Definitions

• What is activation energy?


  The minimum energy for successful reactions
• Why do non-rechargeable alkaline batteries stop working?


  When one reactant is used up
• What do batteries consist of?


  Two or more cells connected in series
• What do chemical cells produce?


  Electricity through chemical reactions
• What happens to the surroundings in an endothermic reaction?


  The temperature of the surroundings decreases
• How does energy change in an endothermic reaction?


  More energy is needed to break bonds
• What occurs in an exothermic reaction?


  Energy is transferred to the surroundings
• What is the relationship between bond energy in exothermic reactions?


  More energy is released from forming bonds
• What do fuel cells require as inputs?


  Fuel and oxygen or air
• How is fuel oxidised in fuel cells?


  Electrochemically within the fuel cell
• What does the overall energy change of a reaction represent?


  The difference in bond energy between reactants and products
• What can reaction profiles show?


  Relative energies, activation energy, and overall change
• What is the definition of an endothermic reaction?


  • Takes in energy from surroundings
  • Surrounding temperature decreases
  • Energy needed to break bonds > energy released
• What is the definition of an exothermic reaction?


  • Transfers energy to surroundings
  • Surrounding temperature increases
  • Energy released from forming bonds > energy needed
• What are the components of a reaction profile?


  • Relative energies of reactants and products
  • Activation energy
  • Overall energy change of the reaction
• How can a rechargeable cell be recharged?


  Chemical reactions are reversed when an external electrical current is supplied.