energy changes

Cards (14)

  • an exothermic reaction is one that causes a rise in temperature to its surroundings. it releases energy
  • an endothermic reaction is one that causes a decrease in temperature in the surroundings. takes in energy
  • reacting particles must collide with sufficient energy in order for bonds to be broken
  • in a chemical reaction:
    • atoms are rearranged
    • old bonds broken
    • new bonds formed
  • activation energy is the minimum amount of energy that particles must have for a reaction to take place
  • catalysts increases the rate of reaction by reducing the activation energy and providing an alternate pathway
  • bond breaking = endothermic
    bond making = exothermic
  • cells release energy by the chemicals inside reacting and releasing electricity
  • simple cells are made by placing 2 different metals into a beaker containing an electrolyte
  • a battery is 2 or more cells connected together
  • in a hydration fuel cell, hydrogen and oxygen are supplied to the cell. the fuel is oxidised to produce a potential difference, the hydrogen is oxidised to produce water
  • fuel cells are becoming more popular as traditional methods involve many stages, are less efficient and more polluting
  • advantages of hydrogen fuel cells:
    • produce water (not a pollutant)
    • lightweight and small
    • no moving parts(unlikely to break down)
  • disadvantages of hydrogen fuel cells:
    • explosive
    • stored in pressurised containers