Now, constant pressure calorimetry is associated with our coffee cup calorimeter. Now we're going to say here it uses the coffee cup calorimeter to determine heat transfers occurring in a liquid solution. Now, a coffee cup calorimeter is basically an insulated Styrofoam cup with a lid. And we're going to say we call it constant pressure because the calorimeter measuring heat is open to the atmosphere where pressure is going to be fixed.
So here we're going to take a look at the images provided to us. We're going to start out with our coffee cup calorimeter here on the left. And when we look at this coffee cup calorimeter, we're going to say it has some key portions to it, one of them being this thermometer given to us on top. So that's going to measure my temperature difference. Then we're going to have here our Styrofoam cover or Styrofoam top. Here, this portion just represents the Styrofoam cup itself. In here we have our water and then finally here we have our stir.
When we place the heated object inside of here, we're going to be able to measure the amount of heat that's being released. Now realize here when it comes to the constant cut on constant pressure calorimeter and this coffee cup calorimeter, we have formulas that are associated with it. We're going to say when both the liquid and calorimeter absorb heat from the hot object, we get the heat lost by the object. So minus Qlost equals plus heat gained by the water plus the heat also gained by the calorimeter.
Now we can expand this a little bit further. We're going to say expanding them to their heat capacity formulas. Where Q=MCΔT, we're going to have Qlost=-MCΔT, Qgained by the water is +MCΔT. And remember for the calorimeter, the mass of it is usually unknown, so we ignore its mass within our formula. So it just becomes the heat capacity of the calorimeter, which is C times change in temperature. So that becomes our equation for constant pressure calorimetry. It's going to be -MCΔT=+MCΔT+CΔT.