 Hi students welcome to year 12 chemistry and the equilibrium and acid reactions topic This is video number nine. We're going to look at equilibria and collision theory. So the key to this particular section is to Recall what we know both about equilibrium and Also about collision theory and see if we can bring these two Concepts together to give us a bit more of an idea about exactly what is going on here So the first thing we need to do is to briefly eat review equilibrium Where we know we have to have a closed system. We need to have a dynamic Process where the rate of the forward reaction is equal to the rate of the reverse reaction We also need to recall that there are no more macroscopic Changes so if the Reaction system was changing color as the reaction proceeded there would be a point where we would see no further color change And that would be a macroscopic property if there was a temperature increase then we would find that the temperature Stabilized at some point whatever that might be So for a Application then of collision theory what we need to do is to I guess look at the fact that when we start any Reaction we're going to have our maximum value For the reactants and we're going to have zero products as the reaction proceeds the number of particles of the products increases and the number of particles of the reactants will decrease at Some point there may be sufficient energy for the particles of product to actually interact with one another and Reform the reactants the numbers of particles are very important and so are the combinations You can see that if we had Just a single particle of a and we were looking at creating a reaction in the Interaction between a and a second substance B then by adding just one more particle We've gone from two to four collisions If we add one more particle of a Then now we have gone from four to six different collisions And likewise if we were to add another particle of B. We would now have Nine possible collisions that may potentially create a reaction now collision theory is not just about particles colliding But it's also about sufficient energy. So we know we've talked about the activation energy that is required for a reaction to proceed and we need to make sure that the amount of energy that Is needed for this reaction is sufficient during each of these collisions Now there are a couple of different things that can affect that amount of energy Temperature increase does generally increase reaction rate us and the use of a catalyst can lower the activation energy But whenever we're looking at any reaction Whether it be an endothermic or an exothermic There's a difference in the amount of activation energy for the forward reaction to what there is for the reverse reaction So we need to make sure that we have made those very clear in terms of our Activation energy for both forward and reverse reactions And the fact that those collisions must occur with sufficient energy in order for both of those to actually occur It means once we do that of course that we can start to look at things like increasing pressure at How it perhaps through a decrease in volume, which is actually pushing the particles closer together more likely for collisions to occur Increasing the temperature is going to make the particles move faster and therefore Is more likely to increase the rate of collisions? increasing the concentration is what we looked at over here and Again more particles means more Opportunities for collisions and hence an increase in the reaction rate And what we want is to make sure that we end up with reaction rates that are equal for the forward and reverse reactions