Urea vs. NaCl
Lieke Wiercx & Rhodé Heddes
OSG Huygens College, The Netherlands
Submission date: 13-04-2011
Summary
In cold winters we spread salt (NaCl) on our roads to prevent ice from forming. At airports they
use urea instead of NaCl to avoid corrosion on airplanes. We use these products to lower the
freezing point of water. This raises the question what the difference is between NaCl and urea
when you look at the melting process. Comparison of the melting of 30,0g of H2O(s) with
3,0g/6,0g NaCl(s) with the melting of 30,0g H2O(s) with 3,1g/6,2g urea resulted in a slightly
faster melting process of the crushed ice treated with urea. Both were considerably faster than the
blank.
Introduction
When airplanes take off or land, the runway
shoudn’t be slippery. So they have to use salt
to lower the freezing point. However they
don’t use NaCl but they use urea to avoid
corrosion on airplanes. Salt lowers the
freezing point of H2O(s). The lowering of the
freezing point depends on the amount of salt.
1 mol/L gives a lowering of 1,86oC(the
freezing-point drepression = kf)(1). When
H2O(l) contains 10% of salt, it freezes by -6
o
C(1). When H2O(l) contains 20% of salt, it
freezes by -16 oC(1). The kf value depends
upon the chemical properties of the salt.
This raises the inquiry question: Does urea
speed up the melting process of H2O(s) more
than NaCl?
Our hypothesis is that urea
increases the melting process
of H2O more than NaCl,
urea
because urea forms a hydrogen bond with
H2O, whereas NaCl forms an ionic bond.
Franken et.al. (2008) state that the hydrogen
bond is stronger than the ionic bond(2). If the
bond, that will form after the breaking of the
current bond, is stronger than the bond
already formed, then the breaking of the
current bonds is easier. That’s why we expect
that the urea will react faster with H2O(s) than
NaCl.
Experimental design
We took fifteen identical burettes and fifteen
identical funnels. Then the funnels were put
on top of the burettes and left at room
temperature(20oC). Each burette was filled
with distilled water until the 50,0ml mark (at
the bottom of the buret) so we could
determine the amount of melted H2O(s).
In all of the fifteen funnels we put 30,0g
crushed ice cubes. Three of them with 3,0g
NaCl(s). Three of them with 3,1g urea (the
same amount of moles as 3,0g NaCl). Three
of them with 6g NaCl(s). Three of them with
6,2g urea. Three of them were blanks.
Every ten minutes we noted the amount of
water that appeared in the burettes. We
continued the measuring until all the ice was
molten.
Accuracy
We used a burette, because that’s an accurate
way to measure. We’ve put the beaker with
crushed ice cubes in the freezer, after we had
weighed them, to make sure that any partially
melted ice was frozen solid and would not be
left behind in the beaker.
1
NaCl
3,0g
0,0 ±0,0
6,9 ±0,2
10,2 ±0,2
13,9 ±0,1
16,8 ±0,2
19,8 ±0,3
21,8 ±0,4
24,0 ±0,5
27,5 ±0,4
28,8 ±0,2
29,7 ±0,3
30,6 ±0,3
31,2 ±0,1
31,2 ±0,1
31,2 ±0,1
31,2 ±0,1
31,2 ±0,1
Urea
3,1g
0,0 ±0,0
7,5 ±0,1
11,2 ±0,2
13,9 ±0,2
17,3 ±0,1
20,3 ±0,2
23,3 ±0,2
25,5 ±0,1
28,1 ±0,1
29,8 ±0,2
31,1 ±0,1
31,5 ±0,0
31,5 ±0,0
31,5 ±0,0
31,5 ±0,0
31,5 ±0,0
31,5 ±0,0
In Table 2 you can see the average of the
amount of the melted water of crushed ice
that was treated with NaCl(6,0g), with
urea(6,2g) and a blank.
In Figure 1 you can see the average of the
amount of the melted water of crushed ice,
that was treated with NaCl(3,0g and 6,0 g),
with urea(3,1g and 6,2g) and a blank, in a
graph.
