energy changes-unit5

Cards (26)

  • Why can't energy be created or destroyed in reactions?
    Because energy is conserved in reactions
  • What happens to the amount of energy in the universe?
    It always stays the same as can’t be created or destroyed
  • What is an exothermic reaction?
    A reaction that transfers energy to surroundings
  • How is an exothermic reaction indicated?
    By a rise in temperature
  • Why is combustion considered exothermic?
    It gives out a lot of energy
  • What type of reaction is neutralization?
    Exothermic reaction
  • What happens in many oxidation reactions?
    They are exothermic and release energy
  • What happens when sodium is added to water?
    It releases energy and moves on surface of water as is oxidised
  • What is a common use of exothermic reactions?
    Hand warmers using iron oxidation
  • How do self-heating cans work?
    They rely on exothermic reactions in bases
  • What is an endothermic reaction?
    A reaction that takes in energy from surroundings
  • How is an endothermic reaction indicated?
    By a fall in temperature
  • Are endothermic reactions common or rare?
    They are much less common than exothermic
  • What happens during thermal decomposition of calcium carbonate?
    It decomposes into calcium oxide and carbon dioxide
  • What is produced when calcium carbonate decomposes?
    Calcium oxide (quicklime) and carbon dioxide
  • How are endothermic reactions used in sports injury packs?
    They cool the pack instantly without refrigeration
  • What are the key differences between exothermic and endothermic reactions?
    • Exothermic reactions release energy; endothermic reactions absorb energy.
    • Exothermic reactions show a rise in temperature; endothermic reactions show a fall in temperature.
    • Exothermic reactions are more common than endothermic reactions.
  • what do réaction profiles show
    -relative energies of reactants and products
    -how energy changes over the course of the reaction
  • which is at a lower energy in an exothermic reaction
    the products are lower than the reactants
  • what does the difference in height of the products and reactants show on an energy profile
    overall energy change
  • what is the difference in height between the reactants and the highest point on the graph in a reaction profile
    activation energy
  • what is activation energy
    the minimum amount of energy needed to start the reaction
  • which is at the lower point for an endothermic reaction profile
    reactants is lower than products
  • what happens to the bonds during chemical reactions
    old bonds are broken and new bonds are formed
  • is bond breaking exothermic or endothermic
    endothermic, energy supplied to break existing bonds
  • is bond formation exothermic or endothermic
    exothermic, energy released when new bons are formed