Energy transfer during exo/endothermic reactions

• Chemical reactions:

  • Energy is conserved in reactions - the overall amount of energy does not change in a reaction - cannot be created or destroyed
  • If the products of reaction store more energy than original reactants, energy has been taken in from surroundings
  • If the products of store less energy than original reactants, energy has been transferred to surroundings
• • Exothermic reactions transfer energy to the surroundings
  • So, the temperature of the surrounding increase
  • Exothermic reactions include combusion, oxidation and neutralisation
• Everyday uses of exothermic reactions are:

  • Hand warmers - iron in air with salt solution catalyst
  • Self heating cans - between chemicals in bases
• • Endothermic reactions take in energy from the surroundings, so the temperature of the surroundings decrease
• • Endothermic reactions include thermal decomposition, and reaction between citric acid and sodium hydrogencarbonate
  • Everyday uses are sport injury packs - become cooler without freezer