 to look at a range of different types of equilibria and how we analyze each of these particularly in terms of the effect that a change in temperature, concentration or pressure will have on the system and how the system is going to respond as a consequence. So let's start to focus in specifically on what happens when we start changing the temperature. So here is our cobalt chloride equilibrium and we've said that there are two versions of cobalt chloride, a pink version and a blue version. The pink version is the hydrated form. We have cobalt chloride hexa 6 hydrate as our product and for our reactants we have cobalt chloride that's the anhydrous version and water molecules. One way we can shift the equilibrium back in this direction is to add heat energy. When we add heat energy what the heat energy is going to do is to heat those little water molecules that are distributed through the solid they'll actually drive them out and it means that we're going to shift the equilibrium in the reverse direction. That is we're going to talk about favoring the reactant side or shifting to the left. These are the terms that we're going to be using and it's very important that you start to describe situations in terms of the change and the Le Chatelier's principle consequence which is that shift back to try and counter the change. So here's a second example. This is nitrogen dioxide as a reactant and dinitrogen tetroxide as a product. This is an exothermic reaction as energy is a product and if energy is a product then we have an exothermic reaction or a delta H is negative. Now what happens if we add heat? If we add heat energy we are increasing the energy of the system which means that this component gets higher. Le Chatelier's principle tells us that the shift is going to counter the change so what we want to do is we want that to become lower. We make that lower by shifting to the left. If we shift to the left then we're going to produce more of the dinitrogen tetroxide and our gas mixture will become slightly browner or darker in color. If we were to cool the mixture then we're actually going to be removing energy. So in this stage we're going to be removing energy from the system so the system will then according to Le Chatelier's principle shift in order to counter the change that is to produce more energy and as a result the solution will favor the mixture, the equilibrium system will then favor the formation of the product or shift to the right and will increase the amount of the dinitrogen tetroxide and of course that means that the mixture will become paler, less brown as more of the colorless component is formed. This is the way that we go about trying to analyze different equilibria in terms of the change that's being affected on the system and how the system is going to respond as a result in order to counter correct that change.