topic 5 - energy changes

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

what is an exothermic reaction

reaction where energy is transferred to the surroundings so that the surroundings temperature increases

examples of exothermic reactions

combustion, oxidation reaction and neutralisation (acid + alkali)

what sign of energy change is an exothermic reaction

negative

what is an endothermic reaction

a reaction where energy is taken in from the surroundings do the surroundings temperature decreases

examples of an endothermic reaction

thermal decomposition, reaction of citric acid and sodium hydrogencarbonate

what sign of energy change is an endothermic reaction

positive

what is activation energy

minimum amount of energy that particles need to react

what is a reaction profile

a graph showing the relative energies of reactants and product, as well as activation energy of the reaction