collision theory

collision theory

in for particles to react when they collide, they must have sufficient energy and collide in correct orientation

exothermic pathway

endothermic pathway

ineffective collisions

particles collide without sufficient kinetic energy to react…the reactive parts of the molecules may not be close enough to each other

effective collisions

collisions of particles leading to bond breaking and a chemical reaction

activation energy

minimum energy needed for colliding particles to successfully collide and cause a chemical reaction

increasing the reaction rate

collision frequency increases…proportion of colliding particles with energy higher than activation energy increases

catalysts 

substance increasing the rate of reaction by lowering activation energy but is unchanged at the end of the reaction

increasing concentration

increased frequency of collisions…the higher the concentration the more reacting particles available per unit volume

increasing pressure

increased frequency of gas molecule collisions

Boltzmann distribution

graph showing number of molecules with particular kinetic energy…shows that only few molecules have more energy than activation energy

increasing temperature 

particles move around more quickly which increases frequency of collisions…proportion of successful collisions increases due proportion of molecules exceeding activation energy increases

presence of catalysts on Boltzmann distribution

lower activation energy results in a greater proportion of molecules in the mixture having sufficient energy to react

homogenous catalysts

catalyst and reactants in a reaction are in the same phase

heterogenous

catalyst and reactions are in different phases of the reaction