Hello students in this module we are going to look at a few important terms related to calorimetry and the very important principle of calorimetry based on which we have a number of questions coming up in the further modules so I want you to pay very, very close attention to this particular module because the concepts that we learn out here is going to be directly applied in the new miracles so to begin with the important terms with calorimetric the first time that I’ll be encountering is thermal capacity now what exactly is thermal capacity now third well capacity is defined the amount of heat required in order to raise the temperature of the entire body by one degree centigrade there is now if i have to compare this with specific heat capacity it is the amount of heat required to raise the temperature off unit mass of a substance by 1D so the difference between thermal capacity and specific heat capacity comes in the fact that it is for the entire body and this is for a unit mass so if i have the relation here which will give me delta Q =  MC Delta C. hence this can also be written as what H into delta T so if I cancel the delta T from both sides of the equation i get my thermal capacity as the product of mass into specific heat capacity so this is a very important relation to be remembered My dear students the unit of thermal capacity is nothing but joules per degree centigrade all joules per Calvin now in this list the next important term that we have is the water equivalent to your students let me tell you water equivalent generally appears in the numerical and I don’t want any one of you to get confused because when we have a mixture present in a calorimeter they don’t mention to us about the mass of  calorimeter or it specific heat capacity they give us directly what is the water equivalent of the calorimeter so from there you should not be confused you should be able to use the concept of water equivalent   very nicely to find out what will be the Rays in the temperature of the calorimeter so here we try to understand what exactly is meant by calorimeter let’s say we have a block whose masses m and it specific heat capacity is C and the change in temperature is delta T so how much heat will be related to this particular block my delta Q is equals to MC delta T now let’s see the same amount of heat i use to raise the temperature of water by an equal difference so the same amount of heat for raising the temperature of water by equal level then how much water should I be taking that is known as the water equivalent so i can write down this Delta Q is nothing but equals to the w into one into delta T whether the delta t will get cancelled from both sides of the equation hence i get the value of my water equivalent is equal to nothing but a product of mass into specific heat capacity having done this let’s just go ahead to look at the basic principle of calorimetric what does it see let’s we have a block which is got to mass m1 specific heat capacity C1 it is a temperature T 1 degree centigrade we’ve got another block whose masses M 2 its specific heat capacity C 2 and it is a temperature t2 now given is temperature t1 is greater than t2 so he is going to flow from the body at a higher temperature to the body at  Lower temperature and this is the direction of the heat flu now after some time there is going to be a state of thermal equilibrium that temperature of both the bodies is going to be equal so the principle of calorimetry states that heat lost by a body at a higher temperature is equal to the heat gain by the body at a lower temperature so having done that what is the amount of heat lost by the body at a higher temperature is m 1 c 1 into t 1 minus t that is a temperature difference for the body at a higher temperature and what is the heat again to buy a body at a lower temperature it is m 2 c 2 t – t2now equating them this is what is the most important principle that we are learning in this particular module now having done that is the temperature of equilibrium and if you solve it we get the temperature of equilibrium as m1 C1 t1 plus m2 c2 t2 divided by m1 c 1 plus m2 C2 so having them the students we will be using the same concept in the  numerical ahead thank you very much.