Since a coffee cup calorimeter is a low tech piece of equipment, we generally do not equip them with high tech calibration devices. The ability of the calorimeter to absorb(or release) heat is called the heat capacity of the calorimeter (C_cal). It is determined through a simple experiment. The heat capcity will have units of ^energy/_temperature (ex. ^J/o_C) and can be determined as follows.

A known mass of cold water is placed in the coffee cup calorimetr and allowed to equilibrate in temeperature with the cups etc. A known mass of hot water is prepared and its temperature determined. The hot water is quickly added to the cold water in the calorimeter. At this point three things occur simultaneously:

• the hot water is cooled
• the cold water is warmed
• the calorimeter is also warmed

• q_cal = C_cal x DT_cal and
• q_{cold water} = mass_{cold water} x DT_{cold water} x 4.184 ^J/o_{C g}
• q_{hot water} = mass_{hot water} x DT_{hot water} x 4.184 ^J/o_{C g}

4.184 ^J/o_{C g} is called the specific heat of water because 4.184 Joules is the amount of heat that must be added or removed from one gram of liquid water to change the temperature of one gram of water by one ^oC.

It is critical to keep track of the signs of all the variables. When finding DT always subtract the initial temperature from the final temperature. In this experiment, two of the DT terms will be equal and the third will differ from the others in both sign and magnitude.

Make sure you have a copy of the coffee cup calorimetry worksheet before continuing.