Wet or Dry Salt?
Elif Kusgozoglu & Lilly Alefs
Zaanlands Lyceum Zaandam, The Netherlands
Summary
The winter is in many countries cold, which means that it can be possible that it is going to snow. This
can be a big problem for a lot of people who drive the car regularly. But what is the solution for this
problem? The solution is: Salt! But what kind of salt, and how can it be as efficient as possible. That is
what we are testing in this experiment. We are going to test either dry salt or wet salt makes ice melt
faster. The result of our experiment is then that brine is more quickly with starting melting the ice.
The explanation for this is, that with brine there’s already water available for the hygroscopic NaCl(s)
molecules, which is not the case with salt.
Introduction
Ice consists of water molecules bounded
together on a regular basis by hydrogen
bonds. Adding salt (sodium and chloride ions)
will brake cause the regular structure. The
water molecules will interact with the ion, and
not just with themselves. The disappearance
of the regular structure is the same as melting.
But what is better to use? Wet or dry salt?
Dry salt is sprankled on the road in the
supplied form. The salt grains attract moisture
from the environment. This creates brine. This
"'water-salt " solution has a lower freezing
point than water. The brine melts the ice that
it touches. The brine also dissolves in the
resulting meltwater and ice continues to melt
till the salinity of the meltwater has become
too small. And if you use brine, then you will
skip the first process, the synthesis of brine.
So the ice smelts earlier, because the brine is
already synthesized. So this raises the
question: What fastens the meltingprogress?
Dry or wet salt?
Our hypothesis is that wet salt makes
ice melt faster. Because when you want to
melt ice with salt, the salt have to become
brine with water to be able to melt the ice,
because brine has a lower meltingpoint than
water. Brine has a melting point ± - 10 ˚C. But
in the beginning there is no H2O(l) available.
But because of the hygroscopic feature of
NaCl(s) a little surface of water on the ice will
soon be formed and speed up the melting
process. But in staid of salt you can put wet
salt, brine, on the ice so there is no need of
synthesis of brine, because it is already there.
So the wet salt will make the ice melt faster,
because it can make the ice melt immediately.
Experiment, procedure and approach
We took two 25 mL measuring cylinder and
two funnels. We placed on each cylinder a
funnel. In the funnel we put crushed ice till the
edge. Then we did the brine, we made with
1.0 gr. salt and a little bit of water, on the
funnel with ice and 1.0 gr salt on the other
funnel with ice.
We did this as fast as possible, so the ice
wasn’t melted before we started. When the
preparation was finished we stared
measuring.
Data gathering and Analysis
We took every minute a look. Then we noted
the results and put it in a graph. We repeted
this four times and calculated the median.
Here on you can say that the results are
trustworthy.
Results
For the observation of the velocity of the melting of the ice we looked every minute how much ice
total melted. We repeted this four times and calculated the median of the four results.
Table 1 presents the amount of melted ice with salt en the amount of melted ice with brine.
Time
(in minutes)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Ice + Brine
(mL)
2,3 ±0,2
3,2 ±0,25
3,8 ±0,2
4,3 ±0,2
4,5
4,8 ±0,1
5,1 ±0,1
5,3 ±0,1
7
5,65.±0,1
5,8 0,1
5,9 ±0,1
6,1 ±0,2
6,4 ±0,1
6,5 ±0,05
6,9 ±0,1
7,3 ±0,2
7,5
7,9 ±0,3
8,1 ±0,2
8,3 ±0,3
Ice + Salt
(mL)
2,30 ±2
2,8 ±0,2
3,2 ±0,1
3,3 ±0,2
3,7 ±0,2
4,1 ±0,1
4,4 ±0,1
4,6 ±0,1
4,8 ±0,1
5,2 ±0,1
5,3 ±0,1
5,5
5,7 ±0,2
6,2 ±0,2
6,5 ±0,2
6,7 ±0,2
7,2 ±0,2
7,5
7,7 ±0.1
7,9 ±0,2
Melted water (mL)
Table 1: Amount of molten ice (mL) after treated with brine and salt.
9
8
7
6
5
Ice + Brine (mL)
4
Ice + Salt (mL)
3
2
1
0
0
5
10
15
20
25
Time (minutes)
Figure 1: averaged measured amount of melted water(in mL) from crushed ice+salt and ice+brine
In Figure 1, in the beginning you see that brine
and salt are going both with the same velocity.