Time
(in min)
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
Blank
NaCl
(in mL)
6,0g
0,0 ±0,0
0,0 ±0,0
3,9 ±0,5
8,3 ±0,5
6,5 ±0,5
12,4 ±0,5
9,3 ±0,6
17,2 ±0,5
11,6 ±0,5 21,3 ±0,4
14,4 ±0,9 24,8 ±0,4
16,7 ±0,8 27,7 ±0,4
18,9 ±0,9 30,5 ±0,2
21,0 ±1,0 32,1 ±0,3
23,1 ±1,0 32,6 ±0,1
24,6 ±1,0 32,6 ±0,1
26,1 ±1,1 32,6 ±0,1
27,3 ±1,3 32,6 ±0,1
28,4 ±1,2 32,6 ±0,1
29,1 ±0,9 32,6 ±0,1
29,8 ±0,4 32,6 ±0,1
30,0 ±0,1 32,6 ±0,1
Urea
6,2g
0,0 ±0,0
8,7 ±0,5
13,1 ±0,4
18,2 ±0,5
22,0 ±0,3
25,3 ±0,6
28,4 ±0,6
31,4 ±0,5
32,7 ±0,6
33,3 ±0,1
33,3 ±0,1
Table 2
Time
Blank
(In min) (in mL)
0
0,0 ±0,0
10
3,9 ±0,5
20
6,5 ±0,5
30
9,3 ±0,6
40
11,6 ±0,5
50
14,4 ±0,9
60
16,7 ±0,8
70
18,9 ±0,9
80
21,0 ±1,0
90
23,1 ±1,0
100
24,6 ±1,0
110
26,1 ±1,1
120
27,3 ±1,3
130
28,4 ±1,2
140
29,1 ±0,9
150
29,8 ±0,4
160
30,0 ±0,1
33,3 ±0,1
33,3 ±0,1
33,3 ±0,1
33,3 ±0,1
33,3 ±0,1
33,3 ±0,1
35
30
25
Melted water (in mL)
Table 1
Results
In our results we can see that the ice with urea
on it melted the fastest. This is made visible
by the steepest line you see in Figure 1. When
you put a higher amount of NaCl or urea on
the ice cubes it melts faster. It took 160
minutes to let the crushed ice in all of the
funnels melt. In Table 1 you can see the
average (in the attachment you can find all the
figures) of the amount of the melted water of
crushed ice that was treated with NaCl(3,0 g),
with urea(3,1g) and a blank.
Blank
20
3,0g NaCl(s)
3,1g urea
15
6,0g NaCl(s)
10
6,2g urea
5
0
0
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
Time (in minutes)
2
Figure 1
Conclusion and discussion
When we look at the results we see that the
ice cubes which were treated with urea melted
faster than the blanks and the ice cubes which
were treated with NaCl. This was expected
because of the hydrogen bond between urea
and H2O. During the inquiry we have tried to
keep the same variables constant: the amount
of crushed ice, the room temperature and the
time taken. The room temperature was a
problem, because we did the inquiry on 2
different days (due to time restrains) and the
room temperature was variable. On the first
day it was 20oC and on the second day it was
21oC. When we use NaCl on the roads it isn’t
20oC, but subzero. This raises futher
questions for inquiry: What will the effect of
a lower temperature be on the melting process
of H2O?
The fact that urea is used instead of NaCl in
the aviation industry raises the question: What
is the corrosion effect of urea on modern
cars?
And would they also benefit from the use of
urea instead of NaCl?
The third avenue of research would be the
impacts on the environment. Which salt
stresses the envirionment less? And is it
economicaly viable for long time use?
Bibliography
1. http://www.zoutman.com/nl/informati
e/wegenzout
2. Peter Franken, Ed Korver, Joris
Schouten, Bertie Spillane, Yvonne
Veldema ( 2008) Chemie overall sk
vwo deel 1, blz.28 & 29
3. The effect of NaCl(s) on ice by Iru, P.,
Luib, A., & Nelem, D. in Journal of
anorgano chemistry (oktober 2010)
3
Attachment
The first day we did the inquiry with a room temperature of 20,3oC.
