Basically, you need to think about how accurate you're going to want to be, and whether you're going to need an expensive, highly accurate, computer controlled, specialist calorimeter or just use one that the laboratory has available, which will probably be something just slightly more advanced than polystyrene coffee cups.
What do you mean by "seting[sic] temp of water equal to solution if using"? Surely you can directly measure the temperature change of a solution with a thermometer.
First you need to calibrate the calorimeter. I will assume you're using polystyrene coffee cups.
The ability of the calorimeter to absorb(or release) heat is called the heat capacity of the calorimeter (Ccal
). It is determined through a simple experiment. The heat capcity will have units of energy/temperature (ex. J/°C) and can be determined as follows.
A known mass of cold water is placed in the coffee cup calorimeter 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
All of the heat is trapped in the calorimeter (we assume none escapes to the surroundings) so the total heat conservation equation is:
(D=Delta, funny greek triangle thingy
0 = qcal
+ qhot water
+ qcold water
= masscold water
x DTcold water
x 4.184 J/°C g
= masshot water
x DThot water
x 4.184 J/°C g
4.184 J/°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 °C.
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.
Now you do whatever experiment you do.
The change in temperature is determined by measuring the initial temperature, T1
, and the maximum temperature, T2
, of the contents of the calorimeter during the experiment. The determination of a precise value for T2
is complicated by the fact that a small heat exchange occurs between the surroundings and the contents of the calorimeter, both during the reaction and after its completion. The rate of exchange depends on the insulating properties of the calorimeter and on the rate of stirring. A correction for this heat loss is made by an extrapolation of a temperature vs. time curve. By extrapolating the linear portion of the curve back to zero time (the time of mixing of the reactants in the calorimeter), T2
is obtained. The value of T2
obtained in this manner is the temperature of the product solution, had the reaction occurred instantaneously with no enthalpy loss to the surroundings.
is the resulting measurement. Then you use 0 = qcal
to get your result.