energy changes

• what is the conservation of energy principle?

  energy is conserved in chemical reactions. the amount of energy in the universe at the end of chemical reactions is the same as before the reaction takes place.
• what is a exothermic reaction? give examples

  a reaction where energy is transferred to the surroundings so that the surrounding temperature increases - combustion, oxidation reactions and neutralisation (acid+ alkali)
• what is a endothermic reaction? give examples

  a reaction where energy is taken in from the surroundings so the surrounding temperature decreases - thermal decomposition,reaction of citric acid and sodium hydrogencarbonate
• what is activation energy?

  the minimum amount of energy that particles need to react
• what is a reaction profile?

  a reaction profile is a graph which shows the relative energies of the reactants and product, as well as the activation energy of the reaction.
• what occurs in a chemical reaction in terms of bond energies? describe exothermic and endothermic reactions in terms of bond breaking/forming.


  energy is supplied to break bonds and energy is released when bonds are made exothermic-energy released from forming bonds is greater than that needed to break the bonds. endothermic -energy need to break bonds is greater than needed to release energy making them