But after one minute the velocity of brine is
becoming faster then the velocity of salt. You
can see this in Figure 1 but you can also
calculate it:
The slope between 0 and 1 minutes:
Ice + Brine: ∆y/∆x = (2,3-0)/(1-0) = 2,3 mL/min
 tan(α) = ∆y/∆x = 2,3/1  α = 67˚
Ice + Salt: ∆y/∆x = (2,3-0)/(1-0) = 2,3 mL/min
 tan(α) = ∆y/∆x = 2,3/1  α = 67˚, so the
slope is for both lines equal.
The slope between 1 and 7 minutes:
Ice + Brine: ∆y/∆x = (5,1-2,3)/7-1) = 0,47
mL/min  tan(α) = ∆y/∆x = 2,8/6  α = 25˚
Ice + Salt: ∆y/∆x = (4,4-2,3)/(7-1) = 0,35
mL/min  tan(α) = ∆y/∆x = 2,1/6  α = 19˚,
so the slope form brine is bigger than salt.
The slope between 7 and 20 minutes:
Ice + Brine: ∆y/∆x = (8,3-5,1)/(20-7) = 0,25
mL/min  tan(α) = ∆y/∆x = 3,2/13  α = 14˚
Ice + Salt: ∆y/∆x = (7,9-4,4)/(20-7) = 0,27
mL/min  tan(α) = ∆y/∆x = 3,5/13  α = 15˚,
so the slope is for both lines almost the same.
Conclusions and Discussion
Looking critically at our experimental
procedure and approach we see that in the set
of experiments of crushed ice without NaCl(s)
– we took the same variables constant: the
amount of crushed ice, the room temperature
and the time taken. We measured the same
dependent variable (volume of the melted
water) and in one of the set-ups we added
brine instead of salt, so that a comparison
between the two set-ups was possible.
As is shown in Figure 1, the melting
process of crushed ice with brine and salt both
started with the same velocity. As you can see
from the result. They both have a slope of 67˚
in the period of 0 till 1 minutes.
The velocity of the ice+brine and
ice+salt started to split after 1 minute. As you
can see in Figure 1; the slope(the velocity) of
ice+brine is 25˚ and that is more than
ice+salt(19˚). So brine makes ice melt faster in
the period 1 till 7 minutes. This phenomenon
was expected because of the hygroscopic
feature of NaCl(s). This expectation concurs
with our observation that immediately after
adding NaCl(s) a layer of water was formed on
the crushed ice.
After about 7 minutes the melting
process of both set-ups – crushed ice+salt and
ice+brine became equal in speed as in
indicated by the same slope for both melting
processes, as you can see in Figure 1; ice+salt
15˚ and ice+brine 14˚. By this we can conclude
that brine after 7 minutes does not have an
effect anymore. An explanation is that the setup with ice+salt have formed brine by it self.
From this results we can conclude that
brine is more quickly with starting melting the
ice. The explanation for this is, that with brine
there’s already water available for the
hygroscopic NaCl(s) molecules, which is not
the case with salt. Because if you only
sprankle NaCl(s) on the road there is not yet
water available to be attracted to the NaCl(s).
But this raises the question: why have
the both lines the same slope at the period 720 minutes? Well, this can be explained. The
explanation for this can be, that the ice+salt
needed seven minutes to form brine by itself.
So the ice which was first influenced by the
set-up with salt is now influenced by brine like
the set up with brine. This means that the
both lines have got the same velocity, but
brine has simply made the most melted
water! Because he could make ice melts
immediately.
Some things that can cause
inaccuracies could be the brine left-overs in
the beaker, this means that the amount of salt
and the amount of salt in the brine were not
the same. Another inaccuracy can be caused
because of the mount of ice in the funnels, we
did put crushed ice till the edge in both
funnels, but we didn’t measure it. We could
prevent this by weighing the crushed ice, but
we could prevent the inaccuracy of the brine
left-overs in the beaker.
Bibliography
-
Chemie in onderzoek, ©H.J. Ubbels
Practical Assignment Chemistry 16-17
ICY – road salt