so what we're really interested in chemistry is using thermochemistry and measuring the kind of heat that it gets transferred in our different kinds of reactions or physical propert Pro processes so we can have a couple of definitions of things we want to study so our system is what we want to study and then our surroundings is everything else so we can look at our different kind of systems we can first think about our exothermic system and our exothermic process so if we have a system that we're studying which releases heat what we're going to see in here is our heat is going to go leave our system and go into the surroundings of whatever is there so you'll have lots of heat that leaves out and we have some sort of cue that's in there and what we can do is we can measure the cue of our surroundings for that exothermic process so after a while what happens with an exothermic process we're going to start out with a certain temperature and as everything gets uh re-equilibrated after the reaction we should see the temperature increase for an exothermic reaction and the opposite thing happens for an endothermic system so if we have some sort of endothermic system heat from the C surroundings are going to have to go into the system so this is really cool we'll start off with a certain temperature and after the reaction is done and it's kind of equal out you we should see that the temperature should actually drop for the entire uh calorimeter so this is a really good way of measuring these kinds of reactions so let me go ahead and show you two different kinds of calorimeters that are common in in the chemistry lab uh and the first one looks really simple but it is astoundingly precise in terms of its measurements and this is what we call a coffee cup calorimeter and what we usually have is some sort of Styrofoam cups you usually have two of them and those act as insulators so that we can isolate what we're trying to study to inside of the coffee cup and we put in there a thermometer which measures the temperature and we have some sort of stir on it and we put a lid on it so that heat doesn't leave the system and so we can do a reaction that's inside of the coffee cup and we can measure the change in temperature based on the thermometer of this reaction and it works really well for a lot of the different kinds of activities so we typically put water in there we can measure the temperature before and after uh we do our activity and be able to measure our um Heat or heat that's being transferred another type of calorimeter is what we call a a bomb calorimeter and what a bomb calorimeter does it keeps our volume very constant so in the previous this is actually what we call um a a uh we keep our pressure uh constant so this is at constant pressure in a bomb calorimeter we keep this at constant volume so we actually seal our reaction in inside of our bombb calorimeter uh in here so we can have this inner vessel that's inside we can actually do a reaction in there that doesn't um that can't see any kind of water so then the cue of this what happens inside of here goes into another outer vessel that has um a liquid in there so inside that liquid can actually absorb and or release kind of um heat to it and then the whole calorimeter will have a a um a heat capacity to it so whenever you see a bomb calorimeter you will typically see a heat capacity for the bomb itself so we can differentiate between the two different reactions but actually the calculations for these aren't that different between the two we can go ahead and follow the law of conservation of energy for both both of these kinds of systems and uh how you navigate these kinds of process is first realizing you have to do some sort of calorimetry and the main concept that comes out is this law conservation energy and this law conservation energy says we can't create um energy we can only transfer it so we have to read our problems very carefully and look for all the cues so what kinds of cues are relevant to it to that problem and the sum of all those cues based on the conservation energy equals zero and so this gives us the kind of concept that our Q of our system which is what we're trying to study and our Q of the surroundings which is everything that's not what we're studying has to equal zero so you will see this as Q of the system equals Q of the surroundings but what gets crazy in kind of thinking about problems sometimes our surroundings or our queue of the system has multiple cues in there so I always like to kind of think about it this way and just take all of our cues and sum them up and make them all equal to zero because there's usually one thing in there you're trying to study and you're trying to analyze