In this video we're going to look at the heat of reaction experiment. In the heat of reaction experiment we're going to mix two substances, in this case an acid and a base. I'm going to measure the heat of reaction that's given off on mixture. To do this we'll use a colorimeter and this is something that will place the beaker into so that it insulates the walls of the beaker. In other words as the reaction is proceeding and giving off heat, the heat that's given off won't be able to leave the colorimeter. We'll measure the increase in temperature in the reaction using a thermometer placed in the colorimeter. The problem is though that even though the colorimeter is insulated some heat will still escape through the walls of the colorimeter. It's not perfect. So we need to first of all calibrate the colorimeter to see how much heat will be lost through the colorimeter. So in the calibration step we'll take 100 ml of hot water and 100 ml of cold water. We'll add the cold water into the colorimeter, put on the lid and measure its temperature. So we'll put in the thermometer and measure the temperature and this is the temperature of the cold water. So our temperature of our warm water here is just under 33 degrees and the temperature of the cold water is just 18 degrees. So in this experiment the cold water is going to gain some heat, the warm water is going to lose some heat. So we'll pour in our warm water and after mixing we'll know the temperature of the solution. The heat lost by the warm water will equal to the heat gained by the cold water plus the heat lost to the walls of the colorimeter. So we see here the temperature of our mixture, TM, is 25 degrees. So we can use this information to work out how much heat was lost to the walls of the colorimeter. It's done very easily using this calculation. We can say that the heat lost by the warm water is equal to the heat gained by the cold water plus the heat lost to the colorimeter. And knowing TC, TW and TM we can work out C-cal, the colorimeter constant. And this will allow us to work out how much heat is being lost to the colorimeter in a reaction. Okay, so let's go on now to the experiment itself. So here I have my acid and base that I'm going to mix. It should both be at the same temperature. We need to check that and that temperature will be the initial temperature T initial. I'll pour one solution into the colorimeter. So here I'm going to pour the base into the colorimeter. And as before I'll assemble the colorimeter and bring my thermometer before I start. Now I can pour in my acid and as this reaction proceeds it's going to form salt and water and it's going to give off heat. So that heat will obviously increase the temperature of the solution. So we pour in our acid and after pouring in a mixing we'll note the final temperature. So we watch the temperature increase and when it levels off that's the final temperature. So here I mix it for a while and now it's at 24 degrees. So I now know my initial temperature, I know my final temperature. So I know how much heat was given off in the reaction. That coupled with information about the colorimeter constant I can work out how much heat was lost to the colorimeter plus how much heat was gained by the reaction. And the heat given up by the reaction is a sum of these two. We can repeat this for different acids. So for example hydrochloric acid, sulfuric acid, ethynoic acid. And these will all give different results for different readings.