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Where does the energy in a reaction come from
reactants contain energy within their chemical bonds
this is known as bond energy/chemical potential energy
define enthalpy
a measure of the total amount fo kinetic and potential energy
given by ‘H’
describe the energy movement when bonds break
energy will be absorbed to overcome the bonds
describe the enrgy movement when bonds form
energy is released because particles must slow down and move closer together
define activation energy
the minimum energy that reactanat molecules must posess in order for reaction to occur
define the transition state
an unstable period during a reaction where bond rearrangements occur to form intermediates
it is usually the hghest energy state in a reaction
describe an endothermic reaction
when the bonds broken are more numerous or stronger than those formed and energy is absorbed from the surrounds
it cools the environment
delta H is a positive value
a larger forwards activation energy
describe an exothermic reaction
if the bonds formed a more nuemrous or stronger than those broken then the reaction will release energy
it heats up the environment
delta H is a negative value
a larger backwards activation energy
what are the 2 types of energy changes
physical and chemical
which type of energy change needs more energy and why
chemical changes need more energy because in chemical change the strong intramolecular bonds must break but in physical change only the weaker intermolecular forces are affected
what reaction is solid to liquid and liquid to gas
endothermic
what reaction is gas to liquid and liquid to solid
exothermic
Note 
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