energy changes

Cards (12)

  • an exothermic reaction transfers energy to the surroundings so the temperature of the surroundings increases
  • example of exothermic reactions are:
    • combustion
    • neutralisation
    • oxidisation reactions
  • an endothermic reaction takes in energy from the surroundings so the temperature of the surroundings decreases
  • the activation energy is the minimum amount of energy that particles must have to react
  • during a chemical reaction, energy must be supplied to break bonds in the reactants
  • what is released when bonds in the product are formed?

    energy
  • sum of energy taken in - sum of energy released to form bonds = overall energy change
  • what does the voltage produced by a cell depend on?
    the type of electrode and electrolyte
  • non-rechargeable cells and batteries have a limiting factor in the chemical reaction, alkaline batteries are an example
  • why are some cells rechargeable?
    the chemical reactions reverse when an external electrical current is supplied
  • advantages of fuel cells:
    • less pollution
    • compact and lightweight
    • reliable
    • high efficiency
  • hydrogen fuel cells use the oxidation of hydrogen to generate a voltage, the only waste product is water