exothermic and endothermic

• what is true about energy in a reaction

  amount of energy at the end of a chemical reaction is the same as before the reaction takes place
• what is an exothermic reaction

  one that transfers energy to the surroundings so the temperature of the surroundings increases
• what is an endothermic reaction

  one that takes in energy from the surroundings so the temperature of the surroundings decreases
• 3 exothermic reaction

  • combustion
  • neutralisation
  • oxidation
• 2 endothermic reactions

  • thermal decomposition
  • citric acid + sodium hydrogencarbonate
• uses of exothermic reaction

  • self-heating cans
  • hand warmers
• use of endothermic reaction

  • sports injury packs
• what is collision theory

  chemical reactions can only occur when reacting particles collide with each other and with sufficient energy
• what is activation energy

  the minimum amount of energy that particles must have to react
• what can a reaction profile show

  • relative energies of reactants and products
  • activation energy
  • overall energy change
• exothermic reaction profile

  .

  A)

  B)

  
• endothermic reaction profile


  .

  
• 2 things that happen to energy in a reaction

  • energy must be supplied to break bonds in the reactants
  • energy is supplied when bonds in the products are formed
• how do you calculate overall energy change

  difference between sum of energy needed to break bonds and sum of energy released when forming bonds
• exo/endothermic reaction in terms of bond energy

  exothermic=energy released from forming new bonds is greater than the energy needed to break bonds and vice versa