energy transfer

• what is the conservation of energy principle?

  energy is conserved in chemical reactions. The amount of energy in the universe at the end of a chemical reaction is the same as before the reaction takes place. If a reaction transfers energy to the surroundings the product molecules must have less energy than the reactants, by the amount transferred
• what is an exothermic reaction?

  transfers energy to the surroundings, so temperature of surroundings increases
• examples of exothermic reactions

  • combustion
  • many oxidation reactions
  • neutralisation
• everyday uses of exothermic reactions

  • self-heating cans
  • hand warmers
• what is an endothermic reaction?

  takes in energy from surroundings so temperature of surroundings decreases
• examples of endothermic reactions

  • thermal decompositions
  • reaction of citric acid & sodium hydrogencarbonate
• everyday use of endothermic reactions

  • sports injury pack