We did the following measurements on the first day:
1. 1st and 2nd measurement blank
2. 1st and 2nd measurement NaCl (3,0g)
3. 1st and 2nd measurement urea (3,1g)
4. 1st measurement NaCl (6,0g)
5. 1st measurement urea (6,2g)
The second day we did the inquiry with a room temperature of 21,0oC.
We did the rest of the measurements on the second day.
Blank
________________________________________________________________________________
Minutes
1st measurement
2nd measurement 3rt measurement
Average
_______________ ______________ ______________ _____________
_______________
0
0,0
0,0
0,0
0,0
10
3,9
3,4
4,3
3,9
20
6,4
6,0
7,0
6,5
30
8,9
9,1
9,9
9,3
40
11,2
11,6
12,1
11,6
50
13,6
14,3
15,3
14,4
60
15,9
16,9
17,4
16,7
70
18,0
19,0
19,8
18,9
80
20,1
21,0
22,0
21,0
90
22,1
23,0
24,1
23,1
100
23,7
24,6
25,6
24,6
110
25,0
26,0
27,2
26,1
120
26,4
27,0
28,6
27,3
130
27,5
28,0
29,6
28,4
140
28,2
29,2
30,0
29,1
150
29,4
30,0
30,0
29,8
160
30,1
30,0
30,0
30,0
4
3,0g NaCl(s)
______________________________________________________________________________
Minutes
1st measurement 2nd measurement 3rt measurement Average
_____________ _____________ _____________ _____________ _______________
0
0,0
0,0
0,0
0,0
10
6,9
6,8
7,1
6,9
20
10,1
10,1
10,4
10,2
30
13,9
13,8
14,0
13,9
40
16,8
16,6
17,0
16,8
50
19,7
19,5
20,1
19,8
60
21,4
21,7
22,2
21,8
70
23,7
23,9
24,5
24,0
80
27,1
27,4
27,9
27,5
90
28,6
28,8
29,0
28,8
100
29,5
29,7
30,0
29,7
110
30,6
30,4
30,9
30,6
120
31,2
31,1
31,2
31,2
130
31,2
31,1
31,2
31,2
3,1g urea
__________________________________________________________________________
Minutes
1st measurement
2nd measurement 3rt measurement
Average
______________ ______________ ______________ _____________
__________
0
0,0
0,0
0,0
0,0
10
7,5
7,6
7,5
7,5
20
11,1
11,3
11,0
11,2
30
13,9
14,0
13,7
13,9
40
17,3
17,4
17,2
17,3
50
20,3
20,5
20,2
20,3
60
23,4
23,5
23,2
23,3
70
25,5
25,5
25,4
25,5
80
28,1
28,2
28,1
28,1
90
29,8
29,9
29,6
29,8
100
31,0
31,2
31,0
31,1
110
31,5
31,5
31,5
31,5
120
31,5
31,5
31,5
31,5
5
6,0g NaCl(s)
_____________________________________________________________________________
Minutes
1st measurement
2nd measurement 3rt measurement
Average
______________ ______________ ______________ ______________ _____________
0
0,0
0,0
0,0
0,0
10
8,3
8,5
8,0
8,3
20
12,4
12,9
11,9
12,4
30
17,1
17,8
16,7
17,2
40
21,3
21,7
21,0
21,3
50
24,8
25,1
24,4
24,8
60
27,7
28,1
27,4
27,7
70
30,5
30,7
30,3
30,5
80
32,0
32,4
31,9
32,1
90
32,6
32,6
32,5
32,6
100
32,6
32,6
32,5
32,6
6,2g urea
_____________________________________________________________________________
Minutes
1st measurement
2nd measurement 3rt measurement
Average
______________ ______________ ______________ ______________ _____________
0
0,0
0,0
0,0
0,0
10
8,4
8,5
9,2
8,7
20
12,7
13,2
13,4
13,1
30
17,7
18,3
18,5
18,2
40
21,7
21,9
22,3
22,0
50
24,7
25,2
25,9
25,3
60
27,8
28,5
29,0
28,4
70
30,9
31,5
31,9
31,4
80
32,2
32,7
33,3
32,7
90
33,3
33,2
33,4
33,3
100
33,3
33,2
33,4
33,3
6