R1.1

• temperature 


  a measure of the average kinetic energy of the particles of a substance
• in a chemical reaction there is no overall energy change, i.e. energy is conserved in chemical reactions
• Energy is required to break bonds and energy is given out when new bonds are formed
• exothermic reaction


  If the energy given out when new bonds are formed in the products is great than the energy required to break the bonds in the reactants when the excess energy is given out to the surroundings as heat
• endothermic reaction


  If the energy given out when new bonds are formed in the products is less than the energy required to break the bonds in the reactants than the excess energy required is taken in from the surroundings
• Endothermic or exothermic chemical reactions involve the transfer of heat between the system and the surroundings
• Enthalpy


  The internal energy stored in chemical bonds
• ΔH has a negative value for exothermic reactions and a positive value for endothermic reactions
• activation energy


  reactant particles need a minimum amount of energy to react to form the products