C3.3 Energy Calculations

Comparing the energy released by fuels
1. Calculating energy released
  1. Energy = mass x specific heat capacity x temp rise
2. A calorimeter can compare energy released
Energy transfer in solutions
1. The equation works for any fluid
Energy level diagrams
1. Energy is measured in kilojoules per mole (kJ/mol)
2. Exothermic reactions
  2. Surroundings get hot
3. Endothermic reactions
  2. surroundings get cooler
4. Activation energy and catalysts
  2. Activation energy is how much energy is needed to start a reaction
  3. Catalysts create an alternate pathway to the products so lower the activation energy
5. Bond breaking and bond making
  1. Endothermic is breaking bonds
  2. Exothermic is making bonds
Calculations using bond energies
1. Bond energy
  1. Energy needed to break a bond between two atoms
  2. Used to work out the energy change
  3. Work out energy to break each reactant then how to make product
    1. We can then tell endothermic or exothermic
Fuel Issues
1. Consequences of burning fuels
  1. supplies are running out
  2. CO2 in the air
  3. Not good
2. Hydrogen Powered Vehicles
  1. Hydrogen + Oxygen => Water
  2. No global warming
  3. safety and storage issues
  4. Using electrolysis still uses fossil fuels so we must oxidise it in a fuel cell

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