Keeping up the standards—Calorimetry
Luke David Farrar
Introduction
Calorimetry is the name given to science investigations using a calorimeter to
measure changes of state, phase, and chemical reactions in terms of the associated heat
transferred. I carried out this technique on boiling water and cold copper, paraffin wax, and
stearic acid. After recording the temperature with thermometers that we had calibrated, this
data was placed into a graph. Using this data, I formed a cooling curve to calculate the rate of
cooling of my samples and to determine the latent heat of fusion of vaporisation (change
from a liquid solid, and liquid gas). During a state change, using a cooling curve, a dot
plot graph will show a flat line as the latent heat is being used to change the state of the
subject.
These experiments were carried out with the same partner, though we worked
independently for most of that time, only sharing results so we could finish in time.
To calibrate the thermometer, I placed it into a beaker containing boiled kettle water
and took three different readings, reheating the water each time, to ensure that my
thermometer was reading close to 100℃. In between readings I cleaned and left the
thermometer at room temperature to ensure that previous readings did not affect the
temperature enough to skew later results.
Hypothesis
The cooling rates will be uniform for the boiling water and copper as there is no state
change, while the cooling rate for the paraffin wax and stearic acid will vary as there is a state
change in both. All the tests will have varyingly higher and lower ranges of temperature.
Null hypothesis
The cooling rates will not be uniform for the 4 experiments and the tests will be
random in their ranges.
Method
Boiling water and cold copper
Equipment—Styrofoam cup, thermometer, clamp stand, lid for cup, kettle, stopwatch,
100ml beaker, copper.
Firstly, the Styrofoam cup is placed alongside the clamp stand—I used two cups to
increase the insulation and reduce heat loss, as well as placing the cups into a 100ml beaker
—then the thermometer is suspended inside of the cup using the clamp stand in a position as
not to touch the cup walls. Next, pour boiling water from the kettle into the cup and start
recording the temperature as soon as possible. I made sure to do this step after setting up the
apparatus to ensure that I did not spill any boiling water on myself for my partner since the
cup was only small and there were multiple tests ongoing around us. This is also why I put
the Styrofoam cup inside of the beaker to ensure that spillages were less likely to occur. I also
ended up not using a lid—though it is recommended if you can—as placing the lid on after
boiling with the thermometer inside would have skewed the data more than not having it on,
in my opinion. As this test was to determine the rate of cooling, the range of temperature was
not as important.
, For 10 minutes, I noted down the temperature in 1-minute intervals to measure the
heat loss of the boiling water.
For the copper sample, this process is repeated, although with some extra steps.
Place the Styrofoam cup(s) with a thermometer in the centre of them—but not
touching the cup, and inside of a 100ml beaker—supported by the clamp stand. Then, weigh
out 100g of copper, placing the sample into the cup, and then pour freshly boiled water up to
the fill line of the 100ml beaker as well. Once again, begin recording the temperature as soon
as the boiling water has been placed in the cup. This time, however, continue to record the
temperature drop for 30 minutes in intervals of 100 seconds. The thermometer used for this
experiment was a digital one, whereas a liquid thermometer was used to record the boiling
water practical so that the data could be compared to make sure that the rates were accurate,
as were the thermometers for later testing.
Paraffin wax and stearic acid
Equipment—Stearic acid, paraffin wax, 250cm3 beaker, boiling tubes, liquid
thermometer, stopwatch, clamp stand, Bunsen burner, tripod and gauze, heatproof mat, graph
paper.
First, pour 200cm3 of water into the 250cm3 beaker and place the beaker onto a tripod
and gauze with a Bunsen burner underneath, heating until boiling. Then, clamp the boiling
tube into place so it is suspended in the centre of the beaker but not touching it. Next, place
the stearic acid/paraffin wax (the steps are the same for both, only the sample is
interchangeable) to fill ¼ of the tube, placing a thermometer inside of it to record the
temperature. Since we did not measure out the paraffin wax and stearic acid to make sure
they were the same size the results are not exact.
Now that the water is boiling and the paraffin wax/stearic acid has been prepared,
placed the boiling tube into the boiling water and record the temperature. After this, record
the drop in temperature every minute for 22 minutes to obtain data to be plotted on a cooling
curve graph.
For both the paraffin wax and stearic acid, the same liquid thermometer was used.
This ensured that the data would not be skewed by different thermometers that may not have
been set correctly or needed to be reheated in between both tests.
Results Boiling water with copper
Boiling water and cold copper Time (seconds) Temperature (℃)
Using these tables I plotted a cooling 0 71
curve graph to display the rate of cooling of the 100 71
boiling water (below) and the boiling water with 200 70
copper (right). A practise graph is also included 300 67
below, though is irrelevant to these results. 400 64
500 62
Boiling water 600 60
Time (minutes) Temperature (℃ ) 700 58
0 96 800 56
1 92 900 55
2 91 1000 56
3 89 1100 54
4 81 1200 51
5 77 1300 50
6 75 1400 49
7 73 1500 48
8 71 1600 47
9 69 1700 46
10 67 1800 45
