Defining the melting energy of ice with and without NaCl
Simone Creemers and Charlotte van Goch
Philips van Horne Weert
April 2011
Summary
In a lot of experiments done around de-icing, the test results are defined by concentrated saline’s in which a large
decrease in freezing point is reached. In this experiment we are investigating the difference in the amount of
energy needed for the ice to melt by comparing the melting process in which no de-icing chemicals are added
and the melting process in which they are added. There are a lot of de-icing chemicals: sodium chloride, calcium
chloride, magnesium chloride, ethylene glycol and urea 1.
For our experiment we have used the de-icing chemical sodium chloride. Our investigation showed us that less
energy is needed to melt ice with sodium chloride than without. We have investigated this by using an isolated
container filled with ice and sodium chloride or only filled with ice. While the ice was melting we measured the
voltage, current and tempreture. With this we made a calculation of the amount of energy used. Our investigation
raised further questions like what the result would be if one used less sodium chloride. What also would be
interesting to investigate is if the addition of CaCl 2 would be more effective then the use of sodium chloride
melting ice.
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Introduction
The addition of road salt speeds the melting process
of ice. But also the amount of added energy affects
the melting process. How much energy is needed to
melt ice? And how much energy is needed to melt
ice when sodium chloride is added? We are going
to investigate the difference in melting energy.
Experiment has shown that 1 mole of sodium
chloride dissolved in H2O(l) lowers the freezing
point of H2O with factor 2.
By adding sodium chloride the following reaction
will occur.
used for the melting process. We built a circuit as
shown in figure 1. In this container we put a
temperature sensor and we connected this sensor to
the computer. In the same container we put each
time 100 grams of crushed ice. In the first
measurement we added no sodium chloride to the
ice. In the second measurement we added 25 grams
of sodium chloride to the ice. We made sure that all
the variables were kept constant.
By constant stirring we made sure that the
temperature of the ice was as similar as possible at
all places in the container. We repeated each
measurement ones.
NaCl (s)  Na+ + ClBecause Sodium Chloride lowers the freezing point
of H2O(l) with factor 2, the ice will melt faster by
adding sodium chloride, hence less energy needed.
Our hypothesis is that the melting process of ice
requires less energy when NaCl is added.
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Figure 1: Circuit
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Experimental procedure and approach
Data gathering and analysis
We took an isolated container. We took an isolated
one because then there would be as less as possible
influence of the environment. And only the energy
we added would cause the melting process. In the
container we added a resistor with 100 %
efficiency. The resistor has 100% efficiency
because all the energy is converted into heat. This
makes it easier to determine how much energy is
We measured until all the ice was melted and had
reached a temperature of 20o C. We let the
computer translate the information it received from
the temperature sensor into a graph using time in
minutes as base of measurement. With this graph
we could analyze the differences and similarities
between the measurements.
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Results
We observed that in the isolated container where
crushed ice and sodium chloride were added, a
much lower temperature was reached. As soon as
the ice had been melted, the temperature did rise
more gradually in the container were sodium
chloride had been added to the ice. The time needed
to melt the ice and heat the water up to 20 oC, was
roughly the same for the container with as well for
the container without sodium chloride.
Although we kept the variables constant the graphs
aren’t identical. Because we had to stir the ice, we
sometimes hit the resistor. This is why there are
some small irregularities in the graphs.
Measurement 1a
Measurement 1b
Graph:
Graph:
Figure 2: De temperature plotted against time using crushed ice
without sodium chloride (measurement 1a)
Figure 3: The temperature plotted against time using crushed ice
without sodium chloride
Table:
Amount ice
Voltage
(gram) (V)
Amperage (I)
Table:
Amount ice
Voltage
(gram) (V)
Amperage (I)
100,02
28,0
2,90
Table 1: Data measurement 1a
101,13
28,0
2,90
Table 2: Data measurement 1b
Measurement 2a
R = U/I = 28,0/2,90 = 9,66 Ohm
Graph:
The resistor is 9,66 Ohm
P = U x I = 28,0 x 2,90 = 81,2 W
E=Pxt
- Without NaCl:
It took an average of 7.0 minutes before all the ice
was melted (figure 2 and 3).
E = 81,2 x 420 = 34 104 J
- With NaCl
It took an average of 4.0 minutes before all the ice
was melted (figure 4 and 5)
Figure 4: The temperature plotted against time using crushed ice
with sodium chloride (measurement 2a)
E = 81,2 x 240 = 19 488 J
Table:
Difference in used energy: 34104 –19488 = 14 661J
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Amount ice
Amount
(gram) NaCl
Voltage
(gram) (V)
Amperage (I)
100,66
25,23
28,0
2,90
Table 3: Data measurement 2a
Measurement 2b
Graph:
Figure 5: The temperature plotted against time using crushed ice
with sodium chloride (measurement 2b)
Table:
Amount ice
Amount
(gram) NaCl
Voltage
(gram) (V)
Amperage (I)
100,02
25,04
28,0
2,90
Table 4: Data measurement 2b
Conclusion and discussion
During this experiment we kept the following
variables constant: the amount of crushed ice, the
voltage, the amperage, the room temperature and
the current flow. The only change we made was
that we added no sodium chloride to the first
measurement and added 25 grams of sodium
chloride to the second measurement. We kept the
variables constant so as to allow a comparison
between the two set-ups.
As shown in figure 2 and 3 the melting process took
a lot of time, but as soon as all the ice had melted,
the temperature increased quickly.
As shown in figure 4 and 5 all the ice was melted at
a lower temperature compared to the ice without
sodium chloride. The temperature rise lasted longer
because the water had to raise more in temperature
as the water without sodium chloride because it
became liquid at a lower temperature. The ice
turned liquid sooner then the ice without sodium
chloride because the sodium chloride affects the
freezing point of water, making it lower.
From our results we can conclude that when sodium
chloride is added to the ice, less energy is needed to
melt the ice than when no sodium chloride is added
to the ice. The difference in used energy is 14 661J.
So when road salt is used, 14 661J J less energy is
needed for melting 100 grams of ice.
We have measured the difference in the amount of
energy needed to melt an x amount of crushed ice
in a container with sodium chloride and without
sodium chloride.
We used a ratio of 25 gram sodium chloride to 100
gram crushed ice.
This made us question what the result would be if
one used less sodium chloride.
What also would be interesting to investigate is if
the addition of CaCl2 would be more effective then
the use of sodium chloride melting ice
Bibliography
1. http://www.akzonobel.com/wegenzout/sys
tem/images/AkzoNobel_Visie_gladheidbe
strijding(1)_tcm116-34524.pdf