Calorimetry Activities

Calorimetry is an experimental method used to investigate heat flow. The heat flow that is investigated can be the result of either a chemical change (ex. a combustion reaction) or physical change (ex. melting). The equipment used to perform the measurement of heat flow is called a calorimeter. These devices can be very simple (ex. calorimeters constructed from coffee cups) or very complicated (ex. computer controlled bomb calorimeters). However, there are general principles that can be applied to all calorimetry experiments.

Heat flow is being measured. The symbol "q" represents heat. Heat is a form of energy, and energy is always conserved (any heat lost by one object will be gained by another and visa versa). For convenience, calorimeters are designed to isolate themselves and their contents from the surrounding environment. Therefore, when we do calorimetry, we can make the following assertion:

0 = qcal + qsys
where qcal is the heat absorbed or released by the calorimeter and where qsys is the heat absorbed or released by the system being studied (this could be a chemical reaction or a physical change).

Obviously, in order for the two "q" terms to add up to zero, one of them must be negative and the other must be positive. When a process evolves heat (heat energy lost) it is called exothermic and "q" has a negative value. When a process absorbs heat (heat energy gained) it is called endothermic and "q" has a positive value.

You can experiment with two kinds of calorimeters at this site: a coffee cup calorimeter or a bomb calorimeter. In the coffee cup calorimeter, you will be able to investigate the heat of solution (DHsol'n) of some ionic compounds in water and/or the specific heat capacity of some metals. In the bomb calorimeter, you will be able to investigate the heat of reaction* (DHrxn) between an organic compound and oxygen. This kind of reaction is called a combustion reaction. Therefore, the heat of reaction can be called a heat of combustion* (DHcomb).

Directions on use of pages . . . Go to either the coffee cup or bomb calorimetry pages and download a worksheet. The coffee cup and bomb calorimetry web sites contain additional instructions for use of those pages. Follow the directions on the worksheets/websites and use the web pages to complete your "experiments".

Coffee Cup Calorimetry
(Constant Pressure)
Bomb Calorimetry
(Constant Volume)
Main Interactive
activities page

*In reality, bomb calorimeters measure the change in energy of a reaction (DErxn). There is a simple relationship between DHrxn and DErxn.
DE is the energy change that occurs in a container of fixed volume, DH is the energy change that occurs in an open container at constant pressure, R is the gas law constant (typically expressed as 8.314 J/Kmole in this equation), T is the Kelvin temperature, and Dng is the change in the number of moles of gas (Dng = moles gas product - moles gas reactant). For most reactions occurring at typical conditions of temperature and pressure, DHrxn and DErxn are nearly equal to one another. You can learn more about why these quantities differ from one another by visiting Dr. Mencer's Heat and Work pages.