell endothermic or exothermic

5. Fuel Issues

   • Consequences of burning fuels
     • supplies are running out
     • CO2 in the air
     • Not good
   • Hydrogen Powered Vehicles
     • Hydrogen + Oxygen => Water
     • No global warming
     • safety and storage issues
     • Using electrolysis still uses fossil fuels so we must oxidise it in a fuel cell