A "Home-Cooked" Experiment in Heat capacity...
Inspiration:
I wanted to design an experiment that would show the differences in heat
capacity for equal volumes of different substances, and I wanted to be able to design the
experiment and run it with things from around the house. I knew that a
pan of simmering water would provide a good, stable heat source, and that
if I filled a Pyrex cup with different materials, I could show that some
materials warm up more slowly than others, and then cool down more slowly
as well. I chose water, alcohol, and air for my three test substances.
Method:
A Pyrex measuring cup was filled with either water, rubbing alcohol, or
air, and then heated in a pan of simmering water (see Figure 1 below).
In the case of the air, a plastic covering was fashioned for the measuring
cup in order to keep the volume of air in the cup contained (see Figure
2 below). Initially, the cup and its contents were at room temperature.
The temperature of the simmering water in the pan was approximately 200
degrees Fahrenheit. A thermometer was placed in the measuring cup in order
to measure the temperature of the contents of the cup. Temperature readings
were taken every minute for ten minutes. The cup was then removed from
the water and placed in a cold water bath (see Figure 3 below), where the
temperature of the cup's contents was again measured every minute for ten
minutes.
Apparatus/Figures:
Figure 1. A picture of the pan of water with the cup set inside, and
a thermometer in the cup. This cup is filled with either water or alcohol.
Figure 2. A picture of the pan of water with the cup set up for air. I
placed a thick piece of plastic wrap over the top of the cup, secured with
a rubber band, then carefully inserted the thermometer through a small hole,
so that it didn't let much air out. This way I could see how the trapped
air's temperature increased.
Figure 3. This figure shows how I created a cold water bath, using another
pan, and a steady stream of cold water from the faucet. This way, the water
in the pan did not heat up very much when I placed the warm cup into it.
Results:
Here is a table and a graph showing the results of the experiment. As you
will see, the water did warm up more slowly than the alcohol, and both the
water and the alcohol were slow to warm up compared to the air. In cooling,
the exact reverse was true. The air cooled fastest, followed by the alcohol,
then the water. This means that the water has the highest Heat capacity of
the three, and the air has the lowest.
| Time | Water | Alcohol | Air |
| 0 min | 75 deg. F | 75 deg. F | 80 deg F |
| 1 min | 80 deg. F | 83 deg. F | 100 deg. F |
| 2 min | 84 deg. F | 93 deg. F | 118 deg. F |
| 3 min | 88 deg. F | 106 deg. F | 138 deg. F |
| 4 min | 94 deg. F | 116 deg. F | 158 deg. F |
| 5 min | 100 deg. F | 126 deg. F | 175 deg. F |
| 6 min | 106 deg. F | 135 deg. F | 185 deg. F |
| 7 min | 112 deg. F | 143 deg. F | 190 deg. F |
| 8 min | 119 deg. F | 150 deg. F | 192 deg. F |
| 9 min | 124 deg. F | 155 deg. F | 193 deg. F |
| 10 min | 129 deg. F | 158 deg. F | 193 deg. F |
Figure 4: Graph of the temperature increase of each substance during
heating. Water clearly warms up the slowest, followed by alcohol, then
air. We say that the water has the "highest Heat capacity", because
it takes more heat energy to raise its temperature.
Figure 5: Graph of the temperature decrease of each substance during
cooling. Air clearly cools down the fastest, followed by alcohol, then
water. We say that the water has a high "Heat capacity" because it
can store so much heat energy.
Copyright 1996 University of California.