Ch 7 Calorimetry

Added: 2026-05-16

[00:00:01]hello so we are going to review calorimetry Kalorama tree is the study of heat transfer and the instrument that we used to do that is called a kilometer or two types of kilometers constant involving kilometres that are called BOM counters as well as constant pressure kilometer in this case we reviewed constant pressure and color on there it's called constant pressure because this thing is exposed to the atmospheric pressure so while no reaction takes place or the heat exchange takes place it's happening under constant pressure this if the pressure here increases Summoner goes out or if you decrease it somewhere comes back in so the pressure remains constant and so this basically is the device to counter that insulates inside from outside so that way you can keep track of the heat exchange as much easier and just to review specific heat capacities yes that refers to the amount of heat energy needed to raise the temperature of one gram of a substance by one degree Celsius so this is a capacity for waters one calorie per gram per degree that means that if you put in one calorie of heat energy into one gram of water this temperature will increase by one degree Celsius or 4.184 joules per gram per degree so the specific heat capacity basically tells you how resistant to change in temperature as substances the larger the specific heat capacity the more heat you have to put into a substance to change its temperature the lower de specific capacity the less amount of heat you have to put into a substance to change its temperature so for example metals have very low specific heat capacities so as soon as you put a little bit of heat into them to temperatures shoot up where as soon as you deduct a little bit of heat from them their temperature drop step water on the other hand has much higher specificity compared to metals so for water you have to put in a lot of heat to move the temperature a little bit or deduct a lot of heat to move the temperature a little bit more that's why if you're heating water you know Italian container you have to put in a lot of heat I'm sorry you put heat into the container the water is luke form even though the metal is getting red-hot because the metal has very little specific capacity so soon as you put a little heat into it its temperature shoots off so let's do a sample question over here so this question says a 20 gram sample of an unknown metal was heated to 98 degrees Celsius and dropped in a constant pressure calorimeter containing 2 grams of ice and 15 grams of water after a thermal equilibrium was reached the final temperature of the system was 1.5 degrees Celsius calculate the specific capacity of the metal assuming the calorimeter does not absorb any heat and no heat was lost to the surroundings so we have a kilometer inside of it we have ice and water and so since we have ice and water we should know what the temperature is it must be zero because that's the only temperature under one atmosphere pressure that the two can coexist and be silver under one atmospheric pressure and so that's why we don't need to give you the initial temperature because if you have ice and water then it must be zero so when you look at this there are several things involved you have the metal sick um that's the heat released herbs or vitamin or you w heat released or absorbed by the water cue ice heat released or absorbed by the ice q water from ice so remember what the metal is is going to release heat to first melt the ice so when the battle releases seen all that heat first goes into melting of ice so the water that's in there just acts as a conductor that transfers the heat from the metal to the ice so the temperature is not gonna grow up above zero till all the ice melts once the metal releases enough heat to melt all the ice then all the extra heat release will go into raising the temperature of the water so anyways this is Q metal Q water q ice q water from ice so what's all ice has melted to do water that water's at zero degrees Celsius just like this water so you have to put heat into it to raise its temperature as well sometimes people combine these two together and Q Cal plus Q surrounding the sum of all these should equal to zero because of the law of conservation of energy so if we're not really seeing heat to the surroundings all the heat exchange is happening inside so the sum of all it should be zero so that means that all the heat released by the metal will be absorbed by the water and the ice in the water comes from ice and none of it goes to anything else so then we write Q metal is the specific capacity of the melt times mass of melt times change in temperature of metal so by debate a formula for specific heat capacity is CS equals Q or m times delta T so that's gonna be from chem 1a so Q is equal to CS times M times delta T so that's where this comes from and so he waters this capacity of water fun since mass times has changed temperature ice heat of fusion times multi ski diffusion firstly about two energy needed to melt 1 mole of ice for I sit 6.1 times 10 to the power 3 joules per mole so adult age fusion all rise times Bowl and this will be given to you specific even water times mass of water coming from ice so that's that water comes from Einsteins delta T so they'll be plugging the numbers so we convert the mass of ice into moles and again you can combine this water from ice with water by simply and instead of using 15 grams and two grounds just put 17 grams here and make this a little shorter but either way it works so then you crunch numbers and you solve for C s model which comes out to be point four joules per